Open AccessHigh-speed off-axis Cavity Ring-Down Spectroscopy with a re-entrant configuration for spectral resolution enhancement
Author(s) -
Jérémie Courtois,
Ajmal Khan Mohamed,
D. Romanini
Publication year - 2010
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.18.004845
Subject(s) - cavity ring down spectroscopy , optics , materials science , optical cavity , free spectral range , spectroscopy , resonator , laser , physics , quantum mechanics
Monitoring of changing samples by Cavity Ring-Down Spectroscopy (CRDS) is possible using fast frequency scans of the laser and/or the cavity resonance. Mode-matched cavity excitation improves performance of fast CRDS but data-points result separated by the cavity Free Spectral Range (FSR): low pressure samples demand long cavities. We demonstrate fast CRDS with off-axis injection of a "re-entrant" resonator yielding FSR/N data-points separation. Our N = 4 short-cavity setup is found to perform well compared with other fast-CRDS implementations. Interestingly, the intrinsic chirped ringing affecting ring-down signals in mode-matched fast-CRDS disappear with off-axis injection. This is due to a fine splitting of the re-entrant-cavity degenerate groups of modes by astigmatism.