Criteria for negative refraction in active and passive media



We review three commonly used conditions that characterize negative refraction in isotropic dielectric-magnetic materials. We show that while all the different conditions are equivalent for passive media, they are distinct for different types of active media. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1804–1807, 2008; Published online in Wiley InterScience ( DOI 10.1002/mop.23489