Structurally Tunable Nonlinear Terahertz Metamaterials using Broadside Coupled Split Ring Resonators

TL;DR

This study demonstrates a tunable nonlinear terahertz metamaterial using stacked split ring resonators on GaAs, where structural alignment controls the nonlinear transmission response at 0.4 THz.

Contribution

It introduces a novel method to control nonlinear terahertz responses through structural positioning of coupled resonator arrays, enabling tunable THz device design.

Findings

Nonlinear transmission varies with incident power due to GaAs carrier dynamics.

Alignment of resonator layers suppresses nonlinear response.

Offset alignment restores nonlinear modulation.

Abstract

We present an experimental and numerical study of a terahertz metamaterial with a nonlinear response that is controllable via the relative structural positioning of two stacked split ring resonator arrays. The first array is fabricated on an n-doped GaAs substrate 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 at 0.4 THz varies in a nonlinear manner with incident terahertz power. The second resonator layer dampens this nonlinear response. In samples where the two layers are aligned, the resonance disappears and total nonlinear modulation of the on-resonance transmission decreases. The nonlinear modulation is restored in samples where an alignment offset is imposed between the two resonator arrays. Structurally tunable metamaterials can therefore act as a design template for tunable nonlinear THz devices by controlling the coupling of confined electric fields to nonlinear phenomena in a complex material substrate or inclusion.