Biomolecular sensors utilizing waveguide modes excited by evanescent fields.

Area of Science:

• Optoelectronics
• Biosensing
• Materials Science

Background:

• Evanescent-field-coupled waveguide-mode sensors offer label-free detection.
• Multi-layer sensor structures are crucial for optimizing performance.
• Kretschmann configuration enables efficient light coupling for sensing.

Purpose of the Study:

• To investigate the properties of waveguide-mode sensors with various thin metal layers.
• To evaluate the sensitivity and stability of sensors based on different metals (Au, Cu, W, Ti).
• To determine the optimal metal layer material for specific sensor applications and environments.

Main Methods:

• Theoretical and experimental investigation of multi-layer sensor structures (SiO2 waveguide, metal layer, high refractive index substrate).
• Utilizing the Kretschmann configuration for optical illumination and reflectivity measurements.
• Analyzing reflectivity changes upon streptavidin-biotin binding to assess sensor performance.

Main Results:

• Reflectivity changes were observed near waveguide resonances, indicating successful binding detection.
• Gold (Au) and Copper (Cu) layers demonstrated superior sensitivity compared to Tungsten (W) and Titanium (Ti) layers.
• Tungsten (W) and Titanium (Ti) layers exhibited enhanced thermal and chemical stability.

Conclusions:

• The choice of thin metal layer material significantly impacts sensor sensitivity and stability.
• Gold and copper are suitable for high-sensitivity applications, while tungsten and titanium are preferred for robust, stable environments.
• Material selection for metal layers should be tailored to the specific sensor application and operating conditions.