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 conductio n 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-colo r holographic recording has been carried out at lambda = 852 nm with a UV g ating 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 diff raction efficiency was observed during 4 h continuous readout, and the bit- error-rate of constructed digital hologram was less than 10(-5). (C) 2000 A merican Institute of Physics. [S0003-6951(00)04213-3].