Abstract

We have developed a simple method for measuring the spatial coherence at the output facet of semiconductor lasers and laser arrays. The method uses a double slit to interfere two points (x and x′) of a device nearfield and to produce Young’s fringes in the far field. We then measure the fringe visibility for a series of points. If the visibility is high for all possible pairings (x, x′), we are assured that the array is operating predominantly in a single transverse mode; however, if the visibility varies over the series it is evidence of multiple modes. For the multimode case, if we assume that the device output can be represented as an unlocked superposition of transverse modes, we can use the measured visibility to determine the relative power in each mode.

© 1987 Optical Society of America