Modelling Self-heating in High-power Single-mode Phase-coupled Linear VCSEL Arrays

We investigate the robustness of single-mode (SM) emission in high-power, large-area rectangular vertical-cavity surface-emitting lasers (VCSELs), emphasizing the impact of self-heating effects. Compared to circular geometries, large-area rectangular VCSELs provide improved heat dissipation thanks to their high geometrical aspect ratio, and higher SM output power by means of their patterned reflectivity obtainable by an array of grating reliefs. Self-heating alters the refractive index of the device. We demonstrate, experimentally and numerically, how the related thermal lensing affects the transverse modes. By misaligning the antinodes of the promoted lasing mode and the surface reliefs, self-heating degrades SM operation if not properly accounted for in the relief position design. Combining thermal and optical models, we propose numerically optimized grating relief geometries ensuring robust SM emission across varying operating temperatures.