Ultralow-Power Double Vertical Junction Microdisk Modulators

One of the most critical elements in a data center transceiver is the optoelectronic modulator. In a silicon-based optoelectronic modulator, the ultimate performance depends on the orientation and positioning of its pn junction(s). In comparison to a conventional, lateral pn junction, a vertical pn junction improves energy efficiency by having a stronger overlap with the resonant optical signal. Adding to this design philosophy, we present two new designs of vertical junction modulators: (i) a double vertical junction, which doubles the interaction length, and (ii) a staggered double vertical junction, which further increases the interaction length by adding a lateral component to the double junction design. In this work, we provide a comprehensive numerical comparison of microring/disk modulators between the conventional, lateral pn junction and our vertical pn junction designs. We demonstrate how our new double vertical junction configurations offer the most promising power performance characteristics, with an energy-efficiency improvement by over a factor of 4. Our work may pave the way for new, energy-efficient silicon modulators in next-generation information processing and communications.