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Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor
Published on: August 30, 2012
Supported planar germanium waveguides for infrared evanescent-wave sensing
Applied Optics
|June 20, 1997
Summary
Miniature infrared (IR) waveguides made of germanium on zinc sulfide efficiently guide light. These waveguides show high surface sensitivity for detecting liquid analytes, increasing with incidence angle.
Area of Science:
- Optoelectronics
- Materials Science
- Spectroscopy
Background:
- Miniaturized optical components are crucial for advanced sensing.
- Infrared (IR) spectroscopy requires efficient light propagation in sensing devices.
Purpose of the Study:
- To fabricate and characterize miniature planar IR waveguides for efficient light propagation.
- To evaluate the potential of these waveguides for evanescent-wave sensing applications.
Main Methods:
- Fabrication of germanium (Ge) on zinc sulfide (ZnS) planar waveguides (30-50 µm thickness, 12 mm length, 2 mm width).
- Characterization of IR light propagation using optical cutoffs and transmittance spectra.
- Assessment of evanescent-wave absorption using liquid samples (e.g., water).
Main Results:
- Efficient propagation of broadband IR light was confirmed by characteristic optical cutoffs.
- Oscillatory interference patterns in transmittance spectra matched waveguide theory.
- Strong evanescent-wave absorption was detected from small liquid droplets on the waveguide surface.
- Surface sensitivity increased with incidence or bevel angle, as predicted by theory.
Conclusions:
- Miniature Ge/ZnS planar waveguides enable efficient IR light propagation.
- These waveguides demonstrate high sensitivity for detecting liquid analytes via evanescent-wave absorption.
- The sensitivity is tunable by adjusting the incidence angle, enhancing sensing capabilities.
