Intrinsic Chirality and Multispectral Spin‐Selective Transmission in Folded Eta‐Shaped Metamaterials

Rana

et al. 2021

Sensors

Chiral materials, which show different optical behaviors when illuminated by left or right circularly polarized light due to broken mirror symmetry, have greatly impacted the field of optical sensing over the past decade. To improve the sensitivity of chiral sensing platforms, enhancing the chiroptical response is necessary. Metasurfaces, which are two-dimensional metamaterials consisting of periodic subwavelength artificial structures, have recently attracted significant attention because of their ability to enhance the chiroptical response by manipulating amplitude, phase, and polarization of electromagnetic fields. Here, we reviewed the fundamentals of chiroptical metasurfaces as well as categorized types of chiroptical metasurfaces by their intrinsic or extrinsic chirality. Finally, we introduced applications of chiral metasurfaces such as multiplexing metaholograms, metalenses, and sensors.

Section: Fundamentals Of Chiroptical Metasurfacesmentioning

confidence: 99%

Section: Types Of Chiroptical Metasurfacesmentioning

confidence: 99%

Chiroptical Metasurfaces: Principles, Classification, and Applications

Rana

et al. 2021

Sensors

Adv Materials Technologies

“…Owing to the intrinsic features of chiral media, circularly polarized waves (CPW) including left circular polarization (LCP) and right circular polarization (RCP) can be discriminately transmitted or absorbed, which is also defined as circular dichroism (CD). Furthermore, when a linearly polarized THz wave impinges upon chiral materials, the outgoing wave can be rotated owing to distinct refractive indices [ 14 ] for LCP and RCP waves induced by the chiral parameters of the structures in question. Therefore, the polarization states of incident THz waves can be regularly manipulated, which facilitates the development of functional devices that can modulate spin state or polarization direction.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Deformation Induced Circular Dichroism in Propeller‐Shaped Terahertz Metamaterials

Han

Zhang

Becton

et al. 2021

Understanding the manipulation of terahertz (THz) waves is of tremendous importance to the development of functional devices with excellent performance in communication and imaging sectors. THz chiral metamaterials (MMs) are emerging as candidates exhibiting selective polarization‐state modulations. Here, mechanically tunable chiral MMs composed of propeller‐shaped units on a pre‐stretched flexible substrate, are proposed. Due to the reversible tensile mechanical deformation induced by the elastic substrate, the structural chirality as well as the circular dichroism (CD) upon circular‐polarized THz incidence are significantly enhanced. The intensity and position of CD spectra can be sensitively regulated by an externally applied strain on the deformable device. Additionally, it is found that CD spectra are highly sensitive to the geometrical configuration, including rotational symmetries and handedness. The MM with the lowest rotational symmetry demonstrates the most prominent CD performance and the opposite structural handedness can reverse CD over the whole spectra, respectively. The reconfigurable THz MM with facile mechanical deformation unfolds a new degree of freedom for tuning the CD while simultaneously shedding light on the development of novel THz modulation in flexible functional devices.

“…Namely, regions of enhanced near-field chirality were numerically shown in periodic arrays of Si NWs 14 and Si NW dimers 15 , as well as in individual hybrid Au-GaAs NWs 16 . In order to assess chiral behaviour in the far-field, the shape of the nanostructure can be made chiral, in which case they exhibit intrinsic chirality 17 , 18 . Intrinsic chirality in NW-based samples was demonstrated in the far-field in Ref.…”

Section: Introductionmentioning

confidence: 99%

Broadband optical spin dependent reflection in self-assembled GaAs-based nanowires asymmetrically hybridized with Au

Petronijevic

Belardini

Leahu

et al. 2021

Sci Rep

Hybridization of semiconductor nanostructures with asymmetric metallic layers offers new paths to circular polarization control and chiral properties. Here we study, both experimentally and numerically, chiral properties of GaAs-based nanowires (NWs) which have two out of six sidewalls covered by Au. Sparse ensembles of vertical, free-standing NWs were fabricated by means of lithography-free self-assembled technique on Si substrates and subsequently covered by Au using tilted evaporation. We report on optical spin-dependent specular reflection in the 680–1000 nm spectral range when the orientation of the golden layers follows the rule of extrinsic chirality. The analysis shows reflection peaks of the chiral medium whose intensity is dependent on the light handedness. We further propose a novel, time-efficient numerical method that enables a better insight into the far-field intensity and distribution of the scattered light from a sparse NW ensembles. The measurements done on three different samples in various orientations show good agreement with theoretical predictions over a broad wavelength range.