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Mid-infrared molecular spectroscopy in the quantum noise limit



David A. Long, Adam J. Fleisher, Qingnan Liu, Joseph T. Hodges


A cavity ring-down spectrometer was used to reach the quantum noise limit in the mid-infrared spectral region. Quantum noise was observed not only in the individual ring-down decay events but also in the corresponding ensemble statistics with a magnitude which is commensurate with theoretical predictions. With this instrument a noise-equivalent absorption coefficient of 2.6×10–11 cm–1 Hz–1/2 was demonstrated with less than a microwatt of optical power incident of the photodetector. We believe that this spectrometer’s combination of high sensitivity and robustness make it well suited for measurements of ultra-trace gas species as well as applications in fundamental physics.
Physical Review Letters


Quantum noise, Cavity ring-down spectroscopy, Mid-infrared


Long, D. , Fleisher, A. , Liu, Q. and Hodges, J. (2016), Mid-infrared molecular spectroscopy in the quantum noise limit, Physical Review Letters, [online], (Accessed May 22, 2024)


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Created March 31, 2016, Updated November 10, 2018