Rapid measurement of cavity ringdown absorption spectra with a swept-frequency laser

Y. He*, B. J. Orr

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


A novel cavity ringdown spectrometer, incorporating a miniature continuous-wave swept-frequency laser that is widely tunable, requires less than 1 s to record wide-ranging absorption spectra with high sensitivity in a single rapid sweep of the laser frequency. The free spectral range of the ringdown cavity defines a sampling grid to measure absorbance-dependent ringdown times at successive cavity-resonance frequencies. The spectrometer has a single-ended transmitter-receiver configuration based on retro-reflected optical-heterodyne detection and exploiting fibre-optical telecommunications components. This swept-frequency approach to cavity ringdown spectroscopy yields a simple, low-cost, compact, rugged, versatile instrument for efficient sensing of gases. The performance of the spectrometer is demonstrated by measuring weak near-infrared rovibrational spectra of carbon dioxide gas within the 1.5-1.6 μm wavelength range.

Original languageEnglish
Pages (from-to)941-945
Number of pages5
JournalApplied Physics B: Lasers and Optics
Issue number8 SPEC. ISS.
Publication statusPublished - Dec 2004

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