Localized parallel parametric generation of spin waves in a Ni81Fe19 waveguide by spatial variation of the pumping field

We present the experimental observation of localized parallel parametric generation of spin waves in a transversally in-plane magnetized Ni81Fe19 magnonic waveguide. The localization is realized by combining the threshold character of parametric generation with a spatially confined enhancement of the amplifying microwave field. The latter is achieved by modulating the width of the microstrip transmission line which is used to provide the pumping field. By employing microfocussed Brillouin light scattering spectroscopy, we analyze the spatial distribution of the generated spin waves and compare it with numerical calculations of the field distribution along the Ni81Fe19 waveguide. This provides a local spin-wave excitation in transversally in-plane magnetized waveguides for a wide wave-vector range which is not restricted by the size of the generation area.