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.
Liquid crystals metalens (LC-ML) has attracted much attention due to its powerful functions in shaping light field with planar structure and its great application potentials. However, LC-MLs usually suffer from large chromatic aberration resulting from high phase dispersion. Here, we propose and demonstrate achromatic imaging at red-green-blue (RGB) wavelengths 450 nm, 526 nm, and 630 nm with optimized wavelength multiplexed phase coding in a single liquid crystals metalens. The optimized wavelength multiplexed phase coding, which works on three operating wavelengths simultaneously, is introduced via the complex field of summation of the individual optical fields at selected RGB wavelength and can be achieved via photo-patterning an azo-dye doped LC. The optical efficiency of the fabricated achromatic liquid crystals metalens can be optimized by applying appropriate voltages. The proposed achromatic LC-ML at multi-wavelengths is easy to fabricate and has a potential application in the display field.
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