Optically Thin Metallic Films for High-Radiative-Efficiency Plasmonics

Abstract

Plasmonics enables deep-subwavelength concentration of light and has become important for fundamental studies as well as real-life applications. Two major existing platforms of plasmonics are metallic nanoparticles and metallic films. Metallic nanoparticles allow efficient coupling to far field radiation, yet their synthesis typically leads to poor material quality. Metallic films offer substantially higher quality materials, but their coupling to radiation is typically jeopardized due to the large momentum mismatch with free space. Here, we propose and theoretically investigate optically thin metallic films as an ideal platform for high-radiative-efficiency plasmonics. For far-field scattering, adding a thin high-quality metallic substrate enables a higher quality factor while maintaining the localization and tunability that the nanoparticle provides. For near-field spontaneous emission, a thin metallic substrate, of high quality or not, greatly improves the field overlap between the emitter environment and propagating surface plasmons, enabling high-Purcell (total enhancement >10(4)), high-quantum-yield (>50%) spontaneous emission, even as the gap size vanishes (3-5 nm). The enhancement has almost spatially independent efficiency and does not suffer from quenching effects that commonly exist in previous structures.

Low-Loss Plasmonic Dielectric Nanoresonators

“…As importantly, the (1, 1) mode exhibits >90% quantum efficiency and >75% photon efficiency. Similar efficiencies are achieved for emitters located throughout the gap region (not shown; adopting the approach in [38]). In the far field [ Fig.…”

Spectral Engineering via Complex Patterns of Circular Nano-object Miniarrays: I. Convex Patterns Tunable by Integrated Lithography Realized by Circularly Polarized Light

“…This example indicates that complex patterns composed of predesigned rings can result in considerable enhancement. The highest fluorescence efficiency can be achieved by positioning tapered antennas like spheres, disks, and tori above thin metals films [37]. These results predict that a combination of thin films and spherical antennas is advantageous in sensing of dipolar emitters.…”

Mapping Fluorescence Enhancement of Plasmonic Nanorod Coupled Dye Molecules

“…The difference between the Purcell factor (total decay rate enhancement) and radiative rate enhancement was attributed to losses in the coupled fluorophore-nanophotonic systems [9]. Good scattering efficiency was demonstrated in the case of core-shell particles and tapered nanoantennas (spheres and tori) aligned above films, whereas directional out-coupling and large degrees of freedom are the advantages of dimer antenna arrays [10][11][12][13]. The existence of an optimal distance to promote dye molecule and nanoresonator coupling was also revealed [10,14].…”