| The current storage system cannot meet the new requirements of the big data era,so it is urgent to find an efficient and safe storage method.Holographic optical storage has the advantages of high storage density,strong stability and low energy consumption,which is particularly prominent in various current storage modes.According to the unique"page"mode,holographic storage has greatly improved the storage speed and storage capacity,which will become an important candidate for the next generation of information storage technology.However,the implementation of mass storage based on stable storage media has been a long-term problem.Therefore,it is imperative to explore advanced optical storage media.The photochromic functional film has excellent optical response and flexible and adjustable spectral range,and has potential application value in optical image copying,image transfer,optical information display and high-density holographic storage.As a typical n-type semiconductor material,tungsten trioxide（WO3）has good optical,electrical and structural characteristics,and has received extensive attention in the fields of optoelectronics and photovoltaic.Most importantly,there are few reports on the research of holographic storage at present.Due to the high recombination rate of WO3 photo-generated electron-hole pairs,the slow migration of carriers and the weak ability of electron reduction,the photochromic efficiency and photo-generated carrier lifetime of WO3 have been greatly affected,resulting in the failure of efficient storage and stable storage of information.Therefore,a lot of work has focused on improving the photochromic properties of WO3,including its own structural modification,noble metal doping and coupling with other semiconductors.The combination of WO3 and polymer materials is considered to be an effective strategy to improve the separation of photogenerated electron-hole pairs.This paper is committed to giving full play to the advantages of WO3 and making up for its disadvantages.By mixing commercial WO3nanoparticles into the two-component polymer matrix,the dispersion and charge transfer ability of WO3 nanoparticles are regulated,and its photochromic characteristics and holographic storage performance are further explored.The specific research work is as follows:（1）WO3 particle film and WO3/polymer composite film were successfully prepared by drop coating method and infrared lamp preheating,and their physical properties were characterized.The effect of different content of polymer on the photochromic properties of WO3 was investigated.The effects of single polyvinyl alcohol（PVA）or polyacrylic acid（PAA）and two-component PVA/PAA polymer matrix on the photochromic response rate and color stability of WO3 were also compared.Through the doping ratio modulation of WO3 and two polymer matrices,it is clear that the 6:1:2 WO3/PVA/PAA film has excellent photochromic properties,and the absorption band edge of WO3/PVA/PAA film has been extended from 400nm to 550 nm,which provides the possibility for multi-wavelength holographic recording and reconstruction.（2）The holographic storage characteristics of WO3/PVA/PAA film and the growth mechanism of holographic grating were studied.The results show that the hydrogen bond and covalent bond interaction between the polymer matrix and WO3 particles accelerate the proton diffusion and electron transfer when WO3 nanoparticles are embedded in the polymer rich in electrons and protons,and the uniform and transparent WO3/PVA/PAA film has appropriate compactness,which plays an important role in isolating oxygen.The contrast of holographic grating stripes is greatly enhanced,and the diffraction efficiency and information readout stability of holographic grating are significantly improved.At the same time,the multi-wavelength holographic storage process of WO3/PVA/PAA thin film is also studied.It is found that the material can realize efficient color holographic storage under broadband excitation.（3）WO3/PVA/PAA thick film was prepared by increasing the concentration of polymer and using drop coating method.The relationship between the diffraction characteristics of the transmission volume holographic grating and the film thickness as well as the writing angle is preliminarily investigated.The results show that the larger the film thickness and the writing angle,the more obvious the volume effect will be under the Bragg condition.At the same time,the diffraction efficiency of the non-tilt grating and the tilt grating are further studied.It is proved that the system has the possibility of realizing multi-dimensional and high-density volume holographic storage.This work has laid a solid foundation for the development of new flexible and efficient holographic memory devices. |
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