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

A monolithically integrated master oscillator power amplifier with a grating outcoupler for emitting a collimated beam is demonstrated. In order to improve 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 are incorporated in a new design of the grating outcoupler. The device was fabricated by a simple process without regrowth. Stable single-mode lasing up to 183 mW output power at a wavelength of 985 nm was obtained under CW operation. As a result of optimization to minimize the divergence angle of the output beam, a well-collimated beam, with a nearly circular profile and divergence angles smaller than 0.28 degrees x 0.38 degrees, was maintained in high-power operation.