High-brightness laser diode arrays

There are many applications where incoherent laser diode arrays are useful if high brightness can be maintained. The light emitted from the facet in high power individual devices is approximately 5 MW/cm2/steradian, but methods are needed to maintain this brightness when a number of devices are combined. The typical output is asymmetric in beam divergence and in source size. Several approaches are being evaluated at NVESD to combine linear and 2D arrays and produce a beam divergence of a few milliradians with a nearly symmetrical output. The approaches being explored include turning mirrors, combinations of refractive and diffractive optics, and novel heat sink packages. In preliminary experiments, micro-optics and diffractive optical elements have been used to colliminate the output from a 20 watt CW linear array and produce a 4 X 6 milliradian beam. Brightnesses of more than 1 MW/cm 2 /steradian are projected with improved components.