Compact optical waveguide grating RI sensor integrated with an Au-ZnO-coated plus-shaped cavity

Area of Science:

• Photonics and Sensing
• Nanomaterials Science
• Biomedical Engineering

Background:

• Refractive index (RI) sensing is crucial for analyzing biological fluids like cerebrospinal fluid (CSF).
• Existing methods may lack the sensitivity or compactness required for rapid clinical diagnostics.
• Surface Plasmon Polaritons (SPPs) offer enhanced light-matter interactions for sensitive detection.

Purpose of the Study:

• To propose and demonstrate a compact optical waveguide grating sensor for ultra-sensitive RI sensing of CSF.
• To leverage a gold (Au)-zinc oxide (ZnO)-coated plus-shaped cavity (PSC) for enhanced sensing performance.
• To investigate the potential for rapid and accurate RI-based diagnosis of CSF samples.

Main Methods:

• Integration of a PSC structure with an optical waveguide grating.
• Utilizing Au-ZnO interface for efficient coupling of guided modes to SPPs.
• Optimization of excitation parameters (optical power, beam half-width, wavelength) and PSC slot width.

Main Results:

• The sensor demonstrated a high sensitivity of 3128.2 (W.m⁻¹)·RIU⁻¹ for the tested RI range of CSF.
• Achieved an auto-correlation coefficient (R²) of 1, indicating excellent linearity and reliability.
• Rigorous optimization of parameters and PSC geometry ensured robust sensing characteristics.

Conclusions:

• The proposed PSC-based Surface Plasmon Resonance (SPR) sensor is a compact, highly reliable, and high-resolution sensing platform.
• This technology shows significant potential for rapid and accurate RI-based diagnosis of CSF.
• The engineered PSC configuration effectively enhances light-matter interaction for ultra-sensitive detection.