Nanocomposite Multilayer Structure for Broadband MIR Negative Refractive Index

The main purpose of this study is designing a structure with the broadband negative refractive index (NRI) in the wavelengths range of 3–5 μm using multilayer structures. In the proposed structure, actually nanocomposite thin films are used to make multilayer waveguide to show effective NRI. In the composite structure, core-shell nanoparticles including metallic core and a dielectric shell with high refractive index are used. Here, it is shown that by increasing the number of composite layers, the bandwidth for NRI can be increased. Therefore, based on simulation results, in eight-layer waveguide, NRI is available in complete 3- to 5-μm MIR band. In this regard, also, the effect of filling factor (in each thin-film layer) on NRI is studied.