Improved Description of the Plasmon Resonance Wavelength Shift in Metallic Nanoparticle Pairs

Abstract : 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.