Photo-induced phenomena in GeS 4 glasses

GeS 4 bulk glasses were prepared by the melt-quench technique and the samples were irradiated by 532-nm linearly polarized light. After the laser treatment, the photo-induced changes of the samples were investigated by UV-1601 spectrophotometer and optical second-order nonlinear tester. The results show that the transmittance of the samples around 532 nm obviously decreases and Bragg reflector forms, which is due to the production of photon-generated carriers. With the increase of laser pulse energy or the extension of irradiation duration, the Bragg reflector increases and gradually tends to be stable. These can be ascribed to the excitationcapture process of the carriers. After irradiation, the relaxation phenomenon results from the release of part of the absorbed energy in the glass matrix. And the fitting equation of the relaxation process is consistent with a conventional Kohlrausch stretched exponential function. The origin of the second harmonic generation (SHG) is because of the dipole reorientation caused by the photo-induced anisotropy in the glass.