A Luneburg lens for spin waves

TL;DR

This paper presents a theoretical design and micromagnetic verification of a Luneburg lens for spin waves, demonstrating enhanced focusing and energy concentration through a graded index profile.

Contribution

It introduces a novel Luneburg lens concept for spin waves, utilizing graded magnetic properties to achieve efficient wave focusing and energy concentration.

Findings

Lens enhances wave amplitude by 5 times at focus

47% of incident energy is concentrated at the focus

Smooth grading of the index maintains good focusing

Abstract

We report on the theory of a Luneburg lens for forward-volume magnetostatic spin waves, and verify its operation via micromagnetic modelling. The lens converts a plane wave to a point source (and vice versa) by a designed graded index, realised here by either modulating the thickness or the saturation magnetization in a circular region. We find that the lens enhances the wave amplitude by 5 times at the lens focus, and 47% of the incident energy arrives in the focus region. Furthermore, small deviations in the profile can still result in good focusing, if the lens index is graded smoothly.