Grating surface plasmon resonance sensor: angular sensitivity, metal oxidization effect of Al-based device in optimal...

Area of Science:

• Optoelectronics
• Nanotechnology
• Chemical Sensing

Background:

• Surface Plasmon Resonance (SPR) sensors are crucial for label-free biosensing.
• Grating-based SPR sensors offer enhanced sensitivity and tunable performance.
• Metal permittivity and analyte refractive index significantly influence SPR sensor performance.

Purpose of the Study:

• To determine the ultimate and maximum wavelength-independent angular sensitivity of grating SPR sensors.
• To investigate the performance of aluminum-based grating SPR sensors, particularly concerning sensitivity and figure of merit.
• To evaluate the impact of metal oxidation on sensor sensitivity and detection error.

Main Methods:

• Theoretical analysis of grating SPR sensor sensitivity under conditions of high metal permittivity.
• Experimental fabrication and characterization of an optimized aluminum-based grating SPR sensor.
• Measurement of angular sensitivity at various wavelengths (0.85 μm and 1.55 μm) before and after aluminum oxidation.

Main Results:

• Achieved maximum angular sensitivities of 493.7 (°/RIU) (single-dip) and 535.9 (°/RIU) (double-dip) for analytes with refractive indices between 1.32 and 1.36.
• Optimized Al-based sensors demonstrated increased sensitivity at longer wavelengths (338.0 (°/RIU) to 396.3 (°/RIU)) before oxidation.
• Metal oxidation caused minor sensitivity degradation (≤3.2%) and introduced a detection error of δn(a)≤1.3e-3.

Conclusions:

• Grating SPR sensors exhibit wavelength-independent ultimate and maximum angular sensitivity under specific conditions.
• Optimized Al-based sensors provide high sensitivity, particularly in the near-infrared, with acceptable performance post-oxidation.
• The sensor design is suitable for sensitive and accurate detection of analytes in the near-infrared spectrum.