Negative refraction in random photonic alloys of polaritonic and plasmonic microspheres

The electromagnetic response of a random binary photonic alloy consisting of plasmonic and polaritonic spheres of micrometer size is examined. As shown from the extended Maxwell-Garnett theory and verified by rigorous multiple-scattering theory, this particular alloy exhibits negative refractive index in certain frequency regions in the infrared regime. Moreover, the calculated negative-refractive-index regions of the random alloy are much wider than those of the corresponding periodic structure of the same type of spheres with the same concentration, when losses are ignored. When loss mechanisms are taken into account in the constituent materials, light dissipation is dominant and a safe prediction of the negative refractive index cannot be drawn.