Fast-speed electrically tunable liquid crystal metasurface for 2π phase modulation at normal and oblique angles of incidence

This study presents an electrically tunable metasurface capable of achieving continuous 2π phase modulation at normal and oblique angles of incidence with high reflectance in the telecom C-band. By using constructive interference between electric dipole (ED) and quadrupole (EQ) resonances, the designed device achieved a peak phase modulation depth of 7.23 radians and reflectance exceeding 60% at normal incidence, as well as consistent 2π phase modulation for off-axis incidence extended to ±2.5°. It also exhibits rapid responses in switching, with a 0.7 ms rise time and 3.5 ms fall time. These findings show the potential of LC-tuned metasurfaces for fast response and off-axis 2π phase modulations.