Optically transparent metamirror with broadband chiral absorption in the microwave region

Single-Layer Achiral Metasurface with Independent Amplitude–Phase Control for Both Left-Handed and Right-Handed Circular Polarizations

“…Metasurfaces, the artificial planar arrangements of various subwavelength resonators, possess exceptional capability of tailoring the amplitude, phase, and polarization of electromagnetic waves. − Given the merits of low loss, small size, and simple fabrication, metasurfaces have drawn great attention and shown versatile applications, such as vortex beam generators, , focusing lenses, , meta-holograms, − surface plasmon polariton couplers, , etc. − Notably, some efforts are devoted to construction of chiral metasurfaces to acquire desired chiral effects. − For instance, numerous transmission-reflection-selective chiral structures are designed to block one state of the CP waves and transmit orthogonal CP waves. − Some ingenious metasurfaces can achieve circular dichroism by devising the chiral structures or introducing loss resistors into meta-atoms. − Furthermore, a range of schemes are proposed to independently control the wavefronts of LCP waves and RCP waves based on the integrated design of scaling-induced propagation phases and rotation-induced geometric phases. − More strikingly, certain multilayer multifunctional metasurfaces are established to tailor the amplitude and phase of orthogonal CP waves utilizing chiral structures with unequal dimensions working at distinct frequencies. , Nevertheless, most of the existing paradigms increase the complexity of the structures to obtain the intrinsic chirality or combine multilayer achiral structures to get the external chirality, and it is difficult for chiral metasurfaces to manipulate the amplitude and phase of orthogonal CP incident waves independently at the same frequency based on the present design mechanisms. In contrast, there are few studies on chiral phenomena generated by single-layer achiral structures, which means that the immense potential of chiral effects lies in simple achiral structures.…”

Graphene-based dual-functional chiral metamirror composed of complementary 90° rotated U-shaped resonator arrays and its equivalent circuit model

“… Dynamic tunability Dual-functional Frequency region Circuit model Max reflection (%) Max. chirality response (%) 10 No No 9.1–11 GHz No 98 CD/93 11 No No 300–375 THz No 90 CCD/43 12 No No 30–50 THz No 99 CD/94 13 No No 285–425 THz No 90 CD/50 14 No No 211–227 THz No 80 CD/63 15 No No 8–12 GHz No 95 CD/88 This work Yes Yes 0.3–4.5 THz Yes 99 LD/96 …”

“…Some chiral metamirrors have been introduced and designed, recently 10 – 15 , but none of them are dynamically controllable, dual-functional, or function in 0.3–4.5 THz frequency region, or use the proposed circuit modeling process. Dual-functional metamirrors are urgently needed in THz intelligent systems to greatly reduce the size of the THz system without needing two different metastructures to produce broadband and multiband reflections.…”

Nonreciprocal coupling induced chiral absorption

“…Reflective mirrors of this category can convert the spin light into hot electrons [24,25] and second harmonic generation signals [26], as well as switch the polarization state of waves upon reflection [27,28]. Multimode resonance [29,30] or resistive elements [31][32][33] can boost the chiral absorption over broad frequency regimes. Gradient distribution of absorptive chiral meta-atoms provide anomalous reflection of the designer spin waves into other diffraction channels [34], spin dependent multiplexer [35], holograms [36] and imaging [37].…”