  A robust wedge setup is proposed to unambiguously demonstrate negative
refraction for negative index metamaterials. We applied our setup to several
optical metamaterials from the literature and distinctly observed the phenomena
of negative refraction. This further consolidates the reported negative-index
property. It is found there generally exists a lateral shift for the outgoing
beam through the wedge. We derived a simple expression for calculating this
beam shift and interestingly, it provides us a strategy to quantitatively
estimate the loss of the wedge material (Im[n]). Addition- ally, we offered a
design of metamaterials, compatible with nano-imprinting-lithography, showing
negative refractive index in the visible regime (around yellow-light
wavelengths). The multi-layer- system retrieval was utilized to extract the
effective refractive index of the metamaterial. It was also intuitively
characterized through our wedge setup to demonstrate corresponding phenomena of
refraction.
