Dissertations / Theses: 'Photonic crystal fibres'

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Xiong, Chunle. "Nonlinearity in photonic crystal fibres." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512286.

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This thesis introduces the linear and nonlinear properties of photonic crystal fibre (PCF), describes the fabrication and characterisation of different PCFs, and demonstrates their applications to supercontinuum (SC) generation and single-photon sources. The linear properties of PCF include endlessly single-mode transmission, highly controllable dispersion and birefringence. These unique properties have made PCFs the best media to demonstrate all kinds of nonlinear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), Raman effects, four-wave mixing and modulation instability (FWM and MI), and soliton effects. The combination of these nonlinear effects has led to impressive spectral broadening known as SC generation in PCFs. The intrinsic correlation of signal and idler photons from FWM has brought PCF to the application of single-photon generation. Four projects about SC generation were demonstrated. The first was visible continuum generation in a monolithic PCF device, which gave a compact, bright (-20 dBm/nm), flat and single-mode visible continuum source extending to short wavelength at 400 nm. The second was polarised SC generation in a highly bire-fringent PCF. A well linearly polarised continuum source spanning 450-1750 nm was achieved with >99% power kept in a single linear polarisation. This polarised continuum source was then applied to tuneable visible/UV generation in a BIBO crystal. The third was residual pump peak removal for SC generation in PCFs. The fourth was to design an all-fibre dual-wavelength pumping for spectrally localised continuum generation. Two projects about photon pair generation using FWM were then demonstrated. One was an all-fibre photon pair source designed in the telecom band for quantum communication. This source achieved >50% heralding efficiency which is the highest in fibre photon pair sources reported so far. Another one was to design birefringent PCFs for naturally narrow band photon pair generation in the Si SPAD high detection efficiency range. 0.122 nm bandwidth signal photons at 596.8 nm were generated through cross polarisation phase matched FWM in a weakly birefringent PCF pumped by a picosecond Ti:Sapphire laser at 705 nm in the normal dispersion regime.

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Corbett, Jason C. W. "Photonic crystal fibres in astronomy." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2661/.

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Photonic crystal fibres (PCF) are a new generation of optical fibre that guide light via a periodic air-silica, photonic crystal structure instead of the more traditional step change in refractive index associated with traditional fibre. Careful design of the photonic structure causes the fibres to behave in interesting new ways and one of main aims of this thesis is to begin the investigation of the uses of PCF's in astronomy. Step index and large mode area (LMA) PCF's are introduced in Chapters 2 and 3, respectively. Chapter 4 then deals with the instrumental simplifications associated with the use of LMA PCF'ร in fibre stellar interferometry showing that up to four step index fibres and associated optics can be replaced with a single LMA fibre. One of the key features of LMA fibres, for astronomy, is that, unlike the step index fibre, the mode field size is independent of wavelength and the fibre can therefore be fed with a pupil image via a field lens. Chapter 5 investigates this important new parameter space showing that contiguous sampling using single mode fibres is now possible for the first time. Further, unlike the direct feed to the LMA fibre, maximised coupling over very large wavebands is now possible using just a single fibre. Chapter 6 deals with another new fibre technology in astronomy: Multi-mode fibre (MMF) to single-mode array (SMA) transitions. These fibre systems break out the modes of the multi-mode fibre into an array of single-mode fibres upon which Bragg gratings can be etched. The SMA is then refused into an output MMF resulting in a multimode device but with single-mode line suppression. The number of modes transmitted is numerically equal to the number of fibres in the SMA and the performance of these devices is investigated on a model telescope showing that only a few tens of modes is required to efficiently transmit either the J or н bands. Finally, Chapter 7 details the experimental investigation of fibre modal noise in high dispersion spectroscopy. This is a photometric error on a resolution element due to fibre modes interfering with each other at very high spectral dispersion. Worryingly, the results show that no current theory exists that can predict the performance of a fibre based high R spectrometer.

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Chen, Lei. "Modelling of photonic crystal fibres." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516842.

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The work in this thesis is to understand, through theory and simulation, a guidance mechanism due to the weak interaction of modes in photonic crystal fibres (PCFs). Firstly, two common kinds of PCFs, that guide light by total internal reflection and by photonic bandgaps, are reviewed. Several typical PCF structures for which light propagation is governed by weak mode interaction are then discussed and particularly compared with bandgap-guiding PCFs. Two independent methods are developed to model a set of related rectangular hollow-core PCF structures. The boundary element method is derived for a general PCF configuration and applied to our model structures. This method numerically provides some basic features about the guided modes, such as the propagation constant and field profile. The calculations show an ideal confinement in our model structure by considering a scalar wave equation and a high dielectric constant at the glass intersections. However, in realistic guidance, both confinement loss and the field of the guided modes indicate a raised leakage due to mode interactions. The analytic methodology starts by solving the ideal case considered in boundary element calculations and leads to analytic solutions for the perfectly guided modes. A perturbation method corresponding to the realistic guidance is then applied to these analytic solutions. This method can provide insight into understanding the formation of leakage through an analysis of mode interactions. An approximate analytic method for obtaining the attenuation of guided modes from the perturbation interaction is demonstrated. Attenuations calculated in this way give good agreement with boundary element results in magnitude and trends in variation. The influences of frequency and fibre parameters on features of the attenuation are also investigated. An overall interpretation of this guidance mechanism and suggestions for fibre optimisation are made in the final chapter, where further development of this work is also proposed.

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Chen, Yong. "Hole control in photonic crystal fibres." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616649.

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Photonic crystal fibres (PCFs) are special fibres with air holes which run along the whole fibre length. These holes not only determine the fibres' unique properties, but also provide a new degree of freedom for fibre modications. In this thesis, we focus on hole control in PCFs from two perspectives: during their fabrication and after they have been made. We found for the first time that the direct information of viscosity was not necessary for description of the fibre drawing process. This conclusion matched our experimental results without recourse to any adjustable fitting parameters. By post-processing of PCFs, which modifies the cladding and core structure and shape, we have achieved a series of novel devices for both linear and nonlinear applications. We have demonstrated fibre devices with cores resembling Young's double slits that have good performance in terms of compatibility and intensity enhancement for a specific application in fibre optic spectrometers. The bulk of this thesis reports on higher-order modes and their nonlinear applications. We achieved all-fibre, low loss and broadband mode converters in highly nonlinear PCFs (HNPCFs) which converted the fundamental mode (LP01) to a higher-order mode (LP02), which can then be converted back if necessary. This higher-order mode has been used for supercontinuum (SC) generation and four wave mixing (FWM) at wavelengths unobtainable for the fundamental mode. This is achieved by utilising the profound dispersion properties of the higher-order mode. We also demonstrated another kind of mode conversion: from the fundamental mode to a Bessel-like beam or its Fourier transform version, an annular beam. Three different methods were implemented experimentally to achieve this non-diffractive, self-healing beam.

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Witkowska, Agata. "Post-processing of photonic crystal fibres and standard fibres." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501641.

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This thesis describes work on fibre transitions made in photonic crystal fibres (PCF) and conventional standard fibres. Three post-processing techniques were used to make the transitions: fibre tapering, ferrule drawing and a new technique – PCF hole inflation. All these methods change the fibre dimensions on a centimeter scale while maintaining very low loss. In the hole inflation technique, cladding holes are pressurized and can be enlarged while heat-treating, unlike other techniques where the holes can only be reduced in size. Controlled hole expansion was used to produce devices for applications such as supercontinuum generation. Furthermore, differential pressurization of holes could create a diversity of core shapes in a PCF section. For example they were investigated to improve interfacing of laser diodes to fibres. Differential pressurization was also used to introduce new cores into PCFs. Introducing a larger core asymmetrically by the original core resulted in a fundamental to second-order mode conversion with a high extinction ratio. Alternatively, similar mode conversion was demonstrated by fusing two unequal standard fibres. Also with standard fibres, low-loss multimode to single-mode fibre transitions were made using a modified fibre fabrication technique. These fibre transitions and optical devices have a wide range of potential applications, for example in supercontinuum generation and low-loss interfacing of fibres to other optical systems.

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Williams, Gareth Owen Scott. "Photochemical kinetics and fluorescence spectroscopy in photonic crystal fibres." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/11747.

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This thesis describes work carried out to demonstrate the use of photonic crystal fibres for the study of photochemistry reaction kinetics and fluorescence spectroscopy. Photonic crystal fibre allows the guidance of light, in a well-defined mode, over long path lengths. When the fibre’s microstructure is filled with a sample solution this, therefore, provides a greatly increased measurement path length and greater light-sample interaction than is possible in conventional spectroscopic systems, leading to enhanced sensitivity whilst greatly reducing the required sample volumes. The use of photonic crystal fibre as a micro reaction chamber for carrying out photochemical reactions and the study of their kinetics was achieved through monitoring the photoisomerisation of two azobenzene-based dyes, Disperse Red 1 and Disperse Orange 1, using real-time UV/Vis absorption spectroscopy. Both the 488 nm excitation laser and the broadband light source for the measurements were co-coupled through the fibre, giving perfect overlap of both with the sample. The fibre used for the measurements was a hollow core kagomé-type fibre with a core diameter of 19μm, giving a sample volume of 2.8 nL cm-1. The 30 cm path-length of the fibre allowed the use of sample concentrations down to 5×10-6 M, over an order of magnitude lower than in a conventional 1cm cuvette, with a sample volume of 90 nl in the core, a reduction of five orders of magnitude over conventional measurements. The kinetics of the photoisomerisation from the trans to the cis isomers of the dyes and the thermally driven cis-to-trans isomerisation could be tracked on the ms timescale, using a grating spectrometer which recorded the entire absorption spectrum of the dye. The data were numerically fitted using a custom model to take into account the properties of the fibre system. This led to the calculation of rate constants for the isomerisation processes in good agreement with those previously measured for these dye systems in bulk solution. Furthermore, the measurement of the dyes in pentane, in which they are highly insoluble, could be achieved due to the low concentrations that could be used; such measurements have not previously been reported. For the study of photonic crystal fibre as a system for the excitation and collection of fluorescence, two types of fibre were used; the same kagomé hollow-core fibre used for the photochemistry absorption measurements and a suspended-core “Mercedes” fibre. This allowed for the excitation of fluorophores in two contrasting environments. In the kagomé fibre fluorophores in bulk solution are excited whilst, in the Mercedes fibre, only fluorophores either on or in close proximity to the silica core interact with the evanescent field of the excitation light. The Fluorescein fluorophore was used initially to measure the detection limits in both fibre types and limits of 2x10-11 M in the kagomé and 10-9 M in the Mercedes fibre were obtained. This equates to 106 molecules in the kagomé fibre, which displays the lower detection limit due to greater light-sample interaction. Two-photon excitation of the Fluorescein fluorophore was then carried out using a mode-locked Ti-Sapphire laser as an excitation source, demonstrating the ability of the fibre system to sustain two-photon excitation of a long (30 cm) path length. The two-photon measurements showed remarkable detection sensitivity allowing detection of fluorescence from 10-9 M solutions of Fluorescein, showing the potential of using PCF for two-photon based experiments which are of particular interest in fields such as photodynamic therapy. A further study was carried out, using the two fibre types, for measurement of the fluorescence lifetime of the Rhodamine B fluorophore. Unperturbed lifetimes could be measured in the fibres showing no interference from the fibre. The measurements confirmed, in reference to known lifetime values, that in the kagomé fibre the excited fluorophores are in the bulk solution with only a minor influence from surface effects, whilst in the Mercedes fibre all of the excited molecules experience interaction with the surface of the silica core. This, therefore, gives a method of locating the fluorophores with respect to the fibre surface and the ability to choose between measurement of bulk solution and long path-length evanescent field-induced fluorescence.

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Uthman, Muhammad. "Finite element characterisation of photonic crystal fibres." Thesis, City University London, 2013. http://openaccess.city.ac.uk/3012/.

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Rigorous numerical simulations have been carried out by using the Finite Element Method (FEM) in order to calculate bending and leakage losses of Photonic Crystal Fibres (PCF). A modal solution approach including the implementations of the conformal transformation and the Perfectly Matched Layer (PML) were undertaken to determine the bending and leakage losses of several designs of Photonic Crystal Fibres. This was carried out by varying key parameters such as the pitch (Λ), diameter (d) and air-filling fraction (d/Λ). Output modal parameters including the effective indices, spot sizes, leakage and bending losses as well as the mode field profiles were obtained. These output parameters were obtained by varying the bending radius (R) from very large values to very low values for different dimensions of the PCF, with results being obtained for Transverse Magnetic and Transverse Electric (quasi-TM and quasi-TE) polarizations. These parameters were calculated by solving the Maxwell’s equations using the H-field vector formulation and with the inclusion of PML to solve complex eigenvalue equations. Generally, it was observed that for all Λ, d/Λ and the polarization considered, as R is reduced from a very high value to lower values, the bending losses increase and there is a sharp increase at some lower values of R. At some very low values of R, some oscillatory behaviour was observed in the curves obtained for the fibre losses, where further investigations were carried out. These oscillations appeared due to degeneration of the fundamental mode with the cladding modes. In most of the cases investigated, there was a correlation in the variation of effective indices the loss values and also in the variation of spot sizes. PCFs with non-identical air-holes were also investigated in which case the d ≠ d2 (diameter of 4 larger air-holes in the first ring) and knowing the values for TM and TE polarizations, it was possible to determine the birefringence, which is the difference between the effective indices for the TM and TE modes and also the loss ratio, which is the ratio of TM loss to that of the TE loss. All the input and output parameters that were considered with the symmetric air-holes were also considered in the case with fibre with asymmetric air-holes study. The results obtained are very important in the design of Single Mode Single Polarization PCF. Results have also been obtained from the studies done of asymmetric arrangement of air-holes which lead to the design of Single Mode Single Polarization PCF. Work was carried out on the design of a tapered PCF that could be efficiently coupled to a single mode fibre, SMF. This was achieved by increasing the number rings up to 10 rings of air-holes in the cladding and having the outermost ring with larger air-holes, the inner rings were near cutoff. This fibre was coupled to a conventional SMF to allow for better tolerance to fabrication errors. There has also been work carried out in polymer fibre namely Teflon and TOPAS in the terahertz regime. The conventional hexagonal arrangement of PCF was simulated and compared to spiral PCF in THz. An improved PCF design having a porous core with hexagonal arrangement and cladding was designed and analysed and low-loss guidance in THz was achieved. Thus overall a number of different PCF designs were considered and their properties evaluated and detailed knowledge has been obtained on potential performance of such fibres.

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Kabir, Saiful. "Finite element modelling of photonic crystal fibres." Thesis, City University London, 2007. http://openaccess.city.ac.uk/8592/.

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Photonic crystal fibre (PCF), a new kind of optical fibre, has many air-holes in their cross-section and has potential applications to new optical communication systems. The main objective of this research is the modelling of photonic crystal fibre to identify the fundamental and higher order quasi-TE and TM modes with square, ,rectangular and circular air holes in a square and hexagonal matrix, by using a rigorous full-vectorial H-field based finite element method (FEM). Besides the modal solutions of the effective indices, mode field profiles, spot sizes, modal hybridness, polarization beat length and group velocity dispersion values for equal and unequal air holes; research was carried out to optimize and design highly birefringent PCF. The variation of modal birefringence is shown through the effect of hole diameters, air hole arrangement, structural asymmetry, operating wavelength, and pitch-distance. Birefringence was enhanced by breaking the structural symmetry and this was verified by using unequal air holes. The diameter of two air holes and four air holes in the first ring was changed to break the rotational symmetry and a comparison between the two designs is made in this work. In this work, highly birefringent PCF is designed with higher operating wavelength, larger d2/A value, lower pitch length for a given structural asymmetry. It is identified that birefringence value increases rapidly when d2 is much larger than d. At lower pitch value, one of the highest birefringence values reported so far at wavelertgth of 1.55 J.Jm for an asymmetric PCF using circular air holes. A single polarization guide PCF structure is also achieved. In this study, it has been identified that for fixed d/A and d2/A value, as operating wavelength is increased, birefringence increases significantly. It can also be identified that for higher d/A values, birefringence changes rapidly with A as their corresponding cutoff condition also approaches. One important validation of this work is the existence of modal birefringence for PCF with six-fold rotational symmetry. It is shown that birefringence value of a simple PCF incorporating circular holes but of different diameters is high compared to polarization maintaining Panda or Bow-tie fibres. This research also aims to investigate the modal leakage losses of PCF, by using a semi-vectorial beam propagation method (BPM) based on the versatile FEM. The robust perfectly matched layer (PML) boundary condition has been introduced to the modal solution approach. The effects of d2/A, operating wavelength and number of air holes have been thoroughly detailed and explained. In this study, it has been identified that the confinement loss decreases significantly with the increased number of rings, lower operating wavelength and lower d2/A value. For special case, PCF with large spot-size provides higher leakage loss.

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Hooper, Lucy. "Photonic crystal fibres for coherent supercontinuum generation." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557820.

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In this research photonic crystal fibres were developed for the purpose of generating coherent supercontinua. Two photonic crystal fibres were fabricated with all-normal group velocity dispersion profiles, with low dispersion at pump wavelengths 800 nm and 1064 nm. Supercontinua generated using these fibres were shown to have superior stability and coherence compared with supercontinua generated in fibres with anomalous dispersion at the pump wavelength. Using a short piece of photonic crystal fibre with all-normal group velocity dispersion, pumped at 1064 nm, a self phase modulation spectrum spanning 200 nm was generated. The supercontinuum was re-compressed using linear chirp compensation to 26 fs, which was within a factor of two of the theoretical transform limit. This demonstrates the high spectral coherence, stability, and almost-linear chirp of the supercontinuum. Simulations showed that pulse compression using a supercontinuum generated in a photonic crystal fibre with anomalous dispersion at the pump wavelength would be limited by shot-to-shot fluctuations in the spectral intensity and phase, and the nonlinear chirp. Using a longer piece of all-normal dispersion photonic crystal fibre, supercontinuum is generated by self phase modulation, and optical wave breaking. A broad flat supercontinuum spanning 700 nm, centred at 1064 nm was generated. This supercontinuum was spectrally filtered, and the pulses obtained analysed in the temporal domain. Clean, stable sub-picosecond pulses were achieved, demonstrating the applicability of such a supercontinuum as part of a compact, tunable laser source. The same experiment was carried out using a photonic crystal fibre with anomalous dispersion at the pump wavelength, resulting in pulses with a large portion of energy contained in broad shoulders, and higher order modes. Interferometric coherence measurements were carried out at 800 nm using a Ti:Sapphire laser. A supercontinuum was generated in all-normal dispersion photonic crystal fibre with low dispersion at 800 nm, spanning 400 nm. Supercontinuum pulses generated by consecutive laser pulses were brought together in time using an interferometer. The interference between consecutive pulses was viewed spectrally, and the interference fringes had high visibility across the whole supercontinuum bandwidth. This demonstrates high spectral coherence. A supercontinuum generated in photonic crystal fibre with anomalous dispersion at 800 nm was tested in the same way, and the interference fringes obtained had lower visibility, indicating low spectral coherence. The research presented demonstrates that photonic crystal fibres with all-normal dispersion profiles can be used to generate supercontinua with high coherence and intensity stability. This type of supercontinuum is applicable to ultra-short pulse compression, and can be spectrally filtered to create a broadband tunable ultra-short laser source.

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Issa, Nader. "Modes and propagation in microstructured optical fibres." University of Sydney. Physics and Optical Fibre Technology Centre, 2005. http://hdl.handle.net/2123/613.

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Microstructured optical fibres (MOFs), also commonly called photonic crystal fibres or holey fibres, describe a type of optical fibre in which continuous channels of (typically) air run their entire length. These `holes' serve to both confine electromagnetic waves within the core of the fibre and to tailor its transmission properties. In order to understand and quantify both of these functions, a new computational algorithm was developed and implemented. It solves for the eigenvalues of Maxwell's wave equations in the two-dimensional waveguide cross-section, with radiating boundary conditions imposed outside the microstructure. This yields the leaky modes supported by the fibre. The boundary conditions are achieved exactly using a novel refinement scheme called the Adjustable Boundary Condition (ABC) method. Two implementations are programmed and their computational efficiencies are compared. Both use an azimuthal Fourier decomposition, but radially, a finite difference scheme is shown to be more efficient than a basis function expansion. The properties of the ABC method are then predicted theoretically using an original approach. It shows that the method is highly efficient, robust, automated and generally applicable to any implementation or to other radiating problems. A theoretical framework for the properties of modes in MOFs is also presented. It includes the use of the Bloch-Floquet theorem to provide a simpler and more efficient way to exploit microstructure symmetry. A new, but brief study of the modal birefringence properties in straight and spun fibres is also included. The theoretical and numerical tools are then applied to the study of polymer MOFs. Three types of fibres are numerically studied, fabricated and characterised. Each is of contemporary interest. Firstly, fabrication of the first MOFs with uniformly oriented elliptical holes is presented. A high degree of hole ellipticity is achieved using a simple technique relying on hole deformation during fibre draw. Both form and stress-optic birefringence are characterized over a broad scaled-wavelength range, which shows excellent agreement with numerical modelling. Secondly, an analysis of leaky modes in real air core MOFs, fabricated specifically for photonic band gap guidance, is then used to identify alternative guiding mechanisms. The supported leaky modes exhibit properties closely matching a simple hollow waveguide, weakly influenced by the surrounding microstructure. The analysis gives a quantitative determination of the wavelength dependent confinement loss of these modes and illustrates a mechanism not photonic band gap in origin by which colouration can be observed in such fibres. Finally, highly multimode MOFs (also called `air-clad' fibres) that have much wider light acceptance angles than conventional fibres are studied. An original and accurate method is presented for determining the numerical aperture of such fibres using leaky modes. The dependence on length, wavelength and various microstructure dimensions are evaluated for the first time for a class of fibres. These results show excellent agreement with published measurements on similar fibres and verify that bridge thicknesses much smaller than the wavelength are required for exceptionally high numerical apertures. The influence of multiple layers of holes on the numerical aperture and capture efficiency are then presented. It shows that a substantial increase in both these parameters can be achieved for some bridge thicknesses. Simple heuristic expressions for these quantities are given, which are based on the physical insight provided by the full numerical models. The work is then supported by the first fabrication attempts of large-core polymer MOFs with thin supporting bridges. These fibres exhibit relatively high numerical apertures and show good agreement with theoretical expectations over a very wide scaled-wavelength range.

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Ortigosa, Blanch Arturo. "Highly birefringent photonic crystal fibres : linear and nonlinear effects." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760818.

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Norton, Richard. "Numerical computation of band gaps in photonic crystal fibres." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501623.

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Photonic crystal fibres are capable of special light guiding properties that ordinary optical fibres do not possess, and efforts have been made to numerically model these properties. The plane wave expansion method is one of the numerical methods that has been used. Unfortunately, the function that describes the material in the fibre n(x) is discontinuous, and convergence of the plane wave expansion method is adversely affected by this. For this reason, the plane wave expansion method may not be every applied mathematician’s first choice method but we will show that it is comparable in implementation and convergence to the standard finite element method. In particular,an optimal preconditioner for the system matrix A can easily be obtained and matrixvector products with A can be computed in O(N logN) operations (where N is the size of A) using the Fast Fourier Transform. Although we are always interested in the efficiency of the method, the main contribution of this thesis is the development of convergence analysis for the plane wave expansion method applied to 4 different 2nd-order elliptic eigenvalue problems in R and R2 with discontinuous coefficients. To obtain the convergence analysis three issues must be confronted: regularity of the eigenfunctions; approximation error with respect to plane waves; and stability of the plane wave expansion method. We successfully tackle the regularity and approximation error issues but proving stability relies on showing that the plane wave expansion method is equivalent to a spectral Galerkin method, and not all of our problems allow this. However, stability is observed in all of our numerical computations. It has been proposed in [40], [53], [63] and [64] that replacing the discontinuous coefficients in the problem with smooth coefficients will improve the plane wave expansion method, despite the additional error. Our convergence analysis for the method in[63] and [64] shows that the overall rate of convergence is no faster than before. To define A we need the Fourier coefficients of n(x), and sometimes these must be approximated, thus adding an additional error. We analyse the errors for a method where n(x) is sampled on a uniform grid and the Fourier coefficients are computed with the Fast Fourier Transform. We then devise a strategy for setting the grid-spacing that will recover the convergence rate of the plane wave expansion method with exact Fourier coefficients.

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Gris, Sanchez Itandehui. "Fabrication and applications of low OH photonic crystal fibres." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577736.

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The aim of this thesis is to consistently fabricate low OH content silica solid-core photonic crystal fibres of different core diameters, identified as low spectral attenuation at 1383 nm. Three different methods are proposed. Two of them are focused on preventing the OH contamination of glass during fabrication whilst the third method is focused on obtaining low OH fibres by reducing the OH content of already contaminated glass. The local attenuation at the ends of these low OH fibres is notoriously worsen when they are exposed to the atmospheric water vapour, the levels of this attenuation depending very strongly with core diameter. The low OH levels achieved (0.19 ppm) in the small-core photonic crystal fibres open the scope to applications in non linear optics where standard levels of absorption are detrimental. In particular, the principle of a widely tunable source (across the OH absorption peak at 1383 nm) delivering femtosecond pulses beyond 2 μm is demonstrated experimentally.

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Travers, John Colins. "Controlling nonlinear optics with dispersion in photonic crystal fibres." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1362.

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Nonlinear optics enables the manipulation of the spectral and temporal features of light. We used the tailorable guidance properties of photonic crystal fibres to control and enhance nonlinear processeswith the aim of improving nonlinearity based optical sources. We utilised modern, high power, Ytterbium fibre lasers to pump either single photonic crystal fibres or a cascade of fibres with differing properties. Further extension of our control was realised with specifically tapered photonic crystal fibres which allowed for a continuous change in the fibre characteristics along their length. The majority of our work was concerned with supercontinuum generation. For continuous wave pumping we developed a statistical model of the distribution of soliton energies arising from modulational instability and used it to understand the optimum dispersion for efficient continuum expansion. A two-fold increase in spectral width was demonstrated, along with studies of the noise properties and pump bandwidth dependence of the continuum. For picosecond pumping we found that the supercontinuum bandwidth was limited by the four wave mixing phase-matching available in a single fibre. A technique to overcome this by using a cascade of fibres with different dispersion profiles was developed. Further improvement was achieved by using novel tapered PCFs to continuously extend the phase-matching. Analysis of this case showed that a key role was played by soliton trapping of dispersive waves and that our tapers strongly enhanced this effect. We demonstrated supercontinua spanning 0.34-2.4 ¹mwith an unprecedented spectral power; up to 5 mW/nm. The use of long, dispersion decreasing photonic crystal fibres enabled us to demonstrate adiabatic soliton compression at 1.06 ¹m. From a survey of fibre structures we found that working around the second zero dispersion wavelength was optimal as this allows for decreasing dispersion without decreasing the nonlinearity. We achieved compression ratios of over 15.

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Stone, James. "Photonic crystal fibres and their applications in the nonlinear regime." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503388.

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This thesis presents several advances in the technology and applications of photonic crystal fibres achieved over the last three years. Chapters 1 and 2 give the background material important to understand the results presented in chapters 3, 4 and 5. In chapter 1, linear properties of optical fibres are described. This chapter focuses particularly on how the engineering of the cladding structure of solid core photonic crystal fibres can be used to vary the fibre properties, most importantly the group index and dispersion. Propagation in all-solid photonic bandgap fibres is also discussed in terms of the anti-resonant reflecting optical waveguide model. Chapter 2 introduces the nonlinear optical effects that are important to understand the work presented in chapters 4 and 5. In chapter 3, a method to reduce bend losses in all-solid photonic bandgap fibres is outlined. The reduction of these losses is achieved by redesigning the high-index inclusions in the cladding structure to suppress cladding modes that strongly couple to the fundamental core-guided mode when the fibre is bent. In chapter 4, a method of tapering photonic crystal fibres in order to decrease the dispersion along their length is described. The tapers are used to compress solitons via adiabatic soliton compression and a combination of adiabatic soliton compression and soliton effect compression, achieving a factor of 15 compression of a transform-limited pulse to below 50 fs. Chapter 5 describes how engineering the cladding structure of photonic crystal fibres can be used to generate shorter frequencies in supercontinuum generation. The method by which this achieved is experimentally verified and then exploited to generate a continuum incorporating the entire visible spectrum using low cost, low maintenance pump sources.

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Bateman, Samuel. "Hollow core fibre-based gas discharge laser systems and deuterium loading of photonic crystal fibres." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648951.

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Research towards the development of a gas-discharge fibre laser using noble gases, with target emission wavelengths in the mid-IR. Additional and separate work on gas treatment methods for managing the formation of photo-induced defects in silica glass.

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Livesey, John Gregor. "Atom guiding in free-space light beams and photonic crystal fibres." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/356.

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Olupitan, Samuel. "Efficient pulse compression at near-infrared region using photonic crystal fibres." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=202703.

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Lombardini, Alberto. "Nonlinear optical endoscopy with micro-structured photonic crystal fibers." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4377.

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Dans cette thèse, nous proposons l'utilisation d'un nouveau type de fibre à cristal photonique, la fibre Kagomé à coeur creux, pour la livraison d'impulsions ultra-courtes en endoscopie non linéaire. Ces fibres permettent la livraison d'impulsions sans distorsion sur une large bande spectrale, avec un faible bruit de fond, grâce à la propagation dans le cœur creux. Nous avons résolu le problème de la résolution spatiale, à l'aide d'une microbille en silice, insérée dans le cœur de la fibre Kagomé. Nous avons développé un système d'imagerie compacte, qui utilise un tube piézo-électrique pour le balayage du faisceau, un système achromatiques de microlentilles et une fibre Kagomé double gaine, spécialement conçue pour l'endoscopie. Avec ce système, nous avons réussi à imager des tissus biologiques, à l'extrémité distale de la fibre (endoscopie), en utilisant des différentes techniques tels que TPEF, SHG et CARS, un résultat qui ne trouve pas d'égal dans la littérature actuelle. L'intégration dans une sonde portable (4,2 mm de diamètre) montre le potentiel de ce système pour de futures applications en endoscopie multimodale in-vivo
In this thesis, we propose the use of a novel type of photonic crystal fiber, the Kagomé lattice hollow core fiber, for the delivery of ultra-short pulses in nonlinear endoscopy. These fibers allow undistorted pulse delivery, over a broad transmission window, with minimum background signal generated in the fiber, thanks to the propagation in a hollow-core. We solved the problem of spatial resolution, by means of a silica micro-bead inserted in the Kagomé fiber large core. We have developed a miniature imaging system, based on a piezo-electric tube scanner, an achromatic micro-lenses assembly and a specifically designed Kagomé double-clad fiber. With this system we were able to image biological tissues, in endoscope modality, activating different contrasts such as TPEF, SHG and CARS, at the distal end of the fiber, a result which finds no equal in current literature. The integration in a portable probe (4.2 mm in diameter) shows the potential of this system for future in-vivo multimodal endoscopy

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Antonopoulos, Grigorios. "Super-enhanced stimulated Raman scattering and particle guidance in hollow-core photonic crystal fibres." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425387.

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Gherardi, David Mark. "Studies of particle and atom manipulation using free space light beams and photonic crystal fibres." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/703.

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Atuba, Sunday. "Generation of a train of ultrashort pulses through the propagation of periodic wave in photonic crystal fibres." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=233638.

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Apriyanto, Haris. "Study, analysis and experimental validation of fiber refractometers based on single-mode, multimode and photonic crystal fibers for refractive index measurements with application for the detection of methane." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0022.

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La mesure de l'indice de réfraction a été étudiée depuis qu'Ernest Abbé aie initialement conçu un réfractomètre en 1869, appelé le réfractomètre d'Abbé. Depuis lors, de nombreux réfractomètres ont été développés tels que le réfractomètre à prisme optique ainsi que le réfractomètre à fibre optique, en raison de leurs applications étendues pour la détection de divers paramètres physiques, biologiques et chimiques. Récemment, un grand nombre de chercheurs ont mis au point des réfractomètres basés sur des fibres optiques, exploitant des mécanismes tels que la résonance des plasmons de surface (SPR), les interférences multimodes, les fibres à réseaux de Bragg (FBG), les fibres à réseaux à longues périodes (LPG), les fibres optiques coniques et la fibre multimode à gaine dénudée. Les capteurs fibrés sont avantageux grâce à leur immunité contre les interférences électromagnétiques, passivité électrique au niveau de la sonde de détection et potentiel de mesure in situ à long terme. Cette thèse concerne le développement de modèles complets fonctionnels et précis pour les réfractomètres à fibres optiques basés sur la modulation d'intensité optique, en particulier la réfractométrie à fibre multimode à gaine dénudée ainsi que les systèmes hybrides associant fibres monomode et multimode, et un réfractomètre hybride tout fibré utilisant des fibres à cristaux photoniques. L'objectif clé de ce travail est de caractériser les performances de ces réfractomètres à fibres optiques basés sur la modulation d'intensité en termes de réponse en puissance, de sensibilité, de résolution et de dynamique de mesure. Les résultats de simulation qui sont corroborés expérimentalement démontrent que la très grande sensibilité obtenue dans la zone II (c'est-à-dire le régime de détection typiquement utilisé pour mesurer l'indice du milieu supérieur à l'indice de gaine mais inférieur ou égal à l'indice du coeur) pour tous les trois réfractomètres. Cependant, la sensibilité dans la Zone (c’est-à-dire le régime de détection pour lequel l’indice du milieu à mesurer est supérieur à celui du coeur) est très faible. Ainsi, un refractomètre fibré hybride monomode-multimode est utilisé pour améliorer la sensibilité dans la Zone III. D'autre part, la sensibilité pour la zone I (c'est-à-dire le régime de détection pour mesurer l’indice du milieu inférieur à l'indice de la gaine) a été améliorée en augmentant l'absorption des ondes évanescentes à l'aide du réfractomètre hybride tout fibré à base de fibres à cristaux photoniques à coeur solide. En termes d'application réelle du réfractomètre à fibre pour la détection biochimique, une preuve de concept pour un capteur du gaz méthane a été démontrée en utilisant les supramolécules de cryptophane-A qui permettent de piéger les molécules du méthane. Le cryptophane-A incorporé dans un film hôte à base de styrène acrylonitrile (SAN) est appliqué sur la zone dénudée du capteur comme une région fonctionnalisée. L'indice de réfraction de cette couche sensible augmente proportionnellement avec l'augmentation de la concentration du méthane, ce qui induit une variation de la puissance optique transmise dans le capteur fibré
Refractive index measurement has been studied since Ernest Abbé initially designed a refractometer in 1869, which is named the Abbé refractometer. Since then, numerous types of refractometers have been developed by employing either the optical prism-based refractometer or the optical fiber-based refractometer, due to their wide-ranging applications such as for sensingvarious physical, biological and chemical parameters. Recently, a large number of researchers have been developing refractometers based on optical fibers, exploiting mechanisms such as surface plasmon resonance (SPR), multimode interference, fiber Bragg gratings (FBG), long period gratings (LPG), tapered optical fibers, and striped-cladding multimode fibers (MMF), for their advantages in immunity against electromagnetic interference, electrical passivity at the sensing probe, and capability to long term in-situ measurement. This thesis concerns the development of comprehensively functional and accurate models for optical fiber refractometers based on optical intensity modulation, in particular for stripped-cladding MMF refractometry as well as hybrid systems involving a combination of single-mode-multimode fiber refractometery and the all-fiber hybrid refractometer using photonic crystal fibers. A key objective of this work is to characterize the performance of these intensity-based optical fiber refractometers in terms of their power response, sensitivity, resolution, and dynamic range. The simulation results which are corroborated experimentally demonstrate very high sensitivity being obtained in Zone II (i.e. the sensing regime typically employed for measuring a sensing medium index higher than the cladding index but less than or equal to the core index) for all three types of refractometers. However, the sensitivity in Zone III (i.e. the sensing regime for which the sensing medium index is higher than the core index) is very low. A hybrid single-mode fiber - multimode fiber configuration is used to improve the sensitivity in Zone III. On other hand, the sensitivity for Zone I (i.e. the sensing regime typically employed for measuring a sensing medium index lower than the cladding index) has been improved by increasing evanescent wave absorption using the all-fiber hybrid refractometer based on solid-core photonic crystal fibers. As a further potential of the fiber refractometer for applications in biochemical sensing, the proof-of-concept for a methane gas sensor has been demonstrated using supramolecular cryptophane-A which enables to trap the methane molecules. Cryptophane-A incorporated into a functionalized film of StyreneAcrylonitrile (SAN) host is applied to a de-cladded region of the sensor as the sensitive region. The refractive index of this functionalized layer increases proportionally with increasing methane concentration, subsequently inducing variations in the transmitted optical power along the fiber sensor

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Unterkofler, Sarah [Verfasser], and Philip J. [Akademischer Betreuer] Russell. "Optofluidic Photonic Crystal Fibres for Biomedical Research in fibra / Sarah Unterkofler. Betreuer: Philip J. Russell." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2013. http://d-nb.info/1035540894/34.

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Amsanpally, Abhilash. "Linear properties of inhibited coupling hollow-core photonic crystal fibers." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0028/document.

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Cette thèse a porté sur les principes de guidage, les propriétés linéaires et les outils de conception autour des fibres à cristal photonique à coeur creux (HC-PCF) à couplage inhibé (IC). Le guidage IC a été démontré comme une manifestation photonique de Q-BiC (état quasi lié dans un continuum) en étudiant des profils asymétriques et dépendants en polarisation dit Fano présentant une bande passante spectrale de 30 GHz. En utilisant le concept de IC, nous reportons la caractérisation linéaire de fibres IC HC-PCF supérieures à l’état de l’art. Par une optimisation de la forme du coeur, une fibre Kagome IC HC-PCF a démontré des pertes très faibles de 8,5 dB/km à 1030 nm associées à une bande passante à 3 dB de 225 nm. Une autre conception avec des entretoises de silice amincies à 300 nm a permis d’atteindre des pertes de 30 dB/km à 780 nm avec une bande de transmission fondamentale record décalée à 670 nm et capable de couvrir toutes les gammes spectrales du Ti:Sa, Yb et Er. Nous avons également travaillé sur la conception et la fabrication de IC HC-PCF présentant une gaine dont la structure est un réseau unique de tubes fins isolés. Une de ces fibres a permis de démontrer une transmission jusqu'à 220 nm avec des pertes records de 7,7 dB/km à ~ 750 nm, tandis qu’une seconde réalisation s’est traduit par une bande fondamentale de plus d’une octave allant de 600 à 1200 nm avec des pertes de 10-20 dB/km. Finalement, cette dernière fibre a été étudiée plus en détail pour déterminer les sources à l’origine des pertes due à la rugosité de surface présente à l’interface du contour du coeur
This thesis reported on guiding principles, linear properties and conceptual design tools of inhibited coupling (IC) guiding hollow-core photonic crystal fibers (HC-PCF). IC guidance was proved as photonic manifestation of Q-BiC (quasi bound-state-in-a-continuum) by investigating asymmetric and polarization dependent Fano profiles with bandwidth of 30 GHz in high resolution transmission spectra. By using IC design concept, we reported on linear characterization of state-of-the-art IC HC-PCFs. Based on core shaping optimization, a Kagome IC HC-PCF demonstrated ultra-low loss down to 8.5 km/km at 1030 nm associated with a 225 nm wide 3-dB bandwidth. Another Kagome design with thinner silica struts of 300 nm exhibited lowest loss of 30 dB/km at 780 nm along with record level fundamental bandwidth spreading down to 670 nm and able to cover the entire Ti:Sa, Yb and Er laser spectral ranges. We also reported on design and fabrication of single-ring tubular lattice IC HC-PCFs. One of these fibers demonstrated transmission down to 220 nm with a record transmission loss of 7.7 dB/km at ~750 nm, while the second one exhibited ultra-broad fundamental band with loss range of 10-20 dB/km over one octave spanning from 600 to 1200 nm. Finally, the second tubular fiber was further investigated for fundamental loss sources due to surface roughness around its core-contour

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Sloanes, Trefor J. "Measurement and application of optical nonlinearities in indium phosphide, cadmium mercury telluride and photonic crystal fibres." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/723.

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The two-photon absorption (TPA) coefficient is measured in indium phosphide (InP) using femtosecond pulses to be 45cm/GW at 1.32μm. Nanosecond pulses are subsequently used to find the free-carrier refractive index cross-section, σ_r, and the free-carrier absorption coefficient, σ_fca. The quantity βσ_r is measured to be -113x10⁻²ºcm⁴/GW at 1.064μm and -84x10⁻²ºcm⁴/GW at 1.534μm. At 1.064μm, with β assumed to be 22cm/GW, the value suggested by theory, σ_r is -5.1x10⁻²ºcm³. Similarly, at 1.534μm, assuming β to be 20cm/GW gives a σ_r value of -4.1x10⁻²ºcm³. Due to refraction affecting the measurements of σ_fca, only an upper limit of 1x10⁻¹⁵cm² can be put on its value. The free-carrier experiments are repeated on two samples of cadmium mercury telluride (CMT) having bandgaps of 0.89eV and 0.82eV. For the first sample, β_σr is measured to be -148x10⁻²ºcm⁴/GW. Assuming β to be 89cm/GW gives a σ_r value of -1.7x10⁻²ºcm³ whilst σ_fca is found to be at most 3x10⁻¹⁵cm². Significant linear absorption occurs in the second sample which generates a large free-carrier population. It is shown that this significantly enhances the nonlinearities. Finally, the results of the work are tested by modelling a nonlinear transmission experiment, and the results found in this work give a closer fit to experimental results than the result of theory. Four-wave mixing (FWM) in a photonic crystal fibre is exploited to create a high output power optical parametric amplifier (OPA). To optimise the OPA conversion efficiency, the fibre length has to be increased to 150m, well beyond the walk-off distance between the pump and signal/idler. In this regime, the Raman process can take over from the FWM process and lead to supercontinuum generation. The OPA exhibits up to 40% conversion efficiency, with the idler (0.9μm) and the signal (1.3μm) having a combined output power of over 1.5W.

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Sloanes, Trefor James. "Measurement and application of optical nonlinearities in indium phosphide, cadmium mercury telluride and photonic crystal fibres /." St Andrews, 2009. http://hdl.handle.net/10023/723.

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28

Thang, Nguyen [Verfasser], and Philip [Akademischer Betreuer] Russell. "Stimulated Raman Scattering in Gas Filled Hollow-Core Photonic Crystal Fibres / Nguyen Thang. Gutachter: Philip Russell." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2013. http://d-nb.info/1065379153/34.

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Stiller, Birgit. "Brillouin scattering in photonic crystal fiber : from fundamentals to fiber optic sensors." Thesis, Besançon, 2011. http://www.theses.fr/2011BESA2019/document.

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Le cadre général dans lequel s’insère ce travail de thèse est celui de l’étude de la diffusion Brillouin dans une nouvelle génération de fibres optiques à cristaux photoniques (PCFs). Ces fibres, qui présentent un arrangement périodique de micro-canaux d’air parallèles le long de la fibre, possèdent en effet des propriétés optiques et acoustiques remarquables et inédites par rapport aux fibres conventionnelles. De façon plus précise, nous montrons dans ce travail, par le biais de simulations numériques et de données expérimentales, que les fibres à cristaux photoniques offrent la possibilité de supprimer ou, à contrario, augmenter les interactions entre les photons et les phonons. Dans une première partie, nous présentons une méthode de cartographie des fluctuations longitudinales de la microstructure des fibres PCFs à l’aide d’un capteur distribué basé sur une méthode innovante d’écho Brillouin. Cette méthode, très sensible et à haute résolution, est directement intéressante pour caractériser et améliorer l’uniformité des PCFs lors de leur fabrication et également pour la détection des différentes contraintes de température et étirement induites le long des fibres. Sur le plan fondamental, notre système de mesure distribuée à haute résolution nous a également permis d’observer, pour la première fois à notre connaissance, le temps de vie des ondes acoustiques dans les fibres à cristaux photoniques et les fibres standard. Par ailleurs, sur le plan technique, nous avons développé une architecture simplifiée de capteur distribué combinant la technique des échos Brillouin et celle de la modulation différentielle par déplacement de phase avec un seul modulateur d’intensité. Nos résultats montrent une résolution centimétrique dans la zone de soudure entre deux fibres optiques à l’aide d’une impulsion de phase de 500 ps. Nous démontrons dans une deuxième partie la suppression directe et passive de la rétrodiffusion Brillouin stimulée dans une fibre optique micro structurée en faisant varier périodiquement le diamètre de la microstructure. Une augmentation de 4 dB du seuil de puissance Brillouin a été obtenue avec une variation de seulement 7% sur une période de 30m. Ce résultat est très intéressant car la diffusion Brillouin est un facteur limitant dans les systèmes de télécommunications par fibre optique et les lasers à fibre. La troisième et dernière partie est consacrée à l’étude numérique et expérimentale de la diffusion Brillouin en avant dans les fibres à cristaux photoniques. En plus de la suppression de la plupart des modes acoustiques transverses, nous montrons que cette diffusion Brillouin est fortement augmentée pour certains modes acoustiques à haute fréquence qui sont piégés au cœur de la microstructure. Nous avons également étudié une fibre à structure multi-échelle qui révèle l’excitation sélective de plusieurs phonons acoustiques à des fréquences allant jusqu’a 2GHz. Ces mesures ont étés confirmées par des simulations numériques basées sur une méthode vectorielle aux éléments finis. L’impact des irrégularités de la microstructure a aussi été mis en évidence.Mots clés : optique non linéaire, diffusion Brillouin, fibres optiques microstructurées, seuil Brillouin, capteurs Brillouin distribués
Brillouin scattering is a fundamental nonlinear opto-acoustic interaction present in optical fibers with important implications in fields ranging from modern telecommunication networks to smart optical fiber sensors. This thesis is aimed at providing a comprehensive theoretical and experimental investigation of both forward and backward Brillouin scattering in next generation photonic crystal fibers in view of potential applications to above mentioned fields. We show in particular that these micro-structured optical fibers have the remarkable ability to either suppress or enhance photon-phonon interactions compared to what is commonly observed in conventional fibers. Firstly, this thesis provides a complete experimental characterization of several photonic crystal fibers using a novel highly-resolved distributed sensing technique based on Brillouin echoes. We perform distributed measurements that show both short-scale and long-scale longitudinal fluctuations of the periodic wavelength-scale air-hole microstructure along the fibers. Our mapping technique is very sensitive to structural irregularities and thus interesting for fiber manufacturers to characterize and improve the fiber uniformity during the drawing process. With this technique, we also report the first experimental observationof the acoustic decay time and the Brillouin linewidth broadening in both standard and photonic crystal fibers. Furthermore, we experimentally demonstrate a simplified architecture of our Brillouin echoes-based distributed optical fiber sensor with centimeter spatial resolution. It is based on differential phase-shift keying technique using a single Mach-Zehnder modulator to generate a pump pulse and a _-phase-shifted pulse with an easy and accurate adjustment of delay. These sensing techniques are also applied to distributed strain measurement. Another aspect of this thesis is the investigation of a novel method for suppressing stimulated Brillouin scattering that is detrimental to optical fiber transmissions and fiber lasers. We experimentally study several fibers and a demonstrate 4 dB increase of the Brillouin threshold in a photonic crystal fiber by varying periodically the core diameter by only7%. The efficiency of this passive technique is verified by use of our distributed sensing technique where the oscillating Brillouin frequency shift is clearly observed.Lastly, we present experimental and numerical results demonstrating the simultaneous vi Abstract frequency-selective excitation of several guided acoustic Brillouin modes in a photonic crystal fiber with a multi-scale structure design. These guided acoustic modes are identified by using a full vector finite-element model to result from elastic radial vibrations confined by the air-silica microstructure. We further show the strong impact of structural irregularities of the fiber on the frequency and modal shape of these acoustic resonances

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Fu, Ling, and n/a. "Fibre-optic nonlinear optical microscopy and endoscopy." Swinburne University of Technology, 2007. http://adt.lib.swin.edu.au./public/adt-VSWT20070521.155004.

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Cancer is a major health problem in the world today. Almost all cancers have a significantly better chance for therapy and recovery if detected at their early stage. The capability to perform disease diagnosis at an early stage requires high-resolution imaging that can visualise the physiological and morphological changes at a cellular level. However, resolving powers of current medical imaging systems are limited to sub-millimeter sizes. Furthermore, the majority of cancers are associated with morphological and functional alterations of cells in epithelial tissue, currently assessed by invasive and time-consuming biopsy. Optical imaging enables visualisations of tissue microstructures at the level of histology in non-invasive means. Optical imaging is suitable for detecting neoplastic changes with sub-cellular resolution in vivo without the need for biopsy. Nonlinear optical microscopy based on multi-photon absorption and higher harmonic generation has provided spectacular sights into visualisation of cellular events within live tissue due to advantages of an inherent sectioning ability, the relatively deep optical penetration, and the direct visualisation of intrinsic indicators. Two-photon excited uorescence (TPEF) from intrinsic cell components and second harmonic from asymmetric supermolecular structures can provide complementary information regarding functionalities and morphologies in tissue environments, thus enabling premalignant diagnosis by detecting the very earliest changes in cellular structures. During the past sixteen years, nonlinear optical microscopy has evolved from a photonic novelty to a well-established laboratory tool. At present, in vivo imaging and long-term bedside studies by use of nonlinear optical microscopy have been limited due to the fact that the lack of the compact nonlinear optical instrument/imaging technique forces the performance of nonlinear optical microscopy with bulk optics on the bench top. Rapid developments of fibre-optics components in terms of growing functionalities and decreasing sizes provide enormous opportunities for innovation in nonlinear optical microscopy. Fibre-based nonlinear optical endoscopy will be the soul instrumentation to permit the cellular imaging within hollow tissue tracts or solid organs that are inaccessible with a conventional optical microscope. Lots of efforts have been made for development of miniaturised nonlinear optical microscopy. However, there are major challenges remaining to create a nonlinear optical endoscope applicable within internal cavities of a body. First, an excitation laser beam with an ultrashort pulse width should be delivered eciently to a remote place where ecient collection of faint nonlinear optical signals from biological samples is required. Second, laser-scanning mechanisms adopted in such a miniaturised instrumentation should permit size reduction to a millimeter scale and enable fast scanning rates for monitoring biological processes. Finally, the design of a nonlinear optical endoscope based on micro-optics must maintain great exibility and compact size to be incorporated into endoscopes to image internal organs. Although there are obvious diculties, development of fibre-optic nonlinear optical microscopy/endoscopy would be indispensible to innovate conventional nonlinear optical microscopy, and therefore make a significant impact on medical diagnosis. The work conducted in this thesis demonstrates the new capability of nonlinear optical endoscopy based on a single-mode fibre (SMF) coupler or a double-clad photonic crystal fibre (PCF), a microelectromechanical system (MEMS) mirror, and a gradientindex (GRIN) lens. The feasibility of all-fibre nonlinear optical endoscopy is also demonstrated by the further integration of a double-clad PCF coupler. The thesis concentrates on the following key areas in order to exploit and understand the new imaging modality. It has been known from the previous studies that an SMF coupler is suitable for twoii photon excitation by transmitting near infrared illumination and collecting uorescence at visible wavelength as well. Although second harmonic generation (SHG) wavelength is farther away from the designed wavelength of the fibre coupler than that of normal TPEF, it is demonstrated in this thesis that both SHG and TPEF signals can be collected simultaneously and eciently through an SMF coupler with axial resolution of 1.8 um and 2.1 um, respectively. The fibre coupler shows a unique feature of linear polarisation preservation along the birefringent axis over the near infrared and the visible wavelength regions. Therefore, SHG polarisation anisotropy can be potentially extracted for probing the orientation of structural proteins in tissue. Furthermore, this thesis shows the characterisation of nonlinear optical microscopy based on the separation distance of an SMF coupler and a GRIN lens. Consequently, the collection of nonlinear signals has been optimised after the investigation of the intrinsic trade-off between signal level and axial resolution. These phenomena have been theoretically explored in this thesis through formalisation and numerical analysis of the three-dimensional (3D) coherent transfer function for a SHG microscope based on an SMF coupler. It has been discovered that a fibreoptic SHG microscope exhibits the same spatial frequency passband as that of a fibreoptic reection-mode non-uorescence microscope. When the numerical aperture of the fibre is much larger than the convergent angle of the illumination on the fibre aperture, the performance of fibre-optic SHG microscopy behaves as confocal SHG microscopy. Furthermore, it has been shown in both analysis and experiments that axial resolution in fibre-optic SHG microscopy is dependent on the normalised fibre spot size parameters. For a given illumination wavelength, axial resolution has an improvement of approximately 7% compared with TPEF microscopy using an SMF coupler. Although an SMF enables the delivery of a high quality laser beam and an enhanced sectioning capability, the low numerical aperture and the finite core size of an SMF give rise to a restricted sensitivity of a nonlinear optical microscope system. The key innovation demonstrated in this thesis is a significant signal enhancement of a nonlinear optical endoscope by use of a double-clad PCF. This thesis has characterised properties of our custom-designed double-clad PCF in order to construct a 3D nonlinear optical microscope. It has been shown that both the TPEF and SHG signal levels in a PCF-based system that has an optical sectioning property for 3D imaging can be significantly improved by two orders of magnitude in comparison with those in an SMF-based microscope. Furthermore, in contrast with the system using an SMF, simultaneous optimisations of axial resolution and signal level can be obtained by use of double-clad PCFs. More importantly, using a MEMS mirror as the scanning unit and a GRIN lens to produce a fast scanning focal spot, the concept of nonlinear optical endoscopy based on a double-clad PCF, a MEMS mirror and a GRIN lens has been experimentally demonstrated. The ability of the nonlinear optical endoscope to perform high-resolution 3D imaging in deep tissue has also been shown. A novel three-port double-clad PCF coupler has been developed in this thesis to achieve self-alignment and further replace bulk optics for an all-fibre endoscopic system. The double-clad PCF coupler exhibits the property of splitting the laser power as well as the separation of a near infrared single-mode beam from a visible multimode beam, showing advantages for compact nonlinear optical microscopy that cannot be achieved from an SMF coupler. A compact nonlinear optical microscope based on the doubleclad PCF coupler has been constructed in conjunction with a GRIN lens, demonstrating high-resolution 3D TPEF and SHG images with the axial resolution of approximately 10 m. Such a PCF coupler can be useful not only for a fibre-optic nonlinear optical probe but also for double-clad fibre lasers and amplifiers. The work presented in this thesis has led to the possibility of a new imaging device to complement current non-invasive imaging techniques and optical biopsy for cancer detection if an ultrashort-pulsed fibre laser is integrated and the commercialisation of the system is achieved. This technology will enable in vivo visualisations of functional and morphological changes of tissue at the microscopic level rather than direct observations with a traditional instrument at the macroscopic level. One can anticipate the progress in bre-optic nonlinear optical imaging that will propel imaging applications that require both miniaturisation and great functionality.

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Yeung, Anson Chi-Ming Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Polymer segmented cladding fibres: cross fibre modelling, design, fabrication and experiment." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2009. http://handle.unsw.edu.au/1959.4/43656.

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This thesis presents the first research on polymer-segmented-cladding-fibre (PSCF), an emerging class of microstructured- optical-fibres (MOFs), which allows single-mode operation with ultra-large-core area. This research covers the modelling, design, fabrication and experiment of the polymer optical cross-fibre (4-period-SCF) whose cross-sectional view resembles a cross. A new wedge waveguide model has been formulated and applied to demonstrate that for any given parameters, the cross fibre gives the same performance for single-mode operation as the N-period-SCFs (for N = 2, 6 and 8). These fibres behave identically if the high-index segment angle, θ1, is the same and the low-index segment angular width, θ2, is sufficiently large for negligible adjacent mode coupling effects. This remarkable finding has significant ramifications for SCF fabrication, design and performance. Theoretical predictions confirmed by experiments demonstrated that a cross-fibre is all that needed to fabricate a large-core single-mode-fibre with no geometry-induced birefringence. The high-index outer ring effects on the cross fibre single-mode performance have been systematically investigated for the first time. The study reveals that the ring index value higher than its core index has very strong effects on single-mode performance. Within a narrow range of θ1, the minimum fibre length required for single-mode operation is reduced but outside this angle range, longer single-mode length is required. Furthermore, the fibre can be anti-guiding if θ1 exceeds the cutoff angle. Incorporating the fabrication constraints, the optimal cross-fibre design with high-index ring is achieved by optimising the relative index difference, high-index segment angle and core-cladding diameter ratio. Two preform-making techniques developed for the cross-fibres fabrication include the cladding-segment-in-tube method and the core-cladding-segment-in-tube method. The innovative approach in these methods overcomes the problems of bubble formation and fractures, which are related to the fibre structure complexity and the polymer intrinsic properties and their processing. It enables the successful drawing of single-mode fibres. This thesis reports the first experimental demonstration of single-mode operation of large-core cross-fibre. Three experimental studies with different cross-fibre designs have demonstrated (i) large-core single-mode operation, (ii) high-index ring effects on fibre performance and (iii) cross-fibre optimal design trial. Apart from this, the 8-period-SCF fibre performance has been demonstrated experimentally.

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Bykov, Dmitry [Verfasser], and Philip St J. [Gutachter] Russell. "Flying particles inside hollow-core photonic crystal fibres and their applications / Dmitry Bykov ; Gutachter: Philip St. J. Russell." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1132817196/34.

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Pierrot, Simonette. "Propagation non linéaire et amplification d'impulsions picosecondes dans des fibres microstructurées dopées ytterbium." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4026/document.

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Intensivement étudié depuis son apparition en 1960, le laser est un outil qui a su trouver sa place au-delà du monde académique : ses performances uniques l'ont rendu indispensable dans nombres d'applications de la vie courante. Les particularités les plus attractives du rayonnement laser sont la directivité de son émission, et le caractère quasi-monochromatique de son rayonnement.La première permet de propager un faisceau laser sur des longues distances, et également de concentrer la lumière sur des cibles aux dimensions extrêmement réduites : on parle de cohérence spatiale de l'émission laser. Cette seule propriété trouve de nombreuses applications : les lecteurs de codes-barres, imprimantes laser, pointeurs lasers en sont des exemples très rependus.La seconde permet d'accorder la bande spectrale étroite de l’émission laser aux bandes d'absorption de certains matériaux, ce qui permet de déposer localement de l’énergie de manière contrôlée. Par ailleurs elle confère au rayonnement laser des propriétés de cohérence temporelle uniques, qui peuvent être exploitées notamment en interférométrie, ouvrant la voie à de très nombreuses applications dans le domaine de la mesure, pour la caractérisation de surfaces optiques, dans les capteurs de position à effet Sagnac, en spectrométrie, pour ne pas citer quelques exemples

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Ghosh, Amar Nath. "Design, simulations et expériences de génération de supercontinuum dans l'infrarouge moyen dans des fibres à cristaux phoniques en verre souple." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCD035.

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Cette thèse de doctorat, financée dans le cadre d’un projet Européen Marie-Curie H2020 SUPUVIR, porte sur la conception et la fabrication de nouvelles fibres optiques de verres infrarouges permettant de produire un large spectre d’émission dans l’infrarouge moyen par génération de supercontinuum. Les applications couvrent la spectroscopie, la détection optique d’espèces chimiques et moléculaires, le traitement des matériaux et l'imagerie biomédicale. Plusieurs fibres optiques avec différents structures photoniques et différent matériaux infrarouges ont été réalisées et étudiées. En collaboration avec l'Institut de technologie des matériaux électroniques à Varsovie, nous avons dans un premier temps développé des fibres microstructurées en verre d’oxyde de métal (PBG81) et nous avons démontré avec ces fibres la génération efficace de supercontinuum de 0.89 µm à 2.5 µm, limité par l’absorption du verre. Ensuite, nous avons conçu en partenariat avec l’Université de Rennes et l’Université Technique du Danemark des fibres microstructurées à base de verres chalcogénures (As38Se62) avec un maintien de la polarisation. Ces fibres ont permis de générer un supercontinuum de 3.1 à 6 µm linéairement polarisé. Les capacités de tenue à la puissance laser de ces fibres chalcogénures ont été également analysées. Afin d’étendre cette bande d’émission, des fibres étirées en verre Ge10As22Se68 à très petit cœur ont été ensuite réalisées. Enfin, nous avons développé un système compact comprenant une série de fibres de silice, de verre fluoré, et de verre chalcogénure, pompé par un laser à fibre à 1.55 µm, et permettant d’étendre la gamme d’émission de 2 à 10 µm. Ces travaux de recherche constituent ainsi une étape importante vers le développement de sources fibrées, stables et compactes pour diverses applications dans l’infrarouge moyen
This doctoral thesis, funded within the framework of a European Marie-Curie H2020 SUPUVIR project, focuses on the design and fabrication of new photonic crystal fibers from infrared soft glasses making it possible to produce a wide emission spectrum in the mid-infrared (IR) wavelength region through generation of supercontinuum (SC). Applications of mid-IR SC sources cover infrared spectroscopy, optical detection of chemical and molecular species, materials processing, and biomedical imaging. An alternative to conventional thermal light sources, mid-IR sources have broad spectral bandwidth like a lamp or Globar and high brightness, which is more than 20 times of the sun focussed in a small spot similar to a laser. Several optical fibers with different photonic structures and different soft glasses have been produced and studied. In collaboration with the Institute of Electronic Materials Technology in Warsaw, heavy metal-oxide glass (PBG81) microstructured fibers were first developed and with these fibers we demonstrated the efficient generation of SC from 0.89 to 2.5 µm, limited by the absorption of the glass. Then, in partnership with the University of Rennes and the Technical University of Denmark, we fabricated microstructured fibers based on chalcogenide glasses (As38Se62) with polarization-maintaining property. These fibers have made it possible to generate a linearly polarized 3.1 to 6 µm supercontinuum. SC bandwidth was further extended between 1 µm and 7.4 µm in taper fibers produced from Ge10As22Se68 glass. The laser power handling capacities of these chalcogenide fibers were also analyzed. Finally, we have developed a compact mid-IR SC system using a fiber cascade comprising of silica, fluoride, and chalcogenide fiber, pumped by a fiber laser at 1.55 µm, and making it possible to extend the emission range from 2 to 10 µm. This research work thus constitutes an important step towards the development of stable and compact fiber SC sources for various applications in the mid-infrared

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Edavalath, Nitin N. [Verfasser], Philip St J. [Akademischer Betreuer] Russell, Philip St J. [Gutachter] Russell, and William [Gutachter] Wadsworth. "Design and fabrication of effectively single mode hollow-core single-ring photonic crystal fibres / Nitin N. Edavalath ; Gutachter: Philip St. J. Russell, William Wadsworth ; Betreuer: Philip St. J. Russell." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2018. http://d-nb.info/1168904137/34.

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Haakestad, Magnus W. "Optical fibers with periodic structures." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1494.

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This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated.

The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied.

In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated.

The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings.

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Azabi, Y. O. "Spiral photonic crystal fibers." Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/19372/.

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This thesis is concerned with the study of special types of photonic crystal fibers (spiral) and their optical properties. The work is carried out using simulation techniques to obtain the modal field profile and properties for the designs. The method used in solving the Maxwell’s equations is the full vectorial finite element method with the implementation of penalty function and perfectly matched layer. The penalty function is used to eliminate nonphysical solutions. The perfectly matched layer is integrated to absorb rays of light traveling away from the core. These rays are absorbed by the layer and do not reflect back to negatively influence the results. The spiral shapes are implemented in the distribution of the holes in the cladding region of the photonic crystal fiber to determine the photonic crystal fiber properties. Three different spirals have been introduced which are equiangular, Archimedean and Fermat’s spiral. The study of the effective refractive index, effective area and dispersion with varying spiral parameters have been carried out and the results are analyzed to understand the effect of each parameter. The variation of similar parameters in the spirals leads to similar variation in the optical properties under consideration. Furthermore, the equiangular spiral photonic crystal fibers (ES-PCF) have been investigated in two different dimensional scales. The scales are in comparison with the wavelength of operation in the first case when core size is larger than the operating wavelength. In this case the total dispersion of the fiber has slightly higher values than the material dispersion but similar curve and slope. On the other hand, when the core size is comparable with the wavelength of operation, the dispersion is varying significantly with varying the spiral parameters. The effective area can be made very small and therefore the nonlinearity of the fiber very large to facilitate non-linear applications such as super continuum generation. The equiangular spiral photonic crystal fiber has been modified slightly where the position of holes in the third ring are shifted further from the center and their size is much bigger. This manipulation is proposed in an algorithm in this thesis to facilitate the fabrication of ES-PCF using an adaptive stack and draw technique. The design shows similar optical behavior to an ideal spiral and its dispersion has been tailored for supercontinuum generation.

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Pfeiffenberger, Neal Thomas. "Single Crystal Sapphire Photonic Crystal Fibers." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77179.

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A single crystal sapphire optical fiber has been developed with an optical cladding that is used to reduce the number of modes that propagate in the fiber. This fiber is the first single crystal sapphire photonic crystal fiber ever produced. Fabrication of the optical cladding reduces the number of modes in the fiber by lowering the effective refractive index around the core, which limits the amount of loss. Different fiber designs were analyzed using Comsol Multiphysics to find the modal volumes of each. The MIT Photonic Bands modeling program was used to see if the first photonic band gap fiber could be achieved theoretically. The fibers were qualified using far field pattern and photodetector measurements as well as gas sensing experiments. The fibers were then exposed to a harsh environment of 1000 °C with a coating of alumina to test the resistance to scattering of the fiber. The fibers were also examined using materials characterization equipment to see how the harsh environments impacted the optical and mechanical stability of the bundled fiber.
Ph. D.

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Adnan, Muhammad. "Experimental platform towards in-fibre atom optics and laser cooling." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0109/document.

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Cette thèse décrit la conception et la réalisation d'une plateforme expérimentale pour le refroidissement par laser et le guidage d’atomes de Rb dans les fibres à cristal photonique à cœur creux (HC-PCF). Cette plateforme a pour but de fournir un système polyvalent pour explorer le refroidissement par laser à l’intérieur des fibres avec l'objectif à plus long terme de réaliser une fibre optique constituée d’un cœur rempli d’atomes froids (micro-cellule photonique). La plateforme a été conçue pour héberger plusieurs expériences sur le guidage d'atomes froids et thermiques ainsi que la spectroscopie dans les HC-PCFs pour répondre à plusieurs questions ouvertes liées par exemple à l'effet de la surface interne des HC-PCFs sur la structure énergétique des atomes ainsi que le piégeage et le refroidissement des atomes. La plateforme comprend une chambre spécifique à vide ultra-élevée (UHV) et un ensemble de lasers pour le refroidissement et le guidage des atomes à l'intérieur du HC-PCF hautement adapté. La chambre UHV a été conçue pour accueillir plusieurs HC-PCFs et deux pièges magnéto-optiques (MOT). Les HC-PCFs ont été conçus et fabriqués avec différents diamètres de cœur, contenu modal et post-traités avec des matériaux différents pour la surface interne du cœur. Par exemple, les diamètres du cœur varient de ~ 30 μm à ~ 80 μm traités avec une couche d'aluminosilicate ou une couche de PDMS afin de fournir un grand espace de paramètres pour évaluer l'effet de la surface sur les atomes confinés dans les fibres. Ainsi, le système a été construit et caractérisé. Le laser de refroidissement/repompage a été stabilisé en fréquence, avec une variance d'Allan de σ(τ)=3,8×10^(-11)/√τ. Avec ce système nous avons généré un MOT avec les deux isotopes du Rb, avec une température de refroidissement faible de l’ordre de 7 μK. La plateforme est maintenant opérationnelle pour entreprendre le premier guidage atomique et explorer la faisabilité du refroidissement des atomes à l'intérieur des HC-PCFs
This thesis reports on the design and fabrication of an experimental platform for in-fibre laser cooling of Rb and atom optics. By in-fibre laser cooling, we mean the long term aim of laser cooling thermal Rb atoms of a Photonic MicroCell (PMC), and subsequently developing what would be cold-atom photonic crystal fibre (PCF). The platform was designed to harbor several experiments on cold and thermal atom guidance and in-fibre spectroscopy so to address several open questions related for example to the effect of the core inner-wall surface on the atom energy structure and on selective fibre mode excitation for atom trapping and cooling. The completed platform comprises a specific and large ultra-high vacuum (UHV) chamber and a set of lasers for both atom cooling and atom guiding inside highly tailored hollow-core PCF (HC-PCF). The UHV chamber was designed to accommodate several HC-PCFs and two magneto-optical traps (MOT). The HC-PCF were designed, fabricated and post-processed to exhibit different core diameter, modal content and core inner surface material. For example, the mode field diameters range from ~30 µm to ~80 µm for the fundamental Gaussian-like core mode, and the surface materials include pure silica, a layer of Aluminosilicate or a layer of PDMS so to provide a large parameter space in assessing the effect of surface on the fibre-confined atoms. The system has been constructed and characterized. The cooling/repumping laser was frequency-stabilized, with measured Allan variance deviation of σ(τ)=3.8×10^(-11)/√τ. With the system we generated MOT with both isotopes of the Rb atom, with a cooling temperature as low as 7 µK. The platform is now operational to undertake the first atom guidance and explore the feasibility of atom cooling inside a HC-PCF

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Santos, Eliane Moura dos. "Processos relacionados a inserção de fluidos para sensoriamento com fibras de cristal fotônico." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278251.

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Orientadores: Luiz Carlos Barbosa, Cristiano Monteiro de Barros Cordeiro
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
Made available in DSpace on 2018-08-11T19:12:29Z (GMT). No. of bitstreams: 1 Santos_ElianeMourados_M.pdf: 4020531 bytes, checksum: 57766702771129e7f4bfe1d0c7852f67 (MD5) Previous issue date: 2007
Resumo: Este trabalho apresenta estudos de como inserir fluidos (líquidos e gases) em fibras ópticas microestruturadas, especialmente fibras de cristal fotônico, também conhecidas como PCF¿s (do inglês Photonic Crystal Fibers). Estas fibras possuem buracos de ar que percorrem todo seu comprimento. Elas podem ser divididas em dois grandes grupos: as de núcleo sólido que guiam luz por reflexão interna total e as de núcleo oco que guiam luz por um mecanismo conhecido como photonic bandgap. Ambos os tipos de fibras permitem várias aplicações em áreas como óptica e fotônica e nos dedicamos aqui à área de sensoriamento a fibra. Nesta área, usamos os microburacos para inserir fluido e dessa maneira manipular as propriedades de guiamento (em fibras de núcleo líquido), deixar a fibra mais sensível a algum parâmetro externo ou para sensoriar o fluido em questão. Nos três casos, precisamos estudar os processos de preenchimentos de fibras microestruturadas. Para este fim, estudamos e desenvolvemos maneiras de inserir fluidos em fibras de núcleos sólidos ou ocos. Usando preenchimento seletivo, produzimos fibras com núcleo líquido, criando uma região de alta interação entre luz e material. Neste trabalho, estudamos diferentes técnicas de preenchimento. A primeira, para fibras de núcleo líquido, é um preenchimento seletivo que pode ser feito usando uma máquina de emendas (splicer) ou um polímero para bloquear os microburacos. O outro consiste em manter as pontas das fibras livres (para medidas ópticas) enquanto o preenchimento é feito. Por fim, usamos o conhecimento desses processos em aplicações como sensoriamento de fluidos ou parâmetros externos e manipulação de propriedades de guiamento da luz
Abstract: This work presents studies of how to insert fluids (liquid and gas) into microstructured optical fibers, especially photonic crystal fibers, also known as PCF¿s. These optical fibers possess air holes that run along its entire length. They can be divided into two major groups: solid core fibers that guide light by total internal reflection and hollow core fibers that guide light by photonic bandgap. Both types of fibers allow several applications in areas such as optics and photonics and we dedicated this work to the fiber-sensing field. In this area we use the micro holes to insert fluids and in this way to manipulate the guidance properties in liquid core fibers, to leave the fiber more sensitive to some external parameter or to sensing the fluid. In these three cases we need to study the filling procedures in microstructured fibers. For this purpose, we studied and developed ways of inserting fluids in hollow and solid core fibers. We produced liquid core fibers, creating a high light-material overlap, using a selective filling technique. In this work we studied different filling techniques. The first one, for liquid core fibers, is a selective filling, which can be done by using a splicer machine or a polymer to block the fiber micro holes. The last one consists of keeping the fiber tips free (for optical measurements) while the filling is done. And finally we used the filling process knowledge in applications like sensing of fluids or external parameters and manipulation of guidance properties
Mestrado
Física Geral
Mestre em Física

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Cordier, Martin. "Photon-pair generation in hollow-core photonic-crystal fiber." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLT024/document.

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Les sources de paires de photons sont un composant essentiel des technologies émergentes en information quantique. De nombreux travaux ont permis des avancées importantes utilisant des processus non linéaires d'ordre 2 dans les cristaux et les guides d'ondes, et d'ordre 3 dans les fibres. Les limitations viennent dans le premier cas, des pertes et en particulier des pertes de couplage avec les fibres optiques et dans le second cas, du bruit dû à l'effet Raman dont le spectre est très large dans les fibres de silice. Ce projet propose une nouvelle architecture basée sur des fibres à cristal photonique à coeur creux (FCPCC) que l'on peut remplir de liquide ou de gaz non linéaire. Cette configuration permet la génération paramétrique de paires de photons corrélés par mélange à quatre ondes sans l'inconvénient de la diffusion Raman. Cette technologie offre une large gamme de paramètres à explorer en s'appuyant sur les propriétés physiques et linéaires contrôlables des FCPCC et la possibilité de remplissage de ces fibres avec des fluides aux propriétés non-linéaires variées. En effet, par une conception judicieuse de la FCPCC et un choix approprié du liquide ou du gaz, il est possible de (i) contrôler la dispersion et la transmission pour générer des photons corrélés sur une large gamme spectrale avec la condition d'accord de phase la plus favorable, (ii) d'ajuster la taille de coeur de la fibre et/ou sa forme pour augmenter sa non-linéarité ou son efficacité de couplage avec d'autres fibres et (iii) de s'affranchir totalement de l'effet Raman si on utilise par exemple un gaz monoatomique, ou d'obtenir des raies Raman fines, aisément discriminables des raies paramétriques dans le cas d'un liquide
Photon pair sources are an essential component of the emerging quantum information technology. Despite ingenious proposals being explored in the recent years based on either second order nonlinear processes in crystals and waveguides or on third order processes in fibers, limitations remain, due to losses and specifically coupling losses in the former case and due to Raman generation in silica, giving rise to a broad spectrum noise in the latter. These limitations have been challenging to lift because of the limited alternative nonlinear materials that fulfil the conditions for the generation of bright and high fidelity photon pairs in integrable photonic structures. In the present project, we develop a new and versatile type of photonic architecture for quantum information applications that offers access to a variety of nonlinear optical materials that are micro-structured in optical fiber forms to generate photon pairs, without the drawback of Raman scattering and with a large design parameter-space. Indeed, with a careful design of the HCPCF along with the appropriate choice of fluid, one can (i) control the dispersion and the transmission to generate photons with the most favourable phase-matching condition over a large spectral range, (ii) adjust the fibre core size and/or shape to enhance nonlinearity or the coupling efficiency with other fibres, (iii) totally suppress the Raman effect in monoatomic gases for instance or have only narrow and separated Raman lines that can thus be easily separated from the useful parametric lines in liquids

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Barbier, Margaux. "Génération de paires de photons corrélés par mélange à quatre ondes spontané dans des fibres microstructurées à coeur liquide." Thesis, Palaiseau, Institut d'optique théorique et appliquée, 2014. http://www.theses.fr/2014IOTA0011/document.

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Une technique couramment employée pour développer les sources de paires de photons corrélés indispensables au domaine des télécommunications quantiques repose sur le processus non linéaire de mélange à quatre ondes, qui peut avoir lieu directement dans le cœur d’une fibre optique. Cette architecture fibrée permet de s’adapter au mieux aux besoins des réseaux de communications quantiques (en particulier en minimisant les pertes par couplage lors de la connexion de la source aux autres composants du réseau). L’utilisation d’une fibre microstructurée plutôt que d’une fibre de silice conventionnelle permet d’ajuster les propriétés de dispersion de la fibre et d’optimiser l’efficacité du processus non linéaire. Cependant, les sources fibrées usuelles, à cœur de silice, présentent une limitation majeure : leur pureté quantique est fortement dégradée par la diffusion Raman spontanée, qui survient elle aussi dans le cœur en silice de la fibre. Pour s’affranchir de ce problème, notre idée est de remplacer le cœur en silice par un cœur liquide, en utilisant une fibre microstructurée à cœur creux rempli d’un liquide non linéaire. Nos recherches nous ont ainsi conduits à faire la première démonstration expérimentale de génération de paires de photons corrélés dans une fibre à cœur liquide, et à montrer que, grâce aux propriétés Raman particulières des liquides (dont le spectre Raman se présente en général sous la forme de raies très fines), il était possible de réduire de plusieurs ordres de grandeur le niveau de diffusion Raman spontanée dans la source. Ce travail ouvre donc la voie au développement de sources de paires de photons corrélés fibrées de très haute qualité quantique
Quantum telecommunication technologies rely on correlated photon pair sources, which are often based on the third-order nonlinear process of spontaneous four-wave mixing in silica-core photonic crystal fibres. A fibred architecture is advantageous because it minimizes the coupling losses between the optical source and the other components of quantum communication networks. Moreover, using a photonic crystal fibre rather than a conventional silica fibre offers the possibility of improving the photon generation (thanks to a small effective core area) and extending the wavelength coverage (thanks to dispersion management through the microstructuration design). However, the performances of silica-core photonic crystal fibre sources are limited in terms of quantum purity, because of the ubiquitous spontaneous Raman scattering process, which is a source of uncorrelated broadband noise photons in silica. We propose an original solution to this Raman problem by replacing the silica core by a liquid core, thanks to a hollow-core photonic crystal fibre filled with a nonlinear liquid. We actually performed the first experimental demonstration of the generation of correlated photon pairs in a liquid-core fibre, and demonstrated that, thanks to the specific Raman properties of liquids (which usually exhibit thin-line Raman spectra), it is possible to reduce the Raman noise level by several orders of magnitude. This work opens the way for the development of high quantum quality correlated photon pair fibred sources

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Hedley, Thomas. "Modelling of photonic crystal fibre." Thesis, University of Bath, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433962.

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McLenaghan, Joanna Siân. "Negative frequency waves in optics : control and investigation of their generation and evolution." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6532.

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This thesis is concerned with various methods for the control and investigation of pulse dynamics in a Photonic Crystal Fibre (PCF) and of the radiation driven by a short pulse. In particular the focus is on pulses in the anomalous dispersion region which would form solitons in the absence of higher order effects. Several different types of radiation can be driven by such pulses if they are perturbed by higher order dispersive and non-linear effects - for example Resonant Radiation (RR) and Negative Resonant Radiation (NRR) two dispersive waves which gain energy at the expense of the pulse. The feature of NRR which is of particular importance is that it is the first observed example of a coupling between positive and negative frequencies in optics. This has only been possible due to recent advances in fields such as PCFs, lasers and analogue systems. As with many scientific discoveries, NRR was found by bringing together ideas and techniques from these different fields. Both the pulse and the driven radiation are investigated using a number of different pulse and PCF parameters. These include power, chirp, polarisation and PCF dispersion. These are used to vary the wavelengths at which the driven radiation occurs as well as its generation efficiency. Furthermore the power and chirp are used to vary where in the PCF the driven radiation is generated by controlling where the driving pulse compresses and spectrally expands. This property is used to investigate different stages in the evolution of the pulse and driven radiation as well as to optimise the generation efficiency of the driven radiation.

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Harlé, Thibault. "Sources fibrées de paires de photons : caractérisation et influence de la non-uniformité." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLO009/document.

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Les sources de paires de photons constituent un bloc de base pour les technologies de traitement et transmission de l'information quantique. Une source consistant en une fibre microstructurée à coeur liquide permet à la fois une réduction du bruit de diffusion Raman, une adaptation simple et efficace aux réseaux de télécommunication quantique, et l'ajustement de ses propriétés d'émission par ingénierie de la microstructure et choix du liquide non linéaire. Ces recherches se concentrent sur l'étude de l'émission de paires de photons d'une telle source, et du mélange à quatre ondes à leur origine. Nous soulignons le manque d'une description quantitative correcte des phénomènes non linéaires à l'origine des paires dans les modèles existants, et en proposons un se basant sur le champ D pour y parvenir. Nous mettons expérimentalement en évidence l'inconsistance avec la forme de spectre usuellement attendue les sources de paires de photons. Pour l'expliquer, nous développons un modèle rendant compte de la non-uniformité du guide, soit la variation de ses propriétés de propagation sur sa longueur. Par une approche analytique initiale simple de cette caractéristique, nous exposons l'étalement du spectre et la diminution du taux maximum d'émission de paires. Une description numérique par morceaux apporte une description plus proche de la réalité et met en lumière la très forte sensibilité du spectre à la non-uniformité. Un autre effet de cette dernière se traduit par la différenciation du spectre selon le sens de propagation de la lumière dans le guide. Lors de l'intrication en polarisation des paires dans un dispositif de type boucle Sagnac, cette non-réciprocité dégrade la visibilité des paires. Pour compenser cet effet, nous proposons une solution simple de symétrisation du profil des fibres à leur fabrication, appuyée par de premiers résultats encourageants. Cette étude ouvre la voie à la prise en compte des non-uniformités inhérentes aux guides réels, impactant fortement leur émission de paires de photons
Photon-pair sources are a basic block for implementation of quantum information and telecommunication. A microstructured fibered source with liquid core induce a Raman scattering noise reduction, and at the same time allows a simple and lossless coupling to telecom network, with an engineering of its emission properties through the structure and liquid choices. This work focus on four-wave mixing leading to photon pairs emission in such a source. As existing models lack a correct emph{quantitative} description of nonlinear phenomena for pairs emission, we propose here one based on the D field to do so. We show a mismatch between the spectrum form usually expected and the experimental one. To explain this, we develop a model describing the effects of guide nonuniformity, meaning variation of its propagation properties along itself. Through an initial and simple analytical approach, we demonstrate the spectrum spreading and the diminution of the maximum of emission pairs rate. With a piece-wise numerical description for real guides, we highlight the very strong sensitivity of the emission spectrum towards nonuniformity. Another effect arising from this feature is the spectrum differentiation depending on the propagation direction within the guide. Upon pairs polarization entanglement by inserting the guide into a Sagnac loop interferometer, such nonreciprocity induces a deterioration of pairs visibility. In order to counteract this effect, we propose, based on first encouraging results, a simple solution involving a symmetrization of fibers profile during their manufacture. This study paves the way for taking into account inherent nonuniformity of real waveguides, which strongly impacts their photon pair emission

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Maurel, Martin. "Dynamique propagative d’impulsions optiques ultra-courtes pour un module de compression à base de fibre creuse." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0116.

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Les lasers de durées ultra-courtes, de l’ordre de la centaine de femtoseconde, sont actuellement des outils incontournables pour bon nombres d’applications industrielles ou académiques. Cependant leurs durées restent limitées par la technologie même de ces dispositifs. Par ailleurs, le développement de nouvelles fibres optiques microstructurées offre un guidage d’impulsions de hautes énergies dans des milieux gazeux permettant de ce fait la génération d’effets non-linéaires moteurs aux dynamiques de compression et de post-compression. Les travaux de cette thèse s’inscrivent donc dans ce contexte. Les études de dynamiques de compression d’impulsions ultra-courtes sont ainsi présentées. Les démonstrations d’auto-compression et de post-compression ont été faites à des longueur d’ondes de 343 nm et 1030 nm pour des régimes d’énergies allant de quelques microjoules à plusieurs centaines de microjoules pour des puissances moyennes jusqu’à 100 W. Des compressions de facteur 29 sont présentées faisant passer des impulsions de 580 fs à 19 fs via une dynamique de compression solitonique. De plus, cette technologie s’est vu intégrée dans une plateforme industrielle installée chez différents clients
Ultra-short pulse laser, hundred femtoseconds, are currently an essential tool for many industrial or academic applications. However, their duration remains limited by the technology which composed this device itself. In addition, development of new microstructured optical fibers offers high-energy pulse guidance in gaseous media, thus allowing the generation of non-linear effects, key parameter for pulse compression and post-compression dynamics. The work of this thesis is therefore part of this context. Studies of ultra-short pulse compression dynamics are presented. Self-compression and post-compression are demonstrated at wavelengths ranging from 343 nm to 1030 nm with energy from few microJoules to several hundred microJoules and average power up to 100 W. Factor 29 of compressions are presented, with solitonic dynamic pulse with duration of 580 fs are compressed down to 19 fs. In addition, this technology has been integrated into an industrial platform installed at various customers' sites

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Ademgil, Huseyin. "Optical properties of novel photonic crystal fibers." Thesis, University of Kent, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509653.

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Bethge, Jens. "Novel designs and applications of photonic crystal fibers." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2012. http://dx.doi.org/10.18452/16470.

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Zuerst wird die Idee einer gechirpten photonischen Kristallfaser vorgestellt. Aus einem stark vereinfachten Modell, die qualitativen Eigenschaften dieses neuen Fasertyps abgeleitet. Hier gelingt es, alle wichtigen Designparameter zu bestimmen. Die hervorragenden Leitungseigenschaften dieser Fasern werden dann in Experimenten demonstriert. Ohne jegliche Dispersionskompensation wird die Übertragung eines 25 fs Impulses in einer 1 Meter langen Faser gezeigt. Wird zusätzlich eine Dispersionskompensation verwendet, lassen sich sogar Impulse mit weniger als 20 fs Dauer übertragen. Im Anschluss daran wird eine photonische Kristallfaser untersucht, die mit einer Flüssigkeit gefüllt ist. Die hergestellte Faser ist dahingehend optimiert, einen hoch effizienten Soliton-Fission Mechanismus zu ermöglichen, der zur Erzeugung von Weißlicht genutzt wird. Diese Weißlicht-Impulse haben eine mit Soliton-Fission bisher noch nie erreichte Energie von 390 nJ. Auf Grundlage einer guten Übereinstimmung mit den experimentellen Resultaten lässt sich aus numerischen Simulationen der zugrunde liegende Effekt bestimmen. Abschließend wird über ein Experiment berichtet, das die nichtlineare Wechselwirkung zwischen zwei Impulsen verschiedener Wellenlänge ausnutzt, um einen optischen Schalter zu verwirklichen. Dieses Experiment erfordert genaueste Kontrolle der Dispersion und der Nichtlinearität in der Faser. Bei der gleichzeitigen Propagation von zwei Impulsen wird ein neuartiger Schalteffekt beobachtet. Beide Impulse haben nahezu die gleiche Gruppengeschwindigkeit, und ihre nichtlineare Wechselwirkung basierend auf Kreuz-Phasen-Modulation wird dadurch deutlich verstärkt. Hiermit wird ein voll funktionsfähiger optischer Transistor mit gutem Schaltkontrast experimentell demonstriert, der insbesondere einen schwachen Impuls einen stärkeren Impuls schalten lässt.
First, the concept of a novel chirped photonic crystal fiber is introduced. The qualitative dispersion and loss properties of this new fiber are theoretically derived. The calculated results agree excellently with experimental data obtained from fabricated fiber samples. The superior guiding properties of this new photonic fiber are demonstrated in two experiments. The delivery of 25 fs pulses over a 1 meter distance is realized without any dispersion compensation. Moreover, using dispersion compensation, the delivery of even sub-20-fs pulses becomes possible. Subsequently, a photonic crystal fiber with a liquid core is investigated, work presents effective methods for the preparation and explains a scheme for successfully reducing the insertion loss. The fiber is optimized to support the highly efficient soliton-fission mechanism at unprecedented pulse energies in white-light supercontinuum generation. Because of the liquid core, the supercontinuum generation scheme can be scaled beyond the peak-power limitations of solid-core fibers. The generation of a two-octave spanning supercontinuum with 390 nJ pulse energy is demonstrated. The experimental results are compared to a numerical simulation and the underlying mechanism is identified. Finally, an experiment is presented that exploits strong nonlinear interaction of two pulses inside a photonic crystal fiber for all-optical switching. A novel effect is observed during the co-propagation of two ultrashort pulses with different wavelengths. Because of the dispersion properties in the chosen fiber, these pulses are propagating at nearly identical group velocities, which dramatically increases the nonlinear interaction via cross-phase modulation between the two pulses. Based on this interaction, a fully functional optical transistor is experimentally demonstrated with good switching contrast. In particular, the demonstrated optical transistor enables switching of a strong pulse by a much weaker pulse.

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Chesini, Giancarlo. "Dispositivos óticos baseados em fibras de cristal fotônico com eletrodos integrados." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277529.

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Orientador: Cristiano Monteiro de Barros Cordeiro
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"
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Resumo: Neste trabalho de mestrado apresentamos o estudo e desenvolvimento de dispositivos óticos totalmente à fibra. Para isso, exploramos as novas possibilidades trazidas pelo advento das fibras de cristal fotônico (PCF's, do inglês Photonic Crystal Fibers). As PCF's são uma classe especial de fibras óticas que apresentam uma estrutura regular de buracos de ar na sua seção transversal, semelhante a um cristal fotônico. As fibras de cristal fotônico, além de apresentarem as vantagens inerentes às fibras óticas tradicionais, possuem novos graus de liberdade intrínsecos. Entre eles, o mais importante é a possibilidade de alterar fortemente as características da fibra através, apenas, do arranjo de buracos. Aqui, desenvolvemos uma fibra de cristal fotônico com dois buracos externos à microestrutura para integração de eletrodos. Posteriormente, um desses eletrodos foi exposto, polindo-se a lateral da fibra, e contato elétrico foi realizado. O elemento de controle do dispositivo ótico é a corrente elétrica que, aplicada ao eletrodo, o esquenta e o faz expandir via efeito Joule. O aumento de temperatura e a compressão causada pela expansão do eletrodo alteram o índice de refração e, portanto, a birrefringência da fibra. Foram realizadas, ainda, simulações utilizando o software comercial Comsol Multiphysics com o objetivo de entender a influência da temperatura e da compressão mecânica no modo ótico guiado pela fibra, bem como encontrar maneiras de otimizar o dispositivo em questã
Abstract: In this work we present a study and the development of all-fiber optical devices. For this purpose we exploited the new possibilities brought by the development of Photonic Crystal Fibers. PCF's are special kind of optical fibers with a regular pattern of air holes in their transverse section, resembling a photonic crystal. Photonic Crystal Fibers not only have the inherent advantages of traditional optical fibers but they have new intrinsic degrees of freedom. Among them, we can quote the possibility of strongly altering the fiber characteristics through the design of the air holes pattern. Here, we developed a photonic crystal fiber with two extra holes for electrode integration. One of these electrodes was exposed by side polishing the fiber and electrical contact to an external circuit was made. The contrai element of the optical device is the electrical current which, when applied to the electrode, heats it up and make it expand by Joule effect. The temperature increase and the compression caused by the electrode expansion alter the refractive index and, consequently, the fiber birefringence. We algo numerically studied the problem through Com sol software. The objective here was to understand the influence of temperature and stress on the light guided mode. In conclusion, we demonstrated in this work the creation of an all-fiber device based on the integration of electrodes to photonic crystal fibers where the element of contrai is the electrical current applied to the electrodes. We algo studied how to improve the parameters concerning the device operation
Mestrado
Física Geral
Mestre em Física

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Santos, Alexandre Bozolan dos. "Geração de supercontínuo em fibra óptica de cristal fotônico com núcleo de água." Universidade Presbiteriana Mackenzie, 2008. http://tede.mackenzie.br/jspui/handle/tede/1484.

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Photonic crystal fibers (PCFs) are optical fibers whose core is surrounded by a regular matrix of holes that is responsible for light confinement and guidance. This new architecture opens new perspectives in the development of nonlinear applications, many of which are based upon the high efficiency with which nonlinearity-driven spectral broadening known supercontinuum generation is obtained in solid-core PCFs. Another asset of PCFs is that their structure can be filled with liquids or gases, which then efficiently interact with the guided light. The possibility of obtaining supercontinuum generation in a PCF whose core is filled with highly nonlinear liquids has been recently theoretically studied. The insertion of liquids in PCFs introduces a new degree of freedom with which the efficiency of nonlinear effects can be maximized. This dissertation describes experimental work, in which the generation of a supercontinuum spectrum is demonstrated in a PCF whose hollow core was selectively filled with distilled water. A maximum broadening of 503nm, measured at -20dB, was obtained with femtosecond pulse pumping at λ=976nm. The comparison with spectra obtained with a 800nm pump and with bulk samples demonstrate that both a low dispersion at the pump wavelength and pump guidance are crucial for the broad output spectrum obtained. Numerical simulations and analyses were also undertaken to complement the study.
Fibras de cristal fotônico (PCF s) são fibras ópticas cujo núcleo é cercado por uma matriz regular de buracos, responsável pelo confinamento e guiamento da luz. Esta nova arquitetura abre novas perspectivas no desenvolvimento de aplicações não-lineares, muitas das quais são baseadas na alta eficiência com que o alargamento espectral não-linear conhecido como geração de supercontínuo é obtido em PCF s de núcleo sólido. Outra característica das fibras de cristal fotônico é que sua estrutura pode ser preenchida com líquidos e gases, que então interagem eficientemente com a luz guiada. A possibilidade de se obter a geração de supercontínuo em uma fibra de cristal fotônico cujo núcleo é preenchido com líquidos altamente não-lineares foi teoricamente estudado recentemente. A inserção de líquidos nas PCF s introduz um novo grau de liberdade, aumentando a eficiência com que os efeitos não-lineares podem ser gerados. Esta dissertação descreve um trabalho experimental no qual é demonstrada a geração de supercontínuo em uma PCF cujo núcleo foi preenchido seletivamente com água destilada. Obteve-se um alargamento máximo de 503nm medido, a -20dB, com o bombeio de pulsos de femtossegundos em 976nm. A comparação com o espectro obtido com o bombeio em 800nm e em amostras volumétricas demonstram que tanto a baixa dispersão no comprimento de onda de bombeio quanto o guiamento dos pulsos são cruciais para a obtenção do largo espectro observado. Simulações e análises numéricas foram também realizadas para complementar o estudo.

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