Finite conductance governs the resonance transmission of thin metal slits at microwave frequencies.
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.
Suckling
J R
JR
Thin Film Photonics Group, School of Physics, University of Exeter, Devon EX4 4QL, United Kingdom.
Hibbins
A P
AP
Lockyear
M J
MJ
Preist
T W
TW
Sambles
J R
JR
Lawrence
C R
CR