TY - JOUR
T1 - Enhancing the sensitivity of mid-IR quantum cascade laser-based cavity-Enhanced absorption spectroscopy using RF current perturbation
AU - Manfred, Katherine M.
AU - Kirkbride, James M.R.
AU - Ciaffoni, Luca
AU - Peverall, Robert
AU - Ritchie, Grant A.D.
PY - 2014/1/1
Y1 - 2014/1/1
N2 - 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 CO2 absorption feature at 1890 cm-1 averaged over 100 ms yielded a minimum detectable absorption of 5.5 × 10-3 Hz-1/2 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.
AB - 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 CO2 absorption feature at 1890 cm-1 averaged over 100 ms yielded a minimum detectable absorption of 5.5 × 10-3 Hz-1/2 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.
UR - http://www.scopus.com/inward/record.url?scp=84919680835&partnerID=8YFLogxK
U2 - 10.1364/OL.39.006811
DO - 10.1364/OL.39.006811
M3 - Article
C2 - 25503003
AN - SCOPUS:84919680835
SN - 0146-9592
VL - 39
SP - 6811
EP - 6814
JO - Optics Letters
JF - Optics Letters
IS - 24
ER -
