Abstract
The sensitivity of mid-IR quantum cascade laser (QCL) off-axis cavity-enhanced absorption spectroscopy (CEAS), often limited by cavity mode structure and diffraction losses, was enhanced by applying a broadband RF noise to the laser current. A pump–probe measurement demonstrated that the addition of bandwidth-limited white noise effectively increased the laser linewidth, thereby reducing mode structure associated with CEAS. The broadband noise source offers a more sensitive, more robust alternative to applying single-frequency noise to the laser. Analysis of CEAS measurements of a absorption feature at averaged over 100 ms yielded a minimum detectable absorption of in the presence of broadband RF perturbation, nearly a tenfold improvement over the unperturbed regime. The short acquisition time makes this technique suitable for breath applications requiring breath-by-breath gas concentration information.
© 2014 Optical Society of America
Full Article | PDF ArticleMore Like This
Luca Ciaffoni, John Couper, Gus Hancock, Robert Peverall, Peter A. Robbins, and Grant A. D. Ritchie
Opt. Express 22(14) 17030-17038 (2014)
Tomás H. P. Pinto, James M. R. Kirkbride, and Grant A. D. Ritchie
Opt. Lett. 43(8) 1931-1934 (2018)
N. Lang, U. Macherius, M. Wiese, H. Zimmermann, J. Röpcke, and J. H. van Helden
Opt. Express 24(6) A536-A543 (2016)