Laser-stimulated birefringence of Ga₂O₃-La₂S_2.95Se_0.05 glasses for optical recording of information

We show an opportunity to change the birefringence of Ga₂O₃ – La₂S_2.95Se_0.05 glasses doped by Er³⁺ and La³⁺ ions at λ = 1150 nm wavelength of cw He-Ne laser under illumination of the femtosecond laser. The variation of the refractive indices was found during illumination by 180 fs laser with frequency about 65 MHz (at wavelength λ = 1045 nm). The laser-stimulated birefringence has been explored versus temperature. The observed laser induced and temperature dependences of the birefringence confirm a huge contribution of anharmonic phonon subsystems which is typical for chalcogenide glasses. Due to an occurrence of local space charge density asymmetry, the efficiency of birefringence is enhanced. The anisotropy effect exists only during the illumination and is diminished during 10…12 s after switching off of the photo-inducing laser treatment. There is observed also a correlation between the occurred grating patterns and the values of the birefringence.