Beam-shaping of laser diode stack for uniform illumination by cylindrical micro-lenses

Abstract

A novel beam-shaping method which obtains nearly uniform illumination for a high-power Laser Diode (LD) stack is introduced. Based on the properties of the angular distribution during the Gaussian beams propagate, a flat-topped beam profile can be achieved by the superposition of Multi-tilted Gaussian beams. Due to the theory above, the individual lensing techniques are introduced to shape the beams of the LD stack. Cylindrical lenses are used to control the divergence-angle of the output beams. By adjusting the offset of each cylindrical micro-lens, each output beam on the fast axis gains the different tilted emitting-angle. Meanwhile the beams on the slow axis are also shaped by a large cylindrical lens. Thus the beam-shaping optical system is designed to reconfigure the beams of a high power LD stack to form a Multi-tilted Gaussian beam shape for a 10°×10° field-angle illumination. The simulation results from ASAP software show that uniform illumination can be obtained in the far-field district. With the proper uniformity and high efficiency, the beam-shaping optical system we have proposed for high-power LD stacks can be well suitable for laser illuminator in laser active imaging and detecting system.