Cascaded diffractive optical elements (DOEs) introduce additional degrees of freedom compared to a single DOE, providing an effective platform for rotation-angle multiplexed optical information encryption. However, cascaded DOE-based image reconstruction is highly sensitive to rotation misalignment, which limits its robustness in practical implementations. From a design perspective, this limitation arises from the insufficient utilization of the phase degrees of freedom provided by cascaded DOE. In this work, a double phase update algorithm is proposed for cascaded DOE design, in which all DOEs participate in phase updating during the iterative process. By more effectively exploiting the available phase degrees of freedom, the proposed method significantly enlarges the rotation tolerance while maintaining comparable reconstruction quality. Numerical simulations demonstrate that the rotation tolerance is extended from 1.21° to 2.78°, corresponding to an improvement of approximately 130%. These results indicate that the proposed design strategy provides an effective approach for improving the robustness of cascaded DOE-based optical information encryption.
Cascaded diffractive optical elements (DOEs) introduce additional degrees of freedom compared to a single DOE, providing an effective platform for rotation-angle multiplexed optical information encryption. However, cascaded DOE-based image reconstruction is highly sensitive to rotation misalignment, which limits its robustness in practical implementations. From a design perspective, this limitation arises from the insufficient utilization of the phase degrees of freedom provided by cascaded DOE. In this work, a double phase update algorithm is proposed for cascaded DOE design, in which all DOEs participate in phase updating during the iterative process. By more effectively exploiting the available phase degrees of freedom, the proposed method significantly enlarges the rotation tolerance while maintaining comparable reconstruction quality. Numerical simulations demonstrate that the rotation tolerance is extended from 1.21° to 2.78°, corresponding to an improvement of approximately 130%. These results indicate that the proposed design strategy provides an effective approach for improving the robustness of cascaded DOE-based 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.
We report a simultaneous image compression and encryption scheme based on solving a typical optical inverse problem. The secret images to be processed are multiplexed as the input intensities of a cascaded diffractive optical system. At the output plane, a compressed complex-valued data with a lot fewer measurements can be obtained by utilizing error-reduction phase retrieval algorithm. The magnitude of the output image can serve as the final ciphertext while its phase serves as the decryption key. Therefore the compression and encryption are simultaneously completed without additional encoding and filtering operations. The proposed strategy can be straightforwardly applied to the existing optical security systems that involve diffraction and interference. Numerical simulations are performed to demonstrate the validity and security of the proposal.
A novel interference-based multiple-image encryption method with high encryption capacity was proposed by position and wavelength multiplexing.For encryption,the original images to be encrypted were divided into two groups,and each group of target images was analytically hidden into two phase only masks by position multiplexing.Subsequently the obtained four phase only masks were further merged into two diffractive phase elements by wavelength multiplexing.The encryption process did not need iterative algorithm and should be implemented digitally,while the decryption process could be performed both digitally and optically.The encryption capacity of the system was evaluated with correlation coefficient,and it was shown that the capacity was greatly improved due to the introduction of both position and wavelength multiplexing.In addition,the robustness of the proposal against noise and occlusion was also investigated,and the results indicated that the proposal is of high robust against noise attack but a little vulnerable to occlusion attack.
Optical encryption inherently provides strong security advantages, with hybrid optoelectronic systems offering additional degrees of freedom by integrating optical and algorithmic domains. However, existing optical encryption schemes heavily rely on electronic computation, limiting overall efficiency, and the physical keys are susceptible to damage, compromising both security and system stability. To overcome these challenges, we introduce the quasi-periodic optical key (Q-POK), which combines long-range order with short-range disorder, enabling enhanced security and robustness against damage within a single platform. By leveraging diffraction symmetry, our design enables optics-driven encryption, effectively shifting the optoelectronic balance toward photonic processing. Moreover, we innovatively apply deep learning to reconstruct the complex optical ciphertext field using only amplitude data and cryptographic keys, simultaneously achieving data compression and improved security. Within this framework, the key space includes continuously tunable parameters such as wavelength, propagation distance, phase modulation, and Q-POK geometry, significantly expanding cryptographic diversity. Our system also demonstrates robust cryptographic reliability by reducing inter-class distances by over 50% and tolerating up to 20% ciphertext loss. Our framework represents a generation of physically grounded, algorithmically enhanced optical cryptosystems—laying a foundational pathway for scalable, hardware-integrated information security paradigms.
Optical encryption inherently provides strong security advantages, with hybrid optoelectronic systems offering additional degrees of freedom by integrating optical and algorithmic domains. However, existing optical encryption schemes heavily rely on electronic computation, limiting overall efficiency, while the physical keys are susceptible to damage, compromising both security and system stability. To overcome these challenges, we introduce the Quasi Periodic Optical Key (QPOK), which combines long range order with short range disorder, enabling enhanced security and robustness against damage within a single platform. By leveraging diffraction symmetry, our design enables optics-driven encryption, effectively shifting the optoelectronic balance toward photonic processing. Moreover, we innovatively apply deep learning to reconstruct the complex optical ciphertext field using only amplitude data and cryptographic keys, simultaneously achieving data compression and improved security. Within this framework, the key space includes continuously tunable parameters such as wavelength, propagation distance, phase modulation, and Q-POK geometry, significantly expanding cryptographic diversity. Our system also demonstrates robust cryptographic reliability by reducing inter-class distances by over 50% and tolerating up to 20% ciphertext loss. Our framework represents a new generation of physically grounded, algorithmically enhanced optical cryptosystems, laying a foundational pathway for scalable, hardware-integrated information security paradigms.
A hybrid encryption and decryption technique for optical information security is proposed. In this method, the iterative Fourier transform algorithm is employed to optimize the encrypted hologram and the decryption key as binary phase-only diffractive optical elements, which were fabricated by electron-beam lithography. In a simple optical setup, the optical decryption is implemented by superimposing the encrypted hologram and the decryption key. Numerical simulation and optical experiment confirm the proposed technique as a simple and easy implementation for optical decryption.