Wavelength reconfigurable photonic switching using thermally tuned micro-ring resonators fabricated on silicon substrate

Micro-ring resonators have been traditionally fabricated using expensive III-V materials such as InP or GaAs. Device tuning is typically to utilize the electro-optic effect of the III-V materials that usually leads to complex device layer structures. As another tuning approach, thermo-optic tuning of micro-ring resonators is commonly achieved by heating up the whole chip. In general, it is more challenging to achieve highly localized heating on a common chip for independent tuning of multiple micro-ring resonators residing on the same substrate. To address these issues, we describe the development of wavelength reconfigurable photonic switching using thermally tuned micro-ring resonators fabricated on a low-cost silicon-on-insulator substrate. Independent tuning of multiple micro-ring resonators, spaced at 250 μm, is realized with highly localized micro heaters (50×50 μm² per heater area) fabricated on the same silicon substrate. Owing to the large thermo-optic effect of silicon (Δn/ΔT=1.8×10^-4 K^-1), 8 mA heating current is sufficient to tune a micro-ring resonator with a 3-dB spectral line width of 0.1 nm by 2.5 nm while creating a minor peak shift of less than 0.04 nm for an adjacent resonator. The switching response time is about 1 ms. A 1×4 wavelength reconfigurable photonic switch device has been demonstrated. With a resonator diameter of approximately 10 μm (greater than 18 nm in free spectral range of each micro-ring resonator), larger port-count switch matrix with wavelength reconfiguration on a small device foot print is feasible for the development of large-scale integrated photonics.