Angle enhanced circular dichroism in bilayer 90°-twisted metamaterial

Abstract

Intrinsic and extrinsic chiral responses have been widely investigated in metamaterials, however the relationship between them has been seldom discussed. We numerically and experimentally demonstrate angle enhanced chiral dichroism and study the separation between intrinsic and extrinsic chiral responses in metamaterial with asymmetrically split aperture dimers. The metamaterial exhibits triple-band resonant circular dichroism at normal incidence. The oblique incidence leads to giant enhancement of circular dichroism at two low-frequency resonances while yields an obvious resonance split of the circular dichroism in the vicinity of the high-frequency resonance. The whole circular dichroism response results from the balance between intrinsic and extrinsic chirality and the circular dichroism spectra at positive and negative angles of incidence exhibit an asymmetry due to the existence of intrinsic chirality. Importantly, the intrinsic chirality in the metamaterial may be individually investigated since extrinsic chiral response may be removed from the total circular dichroism by superimposing two circular dichroism spectra at positive and negative incident angles. The metamaterial will be promising to achieve enhanced chiral response and also separately utilize intrinsic and extrinsic chirality for manipulating the polarization state of light.

Giant polarization anisotropic optical response from anodic aluminum oxide templates embedded with plasmonic metamaterials

“…2(d)] form a chiral triad, giving rise to the chiroptical effect. This mechanism of extrinsic chirality was first identified in nematic liquid crystals [52,53], and later in artificial planar structures [25,26,[54][55][56]. On the other hand, from the electrodynamic point of view, similarly to how it happens in conventional 3D-chiral media, the observed optical activity effect results from the simultaneous presence of electric and magnetic responses in the structure [57,58].…”

Recent Advances in Ultrathin Chiral Metasurfaces by Twisted Stacking

“…This superimposition was recently demonstrated by Lai and colleagues in a 90°-twisted bilayer metasurface comprising split ring resonator arrays (Figure 10). [21] To briefly sum up, ultrathin chiral metasurfaces fabricated from twisted stacking possess programmable chiral optical activities at normal incidence. Spectral features including the sign, magnitude, and spectral position of CD could be modulated by changing the interlayer twist angle, interlayer spacing, layer number, and so on.…”

“…Second, Al is one of the elements that are directly mined with high global production, [161] representing a more economic and sustainable alternative to precious metals like Au. [21] Copyright 2020, The Authors, published by Optical Society of America.…”

“…[6][7][8][9] Recently, beyond noble metal plasmonics, solid-state layered nanomaterials that are rotationally aligned with a defined twist angle are becoming increasingly investigated (Figure 1). Among these are twisted 2D van der Waals (vdW) materials, [10][11][12] twisted single-crystal slabs, [13,14] twisted aligned nanowire thin films, [15][16][17][18] and twisted metasurfaces with periodic subunits [19][20][21] (Figure 2). These chiral stacked materials possessing geometric handedness and optical chirality can be seen as truncated and minimalistic versions of supramolecular liquid crystals in the chiral nematic phase or of 3D chiral photonic crystals.…”

Ultra-wideband, Wide Angle, Asymmetric Transmission based Chiral Metasurface for C and X Band Applications

“…Since the inception of AT phenomenon, many effective design topologies have been published. This includes efficient bi-layered configurations [12][13][14][15][16][17][18][19][20][21][22][23] and tri-layered configurations as well, which take advantage of Fabry Perot-like cavity thereby resulting in broadband AT response [24][25][26][27][28][29][30] .…”