Pump power dependence of femtosecond two-color optical Kerr shutter measurements.

We investigated the pump power dependence of femtosecond two-color optical Kerr shutter (OKS) signals, which showed a damped sinusoidal variation with increasing pump power. The sinusoidal dependence was attributed to the polarization rotation caused by light-induced birefringence effect. The numerical analysis indicated that, the damping of OKS signal intensity could be attributed to the temporal profile change of probe pulse passing through the OKS setup, due to the non-uniform transient refractive index change induced by pump pulse. Because of the large phase shift of probe pulse, the time-resolved OKS signals showed modulated temporal intensity when pump power was increased.