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{similar_to}{lambda}=2{pi}/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}{sup {prime}}={omega}{sub p} leads to the formation of both contrapropagating (k{sup {prime}}={minus}k) and copropagating (k{sup {prime}}=k) idle wave packets of carrier frequency {omega}{sup {prime}}. 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.