Plasmonic Sensors beyond the Phase Matching Condition: A Simplified Approach

Area of Science:

• Photonics and Nanotechnology
• Plasmonics
• Sensor Technology

Background:

• Conventional plasmonic sensor optimization relies on phase matching, often leading to suboptimal performance, even in simple Otto geometry.
• Existing methods for evaluating plasmonic sensor performance can be complex and computationally intensive.

Purpose of the Study:

• To develop a simplified coupled mode theory (CMT) approach for evaluating and optimizing plasmonic waveguide refractive index sensors.
• To provide a rapid and convenient framework for designing dielectric-plasmonic sensor prototypes.

Main Methods:

• A simplified coupled mode theory (CMT) approach is presented, requiring only propagation constant calculations.
• The method avoids the need for complex mode overlap integral calculations, simplifying the analysis.
• The approach is applied to a finite-length silicon-on-insulator-based sensor to evaluate spectral features.

Main Results:

• The simplified CMT accurately predicts wavelength-, device length-, and refractive index-dependent transmission spectra.
• The results are consistent with computationally intensive full-field finite element calculations.
• The method reveals salient spectral features crucial for sensor optimization.

Conclusions:

• The simplified CMT offers a computationally efficient and accurate framework for designing plasmonic waveguide sensors.
• This approach facilitates the rapid prototyping and optimization of refractive index sensors.
• The methodology's applicability extends to fiber plasmonic sensors, broadening its impact.