A Self-Referenced Refractive Index Sensor Based on Gold Nanoislands

Area of Science:

• Plasmonics
• Optical Sensing
• Nanotechnology

Background:

• Localized surface plasmon resonance (LSPR) is sensitive to surrounding refractive index changes.
• Fabry-Pérot cavities offer stable optical resonances.
• Combining LSPR with optical cavities can enhance sensor performance.

Purpose of the Study:

• To develop a self-referenced refractive index optical sensor.
• To leverage the combined resonances of gold nanoislands and a Fabry-Pérot cavity.
• To achieve high sensitivity and stability for biosensing.

Main Methods:

• Fabrication of a planar SiO2/metal Fabry-Pérot cavity with dewetted gold nanoislands.
• Experimental and theoretical analysis of the device's reflectance spectrum.
• Testing the sensor's response to variations in surrounding fluid refractive index.

Main Results:

• The spectral response is a combination of LSPR and Fabry-Pérot cavity resonances.
• The LSPR provides high sensitivity to refractive index changes, while the cavity resonance acts as a reference.
• Achieved spectral sensitivity of 212 nm/RIU and intensity sensitivity of 4.9 RIU^-1.

Conclusions:

• The proposed self-referenced sensor architecture is effective for refractive index sensing.
• The combination of LSPR and Fabry-Pérot resonances enables stable and sensitive measurements.
• The chip-based, low-cost design is promising for compact reflection-mode biosensing platforms.