Characterizations of a thermo-tunable broadband fishnet metamaterial at THz frequencies

[Display omitted] •We numerically study a THz thermo-tunable broadband fishnet metamaterials (MMs).•The MMs consists of a Pyrex spacer sandwiched by two identical fishnet InSb patterns.•The left-handed frequency is thermally controlled via the carrier density of InSb MMs.•The results show a broader negative index band with respect to the rise of temperature.•The LC model and numerical simulations are performed to elaborate the proposed idea. Looking for alterable metamaterials, whose electromagnetic properties can be dynamically and real-time controlled, has attracted a great attention recently. In this paper, we present a numerical study of thermo-tunable polarization-insensitive fishnet metamaterials operating at THz regime. The conventionally used metal is replaced by InSb in which the temperature-dependent conductivity plays a key role in tuning the left-handed frequency. By increasing the temperature of the InSb patterns from 300 to 350K, we show that the left-handed transmission peak can shift from 0.8 to 1.1THz and fractional bandwidth of the negative refractive index goes from 14% to 22%. Thermally increased carrier density of InSb is found to be the reason for the enhanced magnetic resonance and stronger left-handed behavior in addition to the tunability. The equivalent LC circuit model and standard retrieval method are performed to elaborate our proposed idea.