Emergence of point defect states in a plasmonic crystal

Abstract

Plasmonic crystals are well known to have band structure including a bandgap, enabling the control of surface plasmon propagation and confinement. The band dispersion relation of bulk crystals has been generally measured by momentum-resolved spectroscopy using far field optical techniques while the defects introduced in the crystals have separately been investigated by near field 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 flat cylinders protruding out of a metal film 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 confirmed 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 flat cylinders protrusions and adding sequentially additional shells of those in order to eventually forming a plasmonic band-gap crystal encompassing a single point defect. It is demonstrated that a defect-like state already forms with a crystal made up of only two shells.

Combining Highly Monochromatized EELS with CL for Probing Elementary Excitations and Their Interaction

“…peculiarities in the properties of plasmonic nanowires [1] or plasmonic band gap materials with high quality factors [2] optical properties of single photon emitters in h-BN [3] and dechalcogenides stacking effects on excitons in h-BN [4] and the appearance of new excitonic effects in dichalcogenide double layer systems strong coupling effects between plasmon and phonon modes in h-BN coupled to silver nanorods [5].…”

Bridging nano-optics and condensed matter formalisms in a unified description of inelastic scattering of relativistic electron beams

“…It allows to probe a wide range of excitations in solids such as phonons [1], plasmons [2], excitons [3], and core electron-hole excitations [4] over a wide range of energies, typically from 40 meV to thousands of eV. Moreover, the versatility of the electron optical set-ups allows to achieve either high spatial resolution [5] (better than half an Ångström) or high momentum resolution [6,7] (smaller than µm −1 ) or to probe directly the symmetry of the excitations [8]. This variety of experimental configurations is illustrated in Fig.…”

High-Efficiency Coupling of Free Electrons to Sub-λ3 Modal Volume, High-Q Photonic Cavities

“…Indeed, using tunable lasers in conjunction with PINEM, electron energy gain spectroscopy (EEGS) became recently possible, unravelling the predicted 16 promise of a laser spectral resolution with the spatial resolution of an electron. 17−19 At the time being, only few types of cavities, including defects in plasmonic materials, 6,20 spheres subtending whisperinggallery modes, 9,11,19,21 or ring resonators, 18 have been investigated with electron beam techniques. These cavities suffer from either relatively low Q (less than a thousand) and/or large modal volumes.…”

“…At the time being, only few types of cavities, including defects in plasmonic materials, , spheres subtending whispering-gallery modes, ,,, or ring resonators, have been investigated with electron beam techniques. These cavities suffer from either relatively low Q (less than a thousand) and/or large modal volumes.…”