Molecular infrared lasers using resonant laser pumping (review)

A review is given of investigations of the properties and characteristics of middle-infrared pulsed molecular gas lasers using resonant laser pumping. The physical basis and general operating principles of these lasers are presented. Attention is focused on lasers emitting in the 600-900 cm${}^{-1}$ range using $TEA$ $CO_2$ lasers as pump sources. The conditions for formation of the population inversion and theoretical and practical laser systems are studied under the following headings. 1. Excitation and inversion in the fundamental band; at this point, mention is made of the potential usefulness of an $NH_3-N_2$ laser which combines high efficiency, high pulsed and average powers, and tuning in the 770-890 cm${}^{-1}$ range. 2. Excitation of the combination band (or overtone) with inversion in a "hot" band (using $CF_4$, $NOCl$, $CF_3J$, $C_2D_2$, $N_2O$ and other lasers as examples); detailed descriptions are given of a $CF_4$ laser, its physical principles, practical systems, and basic characteristics. 3. Excitation of the fundamental, combination, or difference band with inversion in the difference band ( $N_2O$, $CO_2$ and $OCS$ lasers). 4. Two-photon excitation ($NH_3$, $SF_6$ and $CH_3F$ lasers). The prospects for the development of lasers using resonant laser pumping and the applications of these lasers are discussed.