Structurally Tunable Nonlinear Terahertz Metamaterials

We present a terahertz metamaterial with a nonlinear response, tunable via the relative structural positioning of two stacked resonator arrays. The device consists of two planar arrays of split ring resonators. The first is fabricated on n-doped GaAs and the second array is fabricated vertically above the first using a polyimide spacer layer. Due to GaAs carrier dynamics, the on-resonance terahertz transmission is strongly nonlinear, decreasing by 30% as the incident terahertz power increases. The second resonator layer dampens this nonlinear response. When the two layers are aligned, the total nonlinear modulation of the on-resonance transmission decreases to below 10%. The nonlinear modulation then returns to full strength when the two resonator arrays are shifted laterally away from each other.