An enhanced model for the modulated reflectance spectra of vertical‐cavity surface‐emitting laser structures

Abstract

AbstractModulation spectroscopy has proved to be unique in being able to probe the vital active‐layer quantum well (QW) transitions in vertical‐cavity surface‐emitting lasers (VCSELs). We have been characterising an all‐AlGaAs‐based VCSEL structure designed to operate at high temperatures, using photo‐modulated reflectance (PR) as a function of temperature up to 180 °C. We previously developed an empirical model to fit VCSEL PR spectra when the features from the QW transitions and the Fabry–Perot cavity mode (CM) overlap and interact, and this fitting function has, so far, proved to be very successful. However, the present VCSEL has a particularly high finesse cavity and our established model is unable to fit the unusually detailed interacting CM/QW PR spectra. Here, we perform new reflectivity calculations for this VCSEL structure. These provide new insight into the Seraphin coefficients of the CM, and their inter‐relationship, when they lie near the QW transitions. This deepens our understanding of VCSEL PR lineshapes, yielding an enhanced model which we successfully fit to the temperature‐dependent PR spectra of the present VCSEL. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)