An analog of an electromagnetically induced transparency C4 symmetric device with a silicon array-dielectric layer-Au film F–P cavity is designed. Through the coupling between the waveguide and F–P cavity modes, the polarization-independent terahertz electromagnetic induced transparency (EIT)-like effect is obtained. The coupling analysis between the two types of modes in different orders shows the EIT-like effect, but the orders could affect the EIT-like properties. Moreover, the C4 symmetry structure makes it have polarization-independent characteristics. This research is conducive to obtaining polarization-independent EIT-like devices and to further research on the coupling between different kinds of modes for obtaining EIT-like devices with different performance requirements.
We proposed and numerically demonstrated an analog of electromagnetically induced transparency (EIT) in a Chinese character 王-shaped all-dielectric metasurface in the near-infrared region. Through asymmetric adjustment, the high transmittance EIT-like optical response of both single and double transparency windows can be realized. The EIT-like optical responses are clearly interpreted by the destructive interference between the bright dipolar moment and trapped magnetic dipolar mode through the asymmetric metasurface, and the dark dipolar moment causes the transparency window to split into two peaks. This all-dielectric structure shows a good application prospect in the field of refractive index sensors and slow-light transmission.
When the peak positions of propagating surface plasmon polaritons (SPPs) and localized surface plasmon resonances (LSPRs) become very close to each other in a single nanoparticle array structure, an anticrossing behavior of the surface plasmon resonances (SPRs) peak positions usually occurs, which can considerably enhance the near-field intensity. We first report on the interaction of two types of SPRs in a dimer nanodisk–SiO2 spacer–gold film hybrid sandwich structure. The anticrossing behavior does not appear always due to various modes of LSPRs in such structures. Moreover, a crossing behavior also appears based on the interaction of SPPs and a longitudinal bonding mode of LSPRs. When the anticrossing behavior occurs, a bandgap that changes only with the array period also appears. This bandgap influences the electric field intensity enhancement not only in the anticrossing behavior but also in the crossing behavior. The electric field intensity distribution properties both in the anticrossing behavior and crossing behavior are discussed with reference to the hybrid properties of the SPPs and LSPRs modes. Furthermore, we report on the occurrence mechanisms of these different behaviors.
Dimer nanoparticles in a sandwich structure exhibit a large electric-field intensity enhancement. The dispersion relation between the surface plasmon resonance (SPR) and particle size has not been reported yet, owing to the effects of the particle size, shape, materials, etc. A sandwich structure, which contains a nano-right-triangle dimer array, SiO2 spacer, and Au film, is proposed, with a significant electric-field intensity enhancement and polarization-changing properties. The dependence of the peak positions of the two localized surface plasmon resonance (LSPR) modes as a function of the triangle thicknesses is discussed; different trends are observed for the different LSPR modes. We introduce a concept on the rule for LSPR peak position change, which can contribute to a better understanding of the LSPR modes. In addition, centrosymmetric but not axisymmetric structures, which like in our study exhibit surface plasmon polaritons typically show different responses to a different polarization of the incident light. Here, we showed that our centrosymmetric but not axisymmetric structure can change the linearly polarized light into a circularly or elliptically polarized wave, by surface plasmon-induced polarization properties. Far-field distribution maps are used to study the properties of the surface plasmons-induced circular or elliptic polarization wave. These findings could be employed to better understand the surface plasmon-induced polarization properties showed in previous reports and near-field of surface plasmons. These findings could be employed to better understand the near-field of surface plasmons and polarization properties.
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