Diode laser harmonic spectroscopy applied to in situ measurements of atmospheric trace molecules

With the emergence of lead-salt diode laser technology in the early 1970s, a broad and important i.r. spectral region, roughly 3–30 μm, became accessible to tunable laser spectroscopy. More recent advances in fabrication techniques have provided experimenters with relatively high power (0.1–10 mW), quasi-single-mode, high-temperature (>77K) lasers that are readily adapted to compact automated instruments for field experiments. An especially attractive capability of diode lasers is the ease of using them for simultaneous multiconstituent sampling in the atmosphere. This paper presents a summary description of field instruments for atmospheric research which employ diode lasers and second-harmonic detection. Representative results obtained with some of these instruments are presented.