Two-color nonvolatile holographic recording in Bridgman-grown Ru:LiNbO3 crystals

The Ru:LiNbO3 crystal with the size of phi 25 mm x 70 mm was grown for the first time by the vertical Bridgman method from the congruent melt doped with a high concentration of 0.05 wt% RuO2. The as-grown crystal was dark brown in color without obvious color change along the growth direction. The optical properties of the crystal were studied along the growth axis (Z) by measuring the optical absorption spectra and OH- absorption peaks. The optical inhomogeneity was improved due to the effective suppression of RuO2 evaporation during the Bridgman growth process. The X-cut sample annealed in air at 950 degrees C for 5h exhibited considerable photochromic effect in a wide wavelength range from 360 to 680 nm after the UV illumination. Two-color nonvolatile holographic recording at 632.8 nm was realized in an X-cut as-grown Ru:LiNbO3 crystal with the UV light of 300-400 nm for gating. A high diffraction efficiency of eta = 41.5% and nonvolatile readout with a fixing ratio of 57.8% were achieved. The crystal had a recording sensitivity of S = 0.03 cm/J and a dynamic range of M/# = 5.9/cm. The crystal also exhibited a fast erasability and free light-induced scattering at the recording power density of I-0 = 0.23 W/cm(2), which are favorable for holographic storage. (C) 2007 Elsevier B.V. All rights reserved.