Pump power dependence of Kerr signals in femtosecond cross pump-probe optical Kerr measurements

We investigated the influence of self-diffraction effect on femtosecond cross pump-probe optical Kerr shutter (OKS) measurements for fast response and slow response materials, respectively. In the slow response material of CS2, a fast response resulted from self-diffraction effect was observed in the time-resolved OKS signals, and the signal intensity showed different pump power dependences at different delay time. For the fast response material of bismuth oxide (BI) glass, the pump power dependence of OKS signals varied when the polarization angle was varied. The pump power dependences of OKS signals for the both materials showed that, the OKS signals resulted mainly from laser induced birefringence effect at low pump powers, and the contribution of self-diffraction effect to OKS signals was enhanced with increasing the pump power.