Photoconductive heaters enable control of large-scale silicon photonic ring resonator circuits

Abstract

A multitude of large-scale silicon photonic systems based on ring resonators have been envisioned for applications ranging from biomedical sensing to quantum computing and machine learning. Yet, due to the lack of a scalable solution for controlling ring resonators, practical demonstrations have been limited to systems with only a few rings. Here, we demonstrate that large systems can be controlled only by using doped waveguide elements inside their rings whilst preserving their area and cost. We measure the large photoconductive changes of the waveguides for monitoring rings' resonance conditions across high-dynamic ranges and leverage their thermo-optic effects for tuning. This allows us to control ring resonators without requiring additional components, complex tuning algorithms, or additional electrical I/Os. We demonstrate automatic resonance alignment of 31 rings of a 16 × 16 switch and of a 14-ring coupled resonator optical waveguide (CROW), making them the largest, yet most compact, automatically controlled silicon ring resonator circuits to date.

Automated Adaptation and Stabilization of a Tunable WDM Polarization-Independent Receiver on Active Silicon Photonic Platform

“…2(a)), were varied to maximize the measured photocurrent in each MRR. The photocurrent was obtained by subtracting the IRPH's current when the laser was on from the IRPH's current when the laser was off (dark current) [24]. Thus, we obtained a photocurrent signal that is maximized when the ring's resonance is aligned to the laser's frequency.…”

“…Therefore, halting can result in small input power penalties that depend on the chosen threshold. It is worth mentioning that the IRPHs used has a resolution of 1.5 μW [24] and, thus, the power penalty is expected to be low.…”

Scaling capacity of fiber-optic transmission systems via silicon photonics

“…Therefore, control-based solutions are generally preferred for large-scale integration of MRRs. Recently, Jayatilleka et al [234] proposed a photoconductive heater toward automatic resonator locking for large-scale MRR circuits. Figure 19(a) illustrates the photoconductive heater integrated in an MRR.…”

Topological phases in ring resonators: recent progress and future prospects

“…In integrated photonics, however, disorder in the form of nanometre-scale variations to the rings' height and thickness leads to significant misalignment of the individual rings' resonance frequencies, severely degrading the CROW performance [57]. Therefore, one requires either clever designs that are robust against these fabrication variations [58] or active tuning to compensate for the disorder [44,59].…”

“…(B) Coupled spoof plasmon ring resonators formed by subwavelength metal pillars, adapted from the study by Gao et al [43]. (C) Fourteen-ring coupled resonator optical waveguide on silicon integrated with thermal tuners, adapted from the study by Jayatilleka et al [44]. (D) Coupled fibre loops, where photodiodes are used to monitor the propagation dynamics by tracking the intensity within each loop, adapted from the study by Bisianov et al [45].…”