Abstract
In this study, we present experimentally measured transmission enhancement of microwaves through periodic slit arrays in metallic films. Enhanced transmission peaks and sharp transmission dips are clearly observed around the theoretically expected surface plasmon polariton(SPP) resonance frequencies. Dependence of the transmittance spectra on the geometrical properties of slits is also demonstrated by varying the slit width, slit periodicity and the thickness of metallic films. Transmission peaks and dips are originated from the coupling between the incident light and SPPs which are caused by the slit array that acts like a grating coupler. The obtained results are theoretically explained by solving the Maxwell's equations and by the diffraction theory with appropriate boundary conditions, and they are in good agreement with those calculated by the finite-difference time-domain method.
Highlights
Since the extraordinarily enhanced optical transmission of light through subwavelength hole arrays in metallic films was experimentally reported by Ebbesen, et al in 1998 [1,2], it generated large interest because it showed that much more light can be transmitted through hole array structures than Bethe’s prediction reported in 1944 [3]
The extraordinarily enhanced transmission was clearly observed by the transmission peaks around the first SPP resonance frequencies and the highest value of the peaks is over 0 dB which means that almost 100% transmission was achieved in these frequencies in spite of small slit opening ratios a / p
The enhanced transmission peaks, and the transmission dips exist around the expected SPP resonance frequencies which mean that the transmission is surpressed at those frequencies due to the SPP resonance
Summary
Since the extraordinarily enhanced optical transmission of light through subwavelength hole arrays in metallic films was experimentally reported by Ebbesen, et al in 1998 [1,2], it generated large interest because it showed that much more light can be transmitted through hole array structures than Bethe’s prediction reported in 1944 [3]. Since Hibbins et al have demonstrated the coupling of microwave radiation to SPPs by reflection measurements [13], several experiments have been performed using a single hole or a slit surrounded by periodic grooves and these studies showed the existence of SPP modes on the periodically corrugated metallic surfaces [15,16,17,18,19]. Several studies have shown that the transmittance of the incident radiation is suppressed at the resonant wavelength and redshifted transmission peaks exist near the transmission dips [20] These phenomena can be theoretically explained by scattering matrix by solving the Maxwell’s equations with the surface impedance boundary conditions and diffraction theory [20]. Detailed discussion is addressed concerning the transmission properties related to the geometrical parameters from the comparison of the experimentally measured spectra with theoretically calculated results
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