Highly Sensitive Photopolymer For Holographic Data Storage Based On Phenanthraquinone

Volume holographic data storage,utilizing multiple coherent laser beams to record the information onto the photopolymer materials,is also recognized as a promising new generation optical data storage technology with huge capacity,high write/read speed and is economically sustainable.A lack of appropriate storage medium,however,remains a major obstacle towards volume holographic storage achieving its full practical application potential.The troublesome intrinsic defects of volume shrinkage,poor oxygen resistance and thin thickness have severely inhibited the feasibility of most existing photopolymer functional materials in photolithography for the purpose of high-density volume holographic data storage.On the other hand,the excellent characteristics of low volume shrinkage and long-liftime facilitate phenanthraquinone doped polymethyl methacrylate（PQ/PMMA）photopolymer’s application on multi-dimensional holographic storage as low-cost optical storage medium,however,itself seriously hampered by its inherent poor holographic performance（e.g.the diffraction efficiency,refractive index modulation,especially poor photo-sensitivity and so on）.Accordingly,we put forward new solutions including:Through combining with free radical polymerization and supramolecular chemistry techniques,we herein demonstrate that C₆₀ can dramatically enhance the intensity holographic performance of PQ/PMMA photopolymer（intensity holographic diffraction efficiency increased～50%,photo-sensitivity increased double）,and the angle-multiplexing of 321 gratings and 81 holographic patterns can be readily recorded separately.More surprisingly,although C₆₀ can effectively enhance the intensity holography,it reduces the polarization sensitivity of PQ/PMMA photopolymer,resulting in a substantial weakening of orthogonally polarized holography.Further analysis reveals that the reduction of the polarization sensitivity should originate from the strongπ-πstacking interaction between C₆₀ and PQ,which causes C₆₀and PQ/PMMA construct supramolecular(C₆₀ as the host)and limits the orientation of PQ during the photopolymerization.The constructed supramolecular also leads to a diminished photoinduced anisotropy of PQ/PMMA photopolymer.Then,via introducing 8 methacryl polyhedral oligomeric silsesquioxane（Ma-POSS）,we dramatically enhance the holographic performance of PQ/PMMA photopolymer with excellent characteristics of high-sensitivity,high-diffraction-efficiency and neglectable volume shrinkage for holographic data storage,the photo-sensitivity,diffraction efficiency and volume shrinkage reaching 1.47 cm/J,～75%and～0.09%,respectively.Ma-POSS here dramatically enhances the photo-sensitivity about 5.5 times,increased the diffraction efficiency more than 50%and suppressed the volume shrinkage over 4 times.Further analysis reveals that,Ma-POSS obviously increased the molecular weight by grafting PMMA to be a star-shaped macromolecular.And the residual C=C of POSS-PMMA dramatically increased the photo-sensitivity.Moreover,the star-shaped POSS-PMMA acting as a plasticizer dramatically enhances the mechanical properties and so reduces the photo-induced volume shrinkage of PQ/PMMA.Finally,by the use of the POSS-PMMA/PQ in collinear holography system,it appeared to be promising for fast but low bit error rate in holographic information storage.The current study thence has not only successfully synthesized C₆₀-PQ/PMMA supramolecular and POSS-PMMA/PQ star-shaped photopolymer materials with potential for holographic storage applications,but also investigated the microphysical mechanism of the excellent photo-sensitivity,diffraction efficiency and volume shrinkage,and clarified the thermal-and photo-reaction processes of the C₆₀-PQ/PMMA and POSS-PMMA/PQ photopolymer.The above conclusions have important reference significance for further preparing highly sensitive photopolymer materials.