Nonadiabatic interaction of a propagating wave packet with localized parametric pumping

The interaction of a propagating wave packet (carrier frequency omega, wave number k) with nonadiabatic parametric pumping, localized in a region of size the order of the carrier wavelength L approximately lambda=2pi/k, is studied experimentally in a system of dipolar spin waves in a ferrite film. It is shown that the three-wave parametric interaction omega+omega(')=omega(p) leads to the formation of both contrapropagating (k(')=-k) and copropagating (k(')=k) idle wave packets of carrier frequency omega('). A system of equations derived for the packet envelopes gives a quantitative description of the observed random modulation of the output signal caused by the interference of the input and copropagating idle wave packets.