Chiral metamaterial absorber with high selectivity for terahertz circular polarization waves

Chiral-selective Plasmonic Metasurface Absorber Based on Bilayer Fourfold Twisted Semicircle Nanostructure at Optical Frequency

“…Then, both transmission and re ection coe cients of both LCP and RCP lights can be obtained. Generally, the chiral-selective absorbance A − (ω)/A + (ω) for the LCP/RCP light can be expressed using the equations [14,29]:…”

“…It should be noticed that the cross-polarization transmission coe cients (t +− (ω), t −+ (ω)) and re ection coe cients (r +− (ω), r −+ (ω)) for LCP and RCP lights are very small (< 0.01) due to the high C 4 symmetry of the unit-cell of the designed PMSA, thus negligible. In addition, CD effect is induced by the chiral-selective absorption of two CP lights, which can be expressed as [14,29] resonances. It also can be seen that the co-polarization transmission coe cients (t ++ (ω), t −− (ω)) for RCP and LCP lights are different signi cantly at resoances due to the chiral nature of the proposed PMSA.…”

“…CMSs have gained tremendous interest since it can exhibit exotic EM properties including negative refractive index and optical activity [8,9], asymmetric transmission [10,11], giant CD effect [12][13][14], polarization conversion [15,16], and wave front manipulation [17,18]. Since then, various CMSs structures (such as split-ring, gammadion, spiral wire, L-shaped and so on) have been designed to achieve highly-e cient selective chiral eld enhancement for LCP or RCP light as well as CD effect [19][20][21][22][23][24][25][26][27][28][29][30]. However, most of these CMS focus on the performance of chirality in transmission, while much less attention has been paid to the one in re ection/absorption for CP lights, which are equally important in optical engineering.…”

“…It is well known that the most previous absorbers are applied to linear polarization light, and such designs for CP lights are rarely studied. In fact, CMSs also could be used to construct novel chiral-selective absorbers for CP lights [22,23,[26][27][28][29][30]. For instance, Li et al proposed an ultra-thin chiral-selective absorber based on the L-shaped folded metallic wires, which can only absorb the LCP wave in microwave region [22].…”

“…1(b). Similarly to previous design [29], the top four semicircle nanostructures are connected with the bottom one by copper cylinders, and the radius of copper cylinder is the same with the semicircle wire width, which can increase conductive coupling. The twisted semicircle nanostructure can be viewed as a coupled resonator system, where the strong chiral responses arise from the electric and magneto inductive coupling between the two twisted connected semicircles.…”