紧聚焦飞秒脉冲与石英玻璃相互作用过程中的电子动量弛豫时间研究

本文通过数值模拟(3+1)维扩展的广义非线性薛定谔方程,研究了紧聚焦飞秒激光脉冲在诱导石英玻璃的非线性电离过程中电子动量弛豫时间对于该电离过程的影响.计算结果证明电子动量弛豫时间会直接影响入射脉冲在焦点区域所形成的峰值场强、自由电子态密度和能流等参量的分布态势,因此在与实验结果相比较后发现适合于相互作用过程的电子动量弛豫时间的理论值约为1.27 fs.进一步的研究表明,电子动量弛豫时间与逆韧致吸收效应、雪崩电离的概率、等离子体密度、等离子体的自散焦效果以及间接引起的焦平面位置的移动都有着密切的联系.当前的研究结果表明电子动量弛豫时间在飞秒激光脉冲与物质相互作用的过程中发挥着重要作用.

Analysis of electron momentum relaxation time in fused silica using a tightly focused femtosecond laser pulse

The electron momentum relaxation time is studied systematically in order to understand its effect during the excited nonlinear ionization process in fused silica with an irradiation of tightly focused femtosecond laser pulses. According to the analysis of a (3+1)-dimensional extended general nonlinear Schrödinger equation, the electron momentum relaxation time shows a huge effect on peak intensity, free electron density, and fluence distributions in the focal region of the incident pulse, meanwhile a value of 1.27 fs is thought to meet the present experimental result based on the theoretical model. Further research indicates that the change of electron momentum relaxation time can have significant difference among several nonlinear mechanisms, such as the laser-induced avalanche ionization, reverse bremsstrahlung, self-defocusing of plasma, etc. Results show that the electron momentum relaxation time plays an important role in the process of femtosecond laser pulses interaction with materials.
Keywords： femtosecond laser multiphoton ionization fused silica general nonlinear Schrödinger equation