# Multiplexing Perfect Optical Vortex for Holographic Data Storage
## 3 Results
### Experimental Reconstructed Process in Holographic Data Storage  
To validate the selectivity of the POV and assess the confidentiality of the data storage method, the correctly matched reading beam and a mismatched reading beam were employed to retrieve the stored information. The results of these two scenarios are depicted in Figure 4. When the matched reading beam with a topological charge of \(\ell=-5\) illuminates the POV-multiplexing hologram, the reconstructed image is captured by the CCD. As seen in Figure 4, the reconstructed image exhibits multiple Gaussian points and some useless optical spots. To mitigate the useless optical spots, a mode-selective aperture array is used to effectively eliminate the optical spots and filter out the Gaussian points present in the reconstructed image. Subsequently, each point in the reconstructed point-data page is transformed into a 2-bit data representation by utilizing different intensity thresholds. Specifically, the intensity thresholds were set as \(T_{1}=25\), \(T_{2}=120\), and \(T_{3}=200\). The determination of these thresholds is based on the gray-scale values (\(T_{1},T_{2}\), and \(T_{3}\)) of the data page. The intensity levels of the reconstructed point-data page are represented by \(I_{1}^{2}\), \(I_{2}^{2}\), \(I_{3}^{2}\), and \(I_{4}^{2}\). Therefore, the relationship between the threshold values and intensity levels can be expressed as \(I_{1}^{2}<T_{1}<I_{2}^{2}<T_{2}<I_{3}^{2}<T_{3}<I_{4}^{2}\). It should be noted that the specific values of the thresholds can be adjusted and fixed based on prior experiments. Once determined, these threshold values remain unchanged throughout the experiment. Lastly, by comparing the intensity levels of each point with these thresholds, the data are decoded simultaneously, enabling efficient data storage and retrieval. For example, the first row of the reconstructed point-data page is magnified, and the intensity of the red line is extracted. Based on the extracted results, it is evident that the four intensity levels exhibit distinct differences, making them easily distinguishable. However, in our proposed approach, we employed a mismatched reading beam with a topological charge of \(\ell=0\) to retrieve the stored information. As depicted in Figure 4, the reconstructed image shows the presence of optical spots, while the Gaussian points are notably absent. Moreover, when attempting to extract the intensity of the first row, no discernible information can be obtained. This intriguing observation highlights the selectivity and secrecy of the proposed method based on perfect optical vortices (POV). The absence of Gaussian points in the reconstructed image suggests that the stored information is effectively encoded and protected within the holographic data. The utilization of a mismatched reading beam with a topological charge different from that of the stored data pages ensures that only the intended information can be accessed and deciphered. This enhances the security of the holographic data storage system, making it less vulnerable to unauthorized access or data leakage. Based on the proof-of-principle experiments conducted, our approach achieves a high level of selectivity in retrieving the stored information. Only when the reading beam pre  
Figure 4: Thereconstructed results with the matched reading beam and the mismatched reading beam, respectively. The red lines in extracted results represent the intensity distribution, and the blue lines in extracted results represent the thresholds. cisely matches the topological charge of the stored data pages can the desired information be successfully reconstructed. This selectivity adds an additional layer of security to the system, making it challenging for unauthorized users to access or interpret the stored data. Our proposed approach based on perfect optical vortices (POV) offers enhanced selectivity and secrecy in holographic data storage.