Single-shot, multi-point remote gas sensing by a linearly chirped laser pulse

Area of Science:

• Optics and Photonics
• Spectroscopy
• Environmental Sensing

Background:

• Traditional gas sensing methods often lack the spatial resolution and fast response times required for complex environmental monitoring.
• Long-distance gas detection typically involves trade-offs between sensitivity, spatial resolution, and measurement speed.

Purpose of the Study:

• To develop and demonstrate a novel spectroscopic gas sensing method for long-distance, multi-point detection.
• To achieve high time and spatial resolution in gas analysis over extended ranges.
• To enable accurate spectral measurements without complex frequency-chirping calibration.

Main Methods:

• Utilized a single linearly chirped laser pulse (LCLP) generated by external modulation for spectroscopic analysis.
• Implemented time-division-multiplexing inherent to LCLP for multi-point sensing.
• Employed a multichannel intensity noise compensation mechanism to enhance measurement sensitivity.
• Achieved accurate single-shot spectral measurements due to high intrapulse chirping linearity (∼10⁻⁴ error).

Main Results:

• Demonstrated proof-of-concept with three acetylene gas sensing nodes over a 25-km distance.
• Achieved a time resolution of 280 µs and a spatial resolution of 25 m.
• Reached a sensitivity of 90 ppm for gas detection.
• Validated the method's effectiveness with a 100-ns pulse width and 20-GHz chirping range LCLP.

Conclusions:

• The proposed LCLP-based spectroscopic method offers a novel approach for long-distance, multi-point gas sensing.
• The technique provides significant advantages in time resolution, spatial resolution, and spectral measurement accuracy.
• This method is well-suited for challenging applications requiring fast, spatially resolved gas analysis over long distances.