MULTIPLE-OUTPUT SEMICONDUCTOR RING LASERS WITH HIGH EXTERNAL QUANTUM EFFICIENCY

The external quantum efficiency of semiconductor ring lasers has been significantly improved by introducing output couplers that couple more light out of the ring cavity, Improvements from 10% and 16% to 14% an d 27% of a comparable single 2x2 MMI coupler device were achieved by u sing 3x3 multimode interference (MMI) couplers and dual 2x2 MMI couple rs, respectively. A further increase to the value of 33% (or 2 times t hat of the previous devices) was obtained by AR coating the output fac ets of the dual 2x2 MMI coupler devices. These devices also provided f our output beams as required in an integrated optical time domain mult iplexing (OTDM) system.