R&D: Phase Modulated High Density Collinear Holographic Data Storage System

Optics Express has published an article written by Jinpeng Liu, School of Optics and Photonics, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China, Hideyoshi Horimai, HolyMine Corporation, 2032-2-301 Ooka, Numazu, Shizuoka 410-0022, Japan, Xiao Lin, Yong Huang, and Xiaodi Tan, School of Optics and Photonics, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China

Abstract: “A novel phase modulation method for holographic data storage with phase-retrieval reference beam locking is proposed and incorporated into an amplitude-encoding collinear holographic storage system. Unlike the conventional phase retrieval method, the proposed method locks the data page and the corresponding phase-retrieval interference beam together at the same location with a sequential recording process, which eliminates piezoelectric elements, phase shift arrays and extra interference beams, making the system more compact and phase retrieval easier. To evaluate our proposed phase modulation method, we recorded and then recovered data pages with multilevel phase modulation using two spatial light modulators experimentally. For 4-level, 8-level, and 16-level phase modulation, we achieved the bit error rate (BER) of 0.3%, 1.5% and 6.6% respectively. To further improve data storage density, an orthogonal reference encoding multiplexing method at the same position of medium is also proposed and validated experimentally. We increased the code rate of pure 3/16 amplitude encoding method from 0.5 up to 1.0 and 1.5 using 4-level and 8-level phase modulation respectively.“