Novel Silicon Microring Resonators And Their Applications

Microring resonators(MRRs)are critical building blocks in integrated photonics.Silicon offers them unprecedented reduction in size,which in turn enables large free spectral ranges(FSRs).These microring resonators with large FSRs are suitable for building wavelength multiplexers.There is one drawback,its fabrication sensitivity.A flat-top spectral reponse is one way to make robust filters and multiplexers.A wavelength division multiplexing system carries light signals on different wavelengths.This property of optical communication boosts the communication capacity.However,the cost and power scales with the number of channels.Polarizations and modes of a silicon nanowire provide extra dimensions rather than wavelengths.We proposed novel polarization-selective microring filters.It shows resonances for one polarization mode and depressed resonances for its orthogonal polarization.We fabricated TM-type MRRs and TE-type MRRs.They demonstrated high polarization selectivity over broadband(from 1520nm to1610nm).Its application involves hybrid PDM-WDM systems.We developed cascaded microring filters based on the polarization-selective MRR.The cascaded microring filter has a large free spectral range and a flat-top response with a 3dB bandwidth of 2nm.Based on cascaded microring filters,we built a wavelength multiplexer,with 8 wavelength-channels(channel spacing=400GHz)and high channel isolation(<-25dB).Then we used this wavelength multiplexer to build a 16-channel hybrid PDM-WDM multiplexer and a 32-channel hybrid MDM-WDM multiplexer.A flat-top spectral response is one way to mitigate MRRs'sensitivity to fabrication.Another is post-fabrication trimming.We proposed and experimentally verified a novel approach,local-etching technique.It has a large trimming range and high scalability.Finally,we summarized the progress we made and shared some thoughts about further research works.