Directional coupling of the spin waves in a resonator system of T-shaped magnonic microwaveguide

Abstract

Here, we report an experimental and theoretical study on the directional coupling of spin waves in a T-shaped magnonic microwaveguide. A high-quality yttrium iron garnet film was structured via precise laser ablation to form an integrated resonator system incorporating magnonic-crystal sections. Using Brillouin light scattering spectroscopy alongside micromagnetic simulations based on the Landau–Lifshitz–Gilbert framework, we demonstrate that the resonator element induces Fabry–Pérot-like interference, leading to multi-mode spin-wave propagation and selective energy transfer between the magnonic-crystalline and waveguiding regions. The resonator enables selective excitation of transverse modes, leading to distinct directional coupling regimes: at specific frequencies, spin waves propagate preferentially into either the MC or waveguide sections. Simulations reveal mode interference and bandgap effects, aligning with experimental observations. Resonant modes within the system enable distinct coupling regimes: at specific frequencies, spin waves are directionally routed into either the waveguide or MC section, governed by transverse mode formation and Bragg scattering effects. In this case, the modes of directional coupling of the spin waves are associated with the intersection of the dispersion characteristics of the forward and backward waves for the first and third modes. These findings highlight the potential of resonator-coupled magnonic systems for reconfigurable signal processing, enabling applications such as frequency-division multiplexing, logic gates, and adaptive magnonic circuits with ultra-low-power consumption.