Sensitivity-Enhanced SPR Sensor Based on Graphene and Subwavelength Silver Gratings

Area of Science:

• Photonics and Nanotechnology
• Chemical Sensing
• Materials Science

Background:

• Surface Plasmon Resonance (SPR) sensors are crucial for label-free biomolecular detection.
• Enhancing SPR sensor performance, such as sensitivity and resolution, remains an active research area.
• Graphene integration and subwavelength structures offer new avenues for SPR sensor optimization.

Purpose of the Study:

• To propose and numerically analyze a novel SPR sensor incorporating graphene and subwavelength gratings.
• To investigate the impact of structural parameters on SPR sensor performance metrics.
• To evaluate the sensing capabilities of the designed SPR sensor for detecting refractive index variations.

Main Methods:

• Numerical simulations were conducted to analyze the sensor's optical properties.
• The effects of geometrical parameters on minimum reflectance at resonance (MRR) and full width at half maximum (FWHM) were studied.
• The influence of graphene layer count on sensor sensitivity was systematically investigated.

Main Results:

• Optimized geometrical parameters yielded near-zero MRR (2.9 × 10^-6) and narrow FWHM (approx. 3.5 deg).
• The maximum achievable sensitivity reached 192 degrees per refractive index unit (RIU), significantly outperforming silver-only SPR sensors.
• Detection of ethylene glycol solutions demonstrated a practical sensitivity of 220.67 deg/RIU with excellent linearity.

Conclusions:

• The proposed graphene-based SPR sensor with subwavelength gratings offers superior sensing performance.
• The optimized design exhibits high sensitivity and linearity, suitable for practical sensing applications.
• This work highlights the potential of combining graphene and nanostructured optics for advanced refractive index sensing.