Mechanically Tunable Geometric Phase Optical Element Based on Cholesteric Liquid Crystal Elastomer

ABSTRACT

Modulation or tuning of geometric phase optical elements significantly broaden their working wavebands in multifunctional integration and capability of complex wavefront manipulation. Among various tuning mechanism, mechanical tuning provides a straightforward, energy‐efficient, and fast‐response method. However, current mechanical tuning method mainly focuses on metasurface based geometric phase optical elements, which usually faces complex fabrication process, high fabrication cost, and limited stretching ratio due to the limited elastic properties of metals. Herein, we propose mechanically tunable geometric phase optical element based on cholesteric liquid crystal elastomer (CLCE). Two typical geometric phase optical elements of CLCE grating and CLCE lens have been demonstrated, which shows the dynamic tuning capability both in diffraction angles/focal length, central wavelength, as well as diffraction efficiency during reversible mechanical modulation. Furthermore, an electrically tunable CLCE grating is successfully integrated through combining the CLCE grating with dielectric elastomers actuator, which provides fast tuning capability and compact design in beam manipulation. The proposed mechanical tunable geometric phase optical elements fabricated by CLCE provide a novel strategy for the development of new optical modulation devices in simultaneous wavefront control and dynamic operational band tuning for circularly polarized beam manipulation and display systems.