Terahertz Metasurface Encryption Based on Phase Change Controlled Magnetic Resonance Quenching

We present a terahertz encryption metasurface enabled by the phase-change material Ge₂Sb₂Te₅(GST). A plasmon-induced transparency (PIT) response is formed by bright–dark mode coupling, and switching GST between amorphous and crystalline states modulates transmission by quenching the split-ring magnetic resonance. The resulting transmission contrast supports binary amplitude holography, allowing reversible switching between a non-informative output and a reconstructed holographic image. To enhance security, we integrate Shamir’s visual cryptography: the plaintext is recovered only by decoding and superposing two independent share images mapped to separate metasurfaces. Incorporating VO₂ adds a thermal access dimension for multi-level security.