Nonvolatile two-color holographic recording in Tb-doped LiNbO3

We have found that Tb-doped near-stoichiometric LiNbO3 crystals have three different types of energy levels: ultraviolet (UV) absorption centers just above the valence band, shallow electron traps slightly below the conduction band, and deep traps located about 1.9 eV (lambda approximate to 650 nm) below it. Using this shallow trap as an intermediate energy state, two-color holographic recording has been carried out at lambda = 852 nm with a UV gating light at 313 nm. A few % of diffraction efficiency was achieved, and the measured two-color sensitivity was 0.01-0.02 cm/J. No reduction of diffraction efficiency was observed during 4 h continuous readout, and the bit-error-rate of constructed digital hologram was less than 10(-5). (C) 2000 American Institute of Physics. [S0003-6951(00)04213-3].