Collimating diode laser beams from a large-area VCSEL-array usingmicrolens array

In this letter, we demonstrate the fabrication and bonding of a 1 cm×1 cm monolithic two dimensional (2D) vertical-cavity surface-emitting laser (VCSEL) array. We coupled the array to a matched microlens array to individually collimate light from each laser. We found the beam divergence of the collimated array to be 1.6° (1/e2) for the entire array. Using a 1-cm diameter F2 lens, we were able to focus the collimated beams to a spot of 400 μm in diameter and to couple more than 75% of the array power into a 1-mm core fiber. Our results show that it is possible to uniformly bond large area VCSEL arrays to heat sinks, and to collimate light from each element into parallel beams using a single 2-D microlens array. Our results also show that the brightness of the focused beam can be further increased with a lens to near 10⁵-W/cm² Steradian, a level that is useful for many high-power applications