Phase shift of liquid crystal-induced resonance tuning in dielectric metasurface at telecommunication wavelength

During the last decade, active metasurface has attracted significant attention from academia and industry because of its unparalleled advantages over conventional technologies. Active metasurface using electrically controlled liquid crystal (LC) is one of the most promising types of active metasurface towards industrial applications. In this work, we report a silicon metasurface immersed in a nematic liquid crystal for transmission amplitude modulation. Tunable resonance was realized by applying an AC voltage and the resonance was tuned in the spectral range of 1524 nm ~ 1573 nm, which covers the telecommunication C band. The corresponding phase shift at 1555 nm with a maximum value approaching 2π was measured using a Michelson interferometer, which supports the tuning of metasurface resonance by LC. As a result, the maximal modulation depth in transmission amplitude of 94% as experimentally recorded at 1530 nm. In addition, the high quality of LC photoalignment on metasurface was evaluated by examining the transmitted light intensity between crossed polarizers. The response time of sub-milliseconds can be obtained, thanks to the thin cell thickness of only 1 μm. The high alignment quality and fast response time demonstrated in this work shows a promising future for metasurface-integrated liquid crystal on silicon (meta-LCoS) spatial light modulators (SLMs), especially for telecommunication applications.