Overview of Optical Techniques for Characterization of High-Power Infrared Gas Lasers

High-power lasers typically form a multidisciplinary technological area laced with innumerable challenges in its realization as a practical system. The prime amongst them are infrared gas laser sources, such as carbon dioxide gas dynamic laser, hydrogen fluoride, deuterium fluoride laser, and chemical oxygen iodine laser. Each of these laser systems is associated with a unique as well as complex active medium environment involving intense interaction between lasing and pumping species under specific gas dynamic conditions. The parameters viz., specie concentration of the lasing, pumping mediums and other by-products, medium homogeneity, individual constituent gas flow rate, pressure and temperature at critical locations, and cavity Mach number are very crucial in determining the output of the gas laser system. It is essential to determine these parameters nonintrusively, with necessary precision so as to optimize these lasers especially in case of large-scale systems. Thus, the focus of this paper is to review and discuss the existing applicable optical detection methodologies ranging from the more established methods, such as optical absorption/emission spectroscopy, to very contemporary, such as Raman spectroscopy, cavity ring down spectroscopy, laser-induced fluorescence/planer laser-induced fluorescence, and so on, which are relevant for the diagnostic needs of gas lasers.