Hoffart L, Lassonde P, Légaré F, Vidal F, Sanner N, Utéza O, Sentis M, Kieffer J-C, Brunette I
Département d'Ophtalmologie, Université de la Méditerranée, Marseille, France.
Opt Express. 2011 Jan 3;19(1):230-40. doi: 10.1364/OE.19.000230.
We report measurements of crater diameter and surface ablation threshold as a function of laser fluence in porcine corneal stroma and fused silica with pulse durations of 7 fs (2.7 optical cycles), 30 fs and 100 fs at 800 nm. For laser pulses with Gaussian radial intensity profile, we show experimentally that the square of the crater diameter is a linear function of the logarithm of the fluence in fused silica, while it is closer to a linear function of the fluence in corneal stroma. Extrapolating these relations to zero diameter indicates that for both media the minimum fluence required for surface ablation is reduced with shorter pulse duration. A simple theoretical model suggests that this effect is due to a more significant contribution of photoionization as the laser pulse duration shortens.
我们报告了在800nm波长下，脉冲持续时间分别为7fs（2.7个光学周期）、30fs和100fs时，猪角膜基质和熔融石英中坑径和表面烧蚀阈值随激光能量密度的变化测量结果。对于具有高斯径向强度分布的激光脉冲，我们通过实验表明，在熔融石英中坑径的平方是能量密度对数的线性函数，而在角膜基质中它更接近能量密度的线性函数。将这些关系外推到零直径表明，对于这两种介质，表面烧蚀所需的最小能量密度随着脉冲持续时间的缩短而降低。一个简单的理论模型表明，这种效应是由于随着激光脉冲持续时间缩短，光电离的贡献更为显著。
