Open AccessCombining a difference-frequency source with an off-axis high-finesse cavity for trace-gas monitoring around 3 µm
Author(s) -
P. Malara,
P. Maddaloni,
G. Gagliardi,
P. De Natale
Publication year - 2006
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.14.001304
Subject(s) - finesse , trace gas , optics , absorbance , methane , cavity ring down spectroscopy , materials science , volume (thermodynamics) , absorption spectroscopy , parts per notation , atmospheric pressure , analytical chemistry (journal) , spectral line , spectroscopy , absorption (acoustics) , environmental science , laser , chemistry , physics , fabry–pérot interferometer , meteorology , organic chemistry , chromatography , quantum mechanics , astronomy
High-sensitivity spectroscopy of methane around 3 microm was carried out by means of a 5.5-mW cw difference-frequency generator in conjunction with a high finesse cavity in off-axis alignment. By cavity-output integration a minimum detectable absorption coefficient of 5.7*10-9 cm-1Hz-1/2 was achieved, which compares well with results already reported in the literature. Detection of methane in natural abundance was also performed in ambient air, for different values of total pressure, allowing direct concentration measurements via evaluation of the integrated absorbance of the spectra. In particular, at atmospheric pressure, a minimum detectable concentration of 850 parts per trillion by volume (pptv)*Hz-1/2 was demonstrated.