US 11,719,630 B2
Resonant optical cavity system with optical feedback, suitable for detecting traces of gas by Raman spectroscopy
Alexandre Katchanov, San Jose, CA (US); Kevin Jaulin, Venelles (FR); Tim Stoltmann, Aix-en-Provence (FR); Pierre Cholat, Meyrargues (FR); Lucien Lonigro, Les Milles (FR); and Bruno Giletta, Marseilles (FR)
Assigned to AP2E, Aix-en-Provence (FR)
Appl. No. 17/310,111
Filed by AP2E, Aix-en-Provence (FR)
PCT Filed Jan. 15, 2020, PCT No. PCT/IB2020/050302
§ 371(c)(1), (2) Date Jul. 16, 2021,
PCT Pub. No. WO2020/148671, PCT Pub. Date Jul. 23, 2020.
Claims priority of application No. 1900454 (FR), filed on Jan. 18, 2019.
Prior Publication US 2022/0065778 A1, Mar. 3, 2022
Int. Cl. G01N 21/47 (2006.01); G01J 3/44 (2006.01); G01N 33/00 (2006.01); G01N 21/03 (2006.01)
CPC G01N 21/47 (2013.01) [G01J 3/4412 (2013.01); G01N 21/031 (2013.01); G01N 33/0004 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A method for analyzing gas by Raman spectrometry, the method comprising:
applying a control signal to a laser source to produce a laser beam sweeping a range of frequencies including frequencies of multiple resonant modes of an optical cavity holding gases to be analyzed, the width of the frequency range being less than the resolution of a Raman spectrometer,
supplying the laser beam to an entrance of the optical cavity,
extracting a feedback beam from the optical cavity,
adjusting a phase and an amplitude of the feedback beam,
sending the phase and amplitude adjusted feedback beam to the laser source,
during sweeping of the frequency range, measuring light intensity variations of the laser beam in the optical cavity, and detecting light intensity peaks in the light intensity variations, each light intensity peak corresponding to a resonance mode of the optical cavity, the phase of the feedback beam being adjusted to reduce a deviation between a median time and the time of occurrence of an apex of one of the light intensity peaks, the amplitude of the feedback beam being adjusted to reduce at least an interval of zero intensity between the light intensity peaks, and
acquiring, with a spectrometer sensor, measurements of the spectrum of light inelastically scattered by the laser beam in the optical cavity to determine the nature and/or concentration of gases in the optical cavity.