Abstract

Infrared absorption spectroscopy is an effective spectroscopic technique for studying transient molecules since it combines high spectral resolution and high detection sensitivity. The recent availability of novel nonlinear materials such as AgGaS₂ and AgGaSe₂ makes it now possible to generate narrowband coherent radiation over a wide range (4–18 µm) by means of difference frequency generation. This letter reports on the mixing of a tunable cw dye and dye/Ti:sapphire laser system in a AgGaS₂ crystal 45 mm in length. By using 90° type I phase matching, cw infrared output powers at the 50 µW level can be provided for spectroscopic application. Continuous scans of up to 1 cm^‒1 width have been achieved. Transient molecules can be generated conveniently by excimer laser photolysis with an appropriate precursor. For a sensitivity enhancement a 1 m White cell with a variable optical path length of up to 60 m is employed. The signal is acquired by a transient digitizer interfaced with a computer. First spectra of molecular transients will be presented.

© 1992 Optical Society of America