Kovsh D I, Yang S, Hagan D J, Van Stryland E W
School of Optics, Center for Researchand Education in Optics and Lasers, University of Central Florida, 4000 Central Florida Boulevard, Orlando, Florida 32816-2700, USA.
Appl Opt. 1999 Aug 20;38(24):5168-80. doi: 10.1364/ao.38.005168.
We implement numerical modeling of high-energy laser-pulse propagation through bulk nonlinear optical materials using focused beams. An executable program with a graphical user interface is made available to researchers for modeling the propagation of beams through materials much thicker than the diffraction length (up to 10(3) times longer). Ultrafast nonlinearities of the bound-electronic Kerr effect and two-photon absorption as well as time-dependent excited-state and thermal nonlinearities are taken into account. The hydrodynamic equations describing the rarefaction of the medium that is due to heating are solved to determine thermal index changes for nanosecond laser pulses. We also show how this effect can be simplified in some cases by an approximation that assumes instantaneous expansion (so-called thermal lensing approximation). Comparisons of numerical results with several Z-scan, optical limiting and beam distortion experiments are presented. Possible application to optimization of a passive optical limiter design is discussed.
我们利用聚焦光束对高能激光脉冲在块状非线性光学材料中的传播进行了数值模拟。为研究人员提供了一个带有图形用户界面的可执行程序，用于模拟光束在比衍射长度厚得多的材料中的传播（厚度可达衍射长度的10³倍）。考虑了束缚电子克尔效应和双光子吸收的超快非线性以及与时间相关的激发态和热非线性。求解了描述由于加热导致介质稀疏的流体动力学方程，以确定纳秒激光脉冲的热折射率变化。我们还展示了在某些情况下，如何通过假设瞬时膨胀的近似方法（所谓的热透镜近似）简化这种效应。给出了数值结果与几个Z扫描、光限幅和光束畸变实验的比较。讨论了其在无源光限幅器设计优化中的可能应用。
