The research effort proposed here consists of three parts: MBE growth of nonlinear materials, semiconductor physics of those materials, and nonlinear devices using those materials. Attention will be focused initially on growing GaAs.based structures and devices such as bulk, single. and multiple.quantum.well samples, Fabry.Perot etalons with monolithic mirrors, as well as starting material for nonlinear waveguides and quantum dot structures. The optical properties of the samples will be studied, with special emphasis on the linear and nonlinear optical properties in the spectral regions below the exciton. Studying the absorption tail and its saturation under high excitation is not only very interesting physics, but also helpful for characterizing the quality of the grown samples, and essential for optimum device design and operation. Absorption tail, carrier lifetime, and polarization dependence of the bandgap nonlinearities will be investigated as functions of quantum well widths, growth conditions, and device design. Microlithography and anisotropic etching techniques will be used, to fabricate nonlinear waveguide structures such as directional couplers and Mach.Zehnder interferometers, as well as arrays of semiconductor etalons. Methods to manipulate the carrier lifetime and, hence, the response time of the nonlinear devices will be investigated, and devices will be designed for both low.power operation at relatively low speed and forultrafast optical switching.
