Laser based cavity enhanced optical absorption gas analyzer with laser feedback optimization
First Claim
1. A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising:
- a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror, the cavity having a plurality of optical resonance cavity modes;
a laser that emits continuous wave laser light, wherein the laser is capable of being scanned whereby a mean optical frequency of the laser is adjustable over a range of frequencies, and wherein the laser is responsive to optical feedback light emerging from the cavity;
mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror; and
a detector configured to measure an intensity of the intracavity optical power of light circulating in the cavity and to generate a signal representing the intracavity optical power of light circulating in the cavitywherein the transmissivity of at least one of the cavity mirrors is selected such that the intensity of the optical feedback light impinging on the laser is below a threshold intensity value so as to ensure that a frequency hold interval range of the optical frequency of the laser is smaller than a free spectral range of the cavity.
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Accused Products
Abstract
Optical feedback assisted cavity enhanced absorption spectroscopy systems and methods for measuring trace gases with improved long-term stability and reproducibility include a laser coupled with a resonant optical cavity containing a gaseous medium and having at least two cavity mirrors and a plurality of optical resonance cavity modes. The laser emits continuous wave laser light with a mean optical frequency of the laser being adjustable over a range of frequencies, and the laser is responsive to optical feedback light emerging from the cavity. The transmissivity of at least one of the cavity mirrors is selected such that the intensity of the optical feedback light impinging on the laser is below a threshold intensity value so as to ensure that a frequency hold interval range of the optical frequency of the laser is smaller than a free spectral range of the cavity.
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Citations
30 Claims
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1. A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising:
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a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror, the cavity having a plurality of optical resonance cavity modes; a laser that emits continuous wave laser light, wherein the laser is capable of being scanned whereby a mean optical frequency of the laser is adjustable over a range of frequencies, and wherein the laser is responsive to optical feedback light emerging from the cavity; mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror; and a detector configured to measure an intensity of the intracavity optical power of light circulating in the cavity and to generate a signal representing the intracavity optical power of light circulating in the cavity wherein the transmissivity of at least one of the cavity mirrors is selected such that the intensity of the optical feedback light impinging on the laser is below a threshold intensity value so as to ensure that a frequency hold interval range of the optical frequency of the laser is smaller than a free spectral range of the cavity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 27, 30)
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11. A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising:
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a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror, the cavity having a plurality of optical resonance cavity modes, wherein the cavity has two sets of linearly polarized cavity modes orthogonal to each other; a laser that emits continuous wave laser light, wherein the laser has a linearly polarized output, wherein the laser is capable of being scanned whereby a mean optical frequency of the laser is adjustable over a range of frequencies, and wherein the laser is responsive to optical feedback light emerging from the cavity; mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror; and a detector configured to measure an intensity of the intracavity optical power of light circulating in the cavity and to generate a signal representing the intracavity optical power of light circulating in the cavity wherein an orientation of the laser relative to the cavity is selected so that the output polarization of the laser makes a non-zero angle with respect to the polarization of the cavity modes so that the intensity of the optical feedback light impinging on the laser is below a threshold intensity value so as to ensure that a frequency hold interval range of the optical frequency of the laser is smaller than a free spectral range of the cavity. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 28, 29)
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20. A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising:
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a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror, the cavity having a plurality of optical resonance cavity modes; a laser that emits continuous wave laser light, wherein the laser is capable of being scanned whereby a mean optical frequency of the laser is adjustable over a range of frequencies, and wherein the laser is responsive to optical feedback light emerging from the cavity; mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror; and a detector configured to measure an intensity of the intracavity optical power of light circulating in the cavity and to generate a signal representing the intracavity optical power of light circulating in the cavity wherein the transmissivity of a laser output coupler is selected such that intensity of the optical feedback light impinging on the laser is below a threshold intensity value so as to ensure that a frequency hold interval range of the optical frequency of the laser is smaller than a free spectral range of the cavity.
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21. A method for 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, wherein the laser is responsive to optical feedback light emerging from the cavity, and wherein a mean optical frequency of the laser is adjustable over a range of frequencies, the method comprising:
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coupling the laser light to the cavity via the cavity coupling mirror using mode matching optics, the cavity having a plurality of optical resonance cavity modes; adjusting a mean optical frequency of the laser so as to scan the mean optical frequency of the laser over one or more of the optical resonance cavity modes that have a frequency within said range of frequencies of the laser; selecting the transmissivity of at least one of the cavity mirrors such that intensity of optical feedback light impinging on the laser is below a threshold intensity value so as to ensure that a frequency hold interval range of the optical frequency of the laser is smaller than a free spectral range of the cavity; and measuring an intensity of the intracavity optical power of light circulating in the cavity and generating a signal representing the intracavity optical power of light circulating in the cavity. - View Dependent Claims (22, 23)
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24. A method for 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, wherein the laser is responsive to optical feedback light emerging from the cavity, wherein the laser has a linear polarized output, and wherein a mean optical frequency of the laser is adjustable over a range of frequencies, the method comprising:
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coupling the laser light to the cavity via the cavity coupling mirror using mode matching optics, wherein the cavity has a plurality of optical resonance cavity modes, and wherein the cavity has two sets of linearly polarized cavity modes orthogonal to each other; adjusting a mean optical frequency of the laser so as to scan the mean optical frequency of the laser over one or more of the optical resonance cavity modes that have a frequency within said range of frequencies of the laser; adjusting an orientation of the laser relative to the cavity so that the output polarization of the laser makes a non-zero angle with respect to the polarization of the cavity modes such that the intensity of optical feedback light impinging on the laser is below a threshold intensity value so as to ensure that a frequency hold interval range of the optical frequency of the laser is smaller than a free spectral range of the cavity; and measuring an intensity of the intracavity optical power of light circulating in the cavity and generating a signal representing the intracavity optical power of light circulating in the cavity. - View Dependent Claims (25, 26)
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Specification