Design and construction of a spin-wave lens.

Jan-Niklas Toedt,Mark Mundkowski,Detlef Heitmann,Stefan Mendach,Wolfgang Hansen

doi:10.1038/srep33169

Jan-Niklas Toedt, Mark Mundkowski + Show 3 more

Open Access

https://doi.org/10.1038/srep33169

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Journal: Scientific Reports	Publication Date: Sep 21, 2016
Citations: 33	License type: CC BY 4.0

Affiliation: Universität Hamburg

Abstract

In this work, we present the focusing of a Damon-Eshbach wave in a Ni80Fe20 film by a shaped, discrete transition of the film thickness. We devised an algorithm to determine the required shape of a spin-wave lens. Due to the anisotropy three geometries qualify as plano-convex lenses. One lens geometry has been realized experimentally and the emitted spin-wave pattern is investigated by time-resolved scanning Kerr microscopy.

Highlights

In this work, we present the focusing of a Damon-Eshbach wave in a Ni80Fe20 film by a shaped, discrete transition of the film thickness
Csaba et al simulated a lens for spin waves based on the alteration of a magnetic field[12], the lens was designed in a regime for which spin waves exhibit almost isotropic propagation characteristics, circumventing the, in general strong, anisotropy of the spin-wave propagation. This anisotropy urges the need for an appropriate lens geometry
We constructed an appropriately curved spin-wave lens based on refraction of a spin wave by a step edge in a permalloy

Summary

Lens Design

We consider a lens with a curved boundary line. The shape of the lens is calculated in an iterative fashion, assuming a monochromatic, planar Damon-Eshbach type spin wave as incident wave. The comparably small group velocities associated with spin waves near the Backward-Volume regime results in shorter decay lengths for those spin waves, which would be especially detrimental for lens i due to the long distances between lens boundary and focal spot. Despite these problems, most of which are unique to spin waves, it is remarkable, that the anisotropy of the dispersion enables the appearance of additional geometric solutions which satisfy the condition for a plano-convex focusing lens. The smooth lens was selected to be experimentally realized, since it promises comparably small reflection at the thickness transition, the lowest magnetic inhomogeneities, and emitted wave lengths in the resolvable range of the employed scanning Kerr microscope

Sample Design and Measurement Setup

Experimental Results and Discussion

Conclusion

Additional Information