Sensitivity enhancement in grating coupled surface plasmon resonance by azimuthal control

Area of Science:

• Plasmonics
• Nanophotonics
• Sensor Technology

Background:

• Grating coupled surface plasmon resonance (GCSPR) sensors offer label-free detection.
• Improving the sensitivity of GCSPR sensors is crucial for advanced analytical applications.
• Conventional GCSPR configurations have limitations in achievable sensitivity.

Purpose of the Study:

• To present a novel method for enhancing the sensing capability of GCSPR sensors.
• To achieve a significant increase in sensitivity compared to existing methods.
• To demonstrate the effectiveness of the proposed technique for detecting molecular interactions.

Main Methods:

• Azimuthal rotation of the grating (phi) to excite double surface plasmon polaritons (SPPs) at a single wavelength.
• Tuning the incident wavelength near this condition to merge double SPPs into a spectrally sharp, angularly broad multi-SPP resonance.
• Utilizing the condition where the SPP momentum vector is perpendicular to the incident light momentum.
• Demonstrating the method on a gold (Au) grating surface with a dodecanethiol (C12) self-assembled monolayer (SAM).

Main Results:

• Observed a resonance angle shift as large as 3 degrees using the developed method.
• Simulated sensitivity up to 800 degrees/RIU, an order of magnitude greater than conventional methods.
• Achieved a spectrally sharp but angularly broad multi-SPP resonance.
• Demonstrated enhanced sensitivity compared to fixed grating and prism-coupled Kretschmann configurations.

Conclusions:

• The proposed azimuthal rotation method significantly enhances GCSPR sensor sensitivity.
• This technique enables highly sensitive detection of molecular binding events.
• The achievable sensitivity surpasses conventional GCSPR and Kretschmann configurations, opening new possibilities in biosensing and chemical sensing.