Spin-wave diffraction, caustic beam emission, and Talbot carpets in a yttrium iron garnet film with magnonic Fabry-Perot resonator gratings

We report spin-wave diffraction, caustic beam emission, and the formation of Talbot carpets in an yttrium iron garnet (YIG) film equipped with magnonic Fabry-Perot resonators. The resonator structures are created by patterning cobalt iron boron (Co-Fe-B) nanostripes on the YIG film. Small gaps in the Co-Fe-B nanostripes generate a magnetic field profile within the YIG film, functioning as a slit grating when the resonators block incoming spin waves at specific frequencies. We employ super-Nyquist sampling magneto-optical Kerr effect (SNS-MOKE) microscopy to image the transport of spin waves through the slits and supplement our experimental observations with micromagnetic simulations. For a single slit, we observe a transition from spin-wave diffraction to caustic beam emission as the slit size decreases. These phenomena are influenced by the effective magnetic field within the slit, which varies with the direction of magnetization in either the YIG film or the Co-Fe-B nanostripes. For multiple slits, we detect self-imaging of spin-wave profiles and the formation of Talbot carpets. Furthermore, we demonstrate active tuning of spin-wave interference patterns through magnetic switching in the Fabry-Perot resonators or by rotating the in-plane magnetization of the YIG film. The magnonic grating system described here integrates low-loss spin-wave transport and programmable spin-wave interference, offering potential applications in advanced magnonic computing devices.