Compact all-fiber light-induced thermoelastic spectroscopy for gas sensing

Area of Science:

• Spectroscopy
• Optical sensing
• Fiber optics

Background:

• Traditional light-induced thermoelastic spectroscopy (LITES) faces limitations in size, optical alignment, and integration with photonic circuits.
• Free-space optics setups hinder miniaturization and practical application in sensing systems.

Purpose of the Study:

• To develop a compact all-fiber LITES system for gas sensing applications.
• To overcome the limitations of conventional LITES systems by utilizing an integrated fiber optic approach.

Main Methods:

• A hollow-core photonic crystal fiber was utilized as both a waveguide and a microcapillary gas cell.
• A single-mode fiber tip was employed for precise light delivery to a quartz tuning fork (QTF) surface.
• Experimental optimization of the SMF tip-QTF distance and light excitation position was performed.

Main Results:

• The all-fiber LITES system successfully detected methane.
• A normalized noise equivalent absorption coefficient of 9.66 × 10⁻⁹ cm⁻¹·W·Hz⁻¹/² was achieved at 1 atm and ~297 K.
• The system demonstrates high sensitivity and performance for gas detection.

Conclusions:

• The integration of fiber sensing with LITES enables the creation of compact sensors.
• This all-fiber LITES approach holds potential for long-distance and multi-point gas sensing applications.
• The developed system represents a significant advancement in miniaturized spectroscopic gas sensing technology.