Ultra-Responsive Phase Shifters for Depletion Mode Silicon Modulators

We propose a novel phase shifter design for carrier depletion based silicon modulators, based on an experimentally validated model. We note that the heretofore neglected effect of incomplete ionization will have a significant impact on ultra-responsive phase shifters. We predict a low VπL product of 0.31 V.cm associated with a low propagation loss of 20 dB/cm. This would enable significantly smaller Mach-Zehnder modulators to be constructed that nonetheless would have low drive voltages, with substantial decreases in insertion loss. The proposed fabrication process is of minimal complexity; in particular, no high-resolution lithographic step is required.