Compact, multiplexed, energy-efficient silicon nanophotonic switches

Over the past decade, the benefits of photonics over electronics such as ability to achieve high bandwidth, high interconnectivity, and low latency, together with the high maturity of silicon photonics foundries has spurred robust applications in optical transceivers and in classical and quantum computing. In both application areas, silicon microring resonators (MRRs) using carrier depletion effects in p-n junctions represent the most compact optical switches manufacturable at high volume with 5.2fJ/bit power consumption. Matrix computation approaches as well wavelength-division-multiplexed modulators require several MRRs in series coupled to the silicon waveguide optical bus. Such architectures are potentially limited to ~30 by the limited free-spectral range (FSR) of an individual MRR. However, with ever increasing data volumes, there is a need to process larger matrices and/or modulate more wavelengths in the telecom bands along a single silicon bus channel. Photonic crystal (PC) dielectric structures confine an optical mode to sub-micron mode volumes and have shown the potential to reach 0.1fJ switching energies. Research till date on PC devices have centered on either inline one-dimensional PC nanobeam structures or on two-dimensional PC waveguide coupled microcavity configurations. In this paper, through detailed electrical and optical simulations, we demonstrate the feasibility to achieve compact switches with 1dB insertion loss, 5dB extinction and ~260aJ/bit switching energies in the bus-coupled 1D photonic crystal nanobeam platform. Resonance linewidths <0.1nm and FSR <100nm enable energy efficient computing of larger matrices with ~200 resonators in series separated by ~0.5nm wavelength over the entire C+L bands. Device architectures will be presented.