Comment on “Self-Similar Chain of Metal Nanospheres as an Efficient Nanolens”

A Comment on the Letter by Kuiru Li, Mark I. Stockman, and David J. Bergman, Phys. Rev. Lett. 91, 227402 (2003). The authors of the Letter offer a Reply.

Figure 1

The distribution of field enhancement in the symmetric axis of the self-similar chain between the two smallest spheres (start from the smallest sphere) calculated by the generalized Mie theory (lines) and the 3D-FDTD method (asterisks) with the incident polarization parallel to the symmetric axis. A, B, and C correspond to the cases of Figs. 2(b), 3(b), and 4(a) in Ref. 1, respectively. The solid and dashed lines correspond to with and without consideration of the size-dependent dielectric function of the smallest Ag sphere, respectively. The asterisks in A are calculated by 3D-FDTD. The radius of the smallest Ag sphere $r=5\mathrm{nm}$. The order of the multipoles used in the generalized Mie theory was 30 to ensure the convergence. The Yee cell size used in the 3D-FDTD calculation was set to be $0.5\times 0.5\times 0.5\mathrm{nm}$, and the total number of time steps was set to be 21 000 to ensure the convergence.