Matrices-Controlled Holographic Recording And Reconstruction Of Azopolymers

High diffraction efficiency,high stability and large-capacity holographic storage are critical to the development of society.Poly?Disperse-Red-19-p-phenydiacryate?,i.e.PDR19,based on the advantages of photochromic properties and self-processing ability,have become one of the most typical holographic storage material.Large refractive index modulation for PDR19 can be obtained based on the deformation induced by cis-orientation and trans-cis isomerization during illumination of molecule in repeatable cycles by single visible irradiation,which can be used for information storage.For coherent excitation,however,the trans-molecules at bright regions of holographic fringes can be changed to the cis-ones,which can induce wriggling of the polymer framework and form lager free volume,thus the diffraction efficiency of PDR19 is decayed.Commonly,inorganic nanoparticles are doped into organic polymeric materials to increase holographic efficiency,reducing volume shrinkage,and increasing chemical activity.However,the entanglement of the polymer backbone and the uneven distribution of the nanoparticles all affect the transparency of the material.And the storage stability is damaged.In this paper,a new organic-inorganic composite film is proposed that TiO2 nanoporous films with high optical transparency are used as a nano-template for PDR19 deposition,in which non-destructive readout and efficient holographic storage are realized.The PDR₁₉ organic film was prepared by drop-coating PDR₁₉ solution on the glass and TiO2 nanoporous substrates with different layers?1,3 and 6?.The pure PDR19 film and PDR19/TiO2?n?organic-inorganic composite film were obtained.The relationship among the absorption peak position,the aggregation of azo molecules and the matrix environment were investigated.The comparison of the holographic dynamics of the two kinds of films shows that the TiO2 frameworks play a rigid support role for azopolymer,which is beneficial to suppress the later decline of diffraction efficiency.In addition,the erasure experiment of holographic gratings shows that the TiO2 porous structure is beneficial to inhibit the entanglement of the azpolymer backbone.Azo molecules are easier to achieve reversible conversion of cis-trans isomerization,and the resultant erasable optical storage performance is improved.Besides,PDR19 was dispersed by poly?9-vinylcarbazole??PVK?and then drop-coated into the TiO2 porous structure.The absorption peaks and holographic storage characteristics of pure PDR₁₉,PDR₁₉@PVK,PDR₁₉/TiO₂ and PDR₁₉@PVK/TiO₂ films were compared.The results show that PVK and TiO₂ play a co-dispersion role for PDR₁₉.Diffraction efficiency,chemical activity and reversible light conversion are further optimized in PDR19@PVK/TiO2film.Thereby efficient reversible optical storage and polarization multiplexing storage can be conducted.Efficient updated colorful reconstruction of mixed holographic images was also achieved.