Phase-locked injection laser arrays with variable stripe spacing

A phase-locked injection laser array is described which utilizes variations in spacing of identical lasing elements to vary the coupling between them. In general, phase-locked arrays have been fabricated as periodic structures with uniform coupling, although arrays with different element sizes have been described. An important advantage of the variable spacing array (VSA) structure over those designs is that the fundamental array mode can be readily matched to a uniform pumping profile across the entire array aperture. This allows the variable spacing arrays to be optimized for high-power operation. A coupled-mode analysis indicates that excellent matching of fundamental array mode to a uniform gain distribution can be obtained. However, for some array geometries the operation of array modes other than conventional 0 and 180° phase shift modes is enhanced. Variable spacing arrays have exhibited phase-locked behavior to CW outputs as high as 80 mW (7 elements) and single longitudinal mode operation to powers > 50 mW. Observation of the array emission patterns confirms the results of the coupled-mode analysis.