Stability and excitation of nonlinear guided waves.

摘要

The nonlinear guided-wave format has been considered as the prime architecture for all-optical computing and signal processing. This thesis addresses two fundamental aspects of nonlinear guided waves: stability and excitation. Using both the kinematic and the dynamic approaches, we prove that the evolution (hence the stability) of nonlinear guided waves is governed by the generalized nonlinear Schrodinger equation (gNLSE) which simplifies into the conventional nonlinear Schrodinger equation (NLSE) under certain approximations. Stability of nonlinear guided waves via the gNLSE is studied consistent with the causality requirement, which seems to have been ignored in many previous studies involving the NLSE. The concept of convective and absolute instabilities are introduced.; The grating and the prism excitation, used in the excitation of linear guided waves, are also applicable in the excitation of nonlinear guided waves. However, the efficiency of excitation decreases as the incident intensity increases. There exists a critical intensity beyond which the efficiency of excitation decreases exponentially with the increase in the incident intensity. We propose to use chirped and/or tapered grating to compensate the phase mismatch due to the nonlinear nature of the excitation process. The excitation efficiency can be enhanced to exceed the maximum linear excitation efficiency when proper chirping and tapering are used.; As an example of the application of nonlinear guided waves, the thesis is concluded by studying the surface-enhance second-harmonic generation mediated by the nonlinear surface polariton.