Bistability and Switching in a Rib Waveguide Resonator

Abstract

Photonic data transmission and processing require highly efficient all-optical elements for signal amplification, switching and data storage. It could be shown experimentally that semiconductor planar resonators can be envisaged as promising candidates [1]. In particular, optical bistability, that has been shown to exist in these configurations, opens a wide field of applications. Because the operating frequencies are near the band gap of the direct semiconductors used the nonlinearities are giant. Hence the critical power for nonlinear effects to occur is fairly moderate. In view of these advantages it might be worthwhile to study such resonators in a waveguide scheme because it can be included into integrated optics configurations. In planar resonators one has not to worry about the absorption, being extremely large near the gap, because the overall thickness is only a few micrometers and they are usually operated in reflection. The situation appears more involved in waveguides. Usually one prefers to exploit the transmitted signal in order to separate input and output channels. Moreover the efficiency of the distributed Bragg reflectors, surrounding the cavity, is usually some orders of magnitude less than that of conventional planar mirrors requiring rather long reflectors. Because the cavity length exceeds that of planar resonators considerably too one has to guarantee that the overwhelming part of the resonator is essentially transparent for the guided mode. This has of course the consequence that it does not contribute to any resonant nonlinear effect. Hence we propose a resonator that is only loaded by a thin layer of nonlinear but absorbing material (GaAs) in the cavity region (see Fig.1).