Cryptographic Metasurface Enabled High-Security Information Authentication Using Dual-Beam Off-Axis Illumination

Abstract

Optical information security has become paramount in data-driven technological systems, where metasurface holography has emerged as a transformative paradigm for high-density optical encryption. However, conventional methods remain constrained by fundamental limitations: multiplexed architectures suffer from inherent interchannel crosstalk, while complex cryptographic algorithms introduce impractical computational overhead. Here, we present a breakthrough visual cryptography platform that utilizes a metasurface hologram with dual-beam off-axis illumination for shared information encryption. The cryptographic scheme physically encodes secret information into the geometric phase profile of metasurface-engineered ciphertexts, with decryption strictly requiring synchronized dual-beam off-axis illumination at predetermined angular configurations. Crucially, single-beam interrogation yields only stochastic speckle-like patterns through partial phase retrieval, providing inherent security against unauthorized access. This architecture achieves channel-independent encryption through angular freedom manipulation, eliminating interchannel crosstalk while preventing potential information leakage through spatial frequency separation mechanisms. The off-axis design not only increases the information capacity, but also establishes a multilayered security framework through the angular degrees of freedom. Both numerical simulations and experimental results validate the effectiveness of the proposed method and demonstrate robust encryption and decryption performance. Our method balances encryption complexity and security, providing a promising solution for next-generation optical encryption devices.