Polarization-Modulated Exposure Method for Fabricating Large-Period Liquid Crystal Polarization Gratings

This work presents a polarization-modulated exposure method for fabricating large-period liquid crystal polarization gratings (LCPGs). Conventional fabrication techniques are limited in producing grating periods suitable for small-angle diffraction, restricting the broader integration of LCPGs in beam-steering and polarization-imaging devices. In the proposed approach, a polarization modulation system—composed of a polarizer, birefringent prism, and quarter-wave plate—generates spatially continuous polarization distributions across an expanded beam aperture, enabling the formation of grating periods exceeding 1 mm. Theoretical modeling and fabrication experiments confirm the successful realization of LCPGs with periods up to approximately 1200μm, supporting diffraction angles below 1°while maintaining high polarization selectivity. The resulting gratings exhibit strong potential for small-angle beam separation, multispectral polarization imaging, and chromatic aberration compensation. This technique provides a scalable and efficient route for extending liquid-crystal grating functionality into the mid- and long-wave infrared regimes, offering new design flexibility for high-performance photonic components.