Ionic terahertz metasurface in ultrathin-layered conductive hydrogel by ultrafast laser tailoring

Abstract

The ion-interactive semi-conductive hydrogel emerged as a promising optoelectronic material due to its desirable electrical conductivity, optical clarity, and switchable dielectric properties beyond incumbent inorganic materials. However, developing the actively modulated terahertz (THz) devices via hydrogel remained barely studied at an early stage. Herein, a scalable high-throughput picosecond laser system rapidly tailored hydrogel into ion-interactive dielectric metasurfaces (IDMs). The IDMs exhibited minus permittivity (ɛ < 0 F/m) not belonging to hydrogel, tunable time/frequency modulation, and high-consistency geometries for specific THz wave manipulations. The interplay between anions and the π-conjugated thiophene ring of hydrogel dynamically changed the dielectric properties and electrical conductivity through mixed electron/hole transportation, making IDMs change their microscale electric fields anomalously. Other as-prepared IDMs (split resonators, interleaved antennas, and their array) further confirmed the native capability of generating orbital angular momentum, spatially manipulating THz waves, or tuning frequencies. This work ushers in a new platform to customize and deploy non-metal THz meta devices in batches.