Fishnet Metamaterial: Broadband Negative Refractive Index

A fishnet metamaterial stacks two perforated metal sheets around a thin dielectric spacer so that an incident magnetic field drives antiparallel currents through the holes, forming a resonant current loop with a genuine magnetic response — something no natural material offers at optical frequencies. This simulator renders the fishnet stack in 3D and combines a Drude electric response from the metal wires with a Lorentzian magnetic resonance from the antiparallel-current loop to compute the complex effective index n(ω) = √(ε(ω)μ(ω)) live. Sweep the incident frequency, the hole-size resonance, the inter-layer coupling and the metal damping to watch the transmitted beam flip to the same side of the normal as the incident beam whenever Re(n) drops below zero — the mechanism behind every negative-index demonstration since Smith's original 2000 microwave sample.