SEMICONDUCTOR CIRCULAR RING LASERS FABRICATED WITH THE CRYO-ETCHING TECHNIQUE

GaAs-AlGaAs multiple quantum well semiconductor circular ring lasers w ith a sigma shape were fabricated by using the deep UV laser-assisted cryo-etching technique, Most of the fabricated lasers had external qua ntum efficiencies of more than 18% which were higher than similar devi ces previously reported. The modal spacing observed from the resonance spectrum near threshold was always several times that corresponding t o the circular oscillation of the ring cavity, The observed modal spac ing was quite consistent with the theoretical result based on a couple d-cavity model.