Plasmon-supported transmission of light through nanometric holes in metallic thin films

Numerical field calculations have been employed to study quantitatively the wavelength- dependent interaction of visible light with nanometric holes in metallic screens. Real metals as well as ideal conductors are considered. The transmission efficiency through holes in an ideally conducting screen of finite thickness is found to follow a power law as a function of wavelength with an exponent close to -4. In the case of silver the generation of surface-plasmon polaritons (SPP) at the edges of the holes and their subsequent decay to photons leads to an increase of the transmission with decreasing size parameter and a maximum of the light transmission as a function of the wavelength of the exciting light. At wavelengths longer than that of the transmission maximum the transmission follows again a power law, but with an exponent close to -8. The same exponent is found in the case of holes in thin aluminum films. The additional wavelength dependence is caused by the probability of SPP excitation by the oscillating dipole in the hole. On a metallic screen in a symmetric environment only the symmetric, short-range SPP is excited at the hole, in agreement with expectations. The field enhancement in the aperture is determined quantitatively. The interference of SPPs generated at a linear array of holes is also investigated. (C) 2001 Elsevier Science B.V. All rights reserved.