Open AccessFrequency-locked cavity ring-down Faraday rotation spectroscopy
Author(s) -
Jakob Hayden,
Jonas Westberg,
Charles L. Patrick,
Bernhard Lendl,
Gerard Wysocki
Publication year - 2018
Publication title -
optics letters/optics index
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.524
H-Index - 272
eISSN - 1071-2763
pISSN - 0146-9592
DOI - 10.1364/ol.43.005046
Subject(s) - optics , faraday effect , cavity ring down spectroscopy , rotation (mathematics) , spectroscopy , faraday rotator , physics , materials science , magnetic field , laser , quantum mechanics , geometry , mathematics
Cavity ring-down Faraday rotation spectroscopy (CRD-FRS) is a technique for trace gas measurements of paramagnetic species that retrieves the molecular concentration from the polarization rotation measured as the difference between simultaneously recorded ring-down times of two orthogonal polarization states. The differential measurement is inherently insensitive to nonabsorber related losses, which makes off-resonance measurements redundant. We exploit this unique property by actively line-locking to a molecular transition for calibration-free trace gas concentration retrieval. In addition, we enhance the effective duty-cycle of the system by implementing a Pound-Drever-Hall laser lock to the cavity resonance, which allows for ring-down rates of up to 9 kHz. The system performance is demonstrated by measurements of trace oxygen with a minimum detection limit at the ppmv/√Hz-level.