Switchable THz Guided Mode Enhancement in Subwavelength Thick PTFE — Polyimide Based Metamaterial Devices

We report an efficient approach to enhance terahertz (THz)-guided modes for realizing subwavelength thick metamaterial devices (MMD). Here, a combination of hollow and slitted rings of the vanadium dioxide (
$VO_{2}$
)-based metasurface, having perfect impedance matching with free space, is considered to cause tight coupling in the unit cells while reducing transverse field components of the boundary. The consolidated dielectric layer of polytetrafluoroethylene (PTFE)-polyimide underneath, maintaining a gradual change in refractive indices, brings about further improvement for a broader spectrum. Through strategic and systematic design steps, a maximum impedance bandwidth of 5.68 THz, ranging from 4.42 to 10.10 THz, has been achieved here from a structure thinner than a wavelength. Additionally, mode-independent polarization insensitivity and tunability are attained through the symmetrical unit cell pattern of temperature-dependent
$VO_{2}$
. Optimized design parameters agree with interference cancellation theory too. Validation of our presented design is performed using theoretical analysis based on equivalent circuit theory. The proposed design offers a new avenue for designing ultra-thin broadband absorbers, light modulators, etc.