中波红外激光器的近场远场测试方法及应用

高重频3~5 m中波红外固体激光器由于其多方面的潜在应用而受到了广泛的重视。但该波段激光器输出具有较大的技术难度并且人眼不可见，因此对于此种激光器的近远场测试方法的报道很少。文中首先简要介绍此类激光器的产生原理，然后对激光器近场参数进行了详细测试。最后，在室外180 m距离上通过单点探测器采样进行了中波红外激光器的远场绝对功率密度测量，并与Fresnel衍射积分的理论结果进行了对比。理论和实验结果表明，此激光器波长为3.9 m，具有高平均功率和高重频的特点，功率不稳定度为10%。远场测试结果和理论计算都表明此激光器在远场具有准高斯的光强分布。考虑大气影响，测试得到远场平均能量密度为6.367 nJ/cm2，比大气经验模型计算的结果大1.3倍。该研究将对测试中波红外激光器的参数提供有益的参考，并对此激光器圆场探测器干扰阈值评估具有一定的借鉴作用。

Method of near-and far-field measurement and application for mid-infrared laser

The high-repetition 3-5 μm mid-infrared laser has gain a lot of attention for its potential applications in civil and military.However,there are many technical difficulties to generate this band laser and it is invisible.Therefore,there are rarely such reports about methods of near-and far-field measurements for the lasers.In this article,the near-field measuring for the parameters of laser was conducted at first.Then,the absolute and relative energy density distribution were obtained by the point detector sampling.At last,the infrared imaging system was used to record the image of laser spot received in a far-field screen in the distance of 180 m.The relative energy density distribution could also be simulated by theory of Fresnel diffraction integral of circular aperture.The theoretical and experimental results show that the wavelength of this laser is about 3.9 μm with the properties of high average power,high repetition and stability about 10%.The far-field theoretical results show that the energy density distribution is quasi-Gaussian distribution and agrees well with the average energy density of 6.367nJ/cm2,which is smaller than the evaluation of empirical formula by the factor of 1.3.This work will definitely be helpful to measure the parameters of pulsed high-repetition mid-infrared laser and judge the disturbing threshold for the detectors in more far distance.