Optical effective media with independent control of permittivity and permeability based on conductive particles

We propose and prove that it is possible to decouple the electric and magnetic response of an array of conductive nanoparticles and realize a very wide range of combinations of effective permittivities and permeabilities. The principle exploits the large differences in the Thomas-Fermi screening length for longitudinal electric fields and the classical penetration depth for time-varying transverse magnetic fields. This non-resonant principle allows frequency invariance of the effective material properties with a bandwidth spanning many octaves, orders of magnitude larger than previous resonant metamaterials. An effective medium with a record-high refractive index over broadband is demonstrated as an example.