Programmable liquid crystal photoalignment for Pancharatnam-Berry phase wavefront manipulation

Wavefront manipulation provides a powerful approach for generating complex optical fields. However, realizing sophisticated wavefronts requires both careful phase design and flexible physical implementation. Here, we present a general phase-design framework based on optical interference theory and angular spectrum propagation method, enabling the design for complex focusing functionalities from prescribed optical field distributions. To verify the proposed methodology, we implement the designed phase profiles by developing a programmable photoalignment system based on a liquid-crystal-on-silicon spatial light modulator (LCoS-SLM), which enables arbitrary in-plane liquid crystal polymer (LCP) alignment profiles to be generated through a single-step exposure. The developed system provides a spatial resolution of 3.6 μm and a linear relationship between angle of polarization and input grayscale. By encoding the designed phase distributions into the LC director orientation through the Pancharatnam-Berry (PB) phase, a series of LCP devices producing multiple focal spots, spiral focal lines, 2D and 3D focal distributions, and multi-wavelength focal patterns are designed and fabricated. The measured optical responses show good agreement with theoretical predictions and numerical simulations, demonstrating the validity and versatility of the proposed phase-design framework. This approach provides a viable route for precise wavefront control and the design and fabrication of advanced LC optical devices.