Contribution of the magnetic resonance to the third harmonic generation from a fishnet metamaterial

TL;DR

This study explores how magnetic resonance in a fishnet metamaterial influences third harmonic generation, revealing a distinct angular dependence linked to current distribution, supported by experimental, numerical, and analytical approaches.

Contribution

It provides the first detailed analysis of magnetic resonance effects on third harmonic generation in fishnet metamaterials, combining experimental, numerical, and analytical methods.

Findings

Third harmonic signal peaks at 20° incidence angle during magnetic resonance.

Angular dependence of third harmonic distinguishes magnetic from electric resonances.

Analytical model accurately predicts experimental and numerical results.

Abstract

We investigate experimentally and theoretically the third harmonic generated by a double-layer fishnet metamaterial. To unambiguously disclose most notably the influence of the magnetic resonance, the generated third harmonic was measured as a function of the angle of incidence. It is shown experimentally and numerically that when the magnetic resonance is excited by pump beam, the angular dependence of the third harmonic signal has a local maximum at an incidence angle of {\theta} \simeq 20{\deg}. This maximum is shown to be a fingerprint of the antisymmetric distribution of currents in the gold layers. An analytical model based on the nonlinear dynamics of the electrons inside the gold shows excellent agreement with experimental and numerical results. This clearly indicates the difference in the third harmonic angular pattern at electric and magnetic resonances of the metamaterial.