dielectric materials containing active dielectric-metal composite nanoparticles as double negative materials in the visible

In the visible spectral range, mie resonance-based double negativity has still not been observed in all-dielectric metamaterials due to the lack of dielectrics with sufficiently high refractive indices. in this work, the dielectric materials containing nanospheres of gain-metal nanocomposites are proposed as double negative materials operating in the visible. they are embedded with two types of composite nanospheres: one contributes to the negative permeability via magnetic mie resonance facilitated by gain-assisted high indices of composite nanospheres and the other one to the negative permittivity via plasmonic dipolar resonance in the same spectral range. the figure-of-merit of these materials reaches up to infinity or even can be negative, implying the gain, depending on the structural and material parameters. the proposed materials can find broad applications as loss-free negative index materials in the visible and near-infrared.