Near Infrared Absorption Detection in Picolitre Liquid Volumes Using Fiber Loop Ring-Down Detection
Andrews, Nicholas L. P.
Barnes, Jack A.
MetadataShow full item record
Cavity ring-down spectroscopy is performed using a single-mode fibre loop as an optical cavity. The loop contains absorption cells for either liquids or gases, as well as an erbium-doped fibre amplifier. The fibre amplifier is gain-clamped using a second fibre-loop. Ring-down times can be tuned to permit several hundred roundtrips by adjusting the loss ratio between the two nested loops using a variable optical attenuator. Ring-down measurements were performed either in the time domain or using phase shift measurements. Acetylene gas was detected through a ro-vibrational absorption line of the ν1–ν3 combination band at 1532 nm at a limit of detection of 50 ppm. Liquid 1-octyne and 1-dodecyne were detected in a 1 pL volume at detection limits of ∼20% dilution in dodecane through their C–H stretch vibrational overtone transition.