Novel multiple-image encryption with ultrafast light springs

This research proposed a novel multiple-image encryption scheme using ultrafast light springs. The encryption process begins with the random phase encoding of input images, followed by multiplication with distinct orbital angular momentum (OAM) modes. The modulated signals are then processed using a 4-f ultrashort pulse shaper. The dynamic optical amplitude and phase control of the signal was achieved via a liquid crystal-based spatial light modulator (SLM). The resulting light springs, characterized by helical phase and intensity profiles, are generated through the superposition of multiple laser frequency components. The integration of a double random phase encoding (DRPE) with tailored pulse-shaping operations has further converted the encrypted images to ultrashort pulse springs. This approach extends the temporal characteristics of OAM multiplexing encryption, significantly enhancing the system's encryption capability, key space, and security. The performance of the proposed system is evaluated using multiple security metrics including key sensitive analysis, entropy analysis, correlation analysis, and resistance to attacks. The systematic evaluation demonstrated robustness of this encryption technique and highlighted its potential applications for optical image encryption and real-time secure communication.