Wideband wide-field imaging of spin-wave propagation using diamond quantum sensors

Imaging spin-wave propagation in magnetic materials in a wide frequency range is crucial for understanding and applying spin-wave dynamics. Recently, nitrogen-vacancy (N-V) centers in diamond have attracted attention as sensors capable of quantitatively measuring the amplitude and phase of coherent spin waves. However, the conventional sensing protocol has been limited to detecting spin waves whose frequencies match the resonance frequency of the N-V spins. We demonstrate that by utilizing the ac Zeeman effect, it is possible to image spin waves propagating in an yttrium iron garnet thin film over a wide frequency range up to a maximum detuning of $567\phantom{\rule{0.2em}{0ex}}\mathrm{M}\mathrm{Hz}$ without changing the external magnetic field. Our results expand the applicability of N-V centers for spin-wave sensing and pave the way for quantitative investigations of the dynamics in various magnetic materials, such as metallic ferromagnets and van der Waals magnets.