  The Dzyaloshinskii-Moriya interaction in ultrathin ferromagnets can result in
nonreciprocal propagation of spin waves. We examine theoretically how spin wave
power flow is influenced by this interaction. We show that the combination of
the dipole-dipole and Dzyaloshinskii-Moriya interactions can result in
unidirectional caustic beams in the Damon-Eshbach geometry. Morever,
self-generated interface patterns can also be induced from a point-source
excitation.
