Transmission of polarized light through sub-wavelength slit apertures is studied based on the electromagnetic field distributions obtained in computer simulations. The results show the existence of a cutoff for E|| and a strong transmission (with no cutoff) for E?; here || and ? refer to the direction of the incident E-field relative to the long axis of the slit. These observations are explained by the standard waveguide theory involving inhomogeneous plane waves that bounce back and forth between the interior walls of the slit aperture. We examine the roles played by the slit-width, by the film thickness, and by the real and imaginary parts of the host material's dielectric constant in determining the transmission efficiency. We also show that the slit's sharp edges can be rounded to eliminate highly-localized electric dipoles without significantly affecting the slit's throughput. Finally, interference among the surface charges and currents induced in the vicinity of two adjacent slits is shown to result in enhanced transmission through both slits when the slits are separated by about one half of one wavelength.
"The weaker electric field intensities inside the slit and Au/Si interface were also observed under nonresonance conditions, as shown in Fig. 1(d) and (f). These results indicate that the slit functions as a resonator of the SPP mode , , and that the high intensity SPP mode at the Au/Si interface is excited under resonance conditions. "
[Show abstract][Hide abstract] ABSTRACT: The monolithic integration of a silicon-based plasmonic detector with metal- oxide-semiconductor field-effect transistors (MOSFETs) was demonstrated. The plasmonic detector consisted of a gold film with a nanoslit grating on a silicon substrate and was operated at a free-space wavelength of 1550 nm. The structure of the nanoslit grating was optimized by using the finite-difference time-domain method. The output current from the plasmonic detector was amplified by ~14 000 times using the monolithically integrated MOSFETs. In addition, dynamic operation of the integrated circuit was demonstrated by modulation of the intensity of a beam that was incident to the plasmonic detector.
"Both the film and the nanostrips are made of silver with relative permittivity ε m = -48.8 + i3.16 according to Ref. . The wavelength of the surface plasmon wave on the metal-air interface is usually estimated by formula λ sp "
[Show abstract][Hide abstract] ABSTRACT: The study of the transmission properties of subwavelength apertures has become a very active area of research in electromagnetism. It is generally accepted that structuring the input surface of the metal film by periodic corrugations is very effective in the process of transmission enhancement through single apertures. Here instead of periodic corrugations, we propose to use periodic nano-strips placed before the input surface of the metal film to enhance the transmission of light through a nano-slit milled in the film. Influences of the structural parameters of periodic nano-strips on the transmission enhancement are investigated. The transmission efficiency through a 25nm-width silver nano-slit can be boosted to be ε = 164 when six pairs of nano-strips are placed 50nm distant away from the incident surface of the silver film at lambda0 = 1mum, which is originally ε = 7.8 without any strips. This indicates that a large part of the incident light can be transformed into the localized guided wave with strong intensity, and then more light can flow through the nano-slit. We emphasize that periodic nano-strips can serve as an efficient receiving antenna to harvest light into the nano-slit.
Proceedings of SPIE - The International Society for Optical Engineering 05/2009; DOI:10.1117/12.819919 · 0.20 Impact Factor
"Theoretical and experimental work from several groups now seem to converge on the idea that SPs do play a central role in enhancing the transmission . Similar enhanced transmission effects were also intensely studied for isolated subwavelength slits or slit arrays, showing that the transmission efficiency normalized by the slit area can be well over 100 % . Figure 1a shows a sample nanohole array fabricated on a gold film on a glass slide (refer to section 3 for fabrication details). "
[Show abstract][Hide abstract] ABSTRACT: Large-scale studies of biomolecular interactions required for proteome-level investigations can benefit from a new class of emerging surface plasmon resonance (SPR) sensors: nanohole arrays and surface plasmon (SP) enhanced optical transmission. In this paper we present a real-time, label-free multiplex SPR imaging sensor in a microarray format. The system presented is built around a low-cost microscope with laser illumination, integrated with microfluidics. The specific binding kinetics of biotin and streptavidin are measured from several sensing elements simultaneously, demonstrating the feasibility of using nanohole arrays as a high-throughput SPR microarray sensor.
Proceedings of SPIE - The International Society for Optical Engineering 08/2008; 7035. DOI:10.1117/12.794299 · 0.20 Impact Factor
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