title: 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.
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.|Physics Department and Solid State Institute, Technion , Haifa 320000, Israel.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhen
authors.affiliation: Department of Applied Physics, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Chia Wei
authors.initials: CW
authors.lastname: Hsu
authors.affiliation: Department of Mathematics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Owen D
authors.initials: OD
authors.lastname: Miller
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: John D
authors.initials: JD
authors.lastname: Joannopoulos
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Marin
authors.initials: M
authors.lastname: Soljačić
keywords: light scattering; metallic thin film; nanoparticles; optical nanoantennas; radiative efficiency; spontaneous emission