High-efficiency RGB achromatic liquid crystal diffractive optical elements

Liquid crystal Pacharatnam-Berry phase optical elements (PBOEs) have found promising applications in augmented reality and virtual reality because of their slim formfactor, lightweight, and high optical efficiency. However, chromatic aberration remains a serious longstanding problem for diffractive optics, hindering their broader adoption. To overcome the chromatic aberrations for red, green and blue (RGB) light sources, in this paper, we propose a counterintuitive multi-twist structure to achieve narrowband PBOEs without crosstalk, which plays a vital role to eliminate the chromatic aberration. The performance of our designed and fabricated narrowband Pacharatnam-Berry lenses (PBLs) aligns well with our simulation results. Furthermore, in a feasibility demonstration experiment using a laser projector, our proposed PBL system indeed exhibits a diminished chromatic aberration as compared to a broadband PBL. Additionally, polarization raytracing is implemented to demonstrate the versatility of the multi-twist structure for designing any RGB wavelengths with high contrast ratios. This analysis explores the feasibility of using RGB laser lines and quantum dot light-emitting diodes. Overall, our approach enables high optical efficiency, low fabrication complexity, and high degree of design freedom to accommodate any liquid crystal material and RGB light sources, holding immense potential for widespread applications of achromatic PBOEs.