Doping tunable resonance: Toward electrically tunable mid-infrared metamaterials

We demonstrate metamaterials at the mid-infrared (mid-IR) wavelengths (8-12 μm) that can be widely tuned by doping in adjacent semiconductor epilayers. The metamaterials are based on metallic split ring resonators (SRRs) fabricated on doped indium antimonide (InSb). Finite integral time-domain simulation results and measured transmission data show that the resonance blueshifts when the semiconductor electron carrier concentration is increased while keeping the split ring geometry constant. A resonant wavelength shift of 1.15 μm is achieved by varying the carrier concentration of underlying InSb epilayer from 1× 1016 to 2× 1018 cm-3. This work represents the first step toward active tunable metamaterials in the mid-IR where the resonance can be tuned in real time by applying an electric bias voltage to control the effective carrier density. © 2010 American Institute of Physics.