METHOD AND APPARATUS FOR THE PHOTO-ACOUSTIC IDENTIFICATION AND QUANTIFICATION OF ANALYTE SPECIES IN A GASEOUS OR LIQUID MEDIUM
First Claim
1. A method for the identification and quantification of one or more analyte species present in a gaseous or liquid medium utilizing a laser that outputs a laser beam and a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror, the method comprising:
- coupling the laser beam to the cavity via the cavity coupling mirror using mode matching optics;
applying a periodic dither or modulation waveform to the optical frequency of the laser beam or to the laser itself to thereby induce modulation of the intracavity optical power; and
detecting, at the frequency of the applied dither or modulation waveform or harmonics thereof, a signal representing a varying pressure of the medium within the cavity.
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Abstract
A method and apparatus for the photo-acoustic identification and quantification of one or more analyte species present in a gaseous or liquid medium in low concentration utilizing a laser and a resonant optical cavity containing the medium and having within the cavity at least two partially transparent mirrors, one of which is a cavity coupling mirror and one of which is moveably mounted on an assembly responsive to an input signal.
33 Citations
21 Claims
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1. A method for the identification and quantification of one or more analyte species present in a gaseous or liquid medium utilizing a laser that outputs a laser beam and a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror, the method comprising:
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coupling the laser beam to the cavity via the cavity coupling mirror using mode matching optics; applying a periodic dither or modulation waveform to the optical frequency of the laser beam or to the laser itself to thereby induce modulation of the intracavity optical power; and detecting, at the frequency of the applied dither or modulation waveform or harmonics thereof, a signal representing a varying pressure of the medium within the cavity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification