Negative group velocity and group delay in left-handed media

The dynamics of wave propagation in media with negative index of refraction is analyzed through analytical calculations, simulations, and experiments. For passive media, the circumstances under which the real part of the index can be negative are investigated. Several models for media exhibiting negative refractive index are studied and the transmission characteristics of these media are calculated analytically. It is shown that these models suggest the existence of abnormal group velocity and abnormal group delay bands. Furthermore, the presence of abnormal group delay behavior in several existing Left-Handed Media (LHM) is discovered and analyzed using full wave simulations. Using a free space setup, the transmission characteristics of two split ring resonator and strip wire LHM, designed for operation at K-band frequencies (18--26GHz), are measured. The first LHM, which is 3 unit cells long in the propagation direction, exhibits a maximum negative group delay of -0.9ns whereas the second LHM (4 unit cells long) exhibits a maximum negative group delay of -1.2ns. For both LHM the bandwidth of the negative group delay region was approximately 250MHz.