Phase Modulation For Inter-page Noise Cancellation In Collinear Holographic Storage

The arrival of Big Data Era raised higher requirement for information storage. Volume holographic storage is promising because of its high storage density and high data transmission rate. The complex structure of off-axis holographic storage system is difficult to guarantee its stability, which restricts the development of volume holographic storage. Collinear holographic data storage system is named because the information and reference beams are displayed co-axially by the same SLM. And a reflective structure like CD and DVD is used in the holographic recording disc. The disc driver of collinear holographic storage system is similar to that of traditional optical disc. So it can use advanced servo technology to keep system stability in writing and reading process.Shift multiplexing is the main multiplexing method in collinear holography, leading to the existence of inter-page noise which determines distance of shift multiplexing. It is an important topic to shorten shift tolerance to improve storage density of collinear holography. Phase modulation is widely applied in volume holographic storage. In this article I use phase modulation in information beams to reduce inter-page noise of collinear holographic storage.First, I built the simulation model of collinear holography and then analyzed the influence of different reference beam pattern on Bragg degeneracy and point spread function. Based on the calculation model and shift-multiplexing theory, I simulated the signal intensity decay of reconstructed information beam as recording media shifted. It was proposed to utilize phase modulation to reduce inter-page noise. As media shifted, we could control that the Bragg Degeneracy offset damped signal to reduce inter-page noise. Firstly, I explained the shift multiplexing theory by numerical simulation on a micro level. Then we presented an iterative method to generate a phase plate to modulate information beams. By numerical simulation, I found the phase plate could not only reduce inter-page noise, but also restrain Bragg Degeneracy in inner page. The method we propose is also a reference for phase encoding storage in collinear holography.