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Tesi sul tema "Nonlinear optics"
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1
De, Matos Christiano Jose Santiago. "Nonlinear optics in specialty optical fibres". Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419770.
Testo completo
2
Gao, Xuesong. "Quantum Nonlinear Optics". University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1564662783494271.
Testo completo
3
Goldstein, Elena Vladimirovna 1962. "Nonlinear atom optics". Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/289255.
Testo completoAbstract (sommario):
In contrast to electromagnetic fields, matter-wave fields are intrinsically interacting due to the presence of atom-atom collisions. Hence, matter-wave optics becomes effectively nonlinear as soon as the atomic densities are high enough that collisions can no longer be ignored. The goal of this dissertation is to study selected aspects of atom optics under such conditions. Specifically, Chapter 2 studies the near-resonant dipole-dipole interaction between two atoms in tailored vacua. In contrast to spontaneous emission, whose rate is known to be influenced by the type of vacuum the atom interacts with, we find that the dipole-dipole potential is determined only by the free space vacuum and is not modified either by thermal or squeezed vacua. In addition in the far off-resonance regime we find that the squeezed vacuum results in an additional contribution to the effective potential governing the evolution of the atomic ground state. In the second part of the dissertation, which comprises Chapter 3, we then study several aspects of the many-body theory of atomic ultracold systems in situations where the nonlinearity arises due to the two-body dipole-dipole interaction. After a formal theoretical development we discuss the possibility of using atomic phase conjugation off Bose condensates as a diagnostic tool to access the spatial coherence properties and to measure the lifetime of the condensate. We argue that phase conjugation provides an attractive alternative to the optical methods of probing condensate proposed in the past. We further study the elementary excitations in a multicomponent Bose condensates and determine the quasi-particle frequency spectrum. We show that in that case interferences resulting from cross-coupling between the condensate components can lead to a reversal of the sign of the effective two-body interaction and to the onset of spatial instabilities.
4
Jonsson, Fredrik. "The nonlinear optics of magneto-optic media". Doctoral thesis, KTH, Physics, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2967.
Testo completo
5
FORTENBERRY, RANCE MORGAN. "NONLINEAR OPTICAL PHENOMENA IN ZINC OXIDE WAVEGUIDES (INTEGRATED OPTICS, NONLINEAR COUPLING)". Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183951.
Testo completoAbstract (sommario):
This dissertation reports on the development of a nonlinear surface spectroscopy and the observation of nonlinear optical phenomena using sputtered zinc oxide waveguides. The first is known as Surface Coherent Raman Spectroscopy, or SCRS, and is capable of monolayer sensitivity. The second, discovered during the development of SCRS, is optical limiting and a previously unobserved form of optical switching based on an absorptive nonlinear coupling mechanism. Overviews of the theories of waveguiding, linear coupling, and SCRS are given. Experiments showing that the spectrum of a monolayer coverage of molecules on the surface of a metal oxide waveguide can be obtained using SCRS are reported. For this purpose ZnO waveguides were fabricated using rf magnetron sputtering; the details of which are presented. The results of the characterization of these films, using an optical loss technique, Rutherford backscattering, and X-ray diffraction, are also presented. Experiments are described and data are presented to show the existence of optical limiting and optical switching phenomena in ZnO waveguides. The experimental dependence of these phenomena on input pulse energy, wavelength, temporal pulse width, and type of distributed coupling mechanism is described. Existing nonlinear distributed coupler theory is extended to include the effect of an absorptive nonlinearity and the results of this theory are used to explain some of the characteristic features of the experimental results. A value of n₂ ≅ 2 x 10⁻¹⁶ m²/W for the nonlinear coefficient of sputtered ZnO films is obtained.
6
Meier, Joachim. "DISCRETE NONLINEAR WAVE PROPAGATION IN KERR NONLINEAR MEDIA". Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2900.
Testo completoAbstract (sommario):
Discrete optical systems are a subgroup of periodic structures in which the evolution of a continuous electromagnetic field can be described by a discrete model. In this model, the total field is the sum of localized, discrete modes. Weakly coupled arrays of single mode channel waveguides have been known to fall into this class of systems since the late 1960's. Nonlinear discrete optics has received a considerable amount of interest in the last few years, triggered by the experimental realization of discrete solitons in a Kerr nonlinear AlGaAs waveguide array by H. Eisenberg and coworkers in 1998. In this work a detailed experimental investigation of discrete nonlinear wave propagation and the interactions between beams, including discrete solitons, in discrete systems is reported for the case of a strong Kerr nonlinearity. The possibility to completely overcome "discrete" diffraction and create highly localized solitons, in a scalar or vector geometry, as well as the limiting factors in the formation of such nonlinear waves is discussed. The reversal of the sign of diffraction over a range of propagation angles leads to the stability of plane waves in a material with positive nonlinearity. This behavior can not be found in continuous self-focusing materials where plane waves are unstable against perturbations. The stability of plane waves in the anomalous diffraction region, even at highest powers, has been experimentally verified. The interaction of high power beams and discrete solitons in arrays has been studied in detail. Of particular interest is the experimental verification of a theoretically predicted unique, all optical switching scheme, based on the interaction of a so called "blocker" soliton with a second beam. This switching method has been experimentally realized for both the coherent and incoherent case. Limitations of such schemes due to nonlinear losses at the required high powers are shown.Ph.D.
Other
Optics and Photonics
Optics
7
Yuan, Shuai. "Filamentation induced nonlinear optics". Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25268.
Testo completoAbstract (sommario):
La filamentation du laser femtoseconde provient d'un équilibre dynamique entre l’autofocalisation Kerr et la défocalisation par le plasma autogénéré produit de l’ionisation multiphotonique/tunnel des molécules dans l'air. Ce phénomène a attiré beaucoup d’attention des scientifiques telles que la télédétection de polluants atmosphériques et l'identification moléculaire par l'alignement des molécules. Cependant, il y a une multitude de processus non linéaires lors de la filamentation. Quant à l'application, il est important d'avoir une compréhension des mécanismes physiques présents lors de la filamentation induite par l’optique non linéaire. Étant donné de nombreux de phénomènes et d’applications de la filamentation, cette thèse se concentre sur une partie de ces aspects. Ceux-ci sont la rotation de la polarisation laser dans les gaz atomiques/moléculaires, le processus d’émission laser des molécules d'eau dans l'étalonnage air, lde l'humidité à travers la spectroscopie induite par un filament, ainsi que le renforcement de la fluorescence par un réseau de diffraction de plasma. La rotation de la polarisation laser d'une sonde polarisée initialement linéaire a été étudié dans les gaz atomiques/moléculaires. Dans les gaz atomiques, la biréfringence ultrarapide induite par l’effet Kerr a été mesurée quantitativement. Dans les gaz moléculaires, la biréfringence et les états de polarisation de la production de la sonde ont été modulés à la renaissance rotationnelle de la molécule. Également, nous avons étudié expérimentalement la fluorescence induite par filament à partir des fragments dissociés dans l'air. Les émissions de fluorescence des radicaux libres OH à 308.9 nm et NH à 336.0 nm ont été observés dans l'air. La fluorescence rétrodiffusée par le groupement OH et le groupement NH présentait une augmentation exponentielle accompagnant l'augmentation de la longueur du filament qui indique l’existence de l'émission spontanée amplifiée (ASE). En plus, on étudie la spectroscopie de fluorescence induite par filament à partir du réseau de diffraction pour le plasma. Le réseau de diffraction pour le plasma a été généré par des filaments non colinéaires qui se superposés et synchronisés temporellement dans l'air. Une série de spectres des fragments excités du CN a été observée. L’intensité de fluorescence du radical CN en utilisant un réseau de diffraction par le plasma est beaucoup plus forte que celle utilisant des filaments séparés temporellement.Femtosecond laser filamentation, which originates from a dynamic equilibrium between Kerr self-focusing and defocusing by the self-generated plasma produced by multiphoton/tunnel ionization of air molecules, has attracted a lot of scientific applications such as remote sensing of atmospheric pollutants, molecular identification by the alignment of molecules, etc. However, there are many nonlinear processes taking place during filamentation. From the application point of view, it is important to have a good understanding of the detailed physics behind filamentation induced nonlinear optics. Since there are many nonlinear phenomena and applications for filamentation, the thesis only focuses on few aspects of filamentation. Those are: the polarization rotation in atomic/molecular gases, the lasing action of water molecules in air, the humidity calibration through the filament-induced spectroscopy, as well as the fluorescence enhancement by plasma grating. The polarization rotation of an initially linearly polarized probe pulse was studied in atomic/molecular gases. In atomic gases, the ultrafast birefringence induced by Kerr effect was quantitatively measured. In molecular gases, the birefringence and the polarization states of the output probe were modulated at the rotational revival of molecule. We also experimentally investigate the filament-induced fluorescence from the dissociated fragments in air. Fluorescence emissions from OH free radicals at 308.9 nm and NH free radicals at 336.0 nm were observed in air. The backscattered fluorescence from both OH and NH exhibited an exponential increase with increasing filament length, indicating amplified spontaneous emission. We have further investigated the filament-induced fluorescence spectroscopy from a plasma grating. The plasma grating was generated by non-collinearly overlapping temporally synchronized filaments in air. A series of spectral lines from the excited fragments of CN was observed. The fluorescence intensity from CN radicals in plasma grating was much stronger as compared to the case of temporally separated filaments.
8
Hu, Quanyuan. "Synthesis, characterization and NLO properties of octupolar molecules /". View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202005%20HU.
Testo completo
9
Fu, Ling. "Fibre-optic nonlinear optical microscopy and endoscopy". Australasian Digital Thesis Program, 2007. http://adt.lib.swin.edu.au/public/adt-VSWT20070521.155004/index.html.
Testo completoAbstract (sommario):
Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2007.A thesis submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2007. Typescript. Bibliography: p. 146-162.
10
Tsangaris, Charalambos. "Transverse effects in optical cavities and nonlinear optics". Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/8799.
Testo completo
11
Norris, Greg. "Experimental nonlinear optics for applications in optical microscopy". Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16932.
Testo completoAbstract (sommario):
The motivation of this thesis was to develop efficient and improved optical excitation sources for applications in confocal laser scanning microscopy (CLSM) and multiphoton laser scanning microscopy (MPLSM), with emphasis on extending the wavelength coverage of existing laser sources using nonlinear optical methods. This included quantitative and qualitative structural analysis of periodically poled nonlinear materials using MPLSM. These materials, used in nonlinear optical frequency conversion, rely upon consistent poling lengths for quasi-phase matched operation. The described technique provided a non-destructive assessment of inhomogeneities within the crystal structure, which may impact upon frequency conversion efficiency processes. Following this analysis, innovative pump geometries were investigated for ultra-short pulsed singly resonant synchronously pumped optical parametric oscillators (SPOPOs). Through application of a novel bi-directional pump geometry, an increase in peak power of up to 90 % was observed, with peak powers in excess of 18.8 kW generated. This substantially outperformed any pump geometry previously implemented. This source was then applied to three photon laser scanning microscopy. Next, a visible, wavelength tunable, ultra-short pulsed source based on sum frequency mixing was developed for MPLSM at wavelengths shorter than 700nm. With average output power of ~ 150 mW, the source was applied to MPLSM of biological and non-biological UV excitable samples and results were compared with the longer wavelength Ti:Sappphire system. Finally, a SC source and Ti:Sapphire laser were applied for optical beam induced current (OBIC) microscopy of an InGaN LED to provide information regarding the spectral response of the diode and imaging of the active region. This provided additional information regarding inhomogeneity and hence efficiency.
12
Herrera, Oscar Dario. "Nonlinear Photonics in Waveguides for Telecommunications". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338755.
Testo completoAbstract (sommario):
Bandwidth demands in global telecommunication infrastructures continue to rise and new optical techniques are needed to deal with massive data flows. Generating high bandwidth signals (> 40 GHz) using conventional modulation techniques is hindered by material limitations and fabrication complexities. Similarly, controlling such high bandwidths in both the temporal and spectral domain becomes more problematic using conventional electronic processes. Advances in electro-optic organic materials,
fibers/micro-fluidics integration, and nonlinear optics have significant potential for higher bandwidth modulation and temporal/spectral control. The work presented in this dissertation demonstrates the use of various nonlinear optical effects in new photonic device and system designs towards the generation and manipulation of highspeed optical pulses. First, an all fiber-based system utilizing an integrated carbon disulfide-filled liquidcore optical fiber (i-LCOF) and co-propagating pulses of comparable temporal lengths is presented. The slow light effect was observed in 1-meter of i-LCOF, where 18 ps pulses were delayed up to 34 ps through the use of stimulated Raman scattering. Delays greater than a pulse width indicate a potential application as an ultrafast controllable delay line for time division multiplexing in multi-Gb/s telecommunication systems. Similarly, an optically tunable frequency shift was observed using this system. Pulses experienced a full spectral bandwidth shift at low peak pump powers when utilizing the Raman-induced frequency shift and slow light effects. Numerical simulations of the pulse-propagation equations agree well with the observed shifts. Included in our simulations are the contributions of both the Raman cross-frequency shift and slow light effects to the overall frequency shift. These results make the system suitable for numerous applications including low power wavelength converters. Second, a silica/electro-optic (EO) polymer phase modulator with an embedded bowtie antenna is proposed for use as a microwave radiation receiver. The detection of high-frequency electromagnetic fields has been heavily studied for wireless data transfer. Recently there has been growing interest in the field of microwave photonics. We present the design and optimization of a waveguide with an EO polymer core and silica/sol-gel cladding. The effect of electrodes on the insertion losses and poling efficiency are also analyzed, and conditions for low-loss and high poling efficiency are established. Experimental results for a fabricated device with microwave-response between 10 - 14 GHz are presented. Finally, we present the design for a fast optical switch incorporating silicon as the passive waveguide structure and EO polymer as the active material. The design uses a simple directional coupler with coplanar electrodes and promises to have low cross-talk and high switching speed (on the order of nanoseconds). An initial design for a 1x2 switch is fabricated and tested, and future optimization processes are also presented.
13
Novikova, Irina Borisovna. "Nonlinear magneto-optic effects in optically dense Rb vapor". Texas A&M University, 2004. http://hdl.handle.net/1969.1/364.
Testo completoAbstract (sommario):
Nonlinear magneto-optical effects, originated from atomic coherence, are studied both theoretically and experimentally in thermal Rb vapor. The analytical description of the fundamental properties of coherent media are based on the simplified three- and four-level systems, and then verified using numerical simulations and experimental measurements. In particular, we analyze the modification of the long-lived atomic coherence due to various physical effects, such as reabsorption of
spontaneous radiation, collisions with a buffer gas atoms, etc. We also discuss the importance of the high-order nonlinearities in the description of the polarization rotation for the elliptically polarized light. The effect of self-rotation of the elliptical polarization is also analyzed.
Practical applications of nonlinear magneto-optical effects are considered in precision metrology and magnetometery, and for the generation of non-classical states of electromagnetic field.
14
Liu, Xunmimg. "Nonlinear dynamics in quantum optics /". St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17835.pdf.
Testo completo
15
Li, Ruo-Ding. "Model analysis in nonlinear optics". Doctoral thesis, Universite Libre de Bruxelles, 1991. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/213005.
Testo completo
16
Turner, Peter D. "Organic materials for nonlinear optics /". Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09pht951.pdf.
Testo completo
17
Anscombe, Marcel Philip. "Nonlinear optics with atomic coherence". Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404378.
Testo completo
18
Griffiths, J. "Crystal engineering for nonlinear optics". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599722.
Testo completoAbstract (sommario):
Chapter Two details the design, synthesis and characterisation of some compounds of general formula p-DC6F4A-p’. Donor and acceptor groups are discussed both in the context of maximising the molecular NLO response, and in the context of the promotion of polar chain formation through supramolecular synthons. Of the ten compounds presented in this chapter, nine are noncentrosymmetric. Preliminary NLO measurements show that these nine compounds exhibit an appreciable SHG response. Semi-empirical calculations were performed on these and related systems to determine molecular hyperpolarisabilities. Similar calculations were also used to draw Molecular Electrostatic potential maps for these compounds in an attempt to rationalise the observed packing. Chapter Three discusses some compounds of general formula DC6F4C6F4A. The synthetic difficulties associated with the preparation of these perfluorinated biphenyl derivatives are highlighted, and semi-empirical calculations are used to identify some idealised systems. The syntheses and crystal structures of some methoxy substituted derivatives are reported. Chapters Four and Five discuss some compounds in which donor-acceptor substituted rings are linked by delocalised spacer groups. The synthesis and characterisation of some donor-acceptor substituted aromatic Schiff base compounds is presented in Chapter Four, along with some initial calculations and NLO measurements. Chapter Five describes the design, synthesis and characterisation of some thiazyl chain compounds. UV measurements and preliminary calculations on some of these systems are also presented.
19
McIntyre, Ross. "Pattern formation in nonlinear optics". Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/716.
Testo completo
20
Walmsley, M. "Ultrafast nonlinear optics in semiconductors". Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5498/.
Testo completoAbstract (sommario):
The nonlinear optical phenomena which occur in semiconductor materials on a femtosecond to picosecond timescale have recently generated much interest, especially in the field of telecommunications where the development of all-optical switching devices based on semiconductors promises a considerable reduction in the complexity of design coupled with a large increase in the speed of operation. This thesis examines the underlying ultrafast physical processes with the aim of providing a clear understanding of the mechanisms involved. The two main regimes of operation are investigated, namely off-resonance excitation where virtual processes are important and on-resonance excitation where real carriers are photogenerated, and in each case a particular system of interest is studied. For the virtual regime of operation, a recent proposal is examined which suggests the use of bandstructure engineering for a semiconductor quantum well in order to enhance the nonlinear optical response by the introduction of additional resonant transitions between subbands. A number of descriptions of the device are presented, and it is concluded that the technique does not necessarily lead to an improved response. An example of on-resonance phenomena is provided by the modelling of the fast refractive index changes in semiconductor laser amplifiers which have been observed in recent experiments. A simple physical model is developed which predicts the behaviour seen in the experimental observations. The nonlinear optical response of the laser amplifier promises the development of fast all-optical switching based on these devices. The thesis also examines the difficulties associated with describing the interaction of semiconductor material and electromagnetic field, and in particular looks at the formulation of a gauge invariant procedure for calculating values of the susceptibility. The propagation of a light beam along the plane of a semiconductor quantum well is discussed, and the gauge invariance of susceptibility calculations performed in the so called A.p and E.r gauges is explicitly demonstrated. Finally, a brief exploration is undertaken of the effects of bandstructure on the optical response of a semiconductor, and two quantum well models for the calculation of a more realistic bandstructure are presented which employ infinite and finite wells respectively.
21
Hameed-Muhammed, Muhammed Subhi. "Novel composites for nonlinear optics". Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301715.
Testo completo
22
Geddes, John Bruce. "Patterns, fishing and nonlinear optics". Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186972.
Testo completoAbstract (sommario):
Motivated by a conversation with my brother, a deep sea fisherman off the east coast of Scotland, I review the concepts which unify the topic of pattern formation in nonequilibrium systems. As a specific example of a pattern-forming system, I go on to examine pattern formation in nonlinear optics and I discuss two nonlinear optical systems in considerable detail. The first, counterpropagating laser beams in a nonlinear Kerr medium, results in the prediction and numerical observation of hexagonal patterns in a self-focusing medium, and of square patterns in a self-defocusing medium. Furthermore, a novel Hopf bifurcation is observed which destabilises the hexagons and an explanation in terms of a coupled-amplitude model is given. The other system, namely the mean-field model of propagation in a nonlinear cavity, also gives rise to hexagonal patterns in a self-focusing medium. By extending this model to include the vector nature of the electric field, polarisation patterns are predicted and observed for a self-defocusing medium. Roll patterns dominate close to threshold, while farther from threshold labyrinthine patterns are found. By driving the system very hard, a transition to a regime consisting of polarisation domains connected by fronts is also observed. Finally, numerical algorithms appropriate for solving the model equations are discussed and an alternative algorithm is presented which may be of use in pattern-forming systems in general.
23
Agnew, Amalia. "Quantum-Chemical Investigations of Second- and Third-Order Nonlinear Optical Chromophores for Electro-Optic and All-Optical Switching Applications". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11575.
Testo completoAbstract (sommario):
The past decades have witnessed the development of new materials with large nonlinear optical properties, which have made them attractive candidats for a broad spectrum of breakthrough applications in the electro-optic and photonic fields (e.g., telecommunication and computing). A deeper understanding of the relationship between, on the one hand, the chemical structure and, on the other hand, the electronic and (linear and nonlinear) optical properties has proven useful for the rational design of new efficient materials. Reaching such an understanding has attracted major interest in the scientific community worldwide in both academia and industry. Therefore, the development of new efficient NLO chromophores and materials along with commercial devices of high quality is helped via the establishment of multidisciplinary research teams combining: (i) the theoretical modeling using quantum-chemical computational calculations; (ii) the organic synthesis; (iii) the optical characterization; and (iv) the device fabrication. In this dissertation, quantum-chemistry is used to evaluate the second- and third-order NLO properties of series of new chromophores and take advantage of a feedback loop with the experimental team to understand the structure-property relationships.
24
MOSHREFZADEH, ROBERT SHAHRAM. "THEORY AND FABRICATION OF SUB-MICRON GRATINGS ON NONLINEAR OPTICAL WAVEGUIDES". Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184138.
Testo completoAbstract (sommario):
Because of their compatibility with the planar concept of integrated optics, grating couplers offer the most satisfactory means of coupling light into thin film optical waveguides. The purpose of this dissertation has been to study the behaviour, both theoretically and experimentally, and fabrication of grating couplers in nonlinear waveguides. A theory of nonlinear grating couplers is presented based on a coupled-mode approach. The dependence of coupling efficiency on incident beam intensity, beam size, beam position, incident angle, chirp rate, and waveguide losses have been examined all in the presence of nonlinearities in the waveguide. It is reported that, in the presence of nonlinearities, the coupling efficiency decreases with increasing incident power. Different ways of optimizing the coupling efficiency at high incident power levels are presented. These include adjusting the beam size, the coupling angle, and chirping the grating. A new technique is reported for fabrication of regular period, chirped, and curved photoresist gratings. The experimental arrangement is essentially based on Lloyd's mirror fringes and is characterized by its stability, simplicity, and versatility. We also report on successful use of Reactive Ion-Beam Etching (RIBE) with C₂F₆ gas in producing very smooth and deep gratings with high aspect ratios in different waveguide structures. Experimental coupling efficiencies of up to 40% are reported in polystyrene waveguides using etched grating couplers. Experiments are reported in support of the theoretical findings of this dissertation using a polystyrene waveguide with thermal nonlinearity.
25
Svensson, Barbro Christina. "Nonlinear distributed couplers in zinc-sulfide waveguides". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184500.
Testo completoAbstract (sommario):
Nonlinear phenomena originating from the distributed coupling process were observed when distributed couplers, such as prisms and gratings, were used to couple light into nonlinear ZnS thin film waveguides. The efficiency of the nonlinear distributed coupling process was found to depend on two independent parameters, the angle of the incident beam and the power of the incident beam. Depending on the detuning of the incident angle, from the optimum incident angle at low powers, either optical limiting, power-dependent switching, or power-dependent bistability of the coupling efficiency, and thereby of the in-coupled power, was observed. At zero detuning, a twenty-fold decrease of the coupling efficiency with increasing powers was measured. At a nonzero detuning of the incident angle, power-dependent switching at milliwatt powers was observed. At larger angular detunings, corresponding to the angular width. FWHM, of the coupling peak at low powers, power-dependent bistability was observed, and the width of the bistability loop was found to increase with increasing detunings. All-optical beam scanning via a nonlinear grating coupler was also demonstrated, utilizing a control-signal beam configuration, where the signal beam scanned through an angle of 0.5° when the power of the control beam was varied. The observed nonlinearity in ZnS was positive and of thermal origin. The power-induced change in the refractive index was found to be 0.01 and a relaxation time of 10 μsec was measured. Problems with the long-term stability of the nonlinear distributed coupling process were traced to the occurrence of desorption and adsorption of water vapor in the ZnS films.
26
Johnston, Wesley James. "Nonlinear optics in Bragg-spaced quantum wells". Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/826.
Testo completoAbstract (sommario):
Bragg spaced quantum wells represent a unique class of resonant photonic materials, wherein a photonic bandgap is created by the periodic spacing of quantum wells and the associated variation in the complex susceptibility (index and absorption) of the material. Interest in BSQWs has grown in the past decade due to their large ultrafast nonlinearities and the corresponding large ultrafast reflectivity changes and transmissivity. These nonlinearities are of particular interest in areas of communication technology, where ultrafast all-optical logic components have become increasingly in demand. This research will further investigate BSQWs and the for the first time effects of spin-dependent nonlinear excitation on their photonic band structures. It will also investigate how these effects can be used in all-optical polarization switching and tunable optical buffer (slow light) applications.
27
Rochford, Kent Blair. "Linear and nonlinear optical properties of polydiacetylene waveguides". Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185340.
Testo completoAbstract (sommario):
The linear and nonlinear optical properties of a spin-coated polydiacetylene, [5,7-dodecadiyn-1,12-diol-bis(n-butoxy-carbonyl-methyl-urethane)], or poly(4BCMU), were measured to predict its performance in all-optical devices at 1.319 μm. Material requirements for all-optical devices were identified and figures-of-merit noted. A two-photon absorption figure of merit was verified by numerical simulation of a waveguide device. The refractive index and waveguide loss in spin-coated poly(4BCMU) films were measured. A photo-induced bleaching was observed, and its effect on linear and nonlinear optical properties was quantified. Fabrication of integrated-optical structures using this photobleaching process was demonstrated. The nonlinear refractive index and absorption were measured at 1.319 μm with 60 picosecond laser pulses, using poly(4BCMU) strip-loaded channel waveguides. A novel pulse-modulated interferometer was developed for measuring the intensity-dependent refractive index. The fast electronic contribution was found to be n₂ = (4.8 ± 2.7) x 10⁻⁸ cm²/MW, an a slower thermal contribution of n₂(T) = -(7.9 ± 4.5) x 10⁻¹¹ cm²/MW was measured. The thermal index change was shown to limit the duty cycle of operation for a poly(4BCMU) device. The two-photon absorption coefficient was also measured, yielding γ < 0.25 cm/GW. These values were used to estimate performance of a poly(4BCMU) all-optical device using standard figures-of-merit. For this specific waveguide, the figures-of-merit indicated poor performance. If waveguide losses were neglected, (by assuming improved fabrication for example), and assuming the nonlinearity does not saturate at intensities below the damage threshold, the figures-of-merit improve to useful levels. The limit on duty cycle imposed by thermal effects appears to restrict operation to GHz frequencies of slower.
28
Keilbach, Kevin Anthony 1963. "Nonlinear prism coupling in an organic waveguide". Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276875.
Testo completoAbstract (sommario):
Computer modeling of prism coupling of pulsed laser irradiation at a wavelength of 1064 nm into an organic polymer waveguide with Kerr Law nonlinearities showed that the prism coupling technique was inherent problems that make it difficult to accurately determine the magnitude of the refractive index change. Uncertainty in knowledge of the gap spacing under the prism leads to errors in any estimates of these nonlinear refractive index changes. Results from prism coupling experiments conducted on a polymer waveguide with a pulsed laser are inconclusive.
29
Evans, Christopher Courtney. "Nonlinear optics in titanium dioxide: from bulk to integrated optical devices". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11167.
Testo completoAbstract (sommario):
In this thesis, we explore titanium dioxide (TiO2) for ultrafast, on-chip nonlinear optics by studying it in bulk, thin films, and in integrated nonlinear optical devices. TiO2's large nonlinear index of refraction (30 times that of silica) and low two-photon absorption can enable all-optical switching, logic, and wavelength conversion across wavelengths spanning the telecommunications octave (800–1600 nm). In addition, its high linear index of refraction can enhance optical confinement down to nano-scale dimensions and facilitate the tight waveguide bends necessary for dense on-chip integration. Throughout this thesis, we develop TiO2 as a novel on-chip nonlinear optics platform.Engineering and Applied Sciences
30
Manzoni, Marco Tommaso. "New systems for quantum nonlinear optics". Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461495.
Testo completoAbstract (sommario):
Photons travelling through free space do not interact with each other. This characteristic makes them perfect candidates to carry quantum information over long distances. On the other hand, processing the information they encode requires interaction mechanisms. In recent years, there have been growing efforts to realize strong, controlled interactions between photons by making them interact with individual atoms, which are intrinsically nonlinear objects. This, and the efforts to understand the phenomena that can emerge, have spawned the new field of`"quantum nonlinear optics."
A number of approaches have been pursued to attain near-deterministic atom-photon interactions, including the use of cavities (CQED), of atomic ensembles, and more recently of dielectric nanostructures able to confine light without defocusing, thus enabling the interaction with atoms trapped in the proximity of the structures. While for the CQED case powerful theoretical tools have been developed to treat the interactions of photons, in the case of atomic ensembles, either in free space or coupled to nanophotonic structures, there is a general lack of theoretical methods beyond the linear regime. This relative lack of understanding also implies that there could be rich new physical phenomena that have thus far not been identified. The overall goal of this thesis is to explore these themes in greater detail.
In Chapter 2 of this thesis we develop a new formalism to calculate the properties of quantum light when interfaced with atomic ensembles. The method consists of using a "spin model" that maps a quasi one-dimensional (1D) light propagation problem to the dynamics of an open 1D interacting spin system, where all of the photon correlations are obtained from those of the spins. The spin dynamics can be numerically solved using the toolbox of matrix product states (MPS), thus providing a technique to study strongly interacting photons in the true many-body limit.
In Chapter 3 we investigate the possibility of creating exotic phases of matter using the recently realized photonic crystal waveguide (PCW)-atoms interface. In particular, we examine the consequences that arise from the strong interatomic forces mediated by the exchange of band gap photons, whose strengths also depend strongly on the internal atomic states (¿spins¿). Taking one realistic model, we show that "quantum crystallization" can occur, in which the emergent spatial orders of atoms depend intricately on the spin correlations.
In Chapter 4 we investigate the possibility of implementing second-order nonlinear quantum optical processes with graphene nanostructures, as a more robust alternative to the use of atomic systems. We quantify the second-order nonlinear properties, showing that the tight confinement of surface plasmons (SP) in graphene gives rise to extraordinary interaction strengths at the single-photon level. Finally, we predict that opportunely engineered arrays of graphene nanostructures can provide a second harmonic generation efficiency comparable with that of state-of-the-art nonlinear crystals, with the high Ohmic losses of graphene serving as the fundamental limitation for deterministic processes.
In Chapter 5 we investigate a new paradigm for quantum memories of light based upon ordered atomic arrays. In particular, we show that the strong constructive interference in optical emission can give rise to a significantly enhanced atom-light interface, as compared to a standard, disordered atomic ensemble. In the case of a single, 2D atomic layer, we find the impressive result that a memory realized with 16 atoms can have the same storage efficiency as an atomic ensemble with optical depth larger than 100.Los fotones que viajan por el espacio libre no interactúan entre sí. Esta característica los hace perfectos candidatos para transportar la información cuántica a largas distancias. Por otro lado, el procesamiento de la información que codifican requiere mecanismos de interacción. En los últimos años se han realizado esfuerzos crecientes para realizar interacciones fuertes y controladas entre los fotones y para comprender las leyes subyacentes que describen los fenómenos que pueden surgir, generando así el nuevo campo de la "óptica cuántica no lineal". Mientras que los materiales tridimensionales tienen coeficientes no lineales extremadamente débiles, se pueden obtener interacciones entre los fotones haciéndolos interactuar con átomos individuales, que son objetos intrínsecamente no lineales, teniendo la capacidad de absorber únicamente un solo fotón a la vez. La realización de interacciones determinísticas entre fotones y átomos es uno de los principales retos de la óptica cuántica no lineal. Para eludir las limitaciones debidas a la pequeña sección eficaz óptica de los átomos y el límite de difracción en el espacio libre, se han aplicado diferentes estrategias, entre ellas el uso de cavidades (CQED), de colectividades atómicas y, más recientemente, de nanoestructuras dieléctricas capaces de confinar la luz sin desenfocarse, permitiendo así la interacción con átomos atrapados en la proximidad de esas estructuras. Mientras que para el caso de la CQED se han desarrollado potentes herramientas teóricas para tratar las interacciones de los fotones, en el caso de colectividades atómicas hay una falta general de métodos teóricos más allá del régimen lineal. Esta relativa falta de comprensión también implica que podría haber nuevos fenómenos físicos interesantes que hasta ahora no se han identificado. El objetivo general de esta tesis es explorar estos temas con mayor detalle. En el capítulo 2 de esta tesis desarrollamos un nuevo formalismo para calcular las propiedades de la luz cuántica cuando interactúa con sistemas atómicos. El método consiste en utilizar un"`modelo de espines" que mapea un problema de propagación de luz cuasi unidimensional (1D) a la dinámica de un sistema abierto unidimensional de espines que interactúan entre sí, donde todas las correlaciones de fotones se obtienen a partir de las de los espines. La dinámica de los espines se puede resolver numéricamente utilizando la caja de herramientas de los estados producto de matrices (MPS), proporcionando así una técnica para estudiar los fotones que interactúan fuertemente en el regimen de la física de muchos cuerpos. En el capítulo 3 se investiga la posibilidad de crear fases exóticas de la materia utilizando la interfaz entre guía de ondas de cristales fotónicos (PCW) y átomos recientemente realizada experimentalmente, donde los modos de la banda de frecuencias prohibidas de la PCW se utilizan para mediar las interacciones de largo alcance entre los átomos. Encontramos un rico diagrama de fases de órdenes emergentes. En el capítulo 4 se investiga la posibilidad de implementar procesos ópticos cuánticos no lineales de segundo orden con nano-estructuras de grafeno, como una alternativa más robusta al uso de sistemas atómicos. Cuantificamos las propiedades no lineales de segundo orden, mostrando que el estrecho confinamiento da lugar a extraordinarias fuerzas de interacción a nivel de un solo fotón y predecimos que un diseño apropiado de las nano-estructuras del grafeno permitiría generar el segundo armónico con una eficiencia comparable a la de los cristales no lineales de última generación. En el capítulo 5, investigamos cómo la emisión cooperativa en memorias cuánticas realizadas con reticulos atómicos afecta su eficiencia, encontrando el impresionante resultado de que una memoria realizada con 16 átomos puede tener la misma eficiencia que un gas cuántico atómico de profundidad óptica mayor que 100.
31
Hulshof, Johannes Bernardus Everardus. "Materials for second order nonlinear optics". [S.l. : [Groningen : s.n.] ; University of Groningen] [Host], 1995. http://irs.ub.rug.nl/ppn/.
Testo completo
32
Blake, Iain M. "Conjugated porphyrin systems for nonlinear optics". Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365889.
Testo completo
33
Naguleswaran, Siva. "Time reversal symmetry in nonlinear optics". Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/8166.
Testo completoAbstract (sommario):
Results following from time reversal symmetry are developed for those nonlinear optical processes where a statistical average is required. This extends results found in Rayleigh (and Raman) scattering to nonlinear optical processes of arbitrary order, and generalises those few analyses specific to nonlinear optics. For example, Onsager relations for self-conjugate nonlinear optical processes (when input and output photons form degenerate pairs) are derived, and associated reversality relations generalised. In the nonresonant limit magnetic dipole but not electric quadrupole terms in coherent processes are suppressed. For this and other selection rules a careful treatment is required to obtain gauge invariant conclusions since the relevant electronic operators in multipolar and Coulomb gauges have differing time reversal signatures. For general processes purely electric dipole contributions to natural optical activity are possible when intermediate resonances are present; strong resonances are not required for the domination of this contribution over the traditional contribution. Time reversal symmetry may be used to show the prescription for assigning signs to phenomenological damping factors that is usually associated with the optical susceptibility formalism is incorrect. An experimental test based on electrooptic rotation in fluid media is proposed which may distinguish between this incorrect prescription and the correct prescription. The role time reversal symmetry plays in restricting the number of parameters in Judd-Ofelt theory is elucidated.
34
Stensson, Katarina. "Quantum Optics in 2D Nonlinear Lattices". Thesis, KTH, Tillämpad fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145893.
Testo completo
35
Harvey, Thomas Grierson. "Nonlinear optics of the polydiacetylene pTS". Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/874.
Testo completo
36
Ryder, Elaine. "Nonlinear guided waves in fibre optics". Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/14342.
Testo completoAbstract (sommario):
Optical fibres are widely used in optical communication systems because they can transmit signals in the form of extremely short pulses of quasi-monochromatic light over large distances with high intensities and negligible attenuation. A fibre that is monomode and axisymmetric can support both left- and right-handed circularly polarised modes having the same dispersion relation. The evolution equations are coupled nonlinear Schröinger equations, the cubic terms being introduced by the nonlinear response of the dielectric material at the high optical intensities required. In this thesis we analyse signal propagation in axisymmetric fibres both for a fibre with dielectric properties which vary gradually, but significantly, along the fibre and for a fibre which is curved and twisted but with material properties assumed not to vary along the fibre. For fibres with axial inhomogeneities, we identify two regimes. When the axial variations occur on length scales comparable with nonlinear evolution effects, the governing equations are found to be coupled nonlinear Schröinger equations with variable coefficients. Whereas for more rapid axial variations it is found that the evolution equations have constant coefficients, defined as appropriate averages of those associated with each cross-section. The results of numerical experiments show that a sech-envelope pulse and a more general initial pulse lose little amplitude even after propagating through many periods of an axial inhomogeneity of significant amplitude. For a curved and twisted fibre, it is found that the pulse evolution is governed by a coupled pair of cubic Schröinger equations with linear cross coupling terms have coefficients related to the local curvature and torsion of the fibre. These coefficients are not, in general, constant. However for the case of constant torsion and constant radius of curvature which is comparable to the nonlinear evolution length, numerical evidence is presented which shows that a nominally non-distorting pulse is unstable but the onset of instability is delayed for larger values of torsion.
37
Dhayal, Suman. "Nonlinear and Quantum Optics Near Nanoparticles". Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822820/.
Testo completoAbstract (sommario):
We study the behavior of electric fields in and around dielectric and metal nanoparticles, and prepare the ground for their applications to a variety of systems viz. photovoltaics, imaging and detection techniques, and molecular spectroscopy. We exploit the property of nanoparticles being able to focus the radiation field into small regions and study some of the interesting nonlinear, and quantum coherence and interference phenomena near them. The traditional approach to study the nonlinear light-matter interactions involves the use of the slowly varying amplitude approximation (SVAA) as it simplifies the theoretical analysis. However, SVVA cannot be used for systems which are of the order of the wavelength of the light. We use the exact solutions of the Maxwell's equations to obtain the fields created due to metal and dielectric nanoparticles, and study nonlinear and quantum optical phenomena near these nanoparticles. We begin with the theoretical description of the electromagnetic fields created due to the nonlinear wavemixing process, namely, second-order nonlinearity in an nonlinear sphere. The phase-matching condition has been revisited in such particles and we found that it is not satisfied in the sphere. We have suggested a way to obtain optimal conditions for any type and size of material medium. We have also studied the modifications of the electromagnetic fields in a collection of nanoparticles due to strong near field nonlinear interactions using the generalized Mie theory for the case of many particles applicable in photovoltaics (PV). We also consider quantum coherence phenomena such as modification of dark states, stimulated Raman adiabatic passage (STIRAP), optical pumping in $4$-level atoms near nanoparticles by using rotating wave approximation to describe the Hamiltonian of the atomic system. We also considered the behavior of atomic and the averaged atomic polarization in $7$-level atoms near nanoparticles. This could be used as a prototype to study any $n-$level atomic system experimentally in the presence of ensembles of quantum emitters. In the last chapter, we suggested a variant of a pulse-shaping technique applicable in stimulated Raman spectroscopy (SRS) for detection of atoms and molecules in multiscattering media. We used discrete-dipole approximation to obtain the fields created by the nanoparticles.
38
Compton, Ryan Edward. "Nonlinear Optics in Non-Equilibrium Microplasmas". Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/123146.
Testo completoAbstract (sommario):
ChemistryPh.D.
This dissertation details the nature of subnanosecond laser-induced microplasma dynamics, particularly concerning the evolution of the electron temperature and concentration. Central to this development is the advent of a femtosecond four-wave mixing (FWM) spectroscopic method. FWM (in the form of coherent anti-Stokes Raman scattering (CARS)) measurements are performed on the fundamental oxygen vibrational transition. An analytical expression is provided that accounts for the resonant and nonresonant contributions to the CARS signal generated from the interaction of broadband pump and Stokes pulses. The inherent phase mismatch is also accounted for, resulting in quantitative agreement between experiment and theory. FWM is then used to measure the early-time electron dynamics in the noble gas series from He to Xe following irradiation by an intense (10^14 Wcm-2) nonresonant 80 fs laser pulse. An electron impact ionization cooling model is presented to determine the evolution of electron kinetic energies following ionization. Kinetic energies are predicted to evolve from > 20 eV to < 1 eV in the first 1.5 ns. The initial degree of ionization is determined experimentally via measurement of the Bremsstrahlung background emission, and modeled with a modified ADK theory based on tunnel ionization. Combined, these two descriptions account for the evolution of both the electron temperature and concentration and provide quantitative agreement with the FWM measurements. The model is further tested with measurements of the gas pressure and pump laser intensity on the electron dynamics. The FWM experiments are concluded with a qualitative discussion of dissociative recombination dynamics occurring in molecular microplasmas. The microplasma environment is used as a source for the generation of two-level systems in the excited state manifold of atomic oxygen and argon. These two-level systems are coupled using moderately intense ~1 ps near-infrared (and near-resonant) pulses, resulting in Rabi sidebands with unprecedentedly large shifts in excess of 90 meV. A time-dependent generalized Rabi-cycling model is developed to account for the time-dependence of the laser electric field and subsequently the Rabi frequency. The Rabi radiation is determined to be coherent and tunable (up to 200 meV), providing a new method for ultrashort pulse generation. The dependence of the spectral positions of the Rabi sidebands on laser intensity affords the opportunity to simultaneously determine the ratios of transition dipole moments for the states accessed.
Temple University--Theses
39
Redondo, Loures Cristian. "Negative frequency effects in nonlinear optics". Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3288.
Testo completoAbstract (sommario):
In this thesis we analyse the impact of the new terms that appear in the nonlinear polarisation of the equations relevant to nonlinear x(3) optical materials when the slowly varying envelope approximation (SVEA) is not applied. These new terms introduce new nonlinear interactions between the positive and negative frequency parts of the spectrum of an optical pulse, giving rise to novel nonlinear phenomena that were not present in the usual models based in SVEA, like the ubiquitous nonlinear Schrodinger equation (NLSE). The analysis carried out in this thesis is theoretical, with both numerical simulations and analytical results presented. These results predict new frequency generation processes that can have a considerable impact in ultrashort pulse propagation and supercontinuum generation. We also discuss the experimental need for this extended model, as well as some possible signatures of these novel frequency generation processes in recent experiments.
40
CLEMENTI, MARCO. "Nonlinear Optics in Photonic Crystal Cavities". Doctoral thesis, Università degli studi di Pavia, 2020. http://hdl.handle.net/11571/1317094.
Testo completoAbstract (sommario):
Harnessing the properties of light for technological applications is perhaps the ultimate objective of photonics, whereas the generation, manipulation and detection of light in chip-based structures has an important impact both on industry and on fundamental research1. The integration to semiconductor-based nanostructures makes possible the application of the photonics paradigm to compact devices which on one hand enable the processing of information at high speed, and on the other hand allow to include, onto a single chip, complex experimental apparatuses, opening the way towards novel technological and physical applications. In this perspective, an effective light-matter interaction is primarily important, as this feature greatly enhances capability of integrated optical and opto-electronic devices, in terms of switching time, energy consumption and spectrum of applications.
For these reasons, the development of structures capable to enhance the interaction of light and matter covers great interest in the field of integrated optics. In this thesis work, we investigate on the linear and nonlinear properties of photonic crystal (PhC) microresonators2, a specific type of integrated optical cavity which capabilities to confine the electromagnetic field both in time and space are particularly suited for enhanced photonic devices. In particular, this type of nanostructure benefits from an enhanced nonlinear response with respect to bulk or non-resonant nonlinear devices, and they are characterized by a minimal footprint, a crucial feature in view of integration, thanks to a Bragg-type physical confinement mechanism.
Throughout the work, we focus on three specific topics. The first one consists in the design, fabrication and characterization of PhC cavities realized in silicon suspended membranes, designed for the demonstration of integrated optical frequency combs. These rely on a specific cavity design, engineered to provide equally spaced resonances in energy, as a consequence of the effective confinement potential3. We discuss experimental results showing comb-like resonant spectra and we investigate the possibility to use the structures for the implementation of triply-resonant nonlinear processes, such as four-wave mixing (FWM), with unprecedented conversion efficiency.
In a second part, we investigate on the suitability of a novel material, silicon-rich silicon nitride (SRSN)4, for the fabrication of PhC cavities and their operation as nonlinear devices. We show how SRSN deposited films can be successfully used to fabricate high-quality factor PhC cavities and we experimentally study the generation of second- and third-harmonic under resonant pumping regime.
Finally, we investigate the suitability of otherwise parasitic nonlinear effects, related to two-photon absorption in silicon microcavities, for the implementation of nonlinear properties based on the dynamical thermo-optic response of the material. We show that the PhC platform provides a way to achieve narrow spectral holes and gain windows, associated to a pronounced dispersion. This feature, associated to a dramatic decrease in group velocity, can be exploited to achieve slow-light on a chip exclusively via thermo-optic effect, in a completely novel approach.
1. Thomson, D. et al. Roadmap on silicon photonics. J. Opt. 18, 073003 (2016).
2. Notomi, M. Manipulating light with strongly modulated photonic crystals. Reports Prog. Phys. 73, 096501 (2010).
3. Alpeggiani, F., Andreani, L. C. & Gerace, D. Effective bichromatic potential for ultra-high Q-factor photonic crystal slab cavities. Appl. Phys. Lett. 107, 261110 (2015).
4. Clementi, M. et al. Cavity-enhanced harmonic generation in silicon rich nitride photonic crystal microresonators. Appl. Phys. Lett. 114, 131103 (2019).
41
Turner-Valle, Jennifer 1970. "Nonlinear multilayers as optical limiters". Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288788.
Testo completoAbstract (sommario):
In this work we present a non-iterative technique for computing the steady-state optical properties of nonlinear multilayers and we examine nonlinear multilayer designs for optical limiters. Optical limiters are filters with intensity-dependent transmission designed to curtail the transmission of incident light above a threshold irradiance value in order to protect optical sensors from damage due to intense light. Thin film multilayers composed of nonlinear materials exhibiting an intensity-dependent refractive index are used as the basis for optical limiter designs in order to enhance the nonlinear filter response by magnifying the electric field in the nonlinear materials through interference effects. The nonlinear multilayer designs considered in this work are based on linear optical interference filter designs which are selected for their spectral properties and electric field distributions. Quarter wave stacks and cavity filters are examined for their suitability as sensor protectors and their manufacturability. The underlying non-iterative technique used to calculate the optical response of these filters derives from recognizing that the multi-valued calculation of output irradiance as a function of incident irradiance may be turned into a single-valued calculation of incident irradiance as a function of output irradiance. Finally, the benefits and drawbacks of using nonlinear multilayer for optical limiting are examined and future research directions are proposed.
42
Nee, Phillip Tsefung. "Optical frequency division via periodically-poled-LiNbO₃-based nonlinear optics". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80486.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaves 186-194).
by Philip Tsefung Nee.
Ph.D.
43
Cui, A. G. (Aiguo G. ). "Nonlinear Optical Properties of GaAs at 1.06 micron, picosecond Pulse Investigation and Applications". Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc332605/.
Testo completoAbstract (sommario):
The author explores absorptive and refractive optical nonlinearities at 1.06 [mu]m in bulk, semi-insulating, undoped GaAs with a particular emphasis on the influence of the native deep-level defect known as EL2. Picosecond pump-probe experimental technique is used to study the speed, magnitude, and origin of the absorptive and refractive optical nonlinearities and to characterize the dynamics of the optical excitation of EL2 in three distinctly different undoped, semi-insulating GaAs samples. Intense optical excitation of these materials leads to the redistribution of charge among the EL2 states resulting in an absorptive nonlinearity due to different cross sections for electron and hole generation through this level. This absorptive nonlinearity is used in conjunction with the linear optical properties of the material and independent information regarding the EL2 concentration to extract the cross section ratio [sigma][sub p]/[sigma][sub e] [approx equal]0.8, where [sigma][sub p](e) is the absorption cross section for hole (electron) generation from EL2[sup +] (EL2[sup 0]). The picosecond pump-probe technique can be used to determine that EL2/EL2[sup +]density ratio in an arbitrary undoped, semi-insulating GaAs sample. The author describes the use of complementary picosecond pump-probe techniques that are designed to isolate and quantify cumulative and instantaneous absorptive and refractive nonlinear processes. Numerical simulations of the measurements are achieved by solving Maxwell equations with the material equations in a self-consistent manner. The numerical analysis together with the experimental data allows extraction of a set of macroscopic nonlinear optical parameters in undoped GaAs. The nonlinearities in this material have been used to construct three proof-of-principle nonlinear optical devices for use at 1.06 [mu]m: (1) a weak beam amplifier, (2) a polarization rotation optical switch, and (3) optical limiters.
44
Alam, Mohammad Zahirul. "Experiments in Nonlinear Optics with Epsilon-Near-Zero Materials". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41088.
Testo completoAbstract (sommario):
Nonlinear optics is the study of interactions of materials with intense light beams made possible by the invention of laser. Arguably the most trivial but technologically most important nonlinear optical effect is the intensity-dependent nonlinear refraction: an intense light beam can temporarily and reversibly change the refractive index of a material. However, the changes to the refractive index of a material due to the presence of a strong laser beam are very weak---maximum on the order of $10^{-3}$---and tend to be a small fraction of the linear refractive index. It must be noted that at optical frequencies vacuum has a refractive index of 1 and glass has a refractive index of 1.5. Thus, one of the foundational assumptions of nonlinear optics is that the nonlinear optical changes to material properties are always a small perturbation to the linear response. In the 58-year history of nonlinear optics, one of the overarching themes of research has been to find ways to increase the efficiency of nonlinear interactions.
This thesis is a collection of six manuscripts motivated by our experimental finding that at least in a certain class of materials the above long-standing view of nonlinear optics does not necessarily hold true. We have found that in a material with low refractive index, known as an epsilon-near-zero material or ENZ material, the nonlinear changes to the refractive index can be a few times larger than the linear refractive index, i.e. the nonlinear response becomes the dominant response of the material in the presence of an intense optical beam.
We believe that the results presented in this thesis collectively make a convincing case that ENZ materials are a promising platform for nonlinear nano-optics.
45
Hessenius, Chris. "Novel Cavities and Functionality in High-Power High-Brightness Semiconductor Vertical External Cavity Surface Emitting Lasers". Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301667.
Testo completoAbstract (sommario):
Ever since the first laser demonstration in 1960, applications for laser systems have increased to include diverse fields such as: national defense, biology and medicine, entertainment, imaging, and communications. In order to serve the growing demand, a wide range of laser types including solid-state, semiconductor, gas, and dye lasers have been developed. For most applications it is critical to have lasers with both high optical power and excellent beam quality. This has traditionally been difficult to simultaneously achieve in semiconductor lasers. In the mid 1990's, the advent of an optically pumped semiconductor vertical-external-cavity surface-emitting laser (VECSEL) led to the demonstration of high (multi-watt) output power with near diffraction limited (TEM00) beam quality. Since that time VECSELs covering large wavelength regions have been developed. It is the objective of this dissertation to investigate and explore novel cavity designs which can lead to increased functionality in high power, high brightness VECSELs. Optically pumped VECSELs have previously demonstrated their potential for high power, high brightness operation. In addition, the "open" cavity design of this type of laser makes intracavity nonlinear frequency conversion, linewidth narrowing, and spectral tuning very efficient. By altering the external cavity design it is possible to add additional functionality to this already flexible design. In this dissertation, the history, theory, design, and fabrication are first presented as VECSEL performance relies heavily on the design and fabrication of the chip. Basic cavities such as the linear cavity and v-shaped cavity will be discussed, including the role they play in wavelength tuning, transverse mode profile, and mode stability. The development of a VECSEL for use as a sodium guide star laser is presented including the theory and simulation of intracavity frequency generation in a modified v-cavity. The results show agreement with theory and the measurement of the sodium D1 and D2 lines are demonstrated. A discussion of gain coupled VECSELs in which a single pump area accommodates two laser cavities is demonstrated and a description of mode competition and the importance of spontaneous emission in determining the lasing condition is discussed. Finally the T-cavity configuration is presented. This configuration allows for the spatial overlap of two VECSEL cavities operating with orthogonal polarizations. Independent tuning of each cavity is presented as well as the quality of the beam overlap and demonstration of Type II intracavity sum frequency generation. Future applications to this configuration are discussed in the generation of high power, high brightness lasers operating from the UV to far-infrared and even terahertz regimes.
46
Sabra, Ahmad. "Nonlinear PDE and Optical Surfaces Design". Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/345398.
Testo completoAbstract (sommario):
MathematicsPh.D.
We introduce two models to design near field reflectors in R^3 that solve an inverse problem in radiometry, taking into account the inverse square law of irradiance. The problem leads to a Monge-Ampere type inequality. The surfaces in the first model are strictly convex and require to be far from the source to avoid obstruction. In the second model, the reflectors are neither convex nor concave and do not block the rays even if they are close to the source.
Temple University--Theses
47
Hart, Darlene Louise. "Nonlinear dynamics of multiwave mixing in an optical fiber". Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/30047.
Testo completo
48
Rodgers, John Scott. "Multimode interference in a Kerr nonlinear material". Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/13365.
Testo completo
49
Chen, Xin. "Managing light in engineered nonlinear optical structures". Phd thesis, Canberra, ACT : The Australian National University, 2017. http://hdl.handle.net/1885/142957.
Testo completoAbstract (sommario):
Optical frequency conversion process allows one to generate
coherent light in wavelength ranges that are not readily
available. It is well known that because of dispersion, the phase
mismatch between interacting waves leads to low efficiency of
frequency generation. Quasi-phase matching (QPM) that uses
crystals with a spatial modulation of the second-order nonlinear
coefficient χ(2), also known as nonlinear photonic crystals
(NPC), is an important technique to solve the phase mismatch
problem. With proper design of the quadratic nonlinearity
modulation, one can not only obtain efficient frequency
conversion, but also make diverse applications possible,
including beam and pulse shaping, all-optical processing,
entangled photon generation and manipulation.
This thesis explores the fabrication, properties and
application of various types of NPCs. In particular, we discuss
NPC fabricated in single-domain ferroelectric crystals by using
all-optical poling with near infrared femtosecond laser pulses
and high voltage electric poling; as grown ferroelectric crystals
with random sized ferroelectric domains; and orientation
patterned semiconductors grown by hydride vapour phase epitaxy.
Specifically, this research work involved the following topics:
1. Systematic investigation of a novel technique of direct
writing of ferroelectric domains using near-infrared femtosecond
laser pulses. Domain inversion in a LiNbO3 crystal was realized
by its illumination with ultra-short infrared pulses only,
without applying any external electric field. The quality of the
inverted domains was characterized by Cerenkov second harmonic
microscopy (CSHM) and selective chemical etching, respectively.
The optically poled regions were not confined to the surface, but
extended deep into the crystal. This is a significant result
surpassing the capability of the traditional ultraviolet (UV)
all-optical poling technique. As an experimental
demonstration,Abstract x a QPM structure in a LiNbO3 channel
waveguide was fabricated by this infrared laser poling technique
allowing efficient frequency doubling of 815 nm light beam.
2. Experimental studies of the application of as-grown
calcium barium niobate (CBN) crystal for a broadband frequency
conversion. This frequency conversion process is similar to
broadband harmonic generation in commonly used strontium barium
niobate (SBN) crystal, but results in higher conversion
efficiency reflecting a larger effective nonlinear coefficient of
the
CBN crystal. We also analyzed the spatial distribution of the
intensity of the generated radiation as well as its polarization
properties. This study contributes to a simpler and more
efficient realization of broadband frequency conversion devices
in a wide class of nonlinear optical media.
3. Experimental studies of multistep cascading frequency
conversion processes in a custom-cut periodically poled lithium
niobate crystal. By employing the total internal reflection
inside the sample, we combined quasi-phase matched collinear and
Cerenkov nonlinear sum frequency mixing to achieve enhanced
fourth harmonic generation in a single periodically poled
lithium
niobate crystal.
4. Experimental investigation of nonlinear diffraction in an
orientation-patterned semiconductor. By employing a new
transverse geometry of interaction, nonlinear Cerenkov, nonlinear
Raman-Nath and nonlinear Bragg diffractions were identified
according to different configurations of quasi-phase matching
conditions. The study extends the concept of transverse nonlinear
parametric interaction toward infrared frequency conversion in
semiconductors. It also offers an effective nondestructive method
of visualization and diagnostic of spatial variations of
second-order nonlinearity inside semiconductors.
50
Feaver, Ryan K. "Longwave-Infrared Optical Parametric Oscillator in Orientation-Patterned Gallium Arsenide". University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1324048074.
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