Lock-in white-light-interferometry-based all-optical photoacoustic spectrometer.

Area of Science:

• Spectroscopy
• Optical Physics
• Gas Sensing

Background:

• Photoacoustic spectroscopy (PAS) is a sensitive technique for gas detection.
• Traditional PAS often requires complex setups and can be limited by signal-to-noise ratio.
• All-optical methods offer potential for miniaturization and improved performance.

Purpose of the Study:

• To develop an all-optical photoacoustic spectroscopy system for trace gas detection.
• To enhance signal-to-noise ratio for improved sensitivity.
• To demonstrate the system's capability for detecting trace acetylene (C2H2).

Main Methods:

• Utilized lock-in white-light interferometry for demodulating a fiber-optic Fabry-Perot cantilever microphone.
• Employed a high-speed white-light interferometer with phase-locked spectral sampling.
• Implemented a custom virtual lock-in amplifier for digital signal processing.

Main Results:

• Successfully demonstrated trace acetylene detection in the near-infrared region.
• Achieved a normalized noise equivalent absorption coefficient of 1.1×10^-9 cm^-1 W^-1 Hz^-1/2 for C2H2.
• The system showed improved signal-to-noise ratio through advanced signal processing.

Conclusions:

• The proposed all-optical photoacoustic spectroscopy system is effective for trace gas detection.
• The combination of white-light interferometry and virtual lock-in amplification significantly enhances sensitivity.
• This technology holds promise for sensitive and selective gas analysis applications.