Optical Self‐Tuning of Ferroelectric Metasurfaces Infiltrated with Nematic Liquid Crystals via Photovoltaic Effect

Abstract There is a growing interest in lithium niobate (LN) as a material for integrated optics and metaphotonics. However, the limited strength of the electro‐optic effect remains a challenge for the realization of optical tunability in LN‐based nanophotonic systems. In this paper, a novel approach is introduced to enhance optical tuning. The proposed mechanism exploits the coupling between the photovoltaic effect induced in ferroelectric meta‐atoms under light illumination and a surrounding liquid crystal (LC) medium. Specifically, the LCs can be locally reoriented by the fringe photovoltaic fields generated by the meta‐atoms, whose spatially‐dependent dielectric anisotropy is modelled with a tensor approach. The LC re‐alignment in the vicinity of the meta‐atoms ultimately results in the self‐tuning of the metasurface optical response. The optical tuning of fundamental electric and magnetic metasurface resonances is numerically demonstrated via multiphysics simulations with and without the presence of an external voltage. This can result in high quality factor optical resonances, and their spectral shifts beyond what is achievable with the sole electro‐optic effect. For the first time to the authors' knowledge, the photovoltaic effect is introduced as a tuning strategy in dielectric metasurfaces, opening new opportunities for reconfigurable nanophotonic devices, such as light modulators, optical limiters, and optical sensors.