Abstract
Subwavelength resonant elements are essential building blocks of metamaterials and metasurfaces, which have revolutionized photonics. Despite similarities between different wave phenomena, other types of interactions can make subwavelength coupling significantly distinct; its investigation in their context is therefore of interest both from the physics and applications perspective. In this work, we demonstrate a fully magnonic Gires–Tournois interferometer based on a subwavelength resonator made of a narrow ferromagnetic stripe lying above the edge of a ferromagnetic film. The bilayer formed by the stripe and the film underneath supports two propagative spin-wave modes, one strongly coupled with spin waves propagating in the rest of the film and another almost completely reflected at the ends of the bilayer. When the Fabry–Perot resonance conditions for this mode are satisfied, the weak coupling between both modes is sufficient to achieve high sensitivity of the phase of waves reflected from the resonator to the stripe width and, more interestingly, also to the stripe-film separation. Such spin-wave phase manipulation capabilities are a prerequisite for the design of spin-wave metasurfaces and may stimulate development of magnonic logic devices and sensors detecting magnetic nanoparticles.
Highlights
Subwavelength resonant elements are essential building blocks of metamaterials and metasurfaces, which have revolutionized photonics
Using frequencydomain finite-element (FD-FEM) calculations and micromagnetic simulations we find that this shift depends on the width of the stripe in a non-trivial way: an overall slow and steady increase of the phase shift with stripe width is repeatedly interrupted by sharp phase jumps by 360◦
We have studied theoretically the influence of a narrow ferromagnetic stripe of subwavelength width placed at the edge of a ferromagnetic film on the phase of reflected spin waves (SWs)
Summary
Subwavelength resonant elements are essential building blocks of metamaterials and metasurfaces, which have revolutionized photonics. When the Fabry–Perot resonance conditions for this mode are satisfied, the weak coupling between both modes is sufficient to achieve high sensitivity of the phase of waves reflected from the resonator to the stripe width and, more interestingly, to the stripefilm separation Such spin-wave phase manipulation capabilities are a prerequisite for the design of spin-wave metasurfaces and may stimulate development of magnonic logic devices and sensors detecting magnetic nanoparticles. A breakthrough in the control of reflected and transmitted waves at subwavelength distances has recently been achieved through the use of arrays of nanostructured antennas absorbing and reemitting modified electromagnetic w aves[5,6] These arrays, so-called metasurfaces, are used to obtain anomalous refraction of incident waves or to design flat, ultra-narrow lenses able to form holograms. The effect of a resonator on the phase of the reflected wave has not yet been studied in magnonics; the conditions for the existence of Fabry–Perot resonances and their effect on both reflected and transmitted SWs, especially at subwavelength distances, remain almost u nexplored[19], while both may be key ingredients in creating a magnonic metasurface
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