  Which systems are ideal to obtain negative refraction with no absorption?
Electromagnetically induced transparency (EIT) is a method to suppress
absorption and make a material transparent to a field of a given frequency.
Such a system has been discussed in [1]; however the main limitations for
negative refraction introduced are the necessity of resonant electric and
magnetic dipole transitions, and the necessity of very dense media. We suggest
using frequency translators in a composite system that would provide negative
refraction for a range of optical frequencies while attempting to overcome the
limitations discussed above. In the process of using frequency translators, we
also find composite systems that can be used for refractive index enhancement.
