Post‐Processing‐Free Orbital Angular Momentum Holographic Encryption

Abstract

Orbital angular momentum (OAM) holography provides a promising degree of freedom for optical encryption. However, conventional schemes often rely on discrete vortex sampling, leading to visible concentric ring patterns under direct detection. To conceal such leakage, spatial filter arrays are typically used, but they introduce complexity and remain vulnerable to partial information exposure. A post‐processing‐free OAM holographic encryption scheme based on symmetric grating phase sampling is presented. A pair of complementary pseudo‐orthogonal gratings modulates a single OAM mode into two holographic channels: one encoding the target information and the other carrying structured noise. These channels are coherently multiplexed into a single phase‐only hologram. Upon direct detection, mutual interference conceals the information, which is only revealed when the correct decryption beam collapses the field into a Gaussian‐like mode. It is experimentally validated this approach in both static and dynamic scenarios. Under brute‐force decryption, the recognition accuracy remains below 10%, while correct decryption achieves over 99.8% accuracy. In multi‐frame video experiments, pre‐decryption recognition drops to 5.6%, confirming strong concealment. This compact and filter‐free scheme enables real‐time, high‐security optical encryption, offering a scalable platform for secure imaging, data protection, and photonic communication systems.