  We experimentally demonstrate the generation of spin-wave frequency combs
based on the nonlinear interaction of propagating spin waves in a
microstructured waveguide. By means of time and space-resolved Brillouin light
scattering spectroscopy, we show that the simultaneous excitation of spin waves
with different frequencies leads to a cascade of four-magnon scattering events
which ultimately results in well-defined frequency combs. Their spectral weight
can be tuned by the choice of amplitude and frequency of the input signals.
Furthermore, we introduce a model for stimulated four-magnon scattering which
describes the formation of spin-wave frequency combs in the frequency and time
domain.
