Asymmetric parametric amplification in nonlinear left-handed transmission lines

We study parametric amplification in nonlinear left-handed transmission lines, which serve as model systems for nonlinear negative-index metamaterials. We experimentally demonstrate the amplification of a weak signal in the three following regimes: with the signal in the left-handed band, with the signal in the stop band, and with the signal at a defect frequency. In particular, we demonstrate the amplification of the incident wave by up to 15 dB in the left-handed regime.