Orthogonal hologram memory extending from visible to UV mediated with TaOx/TiO2:Ag heterojunctions.

The photon-energy conversion covering the full spectral wave band is crucial for detecting and storing information. Schottky junctions in nanoscale such as TiO₂:Ag enable multicolor photochromism and information storage in the visible region. However, the photoelectrons from the UV-excited semiconductor cause the loss of information. It has become a big challenge to the data memory of Schottky junctions extending from the visible to UV band. Herein, we construct a stacked heterojunction structure of TaO_x/TiO₂:Ag as a full wave band holographic memory. Coherent green laser beams are utilized to inscribe a Fourier transform hologram, followed by burning a computer-generated hologram in a focused UV laser spot array. The holographic array based on UV photothermal effect presents high refractive index modulation in the stacked layered oxide film. Meanwhile, the excellent UV protection of TaO_x/TiO₂ heterojunctions makes it possible to fully preserve previously written Fourier transform holographic data. Information cross talk between the two kinds of holograms is almost inhibited. This work provides a bright way for high-density data storage, wideband optical detection, and advanced manufacturing of micro-optical components.