https://doi.org/10.1140/epjst/e2013-01990-0
Review
Spectral line-shapes investigation with Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy
1 Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun, Poland
2 National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
3 Instytut Fizyki Doświadczalnej, Wydział Fizyki, Uniwersytet Warszawski, Hoża 69, 00-681 Warszawa, Poland
4 National Metrology Institute of Japan (NMIJ), AIST, Tsukuba Central 3, Tsukuba 305-8563, Japan
5 National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
a e-mail: rciurylo@fizyka.umk.pl
Received: 8 June 2013
Revised: 9 August 2013
Published online: 23 October 2013
A review of recent experiments involving a newly developed Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy (PDH-locked FS-CRDS) system is presented. By comparison to standard FS-CRDS, the PDH lock of the probe laser to the ring-down cavity optimized coupling into the cavity, thus increasing the ring-down signal acquisition rate nearly 300-fold to 14 kHz and reducing the noise-equivalent absorption coefficient by more than an order of magnitude to 7 × 10−11 cm−1. We discuss how averaging approximately 1000 spectra yielded a signal-to-noise ratio of 220000. We also discuss how the spectrum frequency axis was linked to an optical frequency comb, thus enabling absolute frequency measurements of molecular optical transitions at sub-MHz levels. Applications of the spectrometer to molecular line-shape studies are also presented. For these investigations, we use semi-classical line-shape models that consider the influence of Dicke narrowing as well as the speed dependence of the pressure broadening and shifting to fit spectra. We show that the improved precision and spectrum fidelity of the spectrometer enable precise determinations of line-shape parameters. We also discuss the importance of line-shape analysis with regard to the development of new spectroscopic databases as well as in the optical determination of the Boltzmann constant.
© EDP Sciences, Springer-Verlag, 2013
