Hf 4+ Ion Concentration Dependence of Holographic Storage Properties in Hf:Fe:Cu:LiNbO3 Crystals

A series of Hf:Fe:Cu:LiNbO3 crystal with various concentrations of Hf (4+) ion doping are grown in air by the conventional Czochralski technique. The segregation coefficients of the Hf (4+), Fe3+, and Cu2+ ions in the crystals are carried out with an inductively coupled plasma-atomic emission spectrometer. The birefringence gradient method is measured in order to analyze the optical homogeneity of Hf:Fe:Cu:LiNbO3 crystals. The holographic storage properties of Hf:Fe:Cu:LiNbO3 crystals are investigated by the two-wavelength coupling experiment. The result shows that the writing time constant shortens from 529.3 to 214.4 s, and the dynamic range increases from 1.12 to 8.07 with increasing Hf (4+) content in the Hf:Fe:Cu:LiNbO3 crystals.