Sensitive Terahertz Phase Modulation via a Co-Planar HEMT-Switched LC-Dipole Resonant Metasuraface Under Low 2DEG Carrier Concentrations

A terahertz digital phase modulator based on an ultrafast electrically controlled HEMT-embedded metasurface is theoretically and experimentally demonstrated here.Different from traditional delay-line phase shifter, the proposed phase modulator combined the active HEMT 2DEGs with the resonant structure, demonstrating higher reflective efficiency and 2πfull coverage phase shift under low electron densities around 10
¹⁵
/m
²
. The preliminary measurement results show a π phase difference occurs at 0.358 THz with a -8.5 dB attenuation on average, which is in good accordance with the simulation.