  We show that broadband optical magnetism can be achieved through
incorporating multi-scaled 3D metallic meta-elements into Z-shaped nanohole
arrays. The broadband effect arises from the excitation of multiple magnetic
resonances in the meta-elements at different wavelengths. Moreover, the
nanohole arrays exhibit a large transmission difference for left- and
right-handed circularly polarized incident light due to the chiral arrangement
of the meta-elements. More importantly, we have realized experimentally the
broadband behavior for the optical range in Ag nanohole arrays fabricated by
using a shadowing vapor deposition method. Our study opens up new opportunities
for achieving broadband artificial magnetism at visible frequencies which
allows possible applications in plasmonic bio-sensors or energy concentrators.
