Frequency and wavenumber selective excitation of spin waves through coherent energy transfer from elastic waves

Using spin-wave tomography (SWaT), we have investigated the excitation and the propagation dynamics of optically excited magnetoelastic waves, i.e., hybridized modes of spin waves and elastic waves, in a garnet film. By using time-resolved SWaT, we reveal the excitation dynamics of magnetoelastic waves through coherent-energy transfer between optically excited pure-elastic waves and spin waves via magnetoelastic coupling. This process realizes frequency and wavenumber selective excitation of spin waves at the crossing of the dispersion relations of spin waves and elastic waves. Finally, we demonstrate that the excitation mechanism of the optically excited pure-elastic waves, which are the source of the observed magnetoelastic waves, is dissipative in nature.