飞秒激光对氟化镁烧蚀机理研究

Mechanism of femtosecond laser-induced damage in magnesium fluoride

用扫描电镜(SEM)研究了氟化镁在800nm超短脉冲激光作用下的单枪表面烧蚀形貌.根据烧蚀斑面积与激光脉冲能量间的对数关系,测得烧蚀阈值与激光脉宽的关系曲线(55—750fs).计算了导带电子的双光子吸收,改进了多速率方程模型,很好地解释了实验结果.

Single-shot damage morphology of magnesium fluoride induced by femtosecond laser pulse was studied with scanning electron microscope （SEM）. The laser pulses used were 800 nm central wavelength. By the linear relationship between the area of damage spot and the logarithm of the laser energy, we measured the dependence of damage threshold on the pulse duration ranging from 55 femtosecond （fs） to 750 fs. We have calculated the two-photon absorption in the conduction band and improved the multiple-equation model （ Phys. Rev. Lett. 92 187401, 2004）. The experimental results are well explained by our model.