Role of surface plasmon polaritons in the optical response of a hole pair

Abstract

The optical emittance of a hole pair perforated in an opaque metal film is studied from first principles using the coupled-mode method. The geometrical simplicity of this system helps us to understand the fundamental role played by surface plasmon polaritons (SPPs) in its optical response. A SPP interference model without fitting parameters is developed from the rigorous solution of Maxwell's equations. The calculations show that the interference pattern of the hole pair is determined by two scattering mechanisms: (i) the electric field excited by the external illumination at the hole openings before the hole-hole interaction is established and (ii) the re-illumination of the holes by the in-plane SPP radiation. The conditions for constructive and destructive interference only depend on the phase difference provided by each of the two scattering mechanisms.