We demonstrate an off-axis cavity ring-down spectroscopy system, which uses a mid-infrared continuous-wave optical parametric oscillator as a light source. Off-axis injection with re-entrant configuration of the ring-down cavity is used to achieve high spectral resolution while maintaining high measurement speed. This makes the setup suitable for sensitive molecular spectroscopy in the mid-infrared region, particularly for studies that require high temporal resolution. Formaldehyde (H2CO) absorption spectrum at 3.4 μm is measured using the off-axis re-entrant cavity ring-down spectrometer. © 2012 Springer-Verlag.
Peltola, J., Vainio, M., Ulvila, V., Siltanen, M., Metsälä, M., & Halonen, L. (2012). Off-axis re-entrant cavity ring-down spectroscopy with a mid-infrared continuous-wave optical parametric oscillator. Applied Physics B: Lasers and Optics, 107(3), 839–847. https://doi.org/10.1007/s00340-012-5074-x