Omnidirectional spin-wave nanograting coupler

TLDR

Magnonics promises low‑power, high‑speed computing for tasks such as image processing and speech recognition, yet efficient nanoscale coupling to microelectronics remains a critical challenge. The study aims to develop a magnonic grating coupler that converts microwaves into short‑wavelength spin waves with large amplitudes. The authors design a periodically nanostructured magnetic grating that, when excited by a microwave antenna, emits multidirectional short‑wavelength spin waves with greatly enhanced amplitude, and they investigate its performance across different ferromagnetic materials, lattice constants, and magnetic fields. The grating coupler produces multidirectional, high‑amplitude short‑wavelength spin waves, outperforming conventional gratings and enabling straight microwave antennas to act as omnidirectional emitters for integrated magnonic and cellular nonlinear network applications.

Abstract

Magnonics as an emerging nanotechnology offers functionalities beyond current semiconductor technology. Spin waves used in cellular nonlinear networks are expected to speed up technologically, demanding tasks such as image processing and speech recognition at low power consumption. However, efficient coupling to microelectronics poses a vital challenge. Previously developed techniques for spin-wave excitation (for example, by using parametric pumping in a cavity) may not allow for the relevant downscaling or provide only individual point-like sources. Here we demonstrate that a grating coupler of periodically nanostructured magnets provokes multidirectional emission of short-wavelength spin waves with giantly enhanced amplitude compared with a bare microwave antenna. Exploring the dependence on ferromagnetic materials, lattice constants and the applied magnetic field, we find the magnonic grating coupler to be more versatile compared with gratings in photonics and plasmonics. Our results allow one to convert, in particular, straight microwave antennas into omnidirectional emitters for short-wavelength spin waves, which are key to cellular nonlinear networks and integrated magnonics. Spin waves can provide efficient alternatives to microelectronics in applications such as image processing, but are difficult to realize on the nanoscale. Here, the authors develop a magnonic grating coupler, which allows for the conversion of microwaves to short-wavelength spin waves with large amplitudes.