Abstract

We have studied the operation of 2D arrays of vertical-cavity surface-emitting lasers (SELs) in which interelement coherence is maintained via diffraction coupling. SEL subcavities with mirrors M₁ and M₂ are phased locked by reflecting the output of M₂ back into the array with a third mirror M₃, with a round-trip separation from the array of either one-quarter or one Talbot distance. The threshold gain depends on the array fill factor and the particular array mode. For quarter-Talbot cavities the lowest order supermode, which has a single-lobed far field, has the lowest threshold gain for a wide range of fill factors. For large fill factors the threshold gain is low but the supermode gain discrimination is poor. For Talbot cavities our calculation includes the coupling from all neighbors (not just the nearest neighbor), and we find that independent of array size there are four supermodes that are effectively degenerate and that have the lowest threshold gain. All but the "in-phase" supermode can be discriminated against by selective reflection with the mirror M₃. The optimum reflectivity for the mirror M₂ is simply the inverse square magnitude of the coupling matrix eigenvalue.

© 1992 Optical Society of America