Design and analysis of dual-cavity VCSELs

Dual-cavity Vertical-Cavity Surface-Emitting Lasers (VCSELs) provide an effective platform for controlling longitudinal mode behavior. This paper presents a comprehensive numerical investigation of dual-cavity VCSELs with both tuned and detuned cavity configurations, separated by a finite intermediate Distributed Bragg Reflector (DBR). Cold-cavity optical modes, supermode field distributions, and modal parameters are analyzed using a full-vectorial Finite-Difference Frequency-Domain (FDFD) solver implemented in Crosslight’s PICS3D. For tuned cavities, the optical coupling coefficient is extracted directly from the supermode wavelength splitting and correlated with the threshold behavior. For detuned cavities, intentional cavity-length mismatch leads to strong supermode localization and asymmetric gain overlap, resulting in preferential lasing of a single supermode. These results demonstrate that cavity detuning combined with an optimized intermediate DBR thickness provides a robust design approach to control VCSEL’s operation parameters.