Photo-generated metasurfaces for resonant and high modulation of terahertz signals.

We theoretically demonstrate resonant modulation of terahertz (THz) waves with photo-designed metasurfaces. Our approach bypasses the short penetration length issue of the optical pump that prevents photo-generated thick metamaterials. We propose a three-layer semiconductor system of subwavelength thickness that presents 100% modulation of the reflection (or absorption) spectra at around 1 THz when optically actuated. This resonant modulation can be dynamically monitored at high frequency by the optical pump on a broad range of frequencies of Δν/ν=100%. Appropriate 2D photo-printed patterns make the system polarization insensitive and operational for a wide range of incident angles up to 65°.