Abstract

The response of an all-optical nonlinear waveguide Mach-Zehnder interferometer (NLMZ) is analyzed using perturbation theory. The theory provides differential equations that describe the amplitude of the waveguide modes as a function of the propagation distance. To become practical, the waveguide device require nonlinear phase shifts of π or more. Therefore, the theoretical investigation of the device emphasizes its fabrication in bulk galium arsenide (GaAs). For the first time, absorption, carrier diffusion, and thermal effects are included in the theoretical investigation of the NLMZ. The effect of carrier diffusion on the nonlinear response of a GaAs waveguide is demonstrated using a self-consistent numerical method. The effect is heavily dependent on the waveguide geometry, and, therefore, should be included in the analysis of nonlinear semiconductor waveguide devices. However, if the diffusion length is large compared to the mode width, carrier diffusion simplifies the investigation since the nonlinear absorption and index change are uniform across the mode. This assumption is used in the modelling of the NLMZ, which predicts that the device should work in bulk GaAs.

© 1988 Optical Society of America