Towards Adaptively Tuned Silicon Microring Resonators for Optical Networks-on-Chip Applications

We propose to monitor the spectral alignment of silicon microring resonators with an optical carrier in the 1300 / 1550 nm wavelengths by photodetecting the microring internal power using a defect-state-absorption-based silicon photodetector integrated along the microring. We can thereby adaptively tune the resonance wavelength based on the photocurrent to compensate the spectral misalignment using either an integrated electro-optical or thermo-optical tuner. Our analysis suggests that the spectral alignment can be preserved within ~±0.01 nm upon an on-chip temperature variation of 10°C or a carrier wavelength drift of ±60 pm, assuming a closed-loop operation time shorter than 900 μs and a total power consumption of ~0.65 mW for 1550 nm and ~1.1 mW for 1300 nm. As a proof-of-concept, we experimentally demonstrate monitoring the spectral alignment using the photocurrents from a silicon microring carrier-injection switch upon a 10 Gb/s data transmission in 1550 nm, while subjecting the switch to a temperature variation between 20 - 33 °C. We further analyze the feasibility of integrating such an adaptively tuned silicon microring resonator into a single-channel M-input N-output (M × N) optical switch-matrix. Our worst-case analysis suggests that a 16 × 16 switch-matrix in an estimated total footprint of ~640 μm × 480 μm imposes an estimated total power consumption of ~167 mW for 1550 nm, and a 13 × 13 switch-matrix in an estimated total footprint of ~520 μm × 390 μm imposes an estimated power consumption of ~185 mW for 1300 nm.