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采用抽运探测光路,实验研究发现飞秒脉冲激光和连续激光在铬膜表面抽运激发后,当激光功率达到一定程度时,在探测光的透射方向看到了明显的中心暗斑衍射现象。而在没有抽运光激发时,这种暗斑衍射现象又消失。采用二元相位板的理论对这种可逆衍射现象进行了解释,发现低能量密度的飞秒脉冲激光会比高能量密度的连续激光诱导更大的相位变化。实验结果和理论分析均有助于理解弱飞秒脉冲激光及连续激光和铬膜的相互作用的机制。
The experimental results show that the femtosecond pulsed laser and continuous laser are pumped and excited on the chrome film surface. When the laser power reaches a certain level, a clear central dark spot diffraction phenomenon is observed in the transmission direction of the probe light. In the absence of pumping light excitation, this dark spot diffraction phenomenon disappears again. This reversible diffraction phenomenon is explained using the theory of binary phase plates and found that femtosecond pulsed lasers of lower energy density induce larger phase changes than pulsed lasers of high energy density. The experimental results and theoretical analysis are helpful to understand the mechanism of weak femtosecond pulse laser and the interaction between continuous laser and chrome film.