All-diode-laser ultraviolet absorption spectroscopy for sulfur dioxide detection

Ultraviolet radiation around 302 nm was produced by sum-frequency generation in beta-barium borate employing a blue and a near-infrared diode laser. The diode-laser-based spectrometer has a mode-hop-free tuning range of 50 GHz and was used for high-resolution spectroscopic detection of sulfur dioxide. Differential measurements of several gas concentrations, at low pressure as well as at ambient atmospheric pressure, were demonstrated. The detection limit in the first implementation of the instrument was about 20 ppm m at atmospheric pressure, essentially limited by interference fringes. Methods for greatly improving this limit are suggested.