Self-focusing in photorefractive BaTiO3 crystal under external DC electric field

Experimental observations of 1D and 2D self-focusing in a BaTiO3 crystal under externally DC applied electric field are reported. Stationary self-focusing behaviour can be obtained with and without additional uniform illumination.     

Polarization dependence on the holographic recording in spiropyran-doped polymers

We report on the photoinduced anisotropy in the holographic recording in spiropyran doped polymers as a result of the photoizomerization of spiropyran into merocyanine. Photoizomerization is achieved with UV polarized light ( = 355 nm) from the third harmonic of Q-switched Nd:YAG laser. After UV illumination a strong and broad polarization-dependent absorption peak centered 600 nm appears. Absorption holograms were recorded with low power He–Ne lasers with 2.2% output diffraction efficiency for polarization parallel to the polarization of the UV laser. The extremely long lifetime of the merocyanine states (12 days in the dark) and their high resolution makes this material promising as an optical memory element.