- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Plasmonics of regular shape particles, a simple group theory approach
摘要： A simple hand calculation method based on group theory is proposed to predict the near field maps of finite metallic nanoparticles (MNP) of canonical geometries: prism, cube, hexagon, disk, sphere, etc. corresponding to low order localized surface plasmon resonance excitations. In this article, we report the principles of the group theory approach and demonstrate, through several examples, the general character of the group theory method which can be applied to describe the plasmonic response of particles of finite or infinite symmetry point groups. Experimental validation is achieved by collection of high-resolution subwavelength near-field maps by photoemission electron microscopy (PEEM) on a representative set of Au colloidal particles exhibiting either finite (hexagon) or infinite (disk, sphere) symmetry point groups.
关键词： hexagon,disk,photoemission electron microscopy (PEEM),group theory,sphere,surface plasmon resonance
更新于2025-09-23 15:19:57
-
Geometrically navigating topological plate modes around gentle and sharp bends
摘要： Predictive theory to geometrically engineer devices and materials in continuum systems to have desired topological-like effects is developed here by bridging the gap between quantum and continuum mechanical descriptions. A structured elastic plate, a bosoniclike system in the language of quantum mechanics, is shown to exhibit topological valley modes despite the system having no direct physical connection to quantum effects. We emphasize a predictive, first-principles, approach, the strength of which is demonstrated by the ability to design well-defined broadband edge states, resistant to backscatter, using geometric differences; the mechanism underlying energy transfer around gentle and sharp corners is described. Using perturbation methods and group theory, several distinct cases of symmetry-induced Dirac cones, which when gapped yield nontrivial band gaps, are identified and classified. The propagative behavior of the edge states around gentle or sharp bends depends strongly upon the symmetry class of the bulk media and we illustrate this via numerical simulations.
关键词： group theory,valley Hall effect,Dirac cones,topological plate modes,elastic plates
更新于2025-09-11 14:15:04
-
[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Group theoretical route to weakly and strongly protected surface states in 2D and 3D photonic crystals
摘要： Topologically protected surface states in photonic systems, with unique properties such as unidirectional propagation and light con?nement insensitive to thermal or fabrication imperfections, have attracted immense attention over the past ten years. We introduce the notion of weak protection where a topological invariant predicts the existence of surface states in the photonic bulk gap, and strong protection which instead corresponds to the number of glueing points of a surface band with the bulk edges. While strong protection is desired for many key applications such as topologically protected loss-free cavities to boost non-linear interactions, it requires optical reciprocity breaking in two dimensions. We here provide a group theoretical recipe to design weakly protected states on purely dielectric metasurfaces, and genuinely strongly protected states in fully connected 3D photonic crystals. Both design principles can be readily realized by current direct manufacturing techniques, such as electron beam lithography and direct laser writing, respectively.
关键词： topologically protected surface states,strong protection,photonic crystals,group theory,weak protection
更新于2025-09-09 09:28:46