为了研究飞秒激光诱导水光学击穿阈值随激光脉冲参数的变化关系,采用四阶Runge-Kutta方法对飞秒激光诱导水光学击穿的椭球体模型进行了不同脉宽(40~540 fs)、波长(400~1 200 nm)和光斑尺寸(0~200 μm)下的数值模拟。通过控制变量法得出阈值光强与这些激光脉冲参数的关系曲线图,据此定性分析了阈值光强与激光脉冲参数的变化特征趋势。应用光强与功率、能量、辐照曝光量和电场强度之间的关系,得到了它们随激光脉冲参数脉宽、波长和光斑尺寸的动态关系,这为进一步研究飞秒激光与水和含水介质的相互作用提供了理论依据。

For studying the relationship between breakdown thresholds and laser parameters,numerical simulation for ellipsoidal time and space model of femtosecond laser-induced optical breakdown in water was done at different pulse duration (40 fs to 540 fs),wavelength (400 nm to 1 200 nm) and spot size (0 to 200 μm) with a Runge-Kutta method. The figures of threshold intensity as a function of pulse duration,wavelength or spot size were given via variable-controlled method. Some conclusions were presented about the relationship between threshold intensity and laser parameters. At last,the figures of threshold power,energy,radiant exposure or electric field strength as a function of pulse duration,wavelength or spot size were presented,which gives a further theoretical support for the study of femtosecond laser interacting with water and aqueous media.