Direct observation of two-dimensional self-focusing of spin waves in magnetic films

An observation of self-focusing of dipolar spin waves in garnet film media is reported. In particular, we show that the quasistationary diffraction of a finite-aperture spin-wave beam in a focusing medium leads to the concentration of the wave power in one focal point rather than along a certain line (channel). The obtained results demonstrate the wide applicability of nonlinear spin-wave media to study nonlinear wave phenomena using an advanced combined microwave--Brillouin-light-scattering technique for a two-dimensional mapping of the spin-wave amplitudes.