Laser based cavity enhanced optical absorption gas analyzer
First Claim
1. A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising:
- a laser that emits continuous wave laser light;
a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror;
mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror;
a first detector configured to measure an intensity of the laser light incident on the cavity coupling mirror and to generate a first signal representing the intensity of the laser light incident on the cavity coupling mirror;
a second detector configured to measure an intensity of the laser light reflected by the cavity coupling mirror and to generate a second signal representing the intensity of the laser light reflected by the cavity coupling mirror;
a third detector configured to measure an intensity of the intracavity optical power of light circulating in the cavity and to generate a third signal representing the intracavity optical power of light circulating in the cavity; and
an intelligence module that processes the first, second and third signals and produces a normalized output signal that is a linear function of total cavity loss and that is not sensitive to laser-cavity coupling.
2 Assignments
0 Petitions
Accused Products
Abstract
Cavity enhanced absorption spectroscopy systems and methods for detecting trace gases. When the frequency of laser light approaches the frequency of a resonance cavity mode, the laser begins to fill the cavity to that mode. Optical intensity inside the cavity reflects total cavity loss when the laser light frequency coincides with the cavity mode transmission peak. The intra-cavity optical power also depends on the coupling efficiency of the laser beam to the particular cavity mode. Measurement of intensities of three optical signals, namely, intensity of the light incident on to the cavity, intensity of the light reflected from the cavity, and intensity of the intra-cavity optical power, with their appropriate normalization advantageously significantly reduce effects of baseline calibration and drift as the normalized signal only depends on total cavity loss, and not the coupling efficiency, as in traditional approaches.
-
Citations
28 Claims
-
1. A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising:
-
a laser that emits continuous wave laser light; a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror; mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror; a first detector configured to measure an intensity of the laser light incident on the cavity coupling mirror and to generate a first signal representing the intensity of the laser light incident on the cavity coupling mirror; a second detector configured to measure an intensity of the laser light reflected by the cavity coupling mirror and to generate a second signal representing the intensity of the laser light reflected by the cavity coupling mirror; a third detector configured to measure an intensity of the intracavity optical power of light circulating in the cavity and to generate a third signal representing the intracavity optical power of light circulating in the cavity; and an intelligence module that processes the first, second and third signals and produces a normalized output signal that is a linear function of total cavity loss and that is not sensitive to laser-cavity coupling. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
-
-
15. A method of detecting one or more analyte species present in a gaseous or liquid medium using a laser that that emits continuous wave laser light 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 light to the cavity via the cavity coupling mirror using mode matching optics; measuring an intensity of the laser light incident on the cavity coupling mirror generating a first signal representing the intensity of the laser light incident on the cavity coupling mirror; measuring an intensity of the laser light reflected by the cavity coupling mirror and generating a second signal representing the intensity of the laser light reflected by the cavity coupling mirror; measuring an intensity of the intracavity optical power of light circulating in the cavity and generating a third signal representing the intensity of the intracavity optical power of light circulating in the cavity; and processing the first, second and third signals to produce a normalized signal that is a linear function of total cavity loss and that is not sensitive to laser-cavity coupling. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
-
-
27. A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising:
-
a laser that emits continuous wave laser light; a resonant optical cavity defined by at least two cavity mirrors, one of which is a cavity coupling mirror, wherein said medium is located within the cavity; mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror; a first means for measuring an intensity of the laser light incident on the cavity coupling mirror and for generating a first signal representing the intensity of the laser light incident on the cavity coupling mirror; a second means for measuring an intensity of the laser light reflected by the cavity coupling mirror and for generating a second signal representing the intensity of the laser light reflected by the cavity coupling mirror; a third means for measuring an intensity of the intracavity optical power of light circulating in the cavity and for generating a third signal representing the intracavity optical power of light circulating in the cavity; and a means for processing signals received from the first, second and third means for measuring to produce a normalized signal that is a linear function of total cavity loss and that is not sensitive to laser-cavity coupling. - View Dependent Claims (28)
-
Specification