Molecular IR lasers and applications
Molecular IR lasers and applications
Though the Laboratory has performed experiments using CO2 lasers, greatest attention has been given to carbon monoxide lasers (not to be confused with CO2 lasers), which are of interest both from the viewpoint of developing high-power sources of coherent radiation in the mid-IR region of the spectrum and from the viewpoint of molecular kinetics, because an inverse population between vibrational-rotational levels of the CO molecule is due to the vibration-vibration exchange between CO molecules being pronounced nonharmonic oscillators. A CO laser can operate on ~103 vibrational-rotational spectral lines in the basic vibration bands with the vibrational quantum number changed by unity within the wavelength range of 4.6–8.2 μm and on the first overtones within the range of 2.5–4.2 μm. The history of creating and developing CO lasers and the physical principles of their operation (for instance, why the active medium of such a laser should be cooled) can be found in the review [A.A. Ionin, Electric discharge CO lasers, in: M. Endo and R. Walter (eds.), Gas Lasers; CRC Press – Taylor and Francis Group, Boca Raton, Florida, USA, 201 (2007)]. The spectral region of generation of an overtone CO laser overlaps the atmospheric transparency window of ~3.3–4.0 μm; for this reason it can be used for the transfer of high-power radiation in the atmosphere. As a great number of CO laser’s spectral lines is in the spectral regions that include the absorption lines of many explosive and toxic substances, these, not necessarily high-power, lasers can be used for the multi-component gas analysis of such substances. In recent years, LGL’s efforts in studies of CO lasers have been focused on the following trends: development of a compact HF slab discharge-pumped CO laser tunable by frequency within the 5-μm range and generating on overtone transitions (2.5–4.0 μm); development of a CO laser system generating nanosecond pulses; conversion of the radiation frequency of CO lasers in nonlinear crystals with the view of exploring new spectral ranges.
1. A. Ionin, Advanced carbon monoxide laser systems. Proc. SPIE, 8677, 86770F (2013).