Vivek Krishnamurthy, Yijing Chen, and Qian Wang, "MZI-Semiconductor-Based All-Optical Switch With Switching Gain," J. Lightwave Technol. 32, 2433-2439 (2014)
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
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