Femtosecond laser ionization and damage mechanisms in transparent materials

本项目主要研究透明材料中激光脉冲非线性吸收引起的等离子体形成和材料损伤。通过紧密聚焦超短激光脉冲，已经观察到材料损伤的初步证据，激光能量只有5纳焦耳。由于实验中使用的低脉冲能量和紧密聚焦，可以在最小的自聚焦下实现产生永久性损伤的强度，从而可以准确地确定焦点处的场强度。测量各种激光和材料参数的阈值强度为该小组提供了一个机会，以确定飞秒激光与大块介质相互作用中多光子、隧道和雪崩电离过程的相对作用。此外，对不同激光参数下的损伤形态进行详细的研究，将揭示工作中的基本损伤机制，为应用提供有用的信息。

This project focuses on studying plasma formation and material damage produced by nonlinear absorption of laser pulses in transparent materials. By tightly focusing ultrashort laser pulses, preliminary evidence of material damage with as little as five nanoJoule of laser energy has been observed. Because of the low pulse energy and tight focusing used in the experiments, intensities producing permanent damage can be achieved with minimal self-focusing, allowing the field intensity at the focus to be accurately determined. Measuring the threshold intensity for various laser and material parameters affords the group an opportunity to identify the relative role of multiphoton, tunneling, and avalanche ionization processes in femtosecond laser interactions with bulk media. In addition, detailed studies of the damage morphology for different laser parameters will uncover the basic damage mechanisms at work and provide useful information for applications.