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1
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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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.
3
Wright, Fiona Cameron. "Highly polarised ytterbium doped photonic crystal fibre lasers." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=11869.
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Vukovic, Natasha Trivunac. "Optical properties of long photonic crystal fibre tapers." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/301300/.
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In this thesis I investigate optical properties of metre - long tapers. Microstructured optical fibre technology has created new opportunities in a broad range of science and technology. In the work presented in this thesis I have combined the microstructured optical fibre technology with a novel tapering facility in order to develop new applications in the field of nonlinear optics. This thesis concerns development of a novel tapering facility, capable of achieving intermediate length (few tens of cm to ˜10 m) tapers. In comparison with systems presented to date, the novel system has the advantage of the increased control over the desired taper profile and enables efficient fabrication of intermediate taper lengths of potentially arbitrary profiles. During the fabrication the fibre diameter exhibits significant variations, due to various disturbances. A design of the feedback loop for the enhanced control of the output diameter variation is proposed. The system capabilities have been tested and demonstrated in many different examples. The presented results show that the variation of the fibre diameter is within ~1%, which offers possibilities to use the system in various applications. As an example of the intermediate taper length design and application, parabolic pulse generation was investigated. It represents a very attractive pulse shape, since it can propagate at high peak powers while avoiding wave-breaking effect and have a flat and broad spectrum, which could lead to pulse compression applications. This thesis presents numerical modelling and experimental results (restricted to a set of parameters of fibres available from ’stock’) concerning this phenomena. Supercontinuum generation is an area of research that has been attracting scientific interest over several decades. This thesis shows results of a study of supercontinuum generation in intermediate length tapered microstructured optical fibres. A simulation tool has been developed and the procedure to efficiently determine optimum conditions for improving flatness of the supercontinuum spectra has been proposed. The proposed method concerns a ’standard’ microstructured optical fibre, but generally can be extended to different fibre designs.
5
Pearce, Gregory John. "Plane-wave methods for modelling photonic crystal fibre." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436875.
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Reeves, William Henry. "Photonic crystal fibre : the ultra-flattened dispersion regime." Thesis, University of Bath, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275816.
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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.
8
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 liquidePhoton 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
9
Couny, Francois. "Photonic solutions towards optical waveform synthesis." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.478946.
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This thesis presents the development of photonic tools towards the realisation of an optical intensity waveform synthesiser and of an attosecond pulse synthesiser based on the generation and Fourier synthesis of a continuous-wave coherent spectral comb spanning more than 3 octaves (UV to mid-IR) by use of a gas-filled hollow core photonic crystal fibre (HC-PCF).
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Wu, Darran Kin Chun. "Photonic crystal fibre directional coupler : ultrasensitive refractive index sensing." Thesis, The University of Sydney, 2010. https://hdl.handle.net/2123/28912.
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We present a new photonic crystal fibre sensor for label—free refractive index sensing.
The refractive index sensor is based on a directional coupler within a photonic crystal
fibre. The analyte forms a waveguide in the fibre and it possesses strong modal overlap
with the core waveguide, yielding strong light-sample interaction and extreme
sensitivities (104 nm per refractive index units). The performance of the sensor is strongly
dependent on the fraction of the mode that overlaps with the analyte, the coupling length,
and the coupling wavelength. The device is operational for a broad range of refractive
indices (An=0.02) above silica, but requires the analyte to be carefully filled over a
timescale of several minutes via capillary forces. We present a calibrated temperature
compensated dip sensor to minimise the effect of ambient temperature fluctuations, and
imperfect holes in the photonic crystal fibre. We propose a fibre structure with an
enhanced detection limit of 6.66x10'8 RIU, and demonstrate experimentally a measured
detection limit of 1.77x10'7 RIU with commercial fibre.
11
Welch, Matthew G. "Compressing and propagating solitons in hollow core photonic crystal fibre." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520840.
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The development of photonic crystal fibre from conventional optical fibre follows a trend in the development of materials, to create composites and structured materials on smaller and smaller scales. In fact the great success of photonic crystal fibre is largely due to the ability to structure it on scales comparable to the wavelength of light. It is this micron size structure that allows the creation of an (out of plane) optical bandgap in silica and allows hollow core fibre to guide light in an air core freeing the guided mode from the properties of bulk silica. This thesis focuses on the propagation and compression of high peak power optical solitons in hollow core fibre. As the Kerr nonlinear response of air is approximately a thousand times less than that of silica, the air core of hollow core fibre can support much higher peak powers than conventional optical fibre without the manifestation of nonlinear effects, making it ideal for the delivery of high peak power laser pulses. Coupled with this, hollow core fibre has a large region of anomalous dispersion in its transmission window allowing optical pulses to be transmitted as temporal solitons freeing them from the effects of dispersion. The author started his Ph.D. in 2006, three years after the first demonstration of soliton propagation in hollow core fibre and as the first demonstrations of soliton compression in hollow core fibre were being undertaken. Work by the author to build upon these early demonstrations is presented in this thesis in the following manner: Chapters 1, 2 and 3 are theory chapters. Chapter 1 explains the background waveguide theory and theory of nonlinear optics that is used throughout the thesis. Chapter 2 details the properties of photonic crystal fibres focusing on hollow core fibre. Chapter 3 details recent papers relevant to the propagation and compression of solitons in hollow core fibre. Chapters 4, 5 and 6 are experimental chapters reporting work undertaken by the author. Chapter 4 focuses on modifying the nonlinearity of hollow core fibre and measuring the dispersion of hollow core fibre accurately. Chapter 5 focuses on the compression of chirped and unchirped picosecond pulses in dispersion decreasing hollow core fibre tapers. Chapter 6 reports the compression in hollow core fibre of femtosecond pulses centred at 540nm wavelength through soliton effect compression.
12
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.
13
Ventura, Michael James. "Fabrication and characterisation of three-dimensional passive and active photonic crystals." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/35914.
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Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2008.Submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, 2008. Typescript. Bibliography: p. 104-118.
14
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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Light, Philip Stephen. "Photonic microcells for quantum optics applications." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512327.
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This thesis presents the development of photonic microcells for use as the host for coherent optics phenomena and related applications. A photonic microcell consists of a length of hollow-core photonic crystal fibre (HC-PCF) with a gas-filled core that is spliced to conventional optical fibre at either end to seal the gas within the fibre. Towards the goal of demonstrating and assessing the coherence properties of quantum optical effects in photonic microcells, the fabrication of two types of HC-PCF is presented. The established photonic bandgap HC-PCF offers extremely low transmission loss of ~10 dB/km over kilometre distances. However, the fibre has a limited transmission bandwidth of ~50 THz and exhibits modal coupling unfavourable for many applications. Work is presented on the tailoring of this fibre by control and shaping of the core-surround in order to improve its modal properties. A second type of HC-PCF is based on a large-pitch lattice, whose guidance relies on a new mechanism. This fibre exhibits a much improved bandwidth (>1000 THz) and has a relatively higher but still practical loss of ~1 dB/m. The development of photonic microcells at microbar pressure level and with low optical insertion loss is shown, an important step in the improvement of the technology for coherent optics applications which will take advantage of the extreme gas-laser interaction efficiency achieved in HC-PCF. Finally, quantum optical effects are demonstrated in HC-PCF and photonic microcells loaded with both the molecular gas acetylene and atomic vapour rubidium. The observation of electromagnetically induced transparency (EIT) in acetylene-filled HC-PCF represents the first such observation in a molecular gas, while the use of a photonic microcell allows a comparison of many experimental configurations to explore the coherence properties of coherent optical systems in the core of a HC-PCF. Furthermore, EIT is observed unambiguously in a rubidium loaded HC-PCF for the first time, and the anti-relaxation effects of a polymer coating demonstrated in this configuration.
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Bradley, Thomas David. "Atomic vapours filled hollow core photonic crystal fibre for magneto-optical spectroscopy." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616871.
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This thesis describes developments in atomic vapour loading in hollow core photonic crystal fibre (HC-PCF) for fabrication of atomic vapour loaded photonic microcells (PMC). These developments have been targeted at addressing some of the issues associated with loading atomic vapours in confined waveguiding geometries such as increased dephasing and physio-chemical wall absorptions. Atomic vapour loaded HC-PCF and PMC’s have applications in laser metrology, coherent optics and magneto optical spectroscopy. State of the art HC-PCF have been fabricated for loading with atomic vapour including both photonic bandgap (PBG) guiding and inhibited coupling (IC) hypocycloidal core shape Kagome HC-PCF. Record loss of 70 dB/km has been achieved in IC hypocycloid core shape Kagome HC-PCF in the spectral region centred at 800 nm. This fibre retains excellent single mode propagation combined with large core and increased optical bandwidth in comparison with specialist PBG HC-PCF optimised for operation around 800 nm. Aluminosilicate sol-gel coatings have been developed and successfully applied to the inner core wall of HC-PCF’s to reduce the atomic vapour surface interaction. Confining atomic vapours in micron scaled HC-PCF results in increased dephasing rates because of the frequent atom wall collisions. Anti relaxation coating materials have been applied to the inner core wall and the longitudinal relaxation time has been measured in coated and uncoated fibres utilising a magneto optical technique. Additionally sub Doppler transparencies are investigated in anti relaxation coated and uncoated HC-PCF.
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McMillan, Alex. "Development of an all-fibre source of heralded single photons." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557827.
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The preparation of single photons in a pure quantum state is a subject of great interest in physics, enabling the control of light at an unprecedented level. The ease with which certain degrees of freedom of photon states, such as polarisation, can be manipulated, along with the inherent resilience of photons to decoherence, makes them well suited for use as qubits. Recent rapid developments in the transmission and processing of quantum information, as well as the likely technological impact of potential real-world applications such as quantum cryptography and quantum computation, mean that the demand for high performance single photon sources is likely to increase in the near future. One approach to producing single photon states, which are known to be in a well-defined spatio-temporal mode without destructively measuring them, is to take advantage of nonlinear optics. Nonlinear processes can be used to realise frequency conversion by generating a single, correlated pair of photons from an intense pump laser source. The detection of one of the photons from a pair can then be used to indicate the presence of the other photon in the pair, a procedure known as heralding. This thesis describes the development of a source of heralded single photons at 1550 nm, generated directly in the core of a photonic crystal fibre (PCF). By taking advantage of low loss fibre components for the required spectral filtering of the generated photon state, a heralding fidelity of 52% was achieved. The source was designed to be used with a picosecond pulsed fibre laser, making it relatively low cost and maintenance free. With 148 mW of average pump power a heralded output photon rate of 6.4 × 104 s-1 was observed, demonstrating the brightness of the source. The purity of the generated single photons was established by measuring non-classical interference, with a visibility of 70%, between the photons output from this source and a source based on a PPLN waveguide. The fabrication of a series of birefringent PCFs for the generation of spectrally pure state photons at 1550 nm is also discussed. These PCFs will be useful for incorporation in the next generation of high performance, fibre-based photon sources.
18
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.
19
Francis-Jones, Robert J. A. "Active multiplexing of spectrally engineered heralded single photons in an integrated fibre architecture." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690725.
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In recent years, there has been rapid development in processing of quantum information using quantum states of light. The focus is now turning towards developing real-world implementations of technologies such as all-optical quantum computing and cryptography. The ability to consistently create and control the required single photon states of light is crucial for successful operation. Therefore, high performance single photon sources are very much in demand. The most common approach of generating the required nonclassical states of light is through spontaneous photon pair generation in a nonlinear medium. One photon in the pair is detected to "herald" the presence of the remaining single photon. For many applications the photons are required to be in pure indistinguishable states. However, photon pairs generated in this manner typically suffer from spectral correlations, which can lead to the production of mixed, distinguishable states. Additionally, these sources are probabilistic in nature, which fundamentally limits the number of photons that can be delivered simultaneously by independent sources and hence the scalability of these future technologies. One route to deterministic operation is by actively multiplexing several independent sources together to increase the probability of delivering a single photon from the system. This thesis presents the development and analysis of a multiplexing scheme of heralded single photons in high-purity indistinguishable states within an integrated optical fibre system. The spectral correlations present between the two photons in the pair were minimised by spectrally engineering each photonic crystal fibre source. A novel, in-fibre, broadband filtering scheme was implemented using photonic bandgap fibres. In total, two sources were multiplexed using a fast optical switch, yielding an 86% increase in the heralded count rate from the system.
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Chow, Kam Kong. "A raman cell based on hollow core photonic crystal fibre for human breath analysis." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43593.
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Wang, Yingying. "Quantum-fluctuation-initiated coherent Raman comb in hydrogen-filled hollow-core photonic crystal fibre." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545332.
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This thesis explores the generation and the coherence properties of Raman frequency combs that are initiated from vacuum fluctuations using hydrogen-filled hollow-core photonic crystal fibre (HC-PCF). The motivation is to explore a novel route for generating attosecond pulses and waveform synthesis. To this end, work has been undertaken in the design and fabrication of HC-PCF, in the generation of Raman comb with a compact set-up and finally in an experimental demonstration of the mutual coherence between the comb spectral components. Here, the well-established photonic bandgap (PBG) HC-PCF is further developed. Surface mode spectral positions are controlled by chemical etching technique, and a single piece of fibre with two robust bandgaps is fabricated. Furthermore, the second established class of HC-PCF; namely large-pitch Kagome-lattice HC-PCF, has experienced challenging developments. This led to the fabrication of a hypocycloid-core seven-cell Kagome HC-PCF with comparable attenuation value to that of PBG HC-PCF while offering much larger bandwidth. Using the fabricated HC-PCF, different Raman frequency comb systems are developed. In addition to the previously-generated multi-octave Raman frequency comb from a large 1064 nm Nd:YAG Q-switch laser, several more compact version of Raman comb sources have been developed, including one whose lines lay in the visible and UV for applications in forensics and biomedicine. The Raman frequency comb generated inside a length of hydrogen-filled HC-PCF is further investigated by studying the coherence of the Raman lines. Despite of vacuum-fluctuation-initiation, it is demonstrated that the comb has self- and mutualcoherence properties within each single shot, bringing thus the possibility of generating attosecond pulses with non-classical properties.
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He, Wenbin [Verfasser], and Philip [Gutachter] Russell. "GHz-rate harmonically mode-locked fibre laser using optoacoustic effects in photonic crystal fibre / Wenbin He ; Gutachter: Philip Russell." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2018. http://d-nb.info/1156461510/34.
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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 fibréRefractive 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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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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Baccini, Desmond. "Gamma irradiation response of photonic crystal and standard optical fibre Bragg grating sensors for radiation dosimetry." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2019. https://ro.ecu.edu.au/theses/2226.
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This study investigates the use of Optical Fibre Bragg Grating Sensors (FBGs) for Gamma Radiation Dosimetry. A comparative analysis of responses to gamma irradiation between standard commercial FBGs and new generation FBGs written in Photonic Crystal fibre (PCF) were examined under similar regimes and conditions. Current research suggests that the FBGs performance, when exposed to Cobalt-60 gamma irradiation, can suffer cross sensitivity problems resulting from different external effects such as temperature. However, FBGs written in PCFs may be able to overcome these problems due to their design, flexibility of the shape, and size of the micro-holes in a PCF.
Previous research has indicated the Bragg wavelength shift (BWS) of standard FBGs increases with accumulated Gamma dose. This shift appears to be permanent, indicating that gamma irradiation permanently affects the Bragg wavelength of the FBG. To better understand these effects, and determine the suitability of particular FBGs for use in radiation dosimetry, measurements in relation to the effects of pre-irradiation, dose rates and accumulated dose, and relaxation effects were performed on both sets of FBGs. To simulate real time conditions of a radiation dosimeter, the FBGs are examined through three consecutive radiation stages followed by limited recovery times. There is a lack of research in the areas of small recovery times and multiple periods of irradiation. The experimental regime and setup consisting of the three stages with very limited recovery comparing PCF-FBGs and standard FBGs (STD-FBGs) is unique. The experiments and gamma irradiation were conducted at ANSTO (Australian Nuclear Science and Technology Organisation) using the GATRI (Gamma Technology Research Irradiator) irradiation facility. The responses after exposure to gamma irradiation, including relaxation periods between commercially manufactured FBGs written in Germanium (Ge) doped optical fibres, with and without hydrogen loading, along with the standard SMF-28 fibre with Hydrogen are shown. The FBG inscription in PCF was completed at Interdisciplinary Photonics Laboratories (iPL), University of Sydney. The FBGs in each fibre are written by Ultraviolet (UV) low energy irradiation. In nuclear environments, when FBGs have been exposed to gamma irradiation, changes in the Bragg wavelength occur, although the exact cause or trigger is still unclear.
The main outcome of this research has indicated that PCF-FBGs, compared to standard FBGs, are a strong candidate for use in the field of radiation dosimetry. This is due to their very consistent behaviour and recovery aspects after irradiation exposure. This work will compliment established research and help in the absolute quantitative comparison between the individual standard FBGs and PCF-FBGs. It will help in establishing FBGs as a possible replacement to present physical and chemical sensors currently being used as radiation dosimeters.
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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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Schmidberger, Michael J. [Verfasser], Nicolas Y. [Akademischer Betreuer] Joly, and Ben [Akademischer Betreuer] Fabry. "Nonlinear Dynamics in Photonic Crystal Fibre Ring Cavities / Michael J. Schmidberger. Gutachter: Nicolas Y. Joly ; Ben Fabry." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1065045115/34.
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Akowuah, E. K. "Design and analysis of novel photonic crystal fibre and waveguide surface plasmon resonance biosensors operating in aqueous environments." Thesis, University of Kent, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590071.
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Surface plasmon resonance (SPR) sensors provide high sensitivity without the use of molecular labels. Most commercial SPR biosensors are based on the simple, robust and highly sensitive traditional prism-coupled configuration. However, they are not amenable to miniaturization and integration. This has led to a growing interest in the development of robust, portable and highly sensitive SPR sensing devices capable of out of laboratory measurements. This thesis covers the modelling of these sensors, using the full vectorial finite element and the eigenmode expansion methods with the aim of optimising the proposed sensors for operation in aqueous environments. The thesis focuses on designs based on photonic crystal fibres and planar waveguides to achieve highly sensitive and compact platforms capable of multi analyte I channel operation. It is no longer feasible to optimise designs by simply fabricating and testing a large set of possible alternatives. This can be time consuming for complex devices such as SPR sensors. This requires computer models which can simulate the behaviour of the different designs in an accurate and speedy manner. This will make it possible to accurately predict device performance characteristics for different material and structural configurations, thereby affording designers the opportunity to experiment with different system configurations for optimal performance. In order to maintain modelling accuracy, all materials are modelled as dispersive and a full-wave analysis is undertaken. to account for the important frequency dependent effects. At every stage in this research, .,care was taken to bench-mark our results against the best available data, whether numerical or analytical whenever available, in order to validate our work. The effects of structural and material parameters on sensor performance metrics such as sensitivity are thoroughly investigated to arrive at optimised designs.
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Lyytik�inen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing." University of Sydney. School of Physics and the Optical Fibre Technology Centre, 2004. http://hdl.handle.net/2123/597.
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Drawing of standard telecommunication-type optical fibres has been optimised in terms of optical and physical properties. Specialty fibres, however, typically have more complex dopant profiles. Designs with high dopant concentrations and multidoping are common, making control of the fabrication process particularly important. In photonic crystal fibres (PCF) the inclusion of air-structures imposes a new challenge for the drawing process. The aim of this study is to gain profound insight into the behaviour of complex optical fibre structures during the final fabrication step, fibre drawing. Two types of optical fibre, namely conventional silica fibres and PCFs, were studied. Germanium and fluorine diffusion during drawing was studied experimentally and a numerical analysis was performed of the effects of drawing parameters on diffusion. An experimental study of geometry control of PCFs during drawing was conducted with emphasis given to the control of hole size. The effects of the various drawing parameters and their suitability for controlling the air-structure was studied. The effect of air-structures on heat transfer in PCFs was studied using computational fluid dynamics techniques. Both germanium and fluorine were found to diffuse at high temperature and low draw speed. A diffusion coefficent for germanium was determined and simulations showed that most diffusion occurred in the neck-down region. Draw temperature and preform feed rate had a comparable effect on diffusion. The hole size in PCFs was shown to depend on the draw temperature, preform feed rate and the preform internal pressure. Pressure was shown to be the most promising parameter for on-line control of the hole size. Heat transfer simulations showed that the air-structure had a significant effect on the temperature profile of the structure. It was also shown that the preform heating time was either increased or reduced compared to a solid structure and depended on the air-fraction.
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Lyytikäinen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing." Thesis, The University of Sydney, 2004. http://hdl.handle.net/2123/597.
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Drawing of standard telecommunication-type optical fibres has been optimised in terms of optical and physical properties. Specialty fibres, however, typically have more complex dopant profiles. Designs with high dopant concentrations and multidoping are common, making control of the fabrication process particularly important. In photonic crystal fibres (PCF) the inclusion of air-structures imposes a new challenge for the drawing process. The aim of this study is to gain profound insight into the behaviour of complex optical fibre structures during the final fabrication step, fibre drawing. Two types of optical fibre, namely conventional silica fibres and PCFs, were studied. Germanium and fluorine diffusion during drawing was studied experimentally and a numerical analysis was performed of the effects of drawing parameters on diffusion. An experimental study of geometry control of PCFs during drawing was conducted with emphasis given to the control of hole size. The effects of the various drawing parameters and their suitability for controlling the air-structure was studied. The effect of air-structures on heat transfer in PCFs was studied using computational fluid dynamics techniques. Both germanium and fluorine were found to diffuse at high temperature and low draw speed. A diffusion coefficent for germanium was determined and simulations showed that most diffusion occurred in the neck-down region. Draw temperature and preform feed rate had a comparable effect on diffusion. The hole size in PCFs was shown to depend on the draw temperature, preform feed rate and the preform internal pressure. Pressure was shown to be the most promising parameter for on-line control of the hole size. Heat transfer simulations showed that the air-structure had a significant effect on the temperature profile of the structure. It was also shown that the preform heating time was either increased or reduced compared to a solid structure and depended on the air-fraction.
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Yeung, Anson Chi-Ming Electrical Engineering & 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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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-PCFsThis 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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Loewe, Sona [Verfasser], Philip [Akademischer Betreuer] Russell, Philip [Gutachter] Russell, and Alexei [Gutachter] Sokolov. "Angular Momentum Control via Raman Conversion in Twisted Gas-Filled Photonic Crystal Fibre / Sona Loewe ; Gutachter: Philip Russell, Alexei Sokolov ; Betreuer: Philip Russell." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1226428185/34.
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Sharma, Abhinav [Verfasser], Wolfgang [Akademischer Betreuer] Achtziger, Tijmen [Gutachter] Euser, and Philip St J. [Gutachter] Russell. "METROLOGY AND MANIPULATION OF OPTICALLY TRAPPED MICROPARTICLES IN HOLLOW-CORE PHOTONIC CRYSTAL FIBRE / Abhinav Sharma ; Gutachter: Tijmen Euser, Philip St.J. Russell ; Betreuer: Wolfgang Achtziger." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1228214816/34.
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Suresh, Mallika Irene [Verfasser], Philip St J. [Akademischer Betreuer] Russell, Philip St J. [Gutachter] Russell, and Arnaud [Gutachter] Mussot. "Probing Nonlinear Optical Instabilities in Gas-filled Hollow-core Photonic Crystal Fibre / Mallika Irene Suresh ; Gutachter: Philip St.J. Russell, Arnaud Mussot ; Betreuer: Philip St.J. Russell." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1226428177/34.
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Kiwanuka, Ssegawa-Ssekintu. "Supercontinuum radiation for ultra-high sensitivity liquid-phase sensing." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245137.
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The real-time detection of trace species is key to a wide range of applications such as on-line chemical process analysis, medical diagnostics, identification of environmentally toxic species and atmospheric pollutant sensing. There is a growing demand for suitable techniques that are not only sensitive, but also simple to operate, fast and versatile. Most currently available techniques, such as spectrophotometry, are neither sensitive enough nor fast enough for kinetic studies, whilst other techniques are too complex to be operated by the non-specialist. This thesis presents two techniques that have been developed for and applied to liquid-phase analysis, with supercontinuum (SC) radiation used for liquid-phase absorption for the first time. Firstly, supercontinuum cavity enhanced absorption spectroscopy (SC-CEAS) was used for the kinetic measurement of chemical species in the liquid phase using a linear optical cavity. This technique is simple to implement, robust and achieves a sensitivity of 9.1 × 10−7 cm−1 Hz−1/2 at a wavelength of 550nm for dye species dissolved in water. SC-CEAS is not calibration-free and for this purpose a second technique, a time-resolved variant called broadband cavity ring-down spectroscopy (BB-CRDS), was successfully developed. Use of a novel single-photon avalanche diode (SPAD) array enabled the simultaneous detection of ring-down events at multiple spectral positions for BB-CRDS measurements. The performance of both techniques is demonstrated through a number of applications that included the monitoring of an oscillating (Belousov-Zhabotinsky) reaction, detection of commercially important photoluminescent metal complexes (europium(III)) at trace level concentration, and the analysis of biomedical species (whole and lysed blood) and proteins (amyloids). Absorption spectra covering the entire visible wavelength range can be acquired in fractions of a second using sample volumes measuring only 1.0mL. Most alternative devices capable of achieving similar sensitivity have, up until now, been restricted to single wavelength measurements. This has limited speed and number of species that can be measured at once. The work presented here exemplifies the potential of these techniques as analytical tools for research scientists, healthcare practitioners and process engineers alike.
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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 clientsUltra-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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Smith, Brett. "Coherent Anti-Stokes Raman Scattering Miniaturized Microscope." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24281.
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Microscopy techniques have been developed and refined over multiple decades, but innovation around single photon modalities has slowed. The advancement of the utility of information acquired, and minimum resolution available is seemingly reaching an asymptote. The fusion of light microscopy and well-studied nonlinear processes has broken through this barrier and enabled the collection of vast amounts of additional information beyond the topographical information relayed by traditional microscopes. Through nonlinear imaging modalities, chemical information can also be extracted from tissue. Nonlinear microscopy also can beat the resolution limit caused by diffraction, and offers up three-dimensional capabilities. The power of nonlinear imaging has been demonstrated by countless research groups, solidifying it as a major player in biomedical imaging.
The value of a nonlinear imaging system could be enhanced if a reduction in size would permit the insertion into bodily cavities, as has been demonstrated by linear imaging endoscopes. The miniaturization of single photon imaging devices has led to significant advancements in diagnostics and treatment in the medical field. Much more information can be extracted from a patient if the tissue can be imaged in vivo, a capability that traditional, bulky, table top microscopes cannot offer. The development of new technologies in optics has enabled the miniaturization of many critical components of standard microscopes. It is possible to combine nonlinear techniques with these miniaturized elements into a portable, hand held microscope that can be applied to various facets of the biomedical field.
The research demonstrated in this thesis is based on the selection, testing and assembly of several miniaturized optical components for use as a nonlinear imaging device. This thesis is the first demonstration of a fibre delivered, microelectromechanical systems mirror with miniaturized optics housed in a portable, hand held package. Specifically, it is designed for coherent anti-Stokes Raman scattering, second harmonic generation, and two-photon excitation fluorescence imaging. Depending on the modality being exploited, different chemical information can be extracted from the sample being imaged. This miniaturized microscope can be applied to diagnostics and treatments of spinal cord diseases and injuries, atherosclerosis research, cancer tumour identification and a plethora of other biomedical applications. The device that will be revealed in the upcoming text is validated by demonstrating all designed-for nonlinear modalities, and later will be used to perform serialized imaging of myelin of a single specimen over time.
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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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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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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 photonsPhoton-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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Chafer, Matthieu. "Sources lasers innovantes à base de micro-capsules photoniques et par nano-structuration de milieux gazeux." Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0042.
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Depuis leur avènement, les fibres à cristal photonique à cœur creux ont prouvé leur capacité à convertir des fréquences avec une haute efficacité, notamment en jouant sur le phénomène de diffusion Raman stimulée. Dans le cadre d’un contrat CIFRE entre la société GLOphotonics et l’institut de recherche Xlim, ce projet de thèse a consisté à développer ces fibres afin d’améliorer leurs performances optiques pour cibler deux voies d’applications: une industrielle pour proposer un laser compact multi-ligne dans le visible et dans l’UV et une seconde plus fondamentale pour réaliser un synthétiseur d’onde optique. L’amélioration de ces performances repose sur l’exacerbation de l’inhibition du couplage entre le mode du coeur d’air et les modes de silice de la gaine. Pour cela deux types de micro-structures ont été explorées à savoir une maille Kagomé et une maille tubulaire. Plusieurs fibres ont été alors fabriquées démontrant des performances records sur toute une gamme de longueurs d’onde (8,5 dB/km à 1 µm, 7,7 dB/km à 750 nm, 13,8 dB/ km à 549 nm, et autour de 70 dB/km à 355 nm). Concernant la fonctionnalisation de ces fibres, des micro-capsules photoniques ont été conçues et réalisées permettant à la fois de palier au problème de la perméabilité de la silice au gaz (stabilité de la conversion dépassant 12 mois) et de démontrer une conversion de 26 lignes dans le visible. Un produit industriel nommé CombLas a alors été produit puis appliqué à une étude de cytométrie en flux pour étudier l’influence du taux de répétition du laser de pompe. Ce produit a également été étendu à la gamme spectrale de l’UV avec la génération de 24 lignes entre 225-400 nm. Enfin, des travaux plus fondamentaux ont été réalisés consistant à développer un synthétiseur d’onde optique à base de génération Raman dans ces fibres creuses. Une nouvelle dynamique a été observée démontrant le piégeage de molécules d’hydrogène par un réseau optique auto-assemblé de puits de potentiel ultra-profonds et nanométriques. Cela permis de générer un régime Lamb-Dicke de la diffusion Raman stimulée. Des signatures sub-Doppler usuellement vues dans les atomes froids ont été mesurées avec des largeurs de bandes plus étroites de plus de 5 ordres de grandeurs par rapport à ce qui est prédit dans la littérature. Finalement, cette largeur de bande a été optimisée d’un ordre de grandeur en jouant sur la longueur de la fibre et la pression de l’hydrogèneSince their advent, hollow-core photonic crystal fibers have proved to be highly efficient for frequency conversion, especially via by playing with stimulated Raman scattering. Within the frame work of a CIFRE contract between the firm GLOphotonics and the Xlim research institute, this thesis project has consisted in developing these fibers to enhance their optical performances, in order to target two different field of applications: an industrial one to offer a a compact multi-line laser in the visible and UV and a second more fundamental one to realize a optical wave synthesizer. The amelioration of these performances relies on the exacerbation of the inhibition of the coupling between the air core mode and the silica cladding modes. Two types of micro-structures have been explored, a Kagomé and a tubular lattice. Several fibers have been fabricated demonstrating record performances on all a wavelength range (8.5 dB/km at 1 µm, 7.7 dB/km at 750 nm, 13.8 dB/km at 549 nm, and around 70 dB/km at 355 nm). Concerning the functionalization of the fibers, photonic micro-cells have been designed and realized enabling to overcome the problem the permeability of silica to gas (conversion stability over 12 months) and demonstrate a conversion to 26 lines in the visible. An industrial product coined CombLas has been made and used for flow cytometry in order to study the influence of the repetition rate of the pump laser. This product has also been extended to the UV range with 24 lines generated between 225-400 nm. Also, more fundamental research has been realized consisting in developing an optical wave synthesizer based on Raman generation in hollow core fibres where a new dynamic has been observed demonstrating the trapping of hydrogen molecules by an auto-assembled optical lattice of ultra-deep and nano-metric potential wells. This configuration has enabled to generate a Lamb-Dicke regime of stimulated Raman scattering. Sub-Doppler signatures usually found in cold atoms have been measured with linewidths narrower than 5 orders of magnitude than what is predicted in the literature. Finally, this linewidth has been optmised of an order of magnitude by plaing on the length of the fiber and the pressure of hydrogen
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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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Khetani, Altaf. "Photonic crystal fiber as a biosensor." Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27596.
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With the era of technological change at its all time high, advancements in the field of photonics offer us a wide range of innovative potential applications. Over the years photonics has played an important role in modern industries such as telecommunication, sensors and medical imaging. One of the fields which has received a lot of attention is Photonic Crystal Fibers (PCF) for biosensor application. Photonic crystal fiber is a unique type of optical fiber in which continuous channels of (typically) air run their entire length. These 'holes' serve to both confine electromagnetic waves within the core of the fiber and to tailor its transmission properties. The classification of photonic crystal fiber can be solid core PCF where the light is guided by total internal reflection, and Hollow core photonic bandgap fibers (PBF) in which light is guided through the photonic bandgap effect. Simulation of PCF has been done through commercial software known as COMSOL which follows the finite element approach.
The focus of this thesis is on the application of PCF for different sensing applications. Traditionally, solid core PCF has been used for sensing purposes as the cladding channels can be filled with gas or liquid, thus serving as an efficient type of evanescent wave sensing. Hollow core PBF offers huge improvements as the interaction between light and matter is increased by the presence of sample in the core where most of the light is confined.
Conventionally, HC-PBF is used for sensor purposes by selectively filling the core. Here we have used a non-selective filling technique wherein all the channels of PCF are being filled with samples. When the fiber is empty it guides a particular band, and upon filling with other samples, the bandgap is shifted, and depending on this shift one can determine the refractive index of the sample. This type of sensor has been able to detect as low as 10 -5 change in refractive index just by taking a few centimeters of HC-PBF.
Laser Flash Photolysis is one of the leading methods used in photochemistry to determine the transient species such as radicals, excited states or ions, in chemical and biological systems. By using HC-PBF we have replaced the conventional technique of LFP where in a test-tube is used to hold the sample. The sample is excited through a laser and a monitoring beam is used to observe the amount of absorption. The sample required here is on the order of a milliliter which can be scaled down to pico liter by the use of PCF. The LFP results using PCF showed signal enhancement of at least an order of magnitude for samples like xanthone in toluene, xanthone in acetonitryl and water soluble benzoin in methyl viologen.
Raman Spectroscopy is yet another area which had a surge of growth for label free detection of samples. One of the reasons for its popularity is that it provides a unique optical fingerprint of chemicals and biomolecules. In this thesis we have focused on developing HC-PBF for enhancing the Raman signal from the sample. We have obtained an enhancement of over 40 times when using a HC-PBF with a length of 9.5cm. We have also used HC-PBF to study the enhancement of Raman signal from colloidal nanoparticles in an aqueous solution.
Supercontinuum generation is yet another area which has seen tremendous growth through the use of solid core PCF. Here we have covered the excitation of cladding and core mode in an endlessly single mode PCF which has the potential to be used as an effective type of biosensor as the penetration of light in the cladding channels is very strong compared to an evanescent wave field.
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Chen, Raymond M. Eng Massachusetts Institute of Technology. "Photoacoustic photonic crystal fiber gas sensor." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41258.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 89-93).
Photoacoustic spectroscopy (PAS) is a form of laser spectroscopy that has demonstrated very high sensitivity for gas detection. Typically, PAS involves the absorption of a modulated laser beam by the gas species of interest, and the subsequent generation of acoustic waves at the modulation frequency. The amplitude of the acoustic signal, which can be measured by a microphone, can be amplified by several orders of magnitude with a properly designed gas cell used as an acoustic resonator. In recent times, hollow-core photonic crystal fiber (HC-PCF) has emerged as superior gas cell for standard absorption-based laser spectroscopy due to its small size, compatibility with fiber-based optical components, and easily attainable long light-gas interaction path lengths. However, the possibility of utilizing HC-PCF as a gas cell for PAS has yet to be explored. The size and structure of HC-PCF demands that a new method of PA signal detection must be proposed, because the conventional use of microphones for PAS is not applicable. This thesis describes the development of a proposed novel use of HC-PCF as a PA gas cell from theoretical support to experimental realization. A number of unresolved experimental issues prevented data on the performance of the constructed system from being obtained. These problems are discussed, and recommendations for further study, including several proposed measures to overcome these experimental issues, are made in the conclusion to the thesis.
by Raymond Chen.
M.Eng.
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Kiliç, Onur. "Fiber based photonic-crystal acoustic sensor /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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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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El, bassri Farid. "Sources lasers déclenchées nanosecondes : Applications à la spectroscopie Raman cohérente sous champ électrique." Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0060/document.
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Du fait de leur compacité, leur robustesse et leur faible coût, les microlasers impulsionnels nanosecondes constituent des sources particulièrement attractives pour de nombreux systèmes de détection et d'analyse, en particulier les cytomètres en flux ou les dispositifs pour la spectroscopie CARS (Coherent Raman Anti Stokes Scattering). Cependant, ces applications nécessitent des performances améliorées en ce qui concerne la gigue temporelle et la cadence de répétition accessible. Dans sa première partie, cette thèse propose des solutions originales pour atteindre les performances requises à partir de microlasers passivement déclenchés, grâce à la mise en oeuvre d'une cavité hybride couplée, pompée par une onde modulée en intensité. Une cadence de répétition supérieure à 30 kHz avec une gigue demeurant inférieure à 200 ns est atteinte. Le potentiel de microlasers à fibres déclenchés par modulation du gain pour monter en cadence est aussi évalué, montrant que des impulsions à faible gigue, à une cadence de plus de 2 MHz peuvent être produites. Enfin, la dernière partie est consacrée à la mise au point et à l'exploitation d'un nouveau système de spectroscopie CARS assisté par une excitation électrique haute tension. Ce dispositif, réalisé à partir d'un microlaser amplifié, permet de s'affranchir du bruit de fond non résonnant des mesures et de réaliser une analyse spectroscopique fine de la réponse de différents milieux d'intérêt sous champ continu ou impulsionnel, pouvant conduire à une nouvelle méthode de microdosimétrie de champ. Diverses applications, dont la granulométrie à l'échelle micro ou nanométrique ou l'identification de marqueurs pour la biologie, sont démontréesThanks to their compactness, robustness and low cost, pulsed nanosecond microlasers are particularly attractive sources for different detection and analysis systems, particularly flow cytometers or devices for CARS (Coherent Anti Raman Stokes Scattering) spectroscopy. However, these applications require reduced time jitter and increased repetition rate. The first part of this thesis proposes novel solutions to achieve the required performance from passively Q-switched microlasers, which are based on an hybrid coupled-cavity and intensitymodulated pump wave. A repetition rate greater than 30 kHz with jitter remaining lower than 200 ns is reached. Pulsed fiber microlasers operating by gain switching are also studied, showing that pulses with low timing jitter, at a repetition rate of more than 2 MHz can be obtained. The last part is devoted to the development and the implementation of a new system of CARS spectroscopy assisted by a high-voltage electrical stimulation. This device, based on an amplified microlaser, allows to substract the non-resonant background noise in the measurements. Thus, a fine spectroscopic analysis of the response of different environments of interest in continuous or pulsed field can be achieved. It may lead to a new method for field microdosimetry. Various applications, including granulometry at the micro or nanometric scale and the identification of markers for biology, are shown
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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.
Full textAbstract:
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.