Cascaded DOEs for optical information encryption

We propose an optical information encryption approach using azimuth multiplexing, encoding images in cascaded Diffractive Optical Elements (DOEs) with different rotation angles. While the approach works well in simulations, its experimental realization is challenging due to the sensitivity to positional shifts in DOEs. We aim to overcome these issues by enhancing shift tolerance. In this work, four different patterns were encrypted into cascaded DOEs designed using the proposed algorithm. The encrypted pattern can be correctly decrypted when the rotation angle of the first DOE is shifted by 0.5°from the designed rotation angle, indicating that it has a large shift tolerance. This approach is expected to facilitate the experimental realization of the complex optical image encryption system which will be tackled in the next step.