Multifunctional and dynamically tunable terahertz metamaterials based on TiNi shape memory alloy films with a simple design

Abstract

In the terahertz (THz) fields, a crucial point of restricting its development and application is the lack of dynamic and multifunctional materials. In this work, NiTi films are innovatively introduced into the design, and multifunctional and dynamically tunable terahertz metamaterials are proposed. The influence and mechanism of the shape deformation and conductivity changes before and after martensitic transformation on the electromagnetic response are systematically investigated and revealed. Based on the novel NiTi metamaterials, inductance-capacitance (LC) resonance and dipole resonance are used simultaneously for the terahertz filter, and an excellent dual-band filter is obtained. The frequencies of both LC and dipolar resonances can be dynamically tuned to the desired operating frequencies by driving the martensitic transformation. And the resonant frequency of the band-stop filter achieves a dynamic modulation range up to 0.56 THz. Furthermore, the results also show that when martensitic transformation occurs, the terahertz wave transmission can be tuned from 0.78 to 0.04 at 0.47 THz. Moreover, as an excellent switch, the ON state transmittance is one order of magnitude higher than the OFF-state transmittance. In brief, this study provides a new perspective and ideas for developing a tunable dual-band terahertz filter and thermal-induced terahertz switch.