Mechanical Deformation Induced Circular Dichroism in Propeller-Shaped Terahertz Metamaterials

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.