Nonlinear Optical Waveguide Devices in GaAs/AlGaAs

[摘要] This thesis is concerned with the design, characterisation and implementation of an all-optical logic waveguide device. Operation of such a device depends crucially on the fact that it includes a nonlinear material whose refractive index changes if it is subjected to sufficiently intense optical excitation. (This intensity dependance of the refractive index is often expressed by the relation n= no+ n2l, where no is the low intensity refractive index, n2 is the nonlinear coefficient, and I is the intensity of the incident optical radiation.) The optically induced variation in the refractive index is transformed into a nonlinearity in the device transmission by use of certain waveguide properties thus enabling the device to perform all-optical logic operations. The particular work in this thesis concentrates on the Asymmetric Mach-Zehnder Interferometer (AMZI) which is described in Chapter One. The nonlinear material used in this thesis is AlxGa1-xAs because (i), waveguide fabrication technology in this material is well established and reliable, and (ii), the material has a significant optical nonlinearity easily accessible with laser radiation. The thesis begins by introducing nonlinear optical waveguide devices. Chapter Two then reviews the various optical nonlinearities in semiconductors and presents the current theoretical models available for the description of these effects. Chapter Three describes the nonlinear waveguide design process. Included in this chapter are considerations which have to be made for the attainment of optimum optical nonlinear effects. Chapter Four contains the device fabrication details and describes the considerations made during device production. The results of linear and nonlinear characterisation of waveguides are presented in Chapter Five where descriptions of the various experimental details are also given. The Asymmetric Mach Zehnder Interferometer is then examined in Chapter Six where results of both the theoretical and experimental studies are presented. Finally, in Chapter Seven, the conclusions are presented and suggestions for future work are given.

[发布机构] University:University of Glasgow

[关键词] Applied physics, Electrical engineering, Condensed matter physics