In-plane symmetry breaking induced tunable spin-dependent responses and polarization states for terahertz wave

Abstract

Dynamic manipulation of electromagnetic terahertz waves is tremendously desirable to boost the development of favorable functional components of terahertz systems. Reconfigurable chiral metadevices have emerged as promising platforms for active control of spin-dependent responses, however, conventional design principles are restrained by the breakage of out-of-plane symmetries. Here, a type of kirigami-based terahertz metamaterial (MM) is numerically simulated to modulate circular polarization differential transmittance (CPDT) based on the in-plane symmetry breaking. The un-deformed MM empowered with mirror symmetries exhibits indiscriminate propagation for left circular polarization and right circular polarization wave, while the deformed MM with the tensile strain as 24% dramatically facilitates the breakage of in-plane symmetries and retains the CPDT value as high as 0.89. Furtherly, as the tensile strain reaches to 45.5%, the CPDT value is suppressed back to a negligible level and achieves the off-on-off chirality switch function through the continuously stretchable deformation. Moreover, the effect of kirigami cuts, height difference and rotation angle of silicon pillars on the CPDT spectra are also parametrically analyzed. The combination of kirigami technique and terahertz device gives rise to a novel branch of reconfigurable principles, and demonstrates its promising applications of chirality switching, spin-selective manipulation, chiral detection and polarization control.