title: Light absorber based on nano-spheres on a substrate reflector.
abstract: We systematically study a type of plasmonic light absorber based on a monolayer of gold nano-spheres with less than 30 nm in diameters deposited on top of a continuous gold substrate. The influences of particle size, inter-particle distance, particle-substrate spacer size etc on the resonance are studied thoroughly with a 3D finite-element method. We identified that the high-absorption resonance is mainly due to gap plasmon (coupled through particle bodies) when the separation between neighboring nano-spheres is small enough, such as close to 1 nm; at larger particle separations, the resonance is dominated by particle dipoles (coupled through the host dielectric). Experimentally, an absorber was fabricated based on chemically-synthesized gold nanoparticles coated with silica shell. The absorber shows a characteristic absorption band around 810 nm with a maximum absorbance of approximately 90%, which agrees reasonably well with our numerical calculation. The fabrication technique can be easily adapted for devising efficient light absorbers of large areas.
authors.affiliation: Optics and Photonics, School of Information and Communication Technology, KTH - Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden.
authors.forename: Jin
authors.initials: J
authors.lastname: Dai
authors.forename: Fei
authors.initials: F
authors.lastname: Ye
authors.forename: Yiting
authors.initials: Y
authors.lastname: Chen
authors.forename: Mamoun
authors.initials: M
authors.lastname: Muhammed
authors.forename: Min
authors.initials: M
authors.lastname: Qiu
authors.forename: Min
authors.initials: M
authors.lastname: Yan
mesh_terms: D000042:Absorption; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry*; D007909:Lenses; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*
chemical_list: D006046:Gold