Helical Structure Endows Liquid Crystal Planar Optics with a Customizable Working Band

Wavefront control lies in the heart of optics. Multi‐degree orthogonal manipulation of light, especially the on‐demand tailoring of the working band and spatial phase front, is expected to fully exhibit the superiority of photons as information carriers. Here, the recent progress on the customizable working band of liquid crystal planar optics enabled by helical structures is reviewed. Broadband transmissive devices with mirror‐symmetric helical structures, broadband reflective Bragg‐Berry phase elements based on cholesteric liquid crystals, transflective phase modulations of a piecewise twisted structure, and external field shifted bands of planar optics are summarized. In addition to the customization of the geometric phase and working band, manipulation of other optical parameters is discussed. The tremendous self‐assemblies and diverse external field responsiveness make liquid crystals a perfect platform for full‐dimensional manipulation of light. Helical liquid crystal based planar optics with arbitrary geometric phase modulation and customizable working band is reviewed. Recent progress on broadband transmissive, reflective, transflective, and external fields stimulated band tunable planar optics with helical structures is summarized. Full exploitation of the freedom of light is discussed, which may inspire the helical liquid crystal based multi‐degree light modulation.