Narrow-band spectroscopic source of coherent radiation, tunable in the mid-IR range

A description is given of a repetitively pulse source of narrow-band coherent radiation with continuous frequency tuning in the ranges 1.5—1.85 μm and 2.5—3.7 μm, and with energies per pulse up to 8 and 3 mJ, respectively. The source is based on parametric amplification of a weak IR signal from a difference-frequency generator or from a single-mode optical parametric oscillator. This source was used to determine the spectra of IR absorption and of degenerate four-wave mixing, as well as the spectra of excitation of stimulated resonance Raman scattering of light in some molecules under static or supersonic jet conditions.