External cavity diode laser-based off-axis cavity enhanced absorption spectroscopy in the spectral range between 1000 nm and 1620 nm for trace gas measurements

A robust novel off-axis cavity enhanced absorption spectroscopy instrument using three external cavity diode lasers operating between 1000 nm and 1620 nm was developed to analyse trace gas concentrations. A discrete wavelength tuning range of 620 nm (3828 cm(-1)) for the spectral range between 1000 nm (10,000 cm(-1)) and 1620 nm (6172 cm(-1)) was achieved by using three single-mode, narrow-linewidth, widely tunable external cavity lasers. The performance of the off-axis cavity enhanced absorption spectroscopy system was evaluated using ammonia. Using the absorption lines of ammonia at 1531 nm, 1299 nm and 1040 nm, detection limits of approximately 40 ppb, 80 ppb and 250 ppb are demonstrated for 512 averages.