Optical spin-wave detection beyond the diffraction limit

TL;DR

This paper demonstrates a novel magneto-optical method to detect spin waves with wavelengths below the diffraction limit using a metallic grating, enabling high-resolution optical detection in magnonics.

Contribution

The authors introduce a wavelength-selective magneto-optical detection technique for spin waves beyond the diffraction limit, advancing optical detection capabilities in magnonics.

Findings

Detected 700 nm spin waves with a 10 μm laser spot.

Achieved wavelength-selective detection of spin waves.

Enabled optical detection in the short-wavelength exchange regime.

Abstract

Spin waves are proposed as information carriers for next-generation computing devices because of their low power consumption. Moreover, their wave-like nature allows for novel computing paradigms. Conventional methods to detect spin waves are based either on electrical induction, limiting the downscaling and efficiency complicating eventual implementation, or on light scattering, where the minimum detectable spin-wave wavelength is set by the wavelength of the laser. In this Article we demonstrate magneto-optical detection of spin waves beyond the diffraction limit using a metallic grating that selectively absorbs laser light. Specifically, we demonstrate the detection of propagating spin waves with a wavelength of 700 nm using a diffraction-limited laser spot with a size of 10 $\mu$m in 20 nm thick Py strips. Additionally, we show that this grating is selective to the wavelength of the spin wave, providing wavevector-selective spin-wave detection. This should open up new avenues towards the integration of the burgeoning fields of photonics and magnonics, and aid in the optical detection of spin waves in the short-wavelength exchange regime for fundamental research.