Improved Description of the Plasmon Resonance Wavelength Shift in Metallic Nanoparticle Pairs
Résumé
We propose to use the compressed or stretched hyperbola for an efficient description of the plasmon resonance shift as a function of the gap between proximal nanoparticles in arrays of gold pairs. This function overcomes the limitation of describing this behavior by the well-known exponential function as it accounts for the near-field coupling and the far-field radiative coupling between particles . It has the advantage of mathematical simplicity with one dimensionless additional parameter compared to a simple exponential decay. We suggest that this parameter may be the signature of the grating effects. Most importantly this function works well in a wide variety of surrounding media and for nanostructures with arbitrary shapes. We expect that this function is an efficient tool for fundamental studies as it quantifies both the near-field coupling and the grating coupling. It is also a useful tool for applied studies like bio-sensing applications, by providing an improved plasmon ruler equation. Localized surface plasmon resonances in gold pairs are investigated using finite-difference time-domain simulations.