Performances of a pulsed tunable infrared raman laser for spectroscopy

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Abstract
A powerful pulsed widely tunable infrared laser is described. Using the frequency red-shift provided by the stimulated Raman effect in high pressure gaseous hydrogen, the tunability of a Nd : YAG pumped dye laser has been converted down to the mid-infrared range by filtering the third Stokes wave coming out of a capillary Raman cell. Using different dyes pumped by the 532 nm radiation, oscillating from 570 nm to 707 nm, the range of tunability in the infrared extends from 2 μm up to 6 μm continuously. The pulse energy level goes up to ca. 1 mJ near 2 μm (starting from a ca. 100 mJ dye laser). This tunable laser has been tested for spectroscopic applications, using the absorption spectra of a few selected species, including CH 4(v3) and NO(2-0). The effective linewidth is close to 0.35 cm-1. The v4 band at 1 789 cm-1 of the dimer (NO)2 has also been recorded using an absorption cell cooled down to 110 K