CONTROL OF UNIDIRECTIONAL OSCILLATION IN SEMICONDUCTOR ORBITER LASERS

Unidirectional oscillation in a ring-resonator-type semiconductor laser is demonstrated in a square-shaped orbiter laser using an optical feedback mechanism for the first time. The bistable switching phenomenon between the unidirectional and bidirectional oscillation is observed synchronized with the switching of the longitudinal lasing mode. A longitudinal-mode bistability results from the compound cavity system formed by the orbiter laser and the output waveguide. The feedback light from the output waveguide end interferes with the orbiter lasing light. Switching between the unidirectional and bidirectional oscillation is controlled by injecting a current into the output waveguide, which varies the phase condition of the feedback light.