Abstract
We have developed and demonstrated a high-sensitivity trace gas instrument employing two mid- infrared quantum cascade lasers and an astigmatic Herriott sample cell with up to a path length. Several aspects of astigmatic Herriott cell optics have been addressed to enable operation at a high pass number (up to 554), including aberrations and pattern selection to minimize interference fringes. The new instrument design, based on the cell, can measure various atmospheric trace gases, depending on the installed lasers, with multiple trace gases measured simultaneously. Demonstrated concentration noise levels ( average) are per trillion [(ppt) ] for formaldehyde, for carbonyl sulfide, for hydrogen peroxide (), and for nitrous acid (HONO). High-precision measurements of nitrous oxide and methane have been recorded at the same time as high-sensitivity measurements of HONO and .
© 2010 Optical Society of America
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