Tunable silicon microring filters are used to demonstrate CMOS-compatible on-chip wavelength control of Er+ doped
fiber-lasers. The filter uses a 10 μm-diameter microring resonator based on single-mode silicon-on-insulator (SOI) strip
waveguides operating around the telecom range of 1.55 μm. A piece of Er+ doped fiber (EDF) serves as the gain media
which is pumped by a 980 nm laser diode. An on-chip Ni-Cr micro-heater consuming up to 38 mW is capable of tuning
the Si microring filter by 2.3 nm with a lasing linewidths narrower than 0.02 nm. This approach enables arbitrary
multiple wavelength generation on a silicon chip. Possible applications include on-chip and chip-to-chip densewavelength
division multiplexed communications, telecommunications and optical sensor interrogation.
Microring resonators (MRs) are important photonic devices for large-port-count photonic circuits owing to their micrometer-scale device sizes. We describe the implementation of a 4×4 wavelength-reconfigurable photonic switch consisting of eight tunable MRs fabricated on a less expensive material platform: silicon on insulator. Wavelength reconfiguration is achieved through independent thermo-optic tuning of MRs with localized Nichrome microheaters fabricated on the same silicon-on-insulator substrate. A free spectral range of 18 nm and a 3-dB linewidth of 0.1 nm were observed for the fabricated MRs with a diameter of approximately 10 µm. The switch device shows negligible channel crosstalk (<0.01 nm) and moderate switching response time (<1 ms). The switch can potentially be scaled up to benefit the development of large-scale integrated photonics.
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 μm<sup>2</sup> per heater area) fabricated on the same silicon
substrate. Owing to the large thermo-optic effect of silicon (Δn/ΔT=1.8×10<sup>-4</sup> K<sup>-1</sup>), 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.