Study on Supermode Control of External Cavity VCSEL Array with Parallel-Coupled Model

A vertical-cavity surface-emitting laser (VCSEL) is easily made into a two-dimensional array to improve its output power. However, if the near-field complex amplitude output cannot be stabilized in the lowest supermode generated by the fundamental transverse mode, the spot cannot converge on the center normal of the far-field array geometry, and the energy will be diverged. The external cavity is prepared for the VCSEL array, and the output of the array can be stabilized in the lowest order supermode generated by the fundamental transverse mode by supermode control through diffraction coupling. In this study, the parallel-coupled model for the 2-dimensional VCSEL array based on Fresnel diffraction integration was established and used to numerically calculate and analyze the influence on the supermodes' thresholds of different array distributions, array elements' transverse modes and duty ratios versus the length of the external cavity. The simulation results show that the square array provides a wider range of external cavity control length (0.2d(2)/lambda and approximately 0.9 to 1.0d(2)/lambda). The lowest supermode of the fundamental transverse mode can be outputted. For the regular hexagonal array with the length of the external cavity of 0.15d(2)/lambda and 0.6d(2)/lambda. The results have important reference significance for the design of an external cavity VCSEL array, which can control the supermode and obtain VCSEL coherent array beams with high power and near diffraction limits.