Liquid crystal Pancharatnam-Berry optical elements

In this paper, we aim to show that liquid crystal films (LCs) with well-defined molecular orientations are an exceptional platform for flat optical devices based on the Pancharatnam-Berry (PB) phase. Especially, the development of plasmonic photopatterning technique in recent years has made it easy to align liquid crystal molecules in to designer orientation patterns with both high spatial resolution and high throughput and thus enables large scale manufacturing liquid crystal optical devices with low costs. Here we present liquid crystal laser beam shapers and microlenses as two examples to illustrate the design principles and the fabrication processes for liquid crystal flat optical elements. In comparison with flat optical devices made of plasmonic or dielectric metasurfaces, liquid crystal flat optical elements are advantageous due to the high optical efficiencies and low fabrication costs.