Polarization Dependence of Femtosecond Optical Kerr Signals in Bismuth Glasses

Using the optical Kerr shutter (OKS) technique with an 800-nm femtosecond laser, we demonstrated that the response time of the glass was less than 85 fs. The nonlinear refractive-index of Bi₂O₃-B₂O₃-SiO₂ (BI) oxide glass was estimated to be about 2.93times10^{- 15}cm²/W. By measuring the dependence of the OKS signals on the pump power and on the polarization angle between pump and probe beams, we found that the OKS signals arose mainly from the photoinduced birefringence effect, and the polarization dependence of the signals was dependent on the intensity ratio of the pump beam to the probe beam.