Modal characteristics of coupled vertical cavity surface emitting laser diode arrays

The modal characteristics of dual-element coupled vertical cavity surface emitting laser (VCSEL) arrays are analyzed numerically and experimentally. A photonic crystal pattern etched into the top mirror optically defines the two elements of the array that are independently electrically biased. Using a two-dimensional complex waveguide analysis, we incorporate the effects of varying temperature and electron plasma-induced index suppression arising from asymmetric injection. The simulations are compared to experimental characterization of output power, lasing spectra, and far-field beam profile as a function of the two independent injection currents. Three distinct operating regimes are identified for the arrays: single independent local mode; a region of two modes that are primarily localized into a specific cavity; and a region of two supermodes whose fields extend across both elements. This analysis provides a physical intuition for the behavior of the dual-element coupled VCSEL array across its full operating range for emerging applications.