Tunable magnon emission from a nano-optomagnet

TL;DR

This paper demonstrates tunable nanoscale magnon emission in a yttrium iron garnet film using focused laser light on plasmonic nanodiscs, enabling broadband, energy-efficient signal generation without electrical excitation.

Contribution

It introduces plasmonic nanoantennas as reconfigurable nanoscale magnon sources driven solely by optical modulation, advancing nanoscale magnonic device integration.

Findings

Magnons match optical modulation frequencies in GHz range.

Circularly polarized light enhances magnon amplitudes.

Nanodisc size influences plasmonic enhancement and magnon emission.

Abstract

The growing demand for dense, energy-efficient, and high-frequency signal processing continues to drive device miniaturization. While downscaling remains a central challenge, magnons offer a promising solution as nanoscale signal carriers, supporting broadband operation from GHz to THz without moving charge carriers and generating Joule heating. However, their integration at the nanoscale is limited by conventional electrical excitation based on coplanar waveguides, which require metal pads few to hundreds of micrometres in size. Here, we demonstrate tunable magnon emission into a yttrium iron garnet film by focusing microwave-modulated laser light onto an integrated Au nanodisc. Using inelastic light scattering spectroscopy, we observe magnons whose frequencies match the optical modulation frequencies in the GHz frequency regime. The largest magnon amplitudes are found for circularly polarized laser light and specific nanodisc diameters consistent with a plasmon-enhanced inverse Faraday effect. These results establish plasmonic nanoantennas as reconfigurable nanoscale magnon sources, enabling broadband signal generation governed entirely by optical modulation.