Polymer media for holographic data storage

Abstract

Holographic data storage is the most promising technology for new generation optical storage. It has the potential to achieve Terabyte level storage per disk and very high data transfer rate of 10 gigabits per second. However, the dynamic range and the shrinkage of current available photopolymer media is still far from the requirement for Terabyte level recording. To increase the dynamic range and reduce the shrinkage of the media, Sol-gel hybrid nanocomposite materials with high refractive index species introduction is an effective approach. In this project, a photo-polymerisable system, consisting of a porous glass matrix synthesised by Sol-gel with molecular level introduction of high refractive index species HRIS embedded within the system, was studied in terms of holographic storage performances. The effect of the addition of acid on the optical quality of sol-gel glass and the ratio of TEOS to 3-(glycidoxypropyl)trimethoxysilane (GPTMS) on the holographic storage performance was also studied. It was found that the ratio of number of moles of HCl to (GPTMS+TEOS) at 3:1 for GPTMS:TEOS ratio of 5.5:1 would result in a clear photopolymer system. Other concentration of HCl will either make the matrix crack, opaque or result in a wet film – all of which is unsuitable for holographic storage. An optimal GPTMS to TEOS ratio 5.5:1 is obtained; this ratio achieves a refractive index change of 2.84x10-3 for the photopolymer Ethylene glycol phenyl ether acrylate POEA as compared to 9.36x10-4 when there is no HRIS added. This yields an improvement of more than 3 times. The shrinkage also reduced from about 14% of a typical photopolymer system to that of 0.211% of this sol-gel nanocomposite system. There is insignificant scattering with the amount of HRIS.