Graded index lenses for spin wave steering

We use micromagnetic modeling to demonstrate the operation of graded index lenses designed to steer forward-volume magnetostatic spin waves by 90 and 180 degrees. The graded index profiles require the refractive index to diverge in the lens center, which, for spin waves, can be achieved by modulating the saturation magnetization or external magnetic field in a ferromagnetic film by a small amount. We also show how the ${90}^{\circ }$ lens may be used as a beam divider. Finally, we analyze the robustness of the lenses to deviations from their ideal profiles.