High performance total internal reflection type optical switches in silicon-on-insulator

The requirement of a precise and controllable reflection interface in total internal reflection type optical switches is widely acknowledged. When these switches are based upon carrier injection such as those fabricated in silicon-oninsulator the ability to set up a precise reflection interface becomes difficult due to the diffusion of carriers. This diffusion of carriers across the reflection interface creates a refractive index gradient which is likely to cause the input light to be imperfectly reflected into the output port, which is obviously less efficient than reflection from a precise interface in terms of loss due to the absorption by the free carriers and the directivity of the reflected wave. In our work we propose the use of a barrier positioned along the reflection interface, and around a completely enclosed injection region to prevent diffusion of carriers, and therefore set up a precise reflection interface. The barrier will also improve the injection efficiency since the carriers are being injected into a much smaller volume. This will, in turn, lead to a reduced switching current and faster switching speeds. This paper reports the modeling of the device and predicts the bandwidth performance for one specific switch design.