NEMS-Tunable Dielectric Chiral Metasurfaces

Abstract

Active control of strong chiroptical responses in metasurfaces can offer new opportunities for optical polarization engineering. Plasmonic active chiral metasurfaces have been investigated before, but their tunable chiroptical responses are limited due to inherent loss of plasmonic resonances, thus stimulating research in low loss active dielectric chiral metasurfaces. Among diverse tuning methods, electrically tunable dielectric chiral metasurfaces are promising thanks to their potential for on-chip integration. Here, we experimentally demonstrate nanoelectromechanically tunable dielectric chiral metasurfaces with reflective circular dichroism (CD). We show CD in absoulte reflection over 0.85 in simulation and 0.45 experimentally. The devices enable continuous control of CD by induced electrostatic forces from 0.45 to 0.01 with an electrical bias below 3 V. This work highlights the potential of nanoelectromechanically tunable metasurfaces for scalable optical polarization modulators.

Nano-electromechanical spatial light modulator enabled by asymmetric resonant dielectric metasurfaces

“…We numerically investigate the phase modulation, utilizing the nano-electromechanical displacement in lateral directions 27 , 28 . Every two pairs of nano-bars, is either grounded or connected to an external bias in Fig.…”

“…Achieving similar spatial resolution but with an active metasurface would enable high-speed and high-resolution SLMs in a compact footprint 10 . Many seminal works have been proposed in the context of the active metasurfaces, using various active materials or mechanisms such as transparent conducting oxides 1 , 11 , 12 , liquid crystals 13 , electro-optic materials 14 – 17 , phase-change materials 18 , 2D materials 19 – 22 , electromechanical systems 23 – 28 , and semiconductors 29 . The active plasmonic metasurfaces based on transparent conducting oxides 1 , 11 , 12 have successfully achieved complex modulation.…”

Review of optically active and nonlinear chiral metamaterials

“…The device depicts distinct wavelength resonance shifts, thus enabling strong shifts in CD at specific wavelengths. 64 In another example, a gold filmed metamaterial is fabricated on a substrate. By applying a voltage, the metamaterial goes from a 2D thin film to a 3D chiral nanostructure through nano-kirigami folding.…”

“…In this situation, the liquid crystal is able to locally alter the polarization of the incident light, thereby creating an active optical system for spin-selective light absorption in the near-infrared regime. 75 In a similar vein, liquid crystals have been used 64 (b) A gold metamaterial membrane is bolstered by silicon dioxide pillars that sit on a silicon wafer. The silicon and the gold act as electrodes to implement the reconfigurable structure from a 2D orientation to a 3D orientation.…”

High-efficiency modulation of broadband polarization conversion with a reconfigurable chiral metasurface

“…its polarization states. However, the current recongurable chiral metasurfaces always operate in a narrow frequency range and discrete polarization states, [74][75][76][77][78] and broadband continuous modulation of polarization is seldom reported.…”