RESUMO
The excitation of 'designer' surface-plasmon-like modes on periodically perforated metals is demonstrated at microwave frequencies using the classical method of prism-coupling. In addition we provide a complete formalism for accurately determining the dispersion of these surface modes. Our findings fully validate the use of metamaterials to give surface plasmon-like behavior at frequencies below the visible.
Assuntos
Modelos Teóricos , Refratometria/métodos , Ressonância de Plasmônio de Superfície/métodos , Simulação por Computador , Luz , Espalhamento de RadiaçãoRESUMO
We demonstrate optical control over the transmission of terahertz (THz) radiation through a single subwavelength slit in an otherwise opaque silicon wafer. The addition of periodic corrugation on each side of the wafer allows coupling to surface plasmon polaritons, so that light not impinging directly on the slit can contribute to the transmission. A significant enhancement of the THz transmission can be achieved through control of the surface wave propagation length by excitation at optical wavelengths. The observed transmission increase is in distinct contrast to the reduction reported for photoexcitation of arrays of holes in semiconductors.
RESUMO
Fabry-Perot-like resonant transmission of microwave radiation through a single subwavelength slit in a thick aluminum plate is quantified for a range of slit widths. Surprisingly, and in contrast to previous studies [e.g., Phys. Rev. Lett. 86, 5601 (2001)]], the resonant frequency exhibits a maximum as a function of slit width, decreasing as the slit width is reduced to less than 2% of the incident wavelength. This result accords with a new model based on coupled surface plasmon theory taking into account the finite conductivity, and hence permittivity, of the metal. This is contrary to a common assumption that metals can be treated as infinitely conducting in this regime.
