In this paper, we investigate the optical properties of
the double-layer metal films perforated with single apertures by
analysing the coupling of localized surface plasmon polaritons (LSPPs).
It is found that the amplitude and the wavelength of transmission
peak in such a structure can be adjusted by changing the
longitudinal interval D between two films and the lateral
displacements d_{x} and d_{y} which are parallel and
perpendicular to the polarization direction of incident light,
respectively. The variation of longitudinal interval D results in
the redshift of transmission peak due to the change of coupling
strength of LSPPs near the single apertures. The amplitude of
transmission peak decreases with the increase of d_{y} and is less
than that in the case of d_{x}, which originates from the
difference in coupling manner between LSPPs and the localized
natures of LSPPs. 相似文献
Long-range surface plasmon polariton (LRSPP) modes in an
asymmetrical system, in which the thin metal film is sandwiched
between a semi-infinite substrate and a high permittivity polymer
film with a finite thickness, are theoretically calculated and
analyzed. Due to the high permittivity of the polymer film, at
proper polymer film thicknesses, the index-matching condition of the
dielectrics at both sides of the metal can be satisfied for
supporting LRSPP modes, and the electromagnetic field above the
metal can be localized well. It is found that these LRSPP modes have
both long propagation lengths and subwavelength mode expansion above
the metal at the optimal polymer film thicknesses. Furthermore, the
requirements on the refractive index and the thickness of the
polymer film to support LRSPP modes at the optimal thicknesses are
found to be not critical. 相似文献
The p and s-polarized surface plasmon polaritons (SPPs) of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials: dielectrics, negative dielectric permittivity materials, negative magnetic permeability materials, and left-handed materials are comprehensively analysed. The existence regions, dispersion relations, and excitation of SPPs in different frequency regions are investigated in detail. For symmetric slabs, the numbers and the frequency positions of surface polariton branches are quite different. At the same time, the pairs
of the p or s-polarized SPP branches occur in the same frequency range. For asymmetric slabs, the SPP branches in mid- and high-frequency ranges are greatly different. In addition, the slab thickness has a great effect on SPPs of asymmetric and symmetric slabs. The attenuated total reflection spectra for the cases of p and s polarizations in these slabs are also calculated. 相似文献
Surface plasmon polaritons' (SPPs') frequency blue shift is observed in finite-difference time-domain (FDTD) simulation of parallel electron excitation Au bulk structure. Comparing with cold dispersion of SPPs, an obvious frequency blue shift is obtained in low confinement region excitation simulation results. Then, according to SPPs' transverse attenuation characteristics, the excited frequency mode instead of cold dispersion corresponding frequency mode matches it. Thence, this excited mode is confirmed to be SPPs' mode. As is well known the lower the frequency, the smaller the confinement factor is and the lower the excitation efficiency, the wider the bandwidth of excited SPPs is. And considering the attenuation in whole structure, the excited surface field contains attenuation signal. In a low confinement factor region, the higher the SPPs' frequency, the higher the excitation efficiency is, while broadband frequency information obtained in attenuation signal provides high frequency information in stimulation signal. Thence, in the beam-wave interaction, as the signal oscillation time increases, the frequency of the oscillation field gradually increases. Thus, compared with cold dispersion, the frequency of excited SPP is blueshifted This hypothesis is verified by monitoring the time domain signal of excited field in low and high confinement factor regions and comparing them. Then, this frequency-blue shift is confirmed to have commonality of SPPs, which is independent of SPPs' material and structure. Finally, this frequency-blue shift is confirmed in an attenuated total reflection (ATR) experiment. Owing to frequency dependence of most of SPPs' devices, such as coherent enhancement radiation and enhancement transmission devices, the frequency-blue shift presented here is of great influence in the SPPs applications. 相似文献
Surface plasmon polaritons (SPPs) have sparked enormous interest on nanophotonics beyond the diffraction limit for their remarkable capabilities of subwavelength confinements and strong enhancements. Due to the inherent polarization sensitivity of the SPPs [transverse‐magnetic (TM) polarization], it is a great challenge to couple the s‐polarized free‐space light to the SPPs. Here, an ultrasmall defect aperture (<λ2/2) is designed to directionally couple both the p‐ and s‐polarized incident beams to the single SPP mode in a broad bandwidth, which is guided by a subwavelength plasmonic waveguide. Simulations show that hot spots emerge at the sharp corners of the defect aperture when the incident beams illuminate it from the back side. The strong radiative fields from the hot spots are directionally coupled to the SPP mode because of the symmetry breaking of the defect aperture. By adjusting the structural parameters, both the unidirectional and bidirectional SPP coupling from the two orthogonal linear‐polarization incident beams are experimentally demonstrated. The polarization‐free coupling of the SPPs is of importance in circuits for fully optical processing of information with a deep‐subwavelength footprint.
Resonance cavity is a basic element in optics,which has wide applications in optical devices.Coupled cavities(CCs)designed in metal-insulator-metal(MIM)bus waveguide are investigated through the finite difference time domain method and coupled-mode theory.In the CCs,the resonant modes of the surface plasmon polaritons(SPPs)split with the thickness decreasing of the middle baffle.Through the coupled-mode theory analysis,it is found that the phase differences introduced in opposite and positive couplings between two cavities lead to mode splitting.The resonant wavelength of positive coupling mode can be tuned in a large range(about 644 nm)through adjusting the coupling strength,which is quite different from the classical adjustment of the optical path in a single cavity.Based on the resonances of the CCs in the MIM waveguide,more compact devices can be designed to manipulate SPPs propagation.A device is designed to realize flexible multiple-wavelength SPPs routing.The coupling in CC structures can be applied to the design of easy-integrated laser cavities,filters,multiple-wavelength management devices in SPPs circuits,nanosensors,etc. 相似文献
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