A photoactive terahertz modulator based on the Cd3As2 thin film

We experimentally demonstrated an optical controlled terahertz modulator based on the 3D Dirac semimetal Cd3As2 thin film (~100 nm, λ/3000). Utilizing the time-resolved terahertz spectroscopy, the photoactive characters of Cd3As2 thin film are investigated. The measurements reveal that Cd3As2 modulator exhibits a low optical threshold (< 63.5 μJ/cm2) and ultrafast (< 20 ps) broadband (0.2-1.5 THz) modulation of terahertz waves. Moreover, integrated with the metamaterials structures, Cd3As2 could potentially be used as photo-sensitive and ultrafast reconfigurable terahertz resonant plasmonic/meta-device.