Saturated-Absorption Cavity Ring-Down Spectroscopy

Abstract

We report on a novel approach to cavity ring-down spectroscopy with the sample gas in saturated-absorption regime. This technique allows us to decouple and simultaneously retrieve the empty-cavity background and absorption signal, by means of a theoretical model that we developed and tested. The high sensitivity and frequency precision for spectroscopic applications are exploited to measure, for the first time, the hyperfine structure of an excited vibrational state of 17O12C16O in natural abundance with an accuracy of a few parts in 10{-11}.

Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy

“…However, extremely sensitive CRDS setups are constantly developed throughout the infrared region. 31,32 …”

Smaller, faster, cheaper detection of radiocarbon

“…3 In 2010 Galli and his team realized that they could disentangle the effects in a single measurement, and SCAR was born. 4 The trick is to shine enough photons into the gas-filled cavity to saturate the molecules' vibrational transitions: With half the molecules in the excited state and half in the ground state, the gas becomes transparent to light circulating through the cavity. And even after the photon source is turned off, the transparency persists for several microseconds, until the intensity decays enough for excitedstate molecules to relax and reabsorb some of the remaining photons.…”

Atomic and molecular spectroscopy with optical-frequency-comb-referenced IR coherent sources

“…Two years ago, we developed a high-sensitivity technique for trace gas sensing, named saturatedabsorption cavity ring-down (SCAR), in order to overcome the main limitation to the achievable CRD sensitivity, namely variations of the empty-cavity decay rate [13]. The SCAR working principle can be shortly described as follows.…”

“…More specifically, we will show results for atomic helium transitions around 1083 nm wavelength [5][6][7][8][9][10], experiments on CO 2 , CH 3 I and CH 4 in the 3-4.5 m range [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], novel set-ups for interrogation of rotational transitions in simple molecules in the far infrared (THz) range [27,28]. As is described, such experiments have been strictly dependent on the development of highly coherent sources, often harnessing their intrinsic properties, and new methodologies.…”