Department of Physics, Mahindra University, Hyderabad, India.
Department of Electrical Engineering, Mahindra University, Hyderabad, India.
Sci Rep. 2023 Apr 25;13(1):6780. doi: 10.1038/s41598-023-33693-z.
High refractive index dielectic metasurfaces are being increasingly studied for their novel light-matter interactions such as Huygen's lens, absolute transmission and complete absorption. Liquid crystal is a versatile medium with high dielectric anisotropy and hence interaction of light with the dielectric metasurfaces immersed in liquid crystal medium show complex behaviour compared to isotropic media. Most of the investigations on liquid crystal based electromagnetic response of dielectric metasurfaces focus on tunability of resonant frequencies and switching between the resonant states as a function of external stimuli such as electric field, temperature, etc. In the current work we present a detailed numerical investigation based on studies of scattering response, near-field and far-field radiation profiles of cubic Tellurium metasurfaces as a function of liquid crystal orientations in infrared frequencies. We show that the near-field and far-field radiation profiles of primary resonant modes-electric dipoles and magnetic dipoles reorient as a function of liquid crystal orientations. In particular, we study the effect of liquid crystal orientations on novel non-radiative states called anapoles. It is observed that liquid crystal orientations effect the excitation and orientation of anapole states within the Tellurium structures. This paves way for design of an electrically-driven switch between non-radiative and radiative states. Further, controlling the near-field and far-field radiation profiles opens up possibilities in designing liquid crystal based tunable multi-functional metasurfaces which can change the directionality of incident light.
高折射率介电超表面因其新颖的光物质相互作用而受到越来越多的研究，例如惠更斯透镜、绝对透射和完全吸收。液晶是一种具有高介电各向异性的多功能介质，因此与浸入液晶介质中的介电超表面相互作用的光表现出与各向同性介质相比更为复杂的行为。大多数关于基于液晶的介电超表面电磁响应的研究都集中在共振频率的可调谐性以及作为外部刺激（如电场、温度等）函数的共振状态之间的切换上。在当前的工作中，我们基于对立方碲介电超表面散射响应、近场和远场辐射分布的研究，在红外频率下展示了详细的数值研究，这些研究与液晶取向有关。我们表明，主要共振模式——电偶极子和磁偶极子的近场和远场辐射分布会随液晶取向而变化。特别是，我们研究了液晶取向对称为反磁偶极子的新型非辐射态的影响。结果表明，液晶取向影响了碲结构内反磁偶极子态的激发和取向。这为设计电驱动的非辐射和辐射状态之间的开关铺平了道路。此外，控制近场和远场辐射分布为设计基于液晶的可调谐多功能超表面提供了可能性，这种超表面可以改变入射光的方向性。
