Spinelli P, van Lare C, Verhagen E, Polman A
Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands.
Opt Express. 2011 May 9;19 Suppl 3:A303-11. doi: 10.1364/OE.19.00A303.
Metal nanoparticles are efficient resonant plasmonic scatterers for light, and, if placed on top of a high-index substrate, can efficiently couple light into the substrate. This coupling, however, strongly depends on particle shape and surrounding environment. We study the effect of particle shape and substrate refractive index on the plasmonic resonances of silver nanoparticles and we systematically relate this to the efficiency of light scattering into a substrate. The light coupling spectra are dominated by Fano resonances for the corresponding dipolar and quadrupolar scattering modes. Varying the particle shape from spherical to cylindrical leads to large shifts in the Fano resonance for the dipolar mode, reducing the light incoupling integrated over the AM1.5 spectral range. Using a dielectric spacer layer, good light coupling is achieved for cylinders in the near-infrared. An asymmetric environment around the particles turns quadrupolar resonances into efficient radiators as well.
金属纳米颗粒是高效的光共振等离子体散射体，如果放置在高折射率衬底上，能够有效地将光耦合到衬底中。然而，这种耦合强烈依赖于颗粒形状和周围环境。我们研究了颗粒形状和衬底折射率对银纳米颗粒等离子体共振的影响，并系统地将其与光散射到衬底中的效率联系起来。光耦合光谱由相应偶极和四极散射模式的法诺共振主导。将颗粒形状从球形变为圆柱形会导致偶极模式的法诺共振发生大幅偏移，从而降低在AM1.5光谱范围内积分的光入射耦合。使用介电间隔层，在近红外区域可实现圆柱体的良好光耦合。颗粒周围的不对称环境也会使四极共振成为高效辐射体。
