Polarization-dependent and rewritable holographic gratings in Ag/TiO2 nanocomposite films

TiO2 nanoporous films loaded with Ag nanoparticles exhibited distinctive photochromism and photoanisotropy under the visible linearly polarized irradiation. Based on such properties, a pure polarization holographic grating was recorded in the photochromic film using two orthogonal circularly polarized green beams (532 nm) and reconstructed with a red beam (632.8 nm). The diffraction efficiency of the holographic grating and the brightness of the reconstruction image were strongly dependent on the polarization state of the probe beam. The hologram can be erased simply by the irradiation of single green beam. This recording–erasing process can be repeated with little loss, which may be benefited from the reciprocating mobility of Ag+ ions, reversible deformation and re-growth of Ag nanoparticles under the alternate irradiation of linearly and circularly polarized light. The novel nanocomposite system with photoanisotropy makes a new range of applications in the field of high-density optical memory media.