Gap-plasmon-driven spin angular momentum selection of chiral metasurfaces for intensity-tunable metaholography working at visible frequencies

Abstract

Tunable metasurfaces can replace conventional bulky active optical modules to realize practical flat optical devices such as lenses, LiDAR, holography, and augmented reality. However, tunable metasurfaces have generally been limited to switching between two distinct states. Here, we present liquid crystal (LC) integrated chiral metasurfaces, of which the metahologram intensity can be adjusted continuously between fully ‘on’ and ‘off’ states. The chiral metasurface consists of a gap-shifted split ring resonator (SRR), and exhibits spin angular momentum selection that reflects left-circularly-polarized light but perfectly absorbs right-circularly-polarized light (99.9%). The gap-shifted SRR realizes spin angular momentum selection using a metal–dielectric–metal multilayer structure and thereby induces a strong gap-plasmonic response, achieving the maximum calculated circular dichroism in reflection (CDR) of 0.99 at the wavelength of 635 nm. With the chiral metasurface, metaholograms are demonstrated with tunable intensities using LCs that change the polarization state of the output light using an applied voltage. With the LC integrated chiral metasurfaces, 23 steps of polarization are demonstrated for the continuous tuning of the holographic image intensity, achieving measured CDR of 0.91. The proposed LC integrated spin-selective chiral metasurface provides a new resource for development of compact active optical modules with continuously-tunable intensity.

Spin‐Selective Absorption and Geometric‐Phase Modulation via Chiral Metasurface in Triple Bands

“…[35,36] Due to the lack of structural symmetry, there exists the coupling between electric and magnetic fields as electromagnetic waves passing through the chiral metasurface, resulting in polarization modulation properties such as circular dichroism and optical activity. [37] Over the past few years, various chiral metasurfaces have been put forward, many intriguing physical phenomena were demonstrated and an ingenious route to control CP waves with a pre-designed manner was afforded, [38][39][40][41][42][43][44][45] including chiral mirrors with spin-selective transmission, [41][42][43] broadband circular polarizers, [40,46] chiralityinduced negative refraction. [38] Moreover, the spin-selective chiral metasurfaces also have been proposed to manipulate the absorption of CP light under reflection mode, that is, one designed CP wave can be reflected without changing its handedness while absorbing the other orthogonal CP wave.…”

Computing metasurface capable of broad-band switchable anisotropic edge-enhanced imaging

“…45 Fortunately, the development of helicity-multiplexing metasurfaces brings great hope for this research. [46][47][48][49] Here, a helicity-multiplexing metasurface (2D material) is designed based on the propagation phase and the geometry phase, which can dynamically switch between two various anisotropic edge enhancement filters only by transforming the polarization of the incident beam. This metasurface is composed of many nanopillars, which are all prioritized to be appropriate for two independent phase profiles.…”

“…45 Fortunately, the development of helicity-multiplexing metasurfaces brings great hope for this research. 46–49…”

Broad-Band Polarization-Insensitive Metasurface Holography with a Single-Phase Map

“…Apart from this, metasurfaces as coding material for holography have attracted a prodigious amount of attention due to their high resolution, ultracompact size, large viewing angle, and high diffraction efficiency. In the past, various significant achievements such as high-efficiency metaholograms, − multiplexed metaholograms, − and multicolor metaholograms have been reported. Among all types of metasurface-based holograms, polarization-independent metaholograms become a fascinating topic for research due to their exceptional phase controllability to both orthogonal polarization states of the incident light source.…”