Infrared holographic recording in LiNbO3:Cu

Holograms may be recorded in photorefractive LiNbO₃:Cu with pulsed infrared light (wavelength =1064 nm, Q-switched Nd:YAG laser), if the crystals are previously or simultaneously illuminated with a green (=532 nm) light pulse. We study refractive index changes and time constants of as-grown and thermally treated crystals with different copper concentrations. A model explaining this effect is discussed.