Low-threshold InGaAsP ring lasers fabricated using bi-level dry etching

We report a novel bi-level etching technique that permits the use of standa rd photolithography for coupling to deeply etched ring resonator structures . The technique is employed to demonstrate InGaAsP laterally coupled racetr ack ring resonators laser with record low threshold currents of 66 mA. The racetrack laser have curved sections of 150-mu m radius with negligible ben ding loss. The lasers operate continuous-wave single mode up to nearly twic e threshold with a 26-dB side-mode-suppression ratio. Bi-level etching is o f interest for fabrication of mesoscopic or microcavity photonic resonator structures without relying on submicrometer processing.