Surface-plasmon-polariton-driven narrow linewidth magneto-optics in Ni nanodisk arrays

TL;DR

This study demonstrates how to achieve narrow linewidth magneto-optical signals in Ni nanodisk arrays by exploiting surface plasmon polaritons and off-resonance driving, overcoming typical optical losses in magnetic metals.

Contribution

It introduces a novel approach to mitigate optical losses in magnetoplasmonics by using SPPs at a SiO2/Au interface to induce strong magneto-optical responses in Ni nanodisks.

Findings

Spectral linewidth of magneto-optical Kerr effects down to ~25 nm.

Loss mitigation achieved by driving electrons away from plasmon resonance.

Tailoring of magneto-optical responses through structural parameter variation.

Abstract

Magnetoplasmonics exploits interactions between light and magnetic matter at the nanoscale for light manipulation and resonant magneto-optics. One of the great challenges of this field is overcoming optical losses in magnetic metals. Here we exploit surface plasmon polaritons (SPPs) excited at the interface of a SiO2/Au bilayer to induce strong magneto-optical responses on the Ni nanodisks of a periodic array. Using a reference system made of Au nanodisks, we show that optical losses in Ni do hardly broaden the linewidth of SPP-driven magneto-optical signals. Loss mitigation is attained because the free electrons in the Ni nanodisks are driven into forced oscillations away from their plasmon resonance. By varying the SiO2 layer thickness and lattice constant of the Ni nanodisk array, we demonstrate tailoring of intense magneto-optical Kerr effects with a spectral linewidth down to ~25 nm. Our results provide important hints on how to circumvent losses and enhance magneto-optical signals via the design of off-resonance magnetoplasmonic driving mechanisms.