Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references. Also available in electronic version.

As natural chiral materials demonstrate limited circularly dichroic contrasts, enhancement of these polarization dependent signals has long been the focus of chiral metamaterial research. By manipulating the geometric chirality of resonant plasmonic nanostructures, we are capable of enhancing light confinement to amplify chiral modified, nonlinear signals from quantum emitters. The metamaterial demonstrates a linear transmission contrast of 0.5 between left and right circular polarizations and a 20× contrast between second harmonic responses from the two incident polarizations. Nonlinear and linear response images probed with circularly polarized lights show strongly defined contrast. As a second set of experimentation, the chiral center of the metamaterial is opened, providing direct access to place emitters to occupy the most light-confining and chirally sensitive regions. The resulting two-photon emission profiles from circularly polarized excitation displays mirrored symmetry for the two enantiomer structures. The efficiency of the nonlinear signal directly correlates to the chiral resonance of the linear regime. The nonlinear emission signal is enhanced by 40× that of the emitters not embedded in the metamaterial and displays a 3× contrast for the opposite circular polarization. Such manipulations of nonlinear signals with metamaterials open pathways for diverse applications where chiral selective signals are monitored, processed, and analyzed.

The fundamental limitations on the operation of optical bistable devices in a ring cavity and in GaAs etalons are investigated. Experimental results of spontaneous transitions due to shot noise fluctuations are found in good agreement with various "ladder" models, if one allows the counting rates to vary accordingly. Stability analysis for two-photon homogeneously broadened media reveals single-wavelength instabilities for the laser but not for absorptive optical bistability. Appreciable regions of sidemode gain exist for both problems allowing for multiwavelength instabilities to occur. GaAs bistable devices show attractive features such as low power and high speed at room temperature for optical processing. However, experimental evidence in GaAs confirm the computer simulations of bistability that cavity losses, due to unsaturable background absorption, limit the switching power at room temperature. Methods to overcome the different limitations in GaAs devices toward parallel computation are then addressed from a system approach.

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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.)--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.