Integrated Quasi-Optical Terahertz Liquid Sensor Leveraging Mode-Parity-Dependent Interaction with a...

Area of Science:

• Photonics and Sensing
• Integrated Optics
• Terahertz Technology

Background:

• Advancing chemical and biomedical analysis requires high-precision, on-chip sensing.
• Terahertz (THz) sensing offers unique material interaction properties.
• Point-of-care diagnostics and in situ industrial monitoring demand integrated analytical tools.

Purpose of the Study:

• To present an integrated quasi-optical THz liquid sensor on a silicon slab waveguide.
• To demonstrate intrinsic self-calibration using mode-parity-dependent field distributions.
• To enable precise material characterization and simultaneous calibration for continuous monitoring.

Main Methods:

• Fabrication of the sensor using deep reactive ion etching of high-resistivity silicon.
• Integration of a longitudinal cavity within a silicon slab waveguide.
• Utilizing capillary-confined analytes to interact with guided slab modes on resonance.

Main Results:

• Demonstrated alternating resonance peaks sensitive to refractive index and absorption for water and isopropanol.
• Validated linear shifts in frequency and transmission loss corresponding to analyte properties.
• Showcased self-calibrating capability for real-time compensation of system fluctuations.

Conclusions:

• The developed THz sensor enables simultaneous, precise material characterization and calibration.
• The intrinsic self-calibration feature is crucial for automated continuous monitoring applications.
• This technology holds significant potential for in-line process monitoring and high-bandwidth sensing.