CO2 Lasing on Non-Traditional Bands

Abstract

Construction of powerful and efficient laser sources, lasing in various IR ranges, is of importance for further development of a number of trends, e.g., spectroscopy, laser chemistry, sounding of the atmosphere, and metrology. The most natural way to solve this problem is to use unconventional (nontraditional) transitions to produce lasing in commonly used CO2 lasers. The spectral range of CO 2 lasers is greatly increased in lasing on transitions of the so-called band 0111-1110, whose P-branch is in the range of 10.9-11.3 µm. Thorough investigations of gain, vibrational temperatures (T1, T2, T3), and output parameters on lines of the hot band made it possible to achieve efficient lasing both for pulse TEA and for cw longitudinal-discharge CO2 lasers. In studying the lasing spectrum of hot transitions in TEA CO2 lasers some lines not belonging to the 0111-1110 band. We suggested, that these lasing lines belong to higher level transitions, e.g., 1001-2000 (0400), which were called hot, i.e., transitions in which compared to hot transitions two deformation quanta or one symmetric quantum rather than one deformation quantum is added both to the upper and to the lower energy level. In the present work lasing in both a TEA laser and a low-pressure laser with longitudinal discharge on some transitions of the CO2 molecule in the range of 11.0-11.6 µm is reported. The rather high resolution of the spectral equipment used and calculation of transition frequencies on the basis of recent spectroscopic constants made it possible to identify definitively the lasing lines obtained as belonging to the doubly hot bands 0221-1220 and 100l-2000 and the sequence hot band 0112-1111. To find optimum conditions for lasing on the aforementioned bands experimental studies of vibrational temperatures in active media of a TEA CO2 laser and a low-pressure laser with long itudinal discharge were carried out. Earlier the lasing on the 0200(1000)-0110 band of the CO 2 molecule has been obtained in the specific systems at cryogenic temperatures under the lowest efficiency. The optimization of the active medium and its electrical discharge pumping conditions based on the original technique of the temperature model allowed to obtain in the simple TE CO2 laser with UV preionization the powerful lasing on the 0200-0110 band at room temperature. The dependencies of the output and spectral performances of the 16 (14) micrometers lasing vs. a content of the active medium, pumping parameters and cavity characteristics have been carried out. To increase the power performances of the 16 (14) microns CO2 laser the possibility of lasing on the 0201(1001)-0111 band have been experimentally and theoretically investigated under the combined (electrical + optical) excitation of the active medium. The conditions for