飞行光学导光系统中的空气热透镜效应

Atmospheric Thermal Lens in Flying Optics

研究了激光加工用大功率ＣＯ２激光束在飞行光学导光系统中传输所产生的空气热透镜效应。实验发现当飞行光学导光系统中的空气静止时将产生空气热透镜效应，而充以一定压力的压缩空气却可以消除空气热透镜效应。实验表明无热透镜效应时，光束遵循高斯光束传输规律，而有热透镜效应时，光束偏离高斯光束的传输规律，并影响到激光束聚焦焦点的大小和位置。另外通过激光空气热透镜效应的非线性模型计算了热透镜效应所引起的光束传输相对高斯光束的偏离量，理论计算和实验测量相吻合。在此基础上提出了热透镜效应引起光束传输虚束腰和赝束腰的概念。

The atmospheric thermal lens in flying optics induced by high power CO 2 laser during laser materials processing is studied. It is found in experiments that when the air in flying optics is static, atmospheric thermal lens can be induced. However, when the air is filled to the flying optics at certain pressure, atmospheric thermal lens can be eliminated. When there is no thermal lens, laser beam propagation obey the Gaussian theory; when there has thermal lens, laser beam propagation will deviate the Gaussian theory. This will have influence on laser focus size and position. And This deviation is calculated according to the nonlinear mode of laser induced thermal lens. The calculation coincides with the measurement. On the basis of it, two new conceptspseudo beam waist and virtual beam waist are proposed. And the paper points out that virtual beam waist can be used to calculate laser beam propagation but not pseudo beam waist.