Negative refraction without absorption: coherence effects, gain and local field corrections

Negative refraction of electromagnetic radiation is currently one of the most active areas of photonics research. Despite remarkable recent progress, a key challenge remains the realization of negative refraction \textit{without absorption}. We discuss different ways to alleviate this problem: the coupling of an electric and a magnetic resonance together with quantum interference effects similar to EIT; compensation of absorption by introducing gain media. Futhermore surprisingly Clausius-Mossotti local field corrections for magneto-dielectric media in the high density limit result always in negative refraction with vanishing absorption.