Vortex beams [1] exhibit a unique wavefront structure and carry orbital angular momentum (OAM). This OAM is distinct from amplitude, phase, polarization, and light wavelength and can be superimposed to boost information capacity due to the orthogonality of various OAM modes [2]. Consequently, OAM finds applications in high-capacity optical communication systems [[3], [4], [5], [6], [7], [8], [9], [10]], optical tweezers [11,12], multiple photon entanglement [13,14], super-resolution imaging [[15], [16], [17]], and high-precision measurements [[18], [19], [20]]. The development of cryptosystems utilizing OAM as an independent optical key faces limitations due to the absence of topolpgical charge selectivity in the Bragg diffraction formula. This limitation hinders conventional digital holograms from exhibiting OAM selectivity, resulting in the same diffraction pattern for all OAM modes when irradiated by a vortex beam carrying OAM. To tackle this, Fang [21] 2019 introduced a method to acquire OAM-preserving holograms selectively. This technique encodes OAM-specific arrays into holograms. Building on this, Ren [22,23] 2020 showcased a holography type based on complex amplitude hypersurfaces. It allowed lens-free reconstruction of many image channels and confirmed the potential of high-capacity OAM encryption. That year, Zhou [24] added an extra layer of security by using both OAM multiplexing and varied polarization channels for encryption. Two noteworthy advancements were made in 2021. Cheng [25] proposed an OAM multiplexing method across different ellipticity channels, enhancing data storage and security. Meanwhile, Zhu [26] introduced a high-density OAM multiplexing holography approach, improving holography capacity and fidelity. This research paves the way for advanced, secure, and efficient holography.Wang [27] introduced an angular multiplexation of partial helical phase modes in orbital angular momentum holography, improving the holographic information capacity and find widespread applications. Zhang [28] proposed a High-capacity and multi-dimensional orbital angular momentum multiplexing holography to realize three-dimensional multiplexing holography. This research offers potential applications for information storage, optical encryption, and display.

By leveraging the orthogonality of different OAM modes and the OAM conservation principle, OAM selective holography shows promise in achieving optical data storage with intricate security properties. The application of OAM in image encryption is anticipated to pave the way for research into high-security and ultra-large capacity encryption systems. While the topological charge of OAM holography is theoretically infinite, in practice, it is constrained by the Nyquist-Shannon sampling theorem and the limitation of the experimental equipment. Consequently, this paper introduces an image encryption technique utilizing OAM holography and optical multiplexing enabling parallel encryption of large-capacity and large-size image information. Spatial position multiplexing, integrated with OAM holography, enhances the encryption system's capacity while addressing the crosstalk issue in multiple image information. Based on this, the frequency shift technique is introduced to break through the limitation of the photoelectric modulator and realize the encryption of large-size image information beyond the number of SLM pixels. This combination of position multiplexing technique and frequency shift technique result in greater efficiency, enhanced imaging quality, and increased system flexibility in OAM holographic coding. Our research results show that this technique can realize parallel encryption and high-quality decryption of large-capacity and large-size image information with high security, anti-noise, and anti-shear. Section 2 describes the design principle of the system and verifies its effectiveness and feasibility through simulation experiments. Section 3 delves into analyzes of simulation results, demonstrating the method's robust security, noise, and shear resistance. Section 4 summarizes the work of this paper.