Water-vapor detection using asynchronous THz sampling.

Area of Science:

• Spectroscopy
• Terahertz (THz) technology
• Chemical sensing

Background:

• Water vapor detection is crucial in industrial processes.
• Traditional methods may have limitations in harsh environments.
• Terahertz (THz) spectroscopy offers a non-invasive sensing approach.

Purpose of the Study:

• To investigate the use of fiber-coupled THz transmitter/receiver pairs for water vapor detection.
• To assess the feasibility of THz spectroscopy in windowless ceramic combustors.
• To evaluate different THz data acquisition techniques.

Main Methods:

• Utilized a conventional commercial THz transmitter/receiver pair for measurements up to 1.25 THz.
• Employed a prototype THz system with asynchronous optical sampling (ASOPS) for THz signal acquisition without a delay line.
• Used two mode-locked Ti:sapphire lasers for independent transmitter and receiver pumping to record time-domain THz signals.

Main Results:

• Successfully detected water vapor absorption within an alumina transparency window.
• Demonstrated the applicability of the THz measurement approach in a windowless ceramic combustor.
• Obtained asynchronous THz-sampling signals up to 1 THz using ASOPS, showing clear water vapor absorption in room air spectra.

Conclusions:

• Fiber-coupled THz spectroscopy is a viable method for detecting water vapor in challenging industrial environments like ceramic combustors.
• ASOPS technique enables efficient THz signal acquisition without mechanical components.
• The developed THz system shows promise for real-time process monitoring and control.