Measuring spatially resolved phase of nanoscale spin waves

We report on spatially resolved phase measurements of nanoscale spin waves with sub-50 om spatial resolution. We performed micro-focused phase-resolved Brillouinlight scattering experiments utilizinga weaklyinteracting array of Mie- resonators patterned by electron beam lithography on the top of a magnetic thin film. This allowed us to detect nanoscale spin waves and at the same time to achieve a spatial resolution in the order of tens of nanometers, one order of magnitude belowthe optical resolution of the used microscope objective. We were able to measure full dispersion relation for the spin waves in the range from 1 rad/μm to 30 rad/μm. These results demonstrate the feasibility of all-optical phase-resolved characterization of nanoscalespin waves.