Droplet-Shaped-Mesa Vertical-Cavity Surface-Emitting Laser Arrays With Narrow Linewidth and Small Beam Divergence

High-power vertical-cavity surface-emitting laser (VCSEL) arrays are increasingly utilized as light sources in modern lidar and three-dimensional optical sensing systems owing to their strong coherence and high beam quality. In this article, a narrow-linewidth in-phase mode output VCSEL array is demonstrated, employing a droplet-shaped-mesa and evanescent wave, to improve the coupling efficiency and coherence. The maximum coupling efficiency is determined theoretically to be 32.6% with a 77.3° droplet tip angle, exactly twice of the total reflection angle. The wavelength redshift rate of the droplet-shaped-mesa VCSEL array is 0.03 nm/mA, which is 30% that of a single VCSEL. The full width at half maxima (FWHM) of the emission spectrum of the fabricated 1 × 2 VCESL array is 0.14nm, which is 32.5% that of the single device. Finally, the far-field divergences at 1/e<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> peak intensity in the horizontal and vertical directions are 8.3° and 8.6°, respectively, which are 47.1% and 46.6% lower than that of a single VCSEL device of the same size.