Monolithically integrated master oscillator power amplifier with grating coupler for collimated output beam

A monolithically integrated master oscillator power amplifier with a gratin g outcoupler for emitting a collimated beam is demonstrated. In order to im prove the device performance, theoretical simulation is performed based on the beam propagation method, and both compensation for wavefront distortion produced in the amplifier and optimization of the radiation decay factor a re incorporated in a new design of the grating outcoupler. The device was f abricated by a simple process without regrowth. Stable single-mode lasing u p to 183 mW output power at a wavelength of 985 nm was obtained under CW op eration. As a result of optimization to minimize the divergence angle of th e output beam, a well-collimated beam, with a nearly circular profile and d ivergence angles smaller than 0.28 degrees x 0.38 degrees, was maintained i n high-power operation.