Frequency-locked cavity ring-down Faraday rotation spectroscopy

Jakob Hayden, Jonas Westberg, Charles Link Patrick, Bernhard Lendl, Gerard Wysocki

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Cavity ring-down Faraday rotation spectroscopy (CRDFRS) 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.

Original languageEnglish (US)
Pages (from-to)5046-5049
Number of pages4
JournalOptics Letters
Issue number20
StatePublished - Oct 15 2018

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics


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