Narrowing the far field of a Y-junction laser array using a customized spatial filter in an external cavity

Abstract
A study of the spatially resolved spectrum of individual emitters in a Y-junction laser array shows that the array is not completely locked. The use of an external cavity with a novel, customized spatial filter is demonstrated to yield a stable output beam, which increases from 1.25 times the diffraction limit at low power to 1.6 times the diffraction limit at 120 mW without shifting.