Strong chirality in twisted bilayer α-MoO<sub>3</sub>

Spinning thermal radiation has demonstrated applications in engineering, such as radiation detection and biosensing. In this paper, we propose a new spin thermal radiation emitter composed of the twisted bilayer α-MoO3 metasurface; in our study, it provided more degrees of freedom to control circular dichroism by artificially modifying the filling factor of the metasurface. In addition, circular dichroism was significantly enhanced by introducing a new degree of freedom (filling factor), with a value that could reach 0.9. Strong-spin thermal radiation resulted from the polarization conversion of circularly polarized waves using the α-MoO3 metasurface and selective transmission of linearly polarized waves by the substrate. This allowed for extra flexible control of spinning thermal radiation and significantly enhanced circular dichroism, which promises applications in biosensing and radiation detection. As a result of their unique properties, hyperbolic materials have applications not only in spin thermal radiation, but also in areas such as near-field thermal radiation. In this study, hyperbolic materials were combined with metasurfaces to offer a new idea regarding modulating near-field radiative heat transfer.

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“…In this study, the transfer matrix method (TMM) was used to calculate the transmission of the above structures [ 43 ].…”

Section: Theory and Methodsmentioning

confidence: 99%

“…[ 41 ]. Wu et al studied the spin thermal radiation properties of single-layer α-MoO 3 [ 42 ] and double-layer twisted α-MoO 3 structures [ 43 ]. Although the structures mentioned above can excite spin thermal radiation properties, the CD obtained by optimizing the rotation angle and thickness parameters was always very limited.…”

Section: Introductionmentioning

confidence: 99%

Metasurfaces Assisted Twisted α-MoO3 for Spinning Thermal Radiation

Sun

Zhang

et al. 2022

Micromachines

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“…Recent studies show that monocrystalline slabs with intrinsic in-plane optical anisotropy such as α-MoO 3 or hBN can be stacked in a chiral configuration to elicit or enhance optical chirality. [13,14,41] Altering the slab thicknesses during monolayer preparation helps tune the optical performance of chiral stacked structure. The chiral twisting strategy also allows novel optical phenomena, beyond CD, to emerge at the twisted interface.…”

Section: Other Miscellaneous Materials Systemsmentioning

confidence: 99%

“…[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.…”

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confidence: 99%

Recent Advances in Ultrathin Chiral Metasurfaces by Twisted Stacking

et al. 2022

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chiral plasmonic nanoparticles and their self-assembled structures as colloidal suspensions. [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. [22][23][24] Compared to their bulk or multiple-layer counterparts, the fabrication becomes greatly simplified for bilayer or few-layer chiral metamaterials, enabling precise control over the interlayer twist angle to manipulate lightmatter interactions. Ultrathin chiral metamaterials and metasurfaces with tunable optical and chiroptical responses are thus an active field for study.Twisting achiral layered nanostructures in parallel planes enables engineering of the extrinsic chirality and related optical performance. Specifically, the twist angle from counterclockwise rotation of an upper layer with respect to the beneath one is defined to be positive, θ > 0°, leading to a left-handed stacking geometry. [10,18] Accordingly, negative twist angle from clockwise rotation gives rise to the right-handed counterpart. Accurate control over the interlayer rotation angle offers flexible manipulation of properties, especially optical activity, of twisted layered systems of a wide variety of monolayer constituents and dimensions. A well-studied system is twisted bilayer graphene (TBG), catalyzing the research on twisted stacked nanostructures over the past few years, especially as many intriguing properties of magic-angle graphene are uncovered. [28][29][30] The twist angle dependencies of phonon dispersion, [31] optical absorption and reflection, [32,33] circular dichroism (CD) and birefringence, [10,34] second harmonic generation (SHG), [35] and photoresponse [36,37] of TBG have been extensively explored in the past few years. Similar realizations have been reported for twisted nanostructures of other 2D materials such as transition metal dichalcogenides, [38,39] graphitic carbon nitride, [40] and hexagonal boron nitride (hBN), [41] as well as non-2D systems like polymeric thin films or patterned plasmonic nanohole arrays. [42,43] Therefore, there exists fertile ground for chiral metasurface design Artificial chiral nanostructures have been subjected to extensive research for their unique chiroptical activities. Planarized chiral films of ultrathin thicknesses are in particular demand for easy on-chip integration and improved energy efficiency as polarization-sensitive metadevices. Recently, controlled twisted stacking of two or more layers of nanomaterials, such as 2D van der ...

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“…45 In particular, natural hyperbolic biaxial crystals, such as a-MoO 3 , show different optical responses in their three crystalline directions. [46][47][48] Consequently, a-MoO 3 introduces three ENZ frequencies in the infrared range of angular frequencies. 12,13 Previous studies of NFRHT mainly focus on excited polaritons in the negative real component of the permittivity region.…”

Section: Introductionmentioning

confidence: 99%