Long-wave infrared pulsed external-cavity QCL spectrometer using a hollow waveguide gas cell

Area of Science:

• Spectroscopy
• Laser Technology
• Environmental Monitoring

Background:

• Volatile organic compounds (VOCs) are significant air pollutants.
• Detection of VOCs requires sensitive and rapid analytical techniques.
• Mid-infrared spectroscopy offers unique molecular fingerprinting capabilities.

Purpose of the Study:

• To develop and characterize a novel spectrometer for VOC detection.
• To demonstrate the spectrometer's performance using propane as a surrogate.
• To evaluate the system's sensitivity and response time.

Main Methods:

• Construction of a spectrometer utilizing an external cavity pulsed quantum cascade laser.
• Employing a hollow silica waveguide gas cell for sample analysis.
• Testing with propane gas across various concentrations.

Main Results:

• The spectrometer tunes from 10-13 µm, targeting water-free VOC absorption.
• A minimum detectable absorbance of 3.5×10^-5 was achieved at 75s integration time.
• Measurements showed good linearity with propane concentration.

Conclusions:

• The developed spectrometer is suitable for sensitive VOC detection.
• The hollow silica waveguide gas cell enables rapid analysis of small sample volumes.
• This technology offers a promising tool for environmental monitoring and trace gas analysis.