The design of negative refractive index (NRI) metamaterials is an exciting field of research, even though the properties of these materials were predicted over 35 years ago [1]. One characteristic of waves propagating in these structures is that, in the pass-band, the group velocity and the wave vector are anti-parallel, which gives rise to a backward wave (BW) behaviour. Both dielectric and metallic photonic crystals (PCs) with two-dimensional square and triangular lattices of scattering rods have been considered as possible candidates for NRI metamaterials [2-4]. Although in general PCs can produce "negative refraction" with and without BW behavior, in the present study we mostly consider the negative refraction in the BW bands. This paper presents a study of metallic photonic crystals with a 2D square lattice of cross shaped scatterers. It is found that even a small volume fraction of metal (when compared to the rods of Ref. [3]) creates more and wider bands with the required curvature for BW behaviour. Furthermore these bands can easily be tuned and isolated (in the spectrum) by changing the dimensional characteristics of the crosses. Our design process was simplified by first tuning the shapes of the bands with the metallic crosses, and then scaling the bands to the desired frequency by immersing the crosses in a dielectric background.
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