  A novel ring structure is proposed for double negative NIMs at visible light
spectrum with high FOM (e.g. about 11 at a wavelength of 583 nm) and low loss.
Besides the effective medium theory, an equivalent circuit model is also given
to explain physically why our novel structure can give double negative behavior
with low loss. Adapted from the original ring structure, two other types of
structures, namely, disk and nanowire structures, are also given to further
push double negative NIMs toward ultraviolet (UV) spectrum.
