Mechanical Deformation Induced Circular Dichroism in Propeller‐Shaped Terahertz Metamaterials

Abstract

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.

Kirigami‐Inspired Planar Deformable Metamaterials for Multiple Dynamic Electromagnetic Manipulations

“…[27][28][29] To broaden the modulation range, 3D assembly technique is implemented to transform the planar precursor selectively bonded on the pre-stretched substrate into 3D chiral meta-atoms by releasing the stress to eventually tune the spindependent transmission. [30][31][32] Despite of simple composition and superior mechanical characteristics, these mechanically reconfigurable metamaterials are only restricted to tune the spectral responses.…”

3D Flexible Frequency Selective Surface with Stable Electromagnetic Transmission Properties

“…Zhang et al [34] proposed a 3D antenna with reconfigurable resonant frequency by applying stretching strains in different orders on substrate to obtain multistability of the 3D assemblies. Han et al [35,36] introduced a 3D mechanically reconfigured chiral metamaterial prepared by compressing origami structures after releasing prestrain and capable of dynamically tuning circular dichroism by active manipulation. Pan et al [37] proposed a flexible FSS with serpentine metal stripe unit sputtered on a flexible substrate polyimide that can be wrapped around the cylindrical surface with no drift in resonant frequency when the bending angle is below π.…”

“…Han et al. [ 35,36 ] introduced a 3D mechanically reconfigured chiral metamaterial prepared by compressing origami structures after releasing prestrain and capable of dynamically tuning circular dichroism by active manipulation. Pan et al.…”

Rotational Kirigami Tessellation Metasurface for Tunable Chirality

“…However, it is challenging in practical realization where most of the fabricated samples can tune or switch from achiral to only one chiral-selective response. [35][36][37] References [38][39][40][41][42][43][44][45][46][47] present detailed theoretical design, fabrication techniques, and tunable mechanisms for chiral metamaterials and metasurfaces. Most of the reported origami/kirigami structures were fabricated using papers or Kapton films, which are difficult to mechanically transform, not robust, and challenging in the fabrication process.…”

“…Owing to this unique feature of chiral structures, circularly polarized electromagnetic waves such as left-handed circular polarized (LHCP) or right-handed circular polarized (RHCP) waves can be selectively transmitted, reflected, or absorbed. [34][35][36][37] Deformations from flat to folded shapes (2D to 3D structure) can achieve tunable or reconfigurable chirality. In addition, the reconfigurable characteristics between their opposite chiral states (LHCP and RHCP) can realize Kirigami, with a simple mechanical transformation fashion, offers versatile ways and unconventional approaches for realizing cutting-edge tunable devices.…”