Dynamic Beam Switching by Liquid Crystal Tunable Dielectric Metasurfaces

Abstract

Dynamic steering of laser beams by ultra-thin optical metasurfaces is significant research advance for possible applications in remote ranging and sensing. A unique platform for such important functionalities is offered by dielectric metasurfaces having the highest transmission efficiency. However, the realization of dynamically tunable metasurfaces still remains a challenge. Here we demonstrate experimentally the dynamic switching of beam position by all-dielectric metasurfaces composed of silicon nanodisks infiltrated with liquid crystals. In particular, we show the switching of a laser beam from zero to 12 • angle with an efficiency of 50% by heating the metasurface to modify the liquid crystal state from nematic to isotropic. Our results open important opportunities for tunable ultra-thin beam steering metadevices.

Phase-only transmissive spatial light modulator based on tunable dielectric metasurface

“…Firstly, it modifies the permittivity tensor of the LC layer, modulating the refracting index of the environment around the nanoantennas and thus changing the spectral position and intensity of their resonances. 28,36,38 Consequently, the phase induced by the nanoantenna resonances at a particular wavelength changes accordingly. Secondly, the modified permittivity tensor also induces a difference in the phase accumulation in the LC layer itself.…”

“…Recent results have also demonstrated switchable beam deflection at a fixed angle with an LC-integrated gradient metasurface. 28 However, a universal active device which is capable of arbitrary beam manipulation, such as 3D holographic animation or beam steering at multiple angles, has not been demonstrated so far. This type of devices requires uniform pixels which can be switched individually to give rise to the desired phase front, as discussed above.…”

Tunable Metasurfaces Based on Active Materials

“…Later, Komar et al demonstrate electrical tuning of the transmission with similar structures, in which a voltage of 70 V is used to obtain a modulation depth of 75%. More recently, LCs are also used for beam‐steering and controlling the spontaneous emission in Mie‐resonant dielectric metasurfaces . Controlling the efficiency of diffraction into certain orders is realized by a spatially varying silicon nanodisk array infiltrated with LCs .…”

Active control of anapole states by structuring the phase-change alloy Ge2Sb2Te5

“…For the same reason, the majority of research to date still focuses on passive structures, whose functionalities are set in during fabrication and cannot be altered afterward. Whereas there is a growing recognition of the need to realize active dielectric components, most of the published reports so far only display modest resonance shifts [26][27][28][29][30][31][32]. For instance, a pioneering work using liquid crystals as embedding media [27] generates a maximum spectral shift ∆λ ≈ 40 nm at resonance wavelength λ ≈ 1550 nm, corresponding to a relative resonance tuning ∆λ/λ merely 2.6%.…”