Design and Optimization of pn Junctions in Silicon Microdisk Modulators

An optoelectronic modulator is a key building block in silicon photonic telecommunication circuits. The dominant modulation mechanism uses free-carrier depletion in microring resonators, for its combined advantages of high speed, low power, low spatial footprint, and low fabrication cost and complexity. Recent advancements show that a microdisk modulator, with its pn junction oriented vertically, achieves a larger modulation efficiency due to the stronger interaction with the resonant optical mode. In this work, we verify and compare the simulated performance of metaheuristically optimized lateral and vertical pn junction microdisk modulators that are otherwise identical. We also present two new configurations: The double vertical and staggered double vertical pn junction microdisk modulators. Both of these exhibit stronger mode-junction interactions and greater modulation efficiencies than the state-of-the-art designs.