MZI-Semiconductor-Based All-Optical Switch With Switching Gain

In this paper, we propose and design a novel all-optical switch that exhibits switching gain, based on feasibly realizable symmetric passive Mach-Zehnder interferometer with direct bandgap active arms. The switching is based on the absorption modulation of active arms through carrier depletion by a weak data pulse to switch a stronger pump beam. The proposed switch does not require electrical driving, and because of switching gain, it may not require energy-consuming re-shaping and re-amplification stages. Hence, the power requirement is significantly low. We show that by suitably designing the length of the active arms, operating wavelength and operating intensity of the pump beam, a switching gain >2 can be achieved when input signal pulse is less than 1/8× the strength of pump beam. We also show that the slow switch-off time caused by carrier band-filling is circumvented by using an additional delayed signal pulse to deplete carriers in both arms at a faster switch-on rate. With an inherent switching gain, low power operation and a switching speed that can reach ~100 Gbps, it could be a scalable and feasible solution to large scale broadband switching and wavelength conversion for silicon photonics.