Trapping Light with Dark Plasmons In Nanoparticle Arrays

Metal nanostructures concentrate optical fields into highly confined, nanoscale volumes, which is important for applications such as plasmonic nanolasers and white-light generation. However, the short lifetimes of the measured or “bright” plasmons preclude amplification of local fields because of rapid depletion of the plasmon energy. To overcome this problem, we will describe a new type of “dark” or subradiant plasmon that can be supported by 2D arrays of large (> 100 nm, all three dimensions) gold particles. This dark lattice plasmon can be tuned over a broad range of wavelengths simply by changing the nanoparticle height. At resonance, strong coupling between out-of-plane nanoparticle dipolar moments suppresses radiative decay, trapping light in the plane of the array and strongly localizing optical fields on each nanoparticle. This new mechanism can open applications for subradiant plasmons because height-controlled nanoparticle arrays can be manufactured over wafer-scale areas on a variety of substrates.