Optical beam characteristics of Schottky barrier confined arrays of phase-coupled multiquantum well GaAs lasers

The characteristics of phase-coupled laser arrays fabricated using Schottky barriers on the p-contact to confine the current flow to 5 or 10 stripes on 9 μm centers are described. The gain guided laser spots are very equally spaced, and in some cases do not coincide exactly with the position or number of conducting stripes. The self adjusting nature of the active region, together with the phase shift of π between the neighboring
N
laser spots results in extremely smooth far-field patterns consisting of 2 narrow, intense outer lobes, and
N-2
much weaker interior lobes. The mode structure closely approximates the higher order modes observed in wide stripe laser. The separation and width of the outer lobes is defined by diffraction theory, and determined by the separation and number of lasing spots. Deviations from diffraction theory are found in some cases. The contributions to the far field were studied by examining the magnified image of the exit facet as a narrow slit was passed across the far field. The phase contributions present in the far field were studied by introducing a relative phase shift between the two symmetric halves of the far field. The relative phase change modifies the interference pattern of the magnified near-field image, causing a spatial shift of the imaged spots in the plane of the junction.