Abstract

External laser cavities have been used to improve the performance of single-stripe semiconductor lasers, broad-area lasers, and semiconductor-laser arrays. The external laser cavity is no longer restricted to a planar topology, and this provides a degree of flexibility and control over a two-dimensional array that does not exist for a monolithic structure. Micro-optics can be introduced to shape and modify each laser beam; other optical devices, such as spatial filters and gratings, can affect the entire ensemble of beams, assisting in establishing mutual coherence and wave-front control. Several different external cavity structures are compared and contrasted in this presentation. Cavities based on spatial filtering are shown to exhibit good discrimination between lateral modes and can be miniaturized by using graded-index lenses. Talbot cavities can also provide laser coupling and lateral-mode discrimination with overall lengths of a few millimeters. Fractional-Talbot cavities have recently been demonstrated with cavity lengths as small as 200 µm. Finally, interlaced arrays of microlenses and micromirrors have been shown to provide aperture filling and laser coupling with overall cavity lengths of 100 µm.

© 1990 Optical Society of America