Binary plasmonic nanosystems
© 2014 EPFL
By introducing the difference permittivity ratio η=(ε 2−ε 0)/(ε 1−ε 0), the Green matrix method for computing surface plasmon resonances is extended to binary nanostructures. Based on the near field coupling, the interplay of plasmon resonances in two closely packed nanostrips is investigated. At a fixed wavelength, with varying η the resonances exhibit different regions: the dielectric effect region, resonance chaos region, collective resonance region, resonance flat region, and new branches region. Simultaneously, avoiding crossing and mode transfer phenomena between the resonance branches are observed. These findings will be helpful to design hybrid plasmonic subwavelength structures.
In a collaboration with Prof. Gu in the group of Prof. Gong at Peking University, we investigate numerically binary plasmonic systems composed of two different metals.
As a matter of fact, most plasmonic systems investigated so far are made from single material and the interplay between two plasmonic metals produces extremely interesting effects which have not yet been fully investigated.
In this work, by introducing the difference permittivity ratio η between both metals, the Green's matrix method is used to reveal the different modes in the coupled system. Based on the near field interaction, the interplay of plasmon resonances in both metals leads to a very complex behavior. At a fixed wavelength, varying η leads to different regimes and the system explores four different resonances regions: the dielectric effect region, the resonance chaos region, the collective resonance region, the resonance flat region, as well as new branches region. Simultaneously, avoiding crossing and mode transfer phenomena between the resonance branches are observed. These findings will be helpful to design hybrid plasmonic subwavelength structures.
Figure 1: Resonance combination for the perpendicular case with varying permittivity difference ratio ?. Left: Resonance branches, right: resonance capacity for the branches.
Figure 2: Absorption cross sections for a Au–Ag nanostrip system. (a) Parallel case and (b) perpendicular case. Depending on the modes, the energy can be localized on one particle or the other.
This work opens the way to explore novel composite systems composed of several different plasmonic metals and shall further our space for engineering controlled plasmonic resonances.
Check the corresponding publication:PDF External link: doi: 10.1007/s00340-009-3824-1