Abstract
We experimentally demonstrate and image the hybrid nature of surface plasmon
polaritons (SPPs) at visible wavelengths excited in low aspect ratio 1D and 2D periodic
plasmonic structures with periods nearly equal to the resonance wavelengths, fabricated
on thin homogeneous metal-coated glass substrates. A thin homogeneous metal layer was
sandwiched between the substrate and the periodic metal patterns to out-couple the SPPs
as leakage radiation through the substrate. This resulted in the detection of SPP
excitation as transmission peaks in a dark background, as opposed to transmission dips
in a bright background in the structures without the metal layer reported earlier. Due
to the periods being almost equal to the resonance wavelengths, the transmission peaks
were not due to extraordinary transmission phenomenon, but because of the radiative
leakage of wavelength selective SPPs excited on the surface. A cross-axis
polarizer–analyzer was used in broadband leakage radiation microscopy to diminish the
direct zeroth-order transmission and image the real and Fourier plane
characteristics of the SPP transmission. The bright emission of different colors against
a dark background corresponding to the transmission plasmonic resonances for different
periods, in both real and Fourier plane revealed the hybrid nature of excited SPPs, when
the polarizer was positioned at 45
$^\circ$
with respect to the grating vector. The fabricated plasmonic
substrates present interesting opportunities for imaging and sensing
applications.
© 2014 IEEE
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