Comparative Study of Nano-Cylindrical Waveguide and Buried-SiO2 Apertures in Blue InGaN VCSELs

Paper in proceeding, 2025

We study transverse mode control in InGaN-based blue vertical-cavity surface-emitting lasers (VCSELs) by investigating the most common index-guiding structure which is an etched nano-cylinder with and without a refill of SiO2. Using 2−8μm wide aperture diameters, we evaluate key performance metrics-threshold material gain (gth) and modal discrimination. The etched aperture with a 5 nm etch depth exhibited the lowest threshold material gain among the designs studied. Notably, this configuration showed the smallest increase in threshold material gain when the aperture diameter was reduced from 8μm to 2μm. Furthermore, when decreasing the aperture from 8μ m to 4μm, the gth  for the fundamental L P01 mode increased by just 95 cm−1, while still achieving a high modal discrimination of 395 cm−1. These results highlight the ability of the etched aperture to maintain low loss and strong mode selectivity over a practical range of aperture sizes.