We report our progress towards actively stabilized silicon microring switch arrays for optical interconnects using our recently proposed slope-detection method. The stabilization scheme utilizes an in-resonator all-silicon photomonitor that detects the detuning of the microring resonance wavelength from a carrier wavelength at 1550 nm. The photomonitor utilizes linear sub-bandgap surface-state absorption (SSA) on the unpassivated air-silicon waveguide interfaces. Our experiments demonstrate SSA-based photomonitors with a cavity-enhanced responsivity of ~ 1.9- 2.3 mA/W upon a bias voltage of -1 V. We demonstrate actively stablized 2-by-2 microring switch fabrics with intensity variations of ~1 dB over a temperature modulation of ~7 °C among the four transmission channels.
In this paper we review our recent progress in two complementary approaches to photodetectors on silicon photonic chips for on-chip optical interconnection applications, namely epitaxially grown III-V-on-silicon and all-silicon microcavity-enhanced photodetectors, both for the 1550nm wavelengths. On the epitaxially grown III-V-on-silicon photodetectors front, we have demonstrated both normal-incidence and waveguide-butt-coupled p-i-n photodetectors. We simulate the silicon waveguide butt-coupling to the InGaAs absorption region and estimate the absorption efficiency using a three-dimensional finite-difference time-domain method. We optimize the InGaAs absorption region in order to attain a bandwidth of 46 GHz. We also report our latest experimental demonstration of all-silicon microresonator enhanced linear-absorption photodetectors using defect-state absorption in pn-diode-integrated microresonators. Our initial experiments reveal the measured bandwidths to be exceeding 10 GHz.