Microring resonators vertically coupled to buried heterostructure bus waveguides

The authors demonstrate all epitaxial semiconductor microring resonators vertically coupled to buried heterostructure (BH) bus waveguides for the first time. Planar vertically stacked waveguides are successfully grown on BH mesas by conducting a two-step regrowth process. This approach is potentially important for any buried waveguide technology where subsequent surface planarity is required. The measured transmission spectra show resonance dips (1.55 similar to 1.60) mum with quality factors, extinction ratios, and free spectral ranges of 2500 -3.5 dB, and 11 nm, respectively, for 10-mum-radii microrings.