Collective Effects in Second-Harmonic Generation from Split-Ring-Resonator Arrays Optical experiments on second-harmonic generation from split-ring-resonator square arrays show a nonmonotonic dependence of the conversion efficiency on the lattice constant. This finding is interpreted in terms of a competition between dilution effects and linewidth or near-field changes due to interactions among the individual elements in the array. 109 1 American Physical Society (APS) application/pdf