在適當的條件下，正向入射激光束令GaAs量子阱微腔產生方向的不穩定性，並生成橫向光學圖案。方向不穩定性的形成是由於極化子，即光子及量子阱激子的強非線性耦合的本徵態，在微腔內散射的結果。電腦模擬顯示，通過一個非常弱的控制激光束，橫向光學圖案可以從一個方向切換到另一個。它可以作為一個全光學開關，而全光開關可有效地改善計算機的性能。 / 本論文先介紹GaAs量子阱微腔的理論及其數值模擬，以顯示GaAs量子阱微腔能夠產生光學圖案和全光學開關。然而，透過複雜的模擬數據去理解其規律及原理實在太困難。為此，我們發展一個低維的群種競爭模型，以理解這些現象。 / 為了分析群種競爭模型，我們應用了一些數學工具，如Gröbner bases 和廣義判式，以減少計算模型的相圖所需的電腦負荷。此外，我們也利用了突變理論來分類和解釋所有相圖中的相界。這個人口競爭模型使我們對不同物理系統中的圖案生成現象有一個全面的定性理解。 / 在本論文的最後一部分，我們研究量子阱雙微腔，即兩個耦合的微腔，而每個微腔中間也有一個量子阱。透過傳輸矩陣的方法，我們獲得了雙微腔的色散關係，並與實驗結果作比較。我們預期沿著這個研究方向在未來能夠加快實現全光開關。 / Under favorable conditions, laser beams incident normally to a GaAs quantumwell microcavity develop directional instabilities and generate transverse patterns in the far field. The directional instabilities are driven by scattering among polaritons inside the microcavity, where the polaritons are the eigenstates of strong linear coupling between the cavity photons and the excitons inside the quantum-well. It has been predicted that the transverse pattern can be switched from one to another by the use of a very weak control beam. It can serve as an all-optical switching, which can potentially be used to improve computers’ performance. / In this thesis, the theory of the GaAs quantum-well microcavity is first introduced and numerical results showing the formation of patterns and the all-optical switching scheme are presented. However, understanding the patterns and their dynamics through numerical simulations turns out to be very complicated. To this end, we derive a low-dimensional population-competition model for the interpretation of these behaviors. / To facilitate the analysis the population-competition model, we apply mathematical tools such as the Gröbner basis and the generalized discriminant to reduce the computational load in finding the ‘phase diagrams’ of the populationcompetition model. Besides, we also make use of the catastrophe theory to classify and explain all the phase boundaries in the phase diagrams. This population-competition model enables us to acquire an overall qualitative picture of pattern formation in various physical systems. / In the last part of this thesis, we use the transfer-matrix method to study the polariton spectrum of a quantum-well double-microcavity, which is two coupled optical cavities each containing a quantum well, and compare the spectrum with the experimental results. We expect our efforts along this direction could expedite realization of all-optical switching in the future. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Tse, Yuen Chi = 分析橫向光學圖案的低維群種競爭模型 / 謝沅志. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 112-119). / Abstracts also in Chinese. / Tse, Yuen Chi = Fen xi heng xiang guang xue tu an de di wei qun zhong jing zheng mo xing / Xie Yuanzhi. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Optical computation and all-optical switching --- p.3 / Chapter 1.2 --- Nonlinear optics and low-intensity ultra-fast all-optical switching of transverse optical pattern --- p.4 / Chapter 1.3 --- Pattern formation and amplitude equation formalism --- p.6 / Chapter 1.4 --- Semiconductor quantum-well double-microcavity and transfermatrix method --- p.9 / Chapter 2 --- Semiconductor quantum-well microcavity --- p.10 / Chapter 2.1 --- Physical configuration and theroy --- p.10 / Chapter 2.2 --- Simplified models --- p.19 / Chapter 2.3 --- Directional instability and the effect of anisotropy in model PCO-Q --- p.25 / Chapter 2.4 --- Effect of control beam and all-optical switching in PCO-Q --- p.30 / Chapter 2.5 --- Simulation results of model PCO-L, a model without quadratic dependence --- p.33 / Chapter 3 --- Population-competition model --- p.37 / Chapter 3.1 --- Derivation of PC model --- p.37 / Chapter 3.1.1 --- Approximation from the simulation results --- p.38 / Chapter 3.1.2 --- Adiabatic approximation for the field equations --- p.39 / Chapter 3.1.3 --- Revised dynamical equations --- p.40 / Chapter 3.1.4 --- Taylor expansion approximation about phase locking --- p.42 / Chapter 3.1.5 --- Comparison with the simulation results --- p.45 / Chapter 3.1.6 --- Modelling of the control beam --- p.47 / Chapter 3.1.7 --- Reduction in the number of parameters --- p.47 / Chapter 3.2 --- Physical meaning of the simplified PC model --- p.49 / Chapter 3.3 --- Comparison with amplitude equations formalism and others competition models --- p.49 / Chapter 4 --- Mathematical tools --- p.52 / Chapter 4.1 --- Steady states and linear stability analysis --- p.52 / Chapter 4.2 --- Gröbner basis --- p.54 / Chapter 4.3 --- Generalized discriminant --- p.55 / Chapter 4.4 --- Algorithm for conditions for qualitative changes --- p.56 / Chapter 4.5 --- Reduction in computational power --- p.57 / Chapter 4.6 --- Elementary catastrophe theory --- p.58 / Chapter 5 --- Population-competition model analysis --- p.66 / Chapter 5.1 --- Symmetric model L without source term --- p.67 / Chapter 5.2 --- Symmetric model Q without source term --- p.70 / Chapter 5.3 --- Asymmetric model L and Q without source term --- p.74 / Chapter 5.4 --- Symmetric models L and Q with control beam S₂ --- p.80 / Chapter 5.5 --- Asymmetric Model L and Q with control beam S₂ --- p.81 / Chapter 6 --- Semiconductor quantum-well double-microcavity --- p.91 / Chapter 6.1 --- Motivation --- p.91 / Chapter 6.2 --- Transfer-matrix method inside dielectrics --- p.94 / Chapter 6.3 --- Transfer-matrix method across QW --- p.97 / Chapter 6.4 --- Analysis of the QWDM through transfer-matrix method --- p.98 / Chapter 7 --- Conclusion and Outlook --- p.105 / Chapter 7.1 --- Conclusion --- p.105 / Chapter 7.2 --- Outlook --- p.107 / Chapter 7.2.1 --- Extension of the PC model --- p.107 / Chapter 7.2.2 --- Extension of the transfer-matrix method to nonlinear analysis --- p.109 / Bibliography --- p.112 / Chapter A --- Dispersion relations inside QWM --- p.120 / Chapter B --- Analysis on the steady states with and without off-axis instability --- p.122 / Chapter B.1 --- Steady states of E₀ and p₀ --- p.122 / Chapter B.2 --- Analysis on the steady states without off-axis instability --- p.123 / Chapter B.3 --- The effects of instability on E₀ and p₀ --- p.124 / Chapter C --- Analytical derivation of the phase diagram asymmetry versus quadratic terms (δβ1 vs γ) without control beam (S₂ = 0) --- p.127 / Chapter D --- Verification of the elliptic umbilic (D₋₄) singularity --- p.129

An Zhong. / "November 30, 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. [167]-173). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

This thesis discusses nonlinear effects, such as modulation instability and solitons in nano-structured waveguides. The nanoscale optical waveguides have extremely small transverse dimensions, which can provide tight confinement of light. Therefore, by changing the waveguide geometry, the waveguide dispersion can be strongly altered. On the other hand, the confinement also enhances the nonlinear dispersion, allowing for nonlinear optical phenomena supported by dispersion of nonlinearity. The new models governing evolution of the amplitudes of components of the optical waves interacting in the waveguides are derived for continuous wave and pulse wave using perturbation expansion method. The new modulation instability condition is found, as we take into account the dispersion of nonlinearity which is enhanced through a strong variation of the modal profile with the wavelength of light in sub-wavelength waveguides. We demonstrate that this dispersion of nonlinearity can lead to the modulation instability in the regime of normal group velocity dispersion through the mechanism independent from higher order dispersions of linear waves for continuous wave. We address that the new mechanism highly associated with dispersion of nonlinearity in sub-wavelength semiconductor waveguide induces the modulation instability in picsecond regime together with the cascaded generation of higher-order sidebands. The impact of the dispersion of nonlinearity on spectral broadening of short pulses in a silicon waveguide also is considered. We study the temporal evolutions of fundamental and one-ring solitary waves with phase dislocation in dielectric-metal-dielectric waveguides with PT-symmetry and numerically analyze the properties of these nonlinear localized modes and, In particular, reveal different scenarios of their instability.

Thesis (Ph. D.)--Washington State University, May 2007. / Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 130-138).

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Synthesis and physical characterizations of a novel class of zwitterionic organic chromophores were carried out. A series of tetracyanoquinodimethane (TCNQ) derivatives was prepared from reactions with primary and secondary amines. By modifications of the structure it was hoped to optimize their nonlinear properties. The newly synthesized organic chromophores were highly polar, zwitterionic and transparent at wavelengths above 600nm, which is a requirement for waveguide devices at 650nm. The molecular dipole moments were determined experimentally and theoretically. The experimental dipole moments and the theoretical dipole moments were found to be in agreement. The nonlinear optical properties of the new compounds were studied using the Kurtz powder technique. Large second harmonic generation was observed from 7-(2,6, dimethylmorpholino)-7-(4-methylpiperidine)- 8,8-dicyanoquinomethane (25 times urea) as a result of the noncentrosymmetric crystal lattice (P2(_1)2(_1)2(_1)). A large twist between the donor moieties and the benzene ring was found from the crystallographic data, and compared with a theoretical model using an ab initio calculation. Strong fluorescence was observed in the solid states and glass forming solvents at low temperatures. An increase of the quantum yields as a function of viscosity was observed due to the constraining effect of the environment. Variations in the quantum yields from chromophore doped polymeric matrices such as PMMA at room temperature and at low temperature are attributed to the different "free volume" of the polymeric matrices. Possible mechanisms for the emission process in either viscous or non-viscous media are proposed. Photodegradation in solution was observed for illumination by a white light source. In parallel studies photodegradation in PMMA films was observed both in air and under vacuum. A possible photodegradation mechanism via free radicals, compatible with these experimental observations is suggested.

Bibliography: leaves 220-230. / iv, 230, [25] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis performs a modeling study on a number of sterically constrained aryl-alkyne type systems with the results being used to guide subsequent synthetic efforts. Disulfide, silylene, stannyl, oxalate and 1,2-dioxaethyl and 1,3-dioxapropyl linkages are investigated as candidates to constrain the rotation of the tolane substructure. A preliminary Z-scan experiment is developed and is demonstrated as being able to detect optical nonliniarities. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 1997?