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Actively coupled cavity ringdown spectroscopy with low-power broadband sources

: Petermann, C.; Fischer, P.

Postprint (851 KByte; PDF; )

Optics Express 19 (2011), No.11, pp.10164-10173
ISSN: 1094-4087
Journal Article, Electronic Publication
Fraunhofer IPM ()

We demonstrate a coupling scheme for cavity enhanced absorption spectroscopy that makes use of an intracavity acousto-optical modulator to actively switch light into (and out of) a resonator. This allows cavity ringdown spectroscopy (CRDS) to be implemented with broadband nonlaser light sources with spectral power densities of less than 30W/nm. Although the acousto-optical element reduces the ultimate detection limit by introducing additional losses, it permits absorptivities to be measured with a high dynamic range, especially in lossy environments. Absorption measurements for the forbidden transition of gaseous oxygen in air at 760nm are presented using a low-coherence cw-superluminescent diode. The same setup was electronically configured to cover absorption losses from 1.8×10-8 cm -1 to 7.5% per roundtrip. This could be of interest in process analytical applications.