Spatial beam switching and bistability in a diode ring laser

Abstract

We report bistable switching of the output direction in certain triangular diode ring lasers. These lasers operate unidirectionally at large drive currents, with up to 98% of the output power emerging from either the clockwise or the counterclockwise direction. The preferred direction can switch back and forth, with a large hysteresis loop, as the drive current is varied. Up to 20 mW of optical power changes direction at each switch. We propose an explanation based on the theory of two-mode competition via gain saturation.