Congratulations to XM² PGR Natalie Whitehead for her publication on “A Luneburg lens for spin waves“: https://doi.org/10.1063/1.5049470 (Applied Physics Letters 113).
In this article, the researchers 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 refractive index, realized by modulating either the thickness or the saturation magnetization in a circular region. They find that the lens enhances the wave amplitude by about 5 times at the lens focus, and 47% of the incident energy arrives in the focal region. A lens with small deviations from the optimal profile can still result in good focusing if the index is graded smoothly.
Video: ‘Time-dependence of the dynamic magnetisation, mx=Mx/Ms, as the wave packet moves through the Luneburg lens.’