Equal-intensity beam splitter fabricated by segmented half-wave plate for passive laser speckle reduction.

An equal-intensity beam splitter (EIBS) for passive laser speckle reduction is reported. The EIBS consists of a segmented half-wave plate (SHWP) with the designed orientation of the fast axis of each segment, a polarization beam splitter, and a mirror. The SHWP is fabricated using patterned photoalignment material and liquid crystal polymer. Ten laser sub-beams are generated by the twenty-one-pixelated EIBS, where the largest intensity ratio among them is 7.6. Laser temporal and spatial coherences are destroyed because of the optical path delays among the laser sub-beams. The EIBS is used to reduce laser speckle passively, and objective speckle contrast is reduced from 0.82 to 0.33 when all 10 laser sub-beams are used.