Tweaking the Modal Properties of 1.3-μ m Short-Cavity VCSEL—Simulation and Experiment

A modal analysis of both molecular beam epitaxy (MBE)- and metal-organic vapor phase epitaxy (MOVPE)-planarized short-cavity (SC) vertical-cavity surface-emitting lasers (VCSELs) emitting at 1.3 μm is presented. The comparison of simulated threshold gains with experimental threshold current densities, as well as modal gain difference with side-mode suppression ratios, allows the clear identification of design-related limitations with respect to single-mode emission for different active diameters. In particular, the influence of the radial profile of the effective refractive index on the strength of index-guiding is found to depend on the regrowth-type (MBE or MOVPE). Moreover, the impact of strongly absorbing contact layers and surface relief structures on the modal properties of the fundamental mode is investigated. A design proposal for a MOVPE-regrown SC-VCSEL with optimized surface relief structure is given, predicting reduced threshold current densities and increased single-mode optical output powers.