Synthesis of DMAW-PMMA photopolymer with high photosensitivity for volume holographic storage

Holographic storage has been considered as a promising candidate for high density data storage because of its potential for terabyte capacity and high data transfer rate. However, lack of a suitable recording material obstructs further development of holographic storage. Photopolymer material has been demonstrated to be the most attractive recording media due to its advantages of high diffraction efficiency, large dynamic range and low cost. Phenanthraquinone (PQ) doped poly (methyl methacrylate) (PMMA) has attracted much attention due to negligible shrinkage and high refractive index modulation. However, the photosensitivity for holographic recording has been limited by the low solubility of the photosensitizer PQ in methyl methacrylate (MMA). Compared to PQ, (2E,5E)-2,5-bis[[4-(dimethylamino)phenyl]methylene]-cyclopentanone (DMAW) has a higher solubility and higher absorption at the wavelength of 532nm. By doping photosensitive system consisting of photosensitizer DMAW and photoinitiator 1,1',2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-bisimidazole (o-cl-HABI) into PMMA, a novel photopolymer with high photo-sensitivity was fabricated by using injection molding technology. The properties of the spectral absorption and the holographic grating dynamic recording are presented. The results show that the photosensitivity of the photopolymer is greatly improved compared to PQ-PMMA with the largest concentration of PQ doped. The optimized concentration of photoinitiator is about 1 wt.%. The feasibility of applying this new photopolymer to holographic storage of images is experimentally demonstrated.