Accumulation effect of film damage under repetitive laser pulses

In order to study the accumulation effect of film damage under repetitive laser pulses,experimental observations and thermodynamic analysis were carried out. The morphologies damaged by single and multiple laser pulses were observed under a 5000×microscope,then the thermodynamic process between the interaction of laser and plasma was analyzed. Finally the evolution rule of the film damage was found. Both of these two damaged morphologies can be explained by the thermodynamic interactions between laser and laser plasmas. The research results show that: the rough surface of thin film is induced by the laser pulses,which will absorb more laser energy than the beginning. The melt will be removed by the stronger ablation and will be accumulated outside of the laser working area. Since the laser energy is Gaussian distributed,the damaged of multiple laser pulses is centralized and the ablation is limited at the center of laser beam only. This result is a preference for study about film ablation under repetitive laser pulses.