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Tunable diode laser absorption spectroscopy in coiled hollow optical waveguides
Gregory J Fetzer1, Anthony S Pittner, William L Ryder
1Areté Associates, Tucson, Arizona 85711, USA. gfetzer@arete-az.com
Applied Optics
|June 25, 2002
Summary
This study showcases tunable diode laser absorption spectroscopy for detecting carbon dioxide (CO2) and ammonia (NH3) using coiled hollow optical waveguides. This innovative method achieves sensitive gas detection with rapid response times.
Area of Science:
- Analytical Chemistry
- Spectroscopy
- Optical Physics
Background:
- Diode laser absorption spectroscopy (DLAS) is a powerful tool for gas analysis.
- Long-path absorption cells are crucial for enhancing sensitivity in gas detection.
- Traditional long-path cells can be bulky and slow to respond.
Purpose of the Study:
- To develop a compact and responsive system for CO2 and NH3 detection using DLAS.
- To integrate hollow optical waveguides as long-path sample cells in a spectroscopic system.
- To improve the practicality of long-path spectroscopy through novel waveguide design.
Main Methods:
- Utilized a tunable distributed feedback diode laser for absorption measurements.
- Employed coiled hollow optical waveguides as long-path sample cells.
- Implemented a novel waveguide perforation geometry to optimize pneumatic flow and maintain optical path length.
Main Results:
- Demonstrated tunable diode laser absorption spectroscopy for CO2 and NH3 near 1.5 micrometers.
- Achieved a minimum detectable absorbance of 3.5 x 10^-5 in a 3-m waveguide section.
- The coiled waveguide design reduced system size while maintaining sensitivity.
Conclusions:
- Hollow optical waveguides are effective long-path cells for DLAS, offering rapid response and reduced physical footprint.
- The novel waveguide perforation enhances performance for high flow rate applications.
- This approach provides a sensitive and practical method for real-time gas concentration monitoring.