Second-harmonic generation and spectrum modulation by an active nonlinear metamaterial

The nonlinear properties of a metamaterial sample composed of double-layer metallic patterns and voltage controllable diodes are experimentally investigated. Second harmonics and spectrum modulations are clearly observed in a wide band of microwave frequencies, showing that this kind of metamaterial is not only tunable by low dc bias voltage but also behaves strong nonlinear property under a small power incidence. These properties are difficult to be found in normal naturally occurring materials.