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A Laser-Trimming-Assist Wavelength-Alignment Technique for Silicon Microdonut Resonators

A silicon-based microdonut resonator consisting of a multimode microdonut waveguide is realized. The random shift of the resonance wavelength due to the fabrication deviation is greatly reduced to be ~0.91 nm compared with that (~4.93 nm) of those regular microring resonators (on the same chip). For the coupling between the access waveguide and the microdonut waveguide, bent directional couplers are used to suppress the undesired higher-order modes according to the phase-matching condition. A local laser-trimming process with a ~1.1-W blue laser is further applied and can introduce a maximal wavelength shift of ~0.46 nm for the resonance alignment. This letter combines the present microdonut resonator design technique and the local laser-trimming process, which potentially provides a promising approach to realize a micro-resonator array with excellent resonance-wavelength alignment.