Tunneling of ultradirective radiation in metamaterials with zero-average index bandgap

In a zero-average refractive index metamaterial the light propagation is forbidden and a narrow full photonic bandgap is open in correspondence of the frequency where it vanishes and the refractive index is averaged over the volume. However, it should be underlined that Fabry-Perot resonances can open a propagation state inside such a particular type of bandgap. Based on a photonic crystal exhibiting a negative refractive index, it was found that such Fabry-Perot resonant states allow images transmission with subwavelength details. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3646925]