In this Letter, we propose an orbital angular momentum (OAM) sensor to simultaneously measure the dynamic micro-displacement and the direction of a moving object in real time. The micro-displacement of the moving object can be detected by the calculation of the petals' rotation angle caused by the coaxial interference between the measured OAM beam and its reference OAM beam, and the direction (forward or backward) of the moving object can be achieved by the clockwise or anticlockwise of the petals' rotation. We also develop an algorithm to monitor the petals' rotation angle and the rotation direction. The experimental results demonstrate that the proposed sensor can achieve high precision ([Formula: see text]) and a longer measuring range ([Formula: see text]). Additionally, the OAM sensor is sensitive to the topological charge in the OAM mode, the initial distance, and the velocity of the moving object. The sensor can perform the non-contact measurement, so it will be a promising method in micro-vibration sensing, surface unevenness sensing, and microbial movement sensing.
Holographic data storage (HDS) has emerged as a promising technology for high-capacity data storage. In this study, we propose a novel approach to enhance the storage density in HDS through a multiplexing perfect optical vortex (POV) hologram. By utilizing the orthogonality property of POV, different POV-recording holograms can be multiplexed to store multiple data pages within the single hologram. Compared with the conventional optical vortex, the better storage density of POV through proof-of-principle experiments is demonstrated. For the POV-multiplexing hologram of six data pages, each one can be reconstructed successfully. In addition, we investigate the impact of axicon periods and multiplexing numbers on the storage performance. Our results reveal that an appropriate selection of axicon periods and multiplexing numbers is crucial to balance storage density and bit error rate (BER). The proposed multiplexing approach offers a valuable solution for achieving high-density and secure holographic data storage systems.
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