Pump-probe-alternating photothermal interferometry for two-component gas sensing

Area of Science:

• Optoelectronics
• Gas Sensing Technology
• Fiber Optics

Background:

• Photothermal interferometry (PTI) offers high sensitivity for gas detection.
• Traditional PTI systems often require complex setups with multiple lasers.
• Accurate and simultaneous detection of multiple gas components remains a challenge.

Purpose of the Study:

• To develop a high-sensitivity, cost-effective gas sensor for acetylene and methane.
• To implement a pump-probe-alternating technique for multi-gas detection using PTI.
• To analyze and improve the noise characteristics of the PTI system.

Main Methods:

• Utilized hollow-core fiber photothermal interferometry (PTI).
• Employed a pump-probe-alternating technique with two distributed-feedback lasers.
• Implemented time-division multiplexing for photothermal phase modulation and detection.
• Used a 2.5-cm-long hollow-core conjoint-tube fiber.

Main Results:

• Achieved noise-equivalent concentrations of 370 ppb for methane and 130 ppb for acetylene.
• Demonstrated simultaneous detection of both gases with high sensitivity.
• Analyzed and experimentally validated the noise characteristics of the PTI system.

Conclusions:

• The developed PTI system offers a sensitive and cost-effective solution for multi-gas detection.
• The pump-probe-alternating technique eliminates the need for additional lasers, simplifying the setup.
• This approach advances the field of optical gas sensing for environmental and industrial applications.