Modeling of above-threshold operation of 2-D antiguided VCSEL arrays

Single-mode operation of a 2-D (square lattice geometry) antiguided vertical cavity surface emitting laser (VCSEL) array was studied numerically. The VCSEL array is composed of transversely uniform layers including the Bragg mirrors, thin spacer and loss layers located between elements and active layer consisted of 3 quantum wells. Besides, the output facet is patterned by windows in the metal electrode. The lasing mode was found as a result of an iterative procedure consisting of light round-trips in the device and active layer recalculations based on solution of 2D nonlinear diffusion equation for charge carriers. 3D bi-directional beam propagation method was developed for round-trip calculation. For linear stability analysis a number of higher-order optical modes were found in the VCSEL array with gain and index distributions established by the oscillating mode. The in-phase mode with constant phase over the array, out-of-phase mode with alternating phase between elements and modes with mixed symmetry were considered. Calculations were made for various lengths of spacings between elements and sizes of the array. 4x4 and 5x5 laser arrays were studied numerically. Favourable conditions were found for lasing the in-phase mode providing high laser beam quality.