Quasi-exact optical analysis of oxide-apertured microcavity VCSELs using vector finite elements

We report a new full vector finite element model for analyzing the optical properties of azimuthally symmetric oxide-apertured vertical-cavity surface emitting lasers (VCSELs). Our model allows for quasi-exact calculation of the lasing mode blueshift, threshold gain, and field profile. Through a detailed analysis of a sample VCSEL, we ascertain the physical effects which determine diffractive or parasitic mode loss. They are: 1) the background density of parasitic modes and 2) the coupling strength between the lasing mode and the parasitic mode continuum. The coupling strength is in turn determined by the relative alignment between the lasing and parasitic mode propagation vectors and the lasing mode penetration into the oxide region. This analysis improves our understanding of the optical physics of apertured VCSELs and should enable the next leap down in lasing threshold.