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Updated: Jul 2, 2025
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Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
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Mid-Infrared Generated Laser-Induced Grating Signals in Methane-Containing Gas Mixtures as Indicators of Composition,
Anna-Lena Sahlberg1, Dina Hot1, Zhongshan Li1
1Combustion Physics, Department of Physics, Lund University, Lund, Sweden.
Applied Spectroscopy
|February 19, 2024
Summary
Laser-induced gratings (LIGs) offer a sensitive method for measuring gas parameters like composition, pressure, and temperature. This technique leverages strong methane absorption and efficient energy transfer for high signal generation even at low concentrations.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Gas Sensing Technologies
Background:
- Laser-induced gratings (LIGs) are formed by periodic modulations in a medium's refractive index.
- Mid-infrared laser radiation can induce LIGs in gas mixtures containing methane (CH4).
- The temporal profiles of LIG signals contain information about gas properties.
Purpose of the Study:
- To investigate the use of LIGs for measuring gas parameters.
- To determine the specificity of LIG signal temporal profiles to gas composition, pressure, and temperature.
- To assess the sensitivity of LIG signals to low methane concentrations.
Main Methods:
- Generation of LIGs in methane-containing gas mixtures using nanosecond mid-infrared laser pulses.
- Recording temporal profiles of LIG signals by measuring diffracted continuous wave probe radiation.
- Experimental variation of gas composition, pressure, and temperature.
Main Results:
- LIG signal profiles exhibit specificity to gas composition, pressure, and temperature.
- Large LIG signals are achievable even with methane concentrations as low as ~100 parts per million.
- High LIG generation efficiency is attributed to strong methane absorption and exothermic, partner-dependent collisional energy exchange.
Conclusions:
- LIGs provide a highly sensitive method for gas analysis.
- The technique is effective for detecting low concentrations of methane.
- The specificity of LIG signal profiles allows for detailed characterization of gas mixtures.
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