Continuous-wave cavity-ringdown detection of stimulated Raman gain spectra
Date
2009
Authors
Englich, F.V.
He, Y.
Orr, B.J.
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Journal Title
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Journal article
Citation
Applied Physics B: Lasers and Optics, 2009; 94(1):1-27
Statement of Responsibility
F.V. Englich, Y. He and B.J. Orr
Conference Name
Abstract
Cavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuous-wave (cw) stimulated Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser light at ∼ 1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼ 1064.4 nm. This approach is used to measure cw SRG spectra of the ν <inf>1</inf> fundamental rovibrational Raman band of methane gas at ∼ 2916.5 cm<sup>-1</sup>. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals. Moreover, by employing a ringdown cavity in the form of a ring, the SRG-pump and CRD-detected Stokes beams can co-propagate uni-directionally, which significantly reduces Doppler broadening. © 2008 Springer-Verlag.
School/Discipline
School of Chemistry and Physics
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© Springer-Verlag 2008