Differential Sensing with Replicated Plasmonic Gratings Interrogated in the Optical Switch Configuration

Area of Science:

• Plasmonics
• Optical Sensing
• Nanotechnology

Background:

• Plasmonic sensors offer high sensitivity for detecting changes in refractive index.
• Existing sensor designs can be susceptible to drift and environmental perturbations.
• Developing robust and cost-effective sensing platforms is crucial for various applications.

Purpose of the Study:

• To propose and demonstrate a new plasmonic configuration for bulk refractive index sensing.
• To leverage the "optical switch" effect in a grating coupler for enhanced differential measurements.
• To achieve a low limit of detection for improved sensing capabilities.

Main Methods:

• Utilizing a grating coupler with TM-polarized optical beam incidence.
• Monitoring two diffracted orders to enable differential measurements.
• Implementing intensity interrogation with sequential injection of glycerol-water solutions in a fluidic cell.

Main Results:

• Experimental measurements of the optical switch pattern showed good agreement with theoretical predictions.
• Differential measurements effectively canceled common drift and perturbations.
• A limit of detection of approximately 10^-6 RIU (Refractive Index Unit) was experimentally achieved.

Conclusions:

• The proposed plasmonic configuration based on the optical switch effect provides a cost-effective and sensitive sensing solution.
• Differential measurements significantly improve the detection limit and robustness of the sensor.
• This approach holds great promise for real-time sensing and detection of biological species.