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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.
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