Abstract

Varying the laser spacings in diode laser phased arrays provides a potentially useful degree of freedom in the design of these devices. Variable spacing array structures have been proposed for tailoring the supermode field patterns¹ and for achieving supermode discrimination.^2,3 In this work, the supermode structure of nonuniform-spacing arrays is discussed. These structures were analyzed both by using coupled-mode theory and by direct solution of Maxwell’s equations. It was found that varying the laser spacings can be used to tailor the supermode field patterns. In particular, the channel spacings can be designed so that the fundamental supermode exhibits virtually uniform channel excitations, which reduces its beam divergence. However, the variable spacing does not improve the supermode discrimination compared with the case of uniform arrays. In a variable spacing array with N channels, supermodes v and N + 1 − v (v = 1,2, …N) have nearly degenerate modal gains. This is different from the strong supermode discrimination exhibited by chirped (variable channel-width) arrays. New array structures which combine variable channelwidth for supermode control and variable spacing for field pattern tailoring are described.

© 1986 Optical Society of America