Realizing efficient THz circular dichroism using ultra-thin chiral metasurface

Abstract

Circular dichroism is characterized by distinct optical responses for left-handed and right-handed circularly polarized waves widely used for biological monitoring, analytical chemistry, and plasmonic sensing. In this work, we propose a chiral metasurface composed of a Mushroom-shaped (MS) pattern to achieve circular dichroism in reflection mode at THz frequencies. The maximum achieved absorption efficiency is 98.49% for left-handed circularly polarized (LCP) incident wave while for right-handed circularly polarized (RCP) incident wave is 7.39% at the resonant frequency 12.4 THz. This high absorption results in remarkable circular dichroism (CD) of 91. 10%. Moreover, a stable response has been observed with the variation of incident angles from 0° to 30°. Meanwhile, power loss distribution, current distributions, and retrieved effective physical parameters have been used in analyzing the absorption mechanism. The high polarization selective absorption efficiency, angular stability, and compact size qualify the proposed design for a diverse range of THz applications.


Dual-band terahertz chiral metasurface absorber with enhanced circular dichroism based on temperature-tunable InSb for sensing applications

“…Table 1 shows a comparison of the proposed CMA with some recently reported ones. Compared with previous works, 30,32,35,38,41–43 our proposed CMA introduces a temperature-tunable material InSb, which can dynamically adjust the CD effect, and has the advantage of a simple structure. Therefore, the proposed CMA shows superior properties in the material selection, structural design, tunable bandwidth, etc.…”

“…In recent years, CMAs that operate at microwave, terahertz (THz), and even visible frequencies have garnered significant attention because of their chiral-selective absorption with strong CD effects that are significantly greater than those observed in natural materials. 19–34 For instance, Tang et al theoretically and experimentally demonstrated a CMA with η-shaped resonators that exhibited a maximum absorption of over 80% with a CD value of approximately 0.5 in the visible frequencies. 23 Wang et al proposed a dual-band CMA using distorted ‘I’ shaped resonators, which exhibited a maximum absorbance of 95.18% and 91.77% at 12.04 GHz and 14.22 GHz for the LCP waves, respectively, and a maximum CD value of 0.6 at 12.5 GHz.…”

“…27 Qureshi et al designed an ultra-thin CMA with a mushroom-shaped resonator, which achieved maximum absorbances of 98.49% for incident LCP waves and 7.39% for RCP waves at 12.4 THz, resulting in a remarkable CD value of 91.1%. 32 Although these CMAs can produce a giant CD effect, their function and performance cannot be changed after manufacturing, which can be inconvenient for practical application requirements involving complex scenarios such as dynamic imaging and real-time sensing. In fact, active materials such as graphene and vanadium dioxide (VO 2 ) have been incorporated into CMSs to dynamically manipulate the CD effect by external electrical and thermal stimuli.…”

Active anisotropic polarization conversion meta-surface for 6G communication bandgap in the reflection mode

“…Furthermore, 6 G communication near 0.3 THz have been recently reported. Modulating the polarization of the incident wave front has been extensively studied in different regimes of the electromagnetic spectrum [16][17][18][19]. High efficiency and wide bandwidth are the main goals of the researchers.…”

An ultra-thin multifunctional chiral metasurface with asymmetric transmission, cross-polarization conversion, and circular dichroism for Ku- and K-band applications

“…Chiral metasurfaces, which are the two-dimensional counterparts of chiral metamaterials, have received significant interest from researchers due to their potential for reduced cost and simplified fabrication processes. Compared with conventional metasurfaces, chiral metasurfaces have tremendous features, such as a negative refractive index [10], conversion of polarization [11][12][13][14][15][16][17][18][19][20][21], asymmetric transmission (AT) [22][23][24][25][26][27][28][29][30][31][32][33][34], and circular dichroism (CD) [35][36][37][38][39][40].…”