Semiconductor circular ring lasers fabricated with the cryo-etching technique

GaAs-AlGaAs multiple quantum well semiconductor circular ring lasers with a /spl sigma/ shape were fabricated by using the deep UV laser-assisted cryo-etching technique. Most of the fabricated lasers had external quantum efficiencies of more than 18% which mere higher than similar devices previously reported. The modal spacing observed from the resonance spectrum near threshold was always several times that corresponding to the circular oscillation of the ring cavity. The observed modal spacing was quite consistent with the theoretical result based on a coupled-cavity model.