Tunable circular dichroism in a graphene extrinsically chiral L-shaped metasurface

Abstract

In this manuscript, we propose a graphene metasurface composed of an L-shaped pattern to achieve a tunable circular dichroism under oblique incidence in the mid-infrared region. For our graphene extrinsically 3D-chiral structure, there are two graphene localized surface plasmons resonant modes at the wavelength of 11.05 and 16.69 μm. A broad bandwidth circular dichroism between the two modes is generated, so are two bands of negative circular dichroism (circular dichroism is minus). The circular dichroism can be enhanced by increasing the incident angle. Maximal circular dichroism can reach 24.64% when the incident angle is 60°. The mechanism of circular dichroism generation is attributed to the strong interaction between electric and magnetic dipoles. Besides, the circular dichroism can be tuned by changing the Fermi energy and is affected by the intrinsic relaxation time. It will have a wide application in photonic devices, which can promote the development of analytical chemistry and numerous other areas.

Realizing efficient THz circular dichroism using ultra-thin chiral metasurface

“…The proposed structure has high selectivity for LCP and RCP waves, resulting in a strong CD of 0.910 (91.10%), as shown in figure 5(b) at 12.4 THz. In comparison to the class of absorbers [14,35,[37][38][39][40][41][42][43][44], our proposed Mushroom-shaped absorber provides the highest value of CD (91.10%). The achieved bandwidth with absorption efficiency greater than 80% is 12.3-12.5 THz.…”

“…However, the interaction between wave and chiral molecules is usually fragile, resulting in weak CD signals. Researchers have proposed many designs to overcome this issue [14,35,[37][38][39][40][41][42][43]. A twisted Z-shaped nanostructure is proposed in [44] to achieve a CD of 88%.…”

Near-infrared Sb2S3 metasurface with giant and tunable circular dichroism

“…During the past decade, a large number of chiral metasurfaces have been proposed to enhance the strength of CD signal, for example, Z-shaped [4], Mushroom-shaped [5], asymmetric split ring [6], gammadion-shaped [7], and so on. However, these traditional chiral metasurfaces operate within certain wavebands and cannot be applied in some complex scenarios, such as multi-band bio-detection, dynamic imaging, etc To obtain the dynamic CD signal, there has been a lot of work to design reconfigurable metasurfaces using various active materials, including liquid crystals [8], semiconductors (Si) [9,10], two-dimensional materials (graphene) [11][12][13], and phase change materials (VO 2 , Ge 2 Sb 2 Te 5 ) [14][15][16][17][18][19][20] etc.…”

Enhancement of intrinsic chirality based on asymmetric metasurface

“…Chiral metasurfaces represent a class of optical nanostructures notable for their inherent chirality. Chirality is defined as the property whereby an object cannot be superimposed onto its mirror image, analogous to the distinction between lefthandedness and right-handedness [1][2][3]. This distinctive chiral attribute can be realized within molecular structures or micro-nanostructured configurations.…”