Deeply Nonlinear Magnonic Directional Coupler

TL;DR

This paper investigates a nonlinear phenomenon in magnonic directional couplers caused by frequency shifts of spin waves, enabling switchable energy transfer control for integrated magnonic circuits.

Contribution

It reveals a new nonlinear effect where frequency shifts suppress energy transfer, and designs a switchable coupler based on this principle validated by simulations.

Findings

Sharp threshold behavior in energy transfer suppression

Critical power depends on coupling strength and nonlinear shift

Designed a switchable magnonic directional coupler

Abstract

Dipolar coupling between closely spaced magnetic waveguides enables the design of magnonic directional couplers - universal devices capable of functioning as signal combiners, power splitters, demultiplexers, and more. The wavelength-dependent coupling, combined with the weak nonlinear variation of a spin wave's wavelength at constant-frequency, introduces power-dependent characteristics of directional couplers. This property has been leveraged in the development of magnonic logic elements and other applications. Here, we explore another nonlinear phenomenon in a directional coupler arising purely from the nonlinear frequency shift of spin waves. We show that a strong nonlinear frequency shift causes the coupler to behave as if composed of nonidentical waveguides, suppressing the energy transfer between the waveguides. The transition from complete to negligible energy transfer exhibits a sharp threshold behavior, where the critical power is determined by the coupling strength and nonlinear frequency shift parameter. Based on these findings, a switchable directional coupler as a critical component for future integrated magnonic circuits is designed and validated by micromagnetic simulations.