Polarization Holographic Storage Of Ag/TiO₂Nanocomposite Films And Influence Factors Of Photochromism Of Ag Nanoparticles

Holographic data storage with high storage density and rapid transporting rate isconsidered as the most promising development direction in optical storage field.Development of a holographic storage medium is a key factor of restricting itsequipment commercialization. Photochromic materials with erasable and rapidresponse characteristics have a strong competitive advantage in the storage medium.Recently much attention has been given to the multi-photochromism of inorganictitanium/silver nanocomposite film. It has a wide and strong absorption band ofsilver plasma in the visible region, which absorbs different wavelengths of visiblelight, can be transformed to the color close to the incident light. This discoloration andsilver nanoparticles in the film is closely related to optical dissolution behavior. It notonly overcome the problem of thermal stability of organic matter, but also realize theresponse from the near ultraviolet to infrared light regions, resulting in the multi-coloroptical storage.Ag/TiO2composite nanocrystalline film with different distribution densities weregrown using magnetron co-sputtering and ultraviolet light catalytic reduction methods.Morphology, size and distribution of the noble metal nano-crystalline were adjustedby controlling growth parameters resulting in broadening and enhancing the surfaceplasma absorption bands of noble metal.The photo-dissolution of Ag nanoparticles in porous TiO2films is closely relatedto the laser polarization state. Photochromic rate, grating diffraction efficiency andgrating response time characteristics of Ag/TiO2film were strongly dependent onsilver particle size distribution. Polarization holographic gratings (s-s, p-p and s-p) inAg/TiO2nanocomposite films were investigated using Nd:YAG lasers (532nm) aswriting source. The observations can be well explained by the anisotropicphoto-dissolution of Ag nanoparticles, the photo-mobility and reduction of Ag+ions,and the light scattering induced by Ag nanoparticles.A pure polarization holographic grating was recorded in the photochromic filmusing two orthogonal circularly polarized green beams (532nm) and reconstructedwith a linearly polarized red beam (632.8nm). An image was stored in the polarizationhologram and its brightness was dependent on the probe polarization state. The hologram can be erased simply by the irradiation of single green beam. Thisrecording–erasing process can be repeated without obvious losses, which may bebenefited from the reciprocating mobility of Ag+ions and re-growth of Agnanoparticles under the co-action of both the electric gradient force and silver ionconcentration gradient force. In addition, the stability of the Ag nanoparticles wasemphatically studied, through analyzing the experimental data, found that Agnanoparticles can optical dissolved on the semiconductor materials such as titaniumdioxide, zinc oxide. Atmosphere and humidity is the important factors influencing thedissolution rate of silver nanoparticles, the results provides a strong theoreticalsupport for the Ag/TiO2nanocomposite film in optical storage application.