Resonant T-junction magnonic structure as a frequency-selective spin-wave mode converter

Abstract We demonstrate a frequency-selective intermodal spin-wave mode converter based on a T-shaped yttrium iron garnet waveguide with a central square resonator. Using Brillouin light scattering spectroscopy and micromagnetic simulations, we show that excitation of a specific magnetostatic surface spin wave mode in the input arm leads to selective generation of a backward-volume magnetostatic spin wave mode of different transverse order in the orthogonal output arm. This intermodal conversion arises from resonant coupling mediated by the central cavity and is governed by the dispersion asymmetry between the waveguide arms. The resonant T-junction magnonic structure we propose not only functions as a frequency-selective intermodal spin-wave mode converter but also provides a suitable platform for observing bound states in the continuum. The device enables programmable signal routing for magnonic logic and reconfigurable microwave filtering.