A Monolithic Stable-Resonator Semiconductor Laser

Semiconductor lasers with a variety of cavity geometries have been studied for nearly three decades. For wide stripe monolithic lasers (width > 20 μm), nearly all the resonators fabricated so far can be divided into two types: cleaved flat-mirror structures generally employing some form of gain or index guiding [1], and unstable-resonator diode lasers [2,3]. The stable-resonator geometries widely employed in ordinary gas and solid-state lasers [4] have not to date been realized in monolithic semiconductor lasers for a number of reasons. First, the technology to fabricate precisely curved end mirrors has not been widely available until recently. Second, nonlinear saturation and waveguiding effects are strong in semiconductor lasers, and hence lateral gain and index guiding can be expected to deform the modes of stable-resonator lasers at high power levels. Third, the rather weak transverse mode discrimination of stable resonators may not lead to good mode selection in diode lasers having high gain and large output coupling.