Frequency-Division-Multiplexed Multicomponent Gas Sensing with Photothermal Spectroscopy and a Single NIR/MIR...

Area of Science:

• Spectroscopy
• Optical Sensing
• Environmental Monitoring

Background:

• Photothermal spectroscopy offers high sensitivity for gas detection.
• Hollow-core fibers (HCFs) provide long interaction lengths for gas sensing.
• Frequency-division multiplexing (FDM) enables simultaneous detection of multiple gases.

Purpose of the Study:

• To develop a multicomponent gas sensor using HCF photothermal spectroscopy with FDM.
• To demonstrate simultaneous detection of water vapor (H2O), carbon dioxide (CO2), and carbon monoxide (CO).
• To achieve high sensitivity and stability for real-time gas monitoring.

Main Methods:

• Utilized an antiresonant HCF (AR-HCF) as a broadband gas cell (1.39, 2.00, 4.60 μm).
• Employed frequency-division multiplexing (FDM) with modulated NIR/MIR pump lasers.
• Detected photothermal phase modulations using a common probe Fabry-Perot interferometer and lock-in amplifiers.

Main Results:

• Simultaneous detection of H2O, CO2, and CO demonstrated with a 13-cm AR-HCF.
• Achieved limits of detection (LODs) down to 2.7 ppm (H2O), 25 ppb (CO2), and 9 ppb (CO) with 1s integration.
• LODs improved to 222, 1.5, and 0.6 ppb with 1000s averaging.
• Humidity-dependent signals were calibrated using H2O measurements.
• Sensor exhibited good stability (<1.7% fluctuation over 2h).

Conclusions:

• The developed HCF photothermal spectroscopy sensor enables compact, simultaneous, and sensitive multicomponent gas analysis.
• The FDM technique combined with AR-HCF is effective for broadband gas sensing.
• The sensor's stability and calibration method show promise for practical environmental and industrial applications.