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A refractive index from negative to positive of graphene plasmonic crystal at the Dirac-like cone in mid-infrared region
摘要： In this work, two-dimensional plasmonic crystals composed of graphene nanodisks where the chemical potential varies in triangular symmetry are proposed. A special band structure of Dirac-like cone is obtained at the center of Brillouin zone in mid-infrared region. A refractive index of the plasmons from negative to positive is calculated by the method of eigen-fields averaging. Also, the isotropic distribution of the negative/positive effective permeability and permittivity is numerically demonstrated. In addition, the significant propagation characteristics including the reverse Snell’s law effect, deep-sub-wavelength focusing and negative Goos-H?nchen shifts are numerical simulated. The proposed structure may find broad applications in the fields of on-chip plasmonic interconnect, high density plasmonic integrated circuit techniques and nano-imaging in the future.
关键词： Plasmonic crystals,Graphene plasmon,Dirac-like cone,Negative refractive index
更新于2025-09-16 10:30:52
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Ion irradiation of III–V semiconductor surfaces: From self-assembled nanostructures to plasmonic crystals
摘要： Ion-irradiation of semiconductor surfaces has emerged as a promising approach to generate a variety of self-organized nanostructures. Furthermore, the combination of focused-ion-irradiation with molecular-beam epitaxy provides unprecedented design and control of surfaces and interfaces of hybrid materials at the atomic level during fabrication. In this review, we describe the directed self-assembly of nanostructure arrays ranging from islands to nanorods to 3-dimensional nanoparticle (NP) arrays. First, we discuss focused-ion-irradiation of III–V surfaces, which leads to preferential sputtering of group V species, followed by the formation of group III-rich metallic nanostructures. For continued irradiation beyond a threshold dose, the nanoparticle (NP) evolution is determined by the sputtering yield and the local ion beam angle of incidence, resulting in arrays of nanoparticles, nanorods, or nanoparticle chains. In addition to describing the formation of close-packed embedded Ga:GaAs nanocomposites using overgrowth of focused-ion-beam fabricated NP arrays, we discuss the surface plasmon resonances of NP arrays as well as the influence of both surface and buried NP arrays on the GaAs photoluminescence efficiency. Finally, we discuss the potential of “plasmonic crystals” for plasmon-enhanced optoelectronics.
关键词： self-assembled nanostructures,ion irradiation,plasmonic crystals,molecular-beam epitaxy,III-V semiconductor,nanoparticle arrays,surface plasmon resonances,photoluminescence efficiency,focused-ion-beam
更新于2025-09-12 10:27:22
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Homogenization of plasmonic crystals: seeking the epsilon-near-zero effect
摘要： By using an asymptotic analysis and numerical simulations, we derive and investigate a system of homogenized Maxwell’s equations for conducting material sheets that are periodically arranged and embedded in a heterogeneous and anisotropic dielectric host. This structure is motivated by the need to design plasmonic crystals that enable the propagation of electromagnetic waves with no phase delay (epsilon-near-zero effect). Our microscopic model incorporates the surface conductivity of the two-dimensional (2D) material of each sheet and a corresponding line charge density through a line conductivity along possible edges of the sheets. Our analysis generalizes averaging principles inherent in previous Bloch-wave approaches. We investigate physical implications of our ?ndings. In particular, we emphasize the role of the vector-valued corrector ?eld, which expresses microscopic modes of surface waves on the 2D material. We demonstrate how our homogenization procedure may set the foundation for computational investigations of: effective optical responses of reasonably general geometries, and complicated design problems in the plasmonics of 2D materials.
关键词： asymptotic analysis,homogenization,plasmonic crystals,Maxwell’s equations,surface plasmon-polariton,graphene
更新于2025-09-12 10:27:22
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Emergence of point defect states in a plasmonic crystal
摘要： Plasmonic crystals are well known to have band structure including a band gap, enabling the control of surface plasmon propagation and con?nement. The band dispersion relation of bulk crystals has been generally measured by momentum-resolved spectroscopy using far ?eld optical techniques while the defects introduced in the crystals have separately been investigated by near ?eld imaging techniques so far. Particularly, defect related energy levels introduced in the plasmonic band gap have not been observed experimentally. In order to investigate such a localized mode, we performed electron energy-loss spectroscopy (EELS) on a point defect introduced in a plasmonic crystal made up of ?at cylinders protruding out of a metal ?lm and arranged on a triangular lattice. The energy level of the defect mode was observed to lie within the full band-gap energy range. This was con?rmed by a momentum-resolved EELS measurement of the band gap performed on the same plasmonic crystal. Furthermore, we experimentally and theoretically investigated the emergence of the defect states by starting with a corral of ?at cylinders protrusions and adding sequentially additional shells of those in order to eventually form a plasmonic band-gap crystal encompassing a single point defect. It is demonstrated that a defectlike state already forms with a crystal made up of only two shells.
关键词： point defect,band gap,Plasmonic crystals,momentum-resolved spectroscopy,electron energy-loss spectroscopy
更新于2025-09-11 14:15:04