High precision dual-modulation differential terahertz ATR sensor for liquid measurements

Area of Science:

• Terahertz spectroscopy
• Quantum cascade laser applications
• Chemical sensing

Background:

• Terahertz (THz) radiation offers unique properties for non-invasive analysis.
• Current THz sensors face challenges in sensitivity and stability for dilute solutions.
• Attenuated Total Reflection (ATR) geometry is effective for liquid sample analysis.

Purpose of the Study:

• To develop a highly sensitive and stable terahertz sensor for detecting very low concentration solutions.
• To leverage quantum-cascade-laser (QCL) technology and ATR geometry for enhanced sensing.
• To demonstrate the sensor's capability for analyzing diverse chemical and biological samples.

Main Methods:

• Utilized a quantum-cascade-laser (QCL) as the terahertz source.
• Employed an attenuated total reflection (ATR) geometry for sample interaction.
• Implemented a dual-modulation differential approach to enhance signal-to-noise ratio and stability.

Main Results:

• Achieved high sensitivity for detecting solutions at concentrations as low as 1 µM.
• Demonstrated excellent long-term stability of 40 dB, crucial for reliable measurements.
• Validated sensor performance using standard solutions of ions, sugars, and proteins.

Conclusions:

• The developed QCL-based ATR terahertz sensor provides a robust platform for sensitive analysis of dilute solutions.
• This technology significantly expands the potential of terahertz spectroscopy for liquid and biological sample characterization.
• The sensor's high dynamic range and stability pave the way for advanced applications in chemical and biochemical sensing.