Optical axis deviation tolerance for data reading in collinear holographic data storage

The Bragg mismatch of volume holographic gratings enables high-density multiplexed recording, yet high-precision data reading demands strict Bragg matching of the reading light. This study focuses on investigating the tolerance of optical axis deviations of the recording objective lens during data reading in collinear holographic data storage system. Comprehensive analyses and comparisons were conducted on key performance metrics of reconstructed coded data pages, including normalized diffraction intensity, signal-to-noise ratio, and bit error rate. The experimental results indicate that the shift multiplexing interval of this system must be greater than 2 μm. During data reading, the servo precision needs to be maintained within ±200 nm; and the uncorrected system has a tilt angle tolerance of 1.3° for the storage medium. To mitigate the impact of medium tilt, a deep learning-based correction method was proposed. After correction, the system's tilt angle tolerance is enhanced to 3°, which is 2.3 times that of the uncorrected system. These findings provide reliable data support and crucial guidance for improving the storage performance of amplitude-modulated collinear holographic data storage devices and constructing specialized holographic storage servo systems.