Li-cor, Inc.

Picarro, Inc.

Alexander Kachanov

Serguei Koulikov

Barbara A Paldus

Bruce A Richman

Sze Meng Tan

Eric R Crosson

Sergeui Koulikov

Systems and methods for measuring the isotope ratio of one or more trace gases and/or components of gas mixtures such as different gas species present in a gas mixture. The system includes a resonant optical cavity having two or more mirrors and containing a gas, the cavity having a free spectral range that equals the difference between frequencies of two measured absorption lines of different gas species in the gas, or of two different isotopes, divided onto an integer number. The system also includes a continuous-wave tunable laser optically coupled with the resonant optical cavity, and a detector system for measuring an absorption of laser light by the gas in the cavity. The detector system includes one of a photo-detector configured to measure an intensity of the intra-cavity light or both a photo-acoustic sensor configured to measure photo-acoustic waves generated in the cavity and a photo-detector configured to measure an intensity of the intra-cavity light.

Cavity enhanced laser based isotopic gas analyzer

Cavity enhanced absorption spectroscopy systems and methods for detecting trace gases using a resonance optical cavity, which contains a gas mixture to be analyzed, and a laser coupled to the cavity by optical feedback. The cavity has any of a variety of configurations with two or more mirrors, including for example a linear cavity, a v-shaped cavity and a ring optical cavity. The cavity will have multiple cavity resonant modes, or a comb of frequencies spaced apart, as determined by the parameters of the cavity, including the length of the cavity, as is well known. Systems and methods herein also allow for optimization of the cavity modes excited during a scan and/or the repetition rate.

Cavity enhanced laser based gas analyzer systems and methods

Systems and methods for measuring the isotope ratio of one or more trace gases and/or components of gas mixtures such as different gas species present in a gas mixture. The system includes a resonant optical cavity having two or more mirrors and containing a gas, the cavity having a free spectral range that equals the difference between frequencies of two measured absorption lines of different gas species in the gas, or of two different isotopes, divided onto an integer number. The system includes a continuous-wave tunable laser optically coupled with the resonant optical cavity and a detector system for measuring an absorption of laser light by the gas in the cavity. The detector system includes a photo-detector to measure an intensity of the intra-cavity light, or both a photo-acoustic sensor to measure photo-acoustic waves generated in the cavity and a photo-detector to measure an intensity of the intra-cavity light.

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.

Laser based cavity enhanced optical absorption gas analyzer

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.

Laser based cavity enhanced optical absorption gas analyzer with laser feedback optimization

A system for locking a laser with a resonant optical cavity includes a laser that emits a laser beam, a resonant optical cavity having at least two cavity mirrors, one of which is a cavity coupling mirror, mode matching optics configured to couple the laser beam to the cavity via the cavity coupling mirror, means for applying a periodic dither or modulation waveform signal to the optical frequency of the incident laser beam or to the laser itself to thereby induce modulation of the intracavity optical power, and means for enabling a portion of the light emerging from the cavity coupling mirror to enter a cavity of the laser while maintaining an optical phase that results in periodic optical feedback locking whereby a mean optical frequency of the laser matches a resonance peak of the cavity.

Method and apparatus for locking a laser with a resonant cavity

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.

Method and apparatus for the photo-acoustic identification and quantification of analyte species in a gaseous or liquid medium

Improved ease of mode matching to a passive optical cavity is provided by selecting a cavity design that has a predetermined deviation from a reference cavity design having high transverse mode degeneracy. This predetermined deviation tends to be small, so that the first overlap of high-order transverse modes with the lowest order transverse mode in frequency occurs at relatively high transverse mode numbers. Coupling to high-order transverse modes is thereby reduced, since high-order transverse modes having relatively high transverse mode numbers tend to be more difficult to couple to, and tend to have high loss. During assembly of such a cavity, it can be useful to apply a perturbation to the cavity to further optimize mode matching. For example, the length of an enclosed cavity can be adjusted by altering the number and/or length of spacers in the cavity housing.

Cavity enhanced optical spectroscopy with a cavity having a predetermined deviation from a mode degeneracy condition

A gaseous target analyte present as a minor constituent in an admixture with at least one other gaseous species can be detected using a cavity enhanced optical spectrometer by a process comprising the steps of:

Method for detecting a gaseous analyte present as a minor constituent in an admixture

Improved cavity ring down spectroscopy is provided by binning decay time vs. wavelength data into wavelength bins defined by discontinuities in a wavelength monitor signal. Average decay times and average wavelengths are computed for each bin. The optical loss of a target analyte at the average wavelengths is determined from the corresponding average decay times.

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San Jose, CA, United States of America

Alexander Kachanov