A Beam Propagation Method for Distorted Gaussian Beams
A Beam Propagation Method for Distorted Gaussian Beams
复制标题
畸变高斯光束的光束传播方法
DOI：
10.1002/pamm.201900034
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
Pflaum C.
中科院分区：
文献类型：
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作者：
Pflaum C.
畸变高斯光束在光学中有许多应用。其中之一是激光放大器。在激光放大器中，高斯光束由于热透镜效应、偏振效应和增益导引而发生畸变。这导致激光放大器输出端的光束质量下降。一个重要的问题是如何计算这种光束质量的降低以及如何计算放大的光束。现有的光束计算模拟技术存在一些困难。这是为了解决梁的相位和模拟非吸收边界条件的高计算量。我们提出了一种新的光束传输方法，它绕过了这些困难。其思想是将光束分解为高斯光束TEM 00和未知失真函数λ的乘积。这导致了一个有趣的偏微分方程，其中包含一个光束传播对流项。该PDE通过有限元和Crank-Nicolson空间步进离散化数值求解。由此产生的线性方程组求解GMRES。通过ABCD矩阵方法预先计算高斯光束的q参数。这导致了一种高效的仿真技术。该方法可用于模拟高斯光束在激光放大器中的放大过程。
Distorted Gaussian beams arise in several applications in optics. One of them is a laser amplifier. In a laser amplifier a Gaussian beam is distorted by thermal lensing effects, polarization effects and gain guiding. This leads to a decrease of the beam quality at the output of a laser amplifier. An important question is how to calculate this decrease of the beam quality and how to compute the amplified beam. There exist several difficulties of existing simulation techniques for the computation of optical beams. These are the high computational amount in order to resolve the phase of the beam and modelling non‐absorbing boundary conditions. We present a new beam propagation method, which circumvents these difficulties. The idea is to decompose the beam as a product of a Gaussian Beam TEM00 and an unknown distortion function Ξ. This leads to an interesting partial differential equation for Ξ, which contains a beam spreading convection term. This PDE is solved numerically by finite elements and a Crank‐Nicolson space stepping discretization. The resulting linear equation system is solved by GMRES. The q‐parameter of the Gaussian beam is calculated in advance by an ABCD matrix method. This leads to a highly efficient simulation technique. It can be applied to simulate the amplification of Gaussian beams in laser amplifiers.