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Linear optical-feedback cavity ring-down spectroscopy using an interband cascade laser at 3-µm wavelength.
Optics Express
|March 18, 2026
Summary
We developed a new ultra-high vacuum spectrometer for sensitive light hydrocarbon detection. This linear optical-feedback cavity ring-down spectrometer (LOF-CRDS) achieves high sensitivity for gases like acetylene.
Area of Science:
- Spectroscopy
- Analytical Chemistry
- Physical Chemistry
Background:
- High-sensitivity detection of light hydrocarbons is crucial for various scientific applications.
- Existing methods may lack the required sensitivity or specificity for ultra-high vacuum (UHV) environments.
- Cavity ring-down spectroscopy (CRDS) offers high sensitivity but requires further optimization for specific applications.
Purpose of the Study:
- To develop and characterize a linear optical-feedback cavity ring-down spectrometer (LOF-CRDS) for high-sensitivity detection of light hydrocarbons.
- To operate the LOF-CRDS system under ultra-high vacuum (UHV) conditions.
- To demonstrate the system's capability for precise spectroscopic measurements and partial pressure determination.
Main Methods:
- Utilized an interband cascade laser (ICL) operating at 3 µm, targeting strong C-H stretching vibrational modes.
- Employed a high-finesse linear optical-feedback cavity to narrow the laser linewidth and enhance light coupling.
- Performed Allan-Werle analysis to determine the minimum detectable absorption coefficient and assess system stability.
- Conducted spectroscopic measurements of acetylene (C2H2) partial pressure in a UHV chamber.
Main Results:
- Achieved an empty-cavity ring-down time of approximately 18 µs, corresponding to a cavity finesse of ~37,000.
- Determined a minimum detectable absorption coefficient of ~2.5×10⁻¹⁰ cm⁻¹ with an integration time of 100 s.
- Demonstrated a limit of detection for acetylene partial pressure of 2.1×10⁻⁸ mbar for the selected spectral line.
Conclusions:
- The developed LOF-CRDS system is highly effective for sensitive light hydrocarbon detection in UHV environments.
- The system's performance, characterized by high finesse and low detection limits, makes it suitable for demanding spectroscopic applications.
- This technology advances the capability for precise in-situ measurements of trace gases.
