Design and fabrication of an achromatic liquid crystal polarization grating with large deflection angle for visible wavelength

Abstract

Traditional liquid crystal polarization gratings (LCPG) are limited to satisfying the half-wave condition at a single wavelength. However, maintaining the high diffraction efficiency across a broad bandwidth presents a significant challenge. In this study, an achromatic polarization grating with a dual-twist structure and a period of Λ=1.5μm was fabricated utilizing liquid crystal polymers and the photo-alignment technology. The performance of this liquid crystal polarization grating was evaluated with the spectrometer and specific wavelength light sources (632nm, 532nm). The results were compared with theoretical simulations. It is shown that grating can achieve a diffraction efficiency exceeding 90% and a large deflection angle ranging from 18.3° to 26.1° between 470 nm and 660nm.