The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform

Gérard Mégie - One of the best experts on this subject based on the ideXlab platform.

  • Shot-noise-limited dual-Beam Detector for atmospheric trace-gas monitoring with near-infrared diode lasers
    Applied optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectrometre a Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is approximately 10(-4) (expressed in absorbance units). The design and performances of both a simple subtractor and an upgraded feedback subtractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-microm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situ P and T measurements.

  • shot noise limited dual Beam Detector for atmospheric trace gas monitoring with near infrared diode lasers
    Applied Optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectrometre a Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is ∼10-4 (expressed in absorbance units). The design and performances of both a simple substractor and an upgraded feedback substractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-µm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situP and T measurements.

  • Shot-noise-limited dual-Beam Detector for atmospheric trace-gas monitoring with near-infrared diode lasers
    Applied optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectromètre à Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is ∼10-4 (expressed in absorbance units). The design and performances of both a simple substractor and an upgraded feedback substractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-µm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situ P and T measurements.

Ivan Pelivanov - One of the best experts on this subject based on the ideXlab platform.

  • ndt of fiber reinforced composites with a new fiber optic pump probe laser ultrasound system
    Photoacoustics, 2014
    Co-Authors: Ivan Pelivanov, Takashi Buma, Jinjun Xia, Chenwei Wei, Matthew Odonnell
    Abstract:

    Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluation (NDT&E) of composite materials. Current systems for non-contact detection of ultrasound have relatively low sensitivity compared to contact peizotransducers. They are also expensive, difficult to adjust, and strongly influenced by environmental noise. Moreover, laser-ultrasound (LU) systems typically launch only about 50 firings per second, much slower than the kHz level pulse repetition rate of conventional systems. As demonstrated here, most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive, high repetition rate nanosecond fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe Beam Detector. In particular, a modified fiber-optic balanced Sagnac interferometer is presented as part of a LU pump–probe system for NDT&E of aircraft composites. The performance of the all-optical system is demonstrated for a number of composite samples with different types and locations of inclusions.

Georges Durry - One of the best experts on this subject based on the ideXlab platform.

  • Shot-noise-limited dual-Beam Detector for atmospheric trace-gas monitoring with near-infrared diode lasers
    Applied optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectrometre a Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is approximately 10(-4) (expressed in absorbance units). The design and performances of both a simple subtractor and an upgraded feedback subtractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-microm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situ P and T measurements.

  • shot noise limited dual Beam Detector for atmospheric trace gas monitoring with near infrared diode lasers
    Applied Optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectrometre a Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is ∼10-4 (expressed in absorbance units). The design and performances of both a simple substractor and an upgraded feedback substractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-µm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situP and T measurements.

  • Shot-noise-limited dual-Beam Detector for atmospheric trace-gas monitoring with near-infrared diode lasers
    Applied optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectromètre à Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is ∼10-4 (expressed in absorbance units). The design and performances of both a simple substractor and an upgraded feedback substractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-µm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situ P and T measurements.

Matthew Odonnell - One of the best experts on this subject based on the ideXlab platform.

  • ndt of fiber reinforced composites with a new fiber optic pump probe laser ultrasound system
    Photoacoustics, 2014
    Co-Authors: Ivan Pelivanov, Takashi Buma, Jinjun Xia, Chenwei Wei, Matthew Odonnell
    Abstract:

    Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluation (NDT&E) of composite materials. Current systems for non-contact detection of ultrasound have relatively low sensitivity compared to contact peizotransducers. They are also expensive, difficult to adjust, and strongly influenced by environmental noise. Moreover, laser-ultrasound (LU) systems typically launch only about 50 firings per second, much slower than the kHz level pulse repetition rate of conventional systems. As demonstrated here, most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive, high repetition rate nanosecond fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe Beam Detector. In particular, a modified fiber-optic balanced Sagnac interferometer is presented as part of a LU pump–probe system for NDT&E of aircraft composites. The performance of the all-optical system is demonstrated for a number of composite samples with different types and locations of inclusions.

Ivan Pouchet - One of the best experts on this subject based on the ideXlab platform.

  • Shot-noise-limited dual-Beam Detector for atmospheric trace-gas monitoring with near-infrared diode lasers
    Applied optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectrometre a Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is approximately 10(-4) (expressed in absorbance units). The design and performances of both a simple subtractor and an upgraded feedback subtractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-microm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situ P and T measurements.

  • shot noise limited dual Beam Detector for atmospheric trace gas monitoring with near infrared diode lasers
    Applied Optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectrometre a Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is ∼10-4 (expressed in absorbance units). The design and performances of both a simple substractor and an upgraded feedback substractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-µm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situP and T measurements.

  • Shot-noise-limited dual-Beam Detector for atmospheric trace-gas monitoring with near-infrared diode lasers
    Applied optics, 2000
    Co-Authors: Georges Durry, Ivan Pouchet, Nadir Amarouche, Théodore Danguy, Gérard Mégie
    Abstract:

    A dual-Beam Detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectromètre à Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-Beam Detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is ∼10-4 (expressed in absorbance units). The design and performances of both a simple substractor and an upgraded feedback substractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-µm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situ P and T measurements.