Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery
Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery
复制标题
DOI：
10.1103/physrevb.94.024113
复制
发表时间：
2016-07-18
影响因子：
3.7
通讯作者：
Vogel, Alfred
中科院分区：
文献类型：
--
作者：
Linz, Norbert;Freidank, Sebastian;Vogel, Alfred
在水中的飞秒光击穿的阈值的波长依赖性提供了多光子，隧穿和雪崩电离的相互作用的信息，并在激光手术中的参数选择的兴趣。我们测量了从紫外到近红外波长的气泡阈值，发现随着波长λ的增加，辐照度阈值不断降低。结果进行了比较，假设的带隙为9.5 eV的数值模型的预测，并认为存在一个单独的启动通道，通过激发价带电子到溶剂化状态，然后快速上转换到导带。拟合实验数据产生的电子碰撞时间约为1 fs和估计的能力的起始通道。使用该碰撞时间，击穿动力学进行了探讨，λ = 2 μ m。辐照度阈值首先继续降低，但对于长于1.3 μ m的波长稳定下来。这为波长约为1.3和1.7 μ m的激光手术开辟了前景，这是有吸引力的，因为它们对散射组织的穿透深度很大。
The wavelength dependence of the threshold for femtosecond optical breakdown in water provides information on the interplay of multiphoton, tunneling, and avalanche ionization and is of interest for parameter selection in laser surgery. We measured the bubble threshold from ultraviolet to near-infrared wavelengths and found a continuous decrease of the irradiance threshold with increasing wavelength lambda. Results are compared to the predictions of a numerical model that assumes a band gap of 9.5 eV and considers the existence of a separate initiation channel via excitation of valence band electrons into a solvated state followed by rapid upconversion into the conduction band. Fits to experimental data yield an electron collision time of approximate to 1 fs and an estimate for the capacity of the initiation channel. Using that collision time, the breakdown dynamics were explored up to lambda = 2 mu m. The irradiance threshold first continues to decrease but levels out for wavelengths longer than 1.3 mu m. This opens promising perspectives for laser surgery at wavelengths around 1.3 and 1.7 mu m, which are attractive because of their large penetration depth into scattering tissues.