Design of two-dimensional diffractive optical elements for beam shaping of white light

Laser diodes (LDs) can not only be used for solid-state illumination, but also have broad applications in visible light communication (VLC) due to large modulation bandwidth. In order to realize the bifunctional applications of both laser illumination and visible light communication, the red-green-blue (RGB) LDs of synthetic white light should have the same shape and uniform intensity in the illumination region. Here, we propose and demonstrate the beam shaping and uniformity function at red-green-blue wavelengths of 450 nm, 532 nm, and 625 nm by a single two-dimensional diffractive optical element (DOE). By using the iterative algorithm in conjunction with the optimization algorithm and variable weight, the proposed device can achieve an average energy efficiency of 81.27% and an average light spot uniformity of 91.64% under RGB trichromatic lighting conditions. Experimental fabrication of the proposed DOE was fabricated using UV laser direct writing photolithography, and the experimental results show that an average energy efficiency of 60.25% and an average uniformity of 83.76% of a rectangular spot at three wavelengths of RGB can be obtained, and excellent beam shaping and homogenization under composite white light illumination can also be achieved by the fabricated two-dimensional DOE.