Electric and magnetic dipole coupling in near-infrared split ring metamaterial arrays

We present experimental observations of strong electric and magnetic interactions between split ring resonators (SRRs) in metamaterials. We fabricated near-infrared (1.4 $\mu$m) planar metamaterials with different inter-SRR spacings along different directions. Our transmission measurements show blueshifts and redshifts of the magnetic resonance, depending on SRR orientation relative to the lattice. The shifts agree well with a simple model with simultaneous magnetic and electric near-field dipole coupling. We also find large broadening of the resonance, accompanied by a decrease in effective cross section per SRR with increasing density. These effects result from superradiant scattering. Our data shed new light on Lorentz-Lorenz approaches to metamaterials.