Vertically coupled microring resonators using polymer wafer bonding

A new technique is presented to make vertically coupled semiconductor microring resonators that eases the fabrication process with devices more robust to ring-to-waveguide misalignments. Single-mode microring optical channel dropping filters are demonstrated for the first time in this configuration with Qs greater than 3000 and an on-resonance channel extinction greater than 12 dB. A 1×4 multiplexer/demultiplexer crossbar array with second-order microrings was also made and exhibited channel-to-channel crosstalk lower than 10 dB