Elimination of the Coherent Artifact in a Pump-Probe Experiment by Directly Detecting the Background-Free Diffraction Signal

The influence of the coherent artifact in a semiconductor Ga-doped ZnO film on femtosecond pump-probe measurement is studied. The coherent artifact mixed into the pump-probe signal can be directly inspected by detecting the background-free first-order diffraction signal induced by the interference between the pump and probe pulses. Experimental results show that by varying the polarization angle or adjusting the relative intensity between the pump and probe pulses, the coherent artifact can be eliminated from the pump-probe measurement.