POPURATION INVERSION IN FLAME EXCITED BY MICROWAVE FOR COMBUSTION DERIVED LASER EMISSION

开发高功率、高效率的激光器是实现激光功率工业应用的必要条件。传统激光器的激发仅依赖于电力。这种激光器不仅需要巨大的电力才能发出高功率，而且很难引入一种利用激光发射有效能量以外的能量的系统。这项工作的目的是开发一种高效的高功率激光系统，该系统由燃料的燃烧能量和/或辅助电力产生，用于制造。研究了微波增强甲烷-空气混合物在陶瓷燃烧器中的燃烧，探讨了一种新型激光发射的原理。结果表明，假设的分子能级玻尔兹曼分布受到扰动。用CO_2激光器检测到一个小的信号增益，它表示入射光束在介质中的放大水平。当频率为2.45 GHz的微波照射燃烧区时，两个MCT光电探测器的信号比增加，表明波长为10.6 μm的红外辐射放大。另一方面，利用傅里叶红外光谱分析了微波辐照火焰对红外辐射的吸收。微波激发效应影响了H_2O和CO_2分子在2.7和4.2 μm波段的吸收，使得高于大能级的高能级分子占比大于热力学平衡态。此外，拉曼光谱分析也证实了这种效应。这些事实暗示了微波辐照燃烧衍生激光发射的可能性。

Development of high power and high efficient laser is necessary for introducing industrial applications of laser power. Excitation of the conventional lasers is dependent of only electric power. Such lasers don't only require huge electricity in order to emit a high power, but also it is difficult to introduce a system utilizing energy except for the effective energy for laser emission. The objective of this work is to develop the efficient system of a high power laser derived by combustion energy of fuels and/or auxiliary electricity for manufacturing.Microwave enhanced combustion of methane-air mixture in a ceramic burner is studied to examine the principle of a new laser emission. The results suggest perturbation of the assumed Boltzmann distribution of molecular energy levels. A small signal gain, which represents the level of amplification of an incident beam in a medium, was detected using a CO_2 laser. An increase in the signal ratio of two MCT photodetectors when the combustion zone was irradiated by microwave of 2.45 GHz in the frequency indicates amplification of infrared radiation at 10.6 μm in wavelength. On the other hand, absorption of infrared radiation in the flame irradiated by microwave was analyzed spectroscopically by the FT-IR. The absorption in 2.7 and 4.2 μm bands of H_2O and CO_2 molecules was influenced by the effect of excitation to energy levels by microwave so that the population of molecules at upper energy levels than the grand level becomes greater than a thermo-dynamic equilibrium state. In addition, this effect was confirmed by Raman spectroscopic analysis as well. These facts imply the possibility of combustion derived laser emission by irradiation of microwave.