Transverse modes and patterns in electrically pumped vertical cavity surface-emitting semiconductor lasers

Abstract

Vertical-cavity surface-emitting semiconductor lasers (VCSELs) show considerable promise as high-speed spatial light modulators, high-brightness displays, and light sources for parallel optical computing or free-space communication systems. In each of these applications, it is essential to control the transverse mode characteristics. From a more fundamental aspect, VCSELs can provide very large Fresnel numbers (>100), enabling study of a rich variety of spatio-temporal dynamics.1 One important question relates to the symmetry of the modes relative to that of the laser structure, any defects or nonlinear phenomena (self-focusing, many-body effects, gain saturation etc.). Here we report the results of measurements of transverse mode spectra well above lasing threshold, and how these mode spectra can be controlled by external light injection. Our results differ from observations in other lasers,2 in that both Gauss-Hermite modes and Gauss-Laguerre modes were excited in the same laser under the same operating conditions.