All-silicon mode-mixing router based on the plasma-dispersion effect

This paper reports on the theoretical and numerical description of an optoelectronic router integrated in a silicon-on-silicon waveguide structure. The device is based on the mode-mixing principle together with the injection-induced optical phase shift. The structure consists of a single-mode all-silicon input waveguide, followed by a two-mode section, which acts as the active region, and a single-mode output Y-branch to separate the two output channels. The fundamental mode from the input waveguide excites both the fundamental mode and the first higher-order mode in the active region. The spatial interference between these propagating modes produces a periodically repeated optical intensity distribution along the propagation axis. Moreover, the active region is designed to allow a pi shift between the two modes when a bipolar mode field effect transistor, which injects and controls the free carrier plasma inside the active region, is driven from the OFF state to the ON state. By doing so, it is possible to steer light from one output channel to the other. Electrical and optical simulations have been carried out for the evaluation of the performance of the device. These simulations show optical propagation losses around 3 dB cm(-1), an overall crosstalk of -10 dB, a transient rise time of 8.2 ns and a fall time of 7.2 ns.