Spatially-Localized Second Harmonic Generation via Spin Wave Concentration in Patterned YIG Structures

TL;DR

This paper demonstrates how geometric patterning of YIG structures can locally generate and enhance second harmonic magnon signals, enabling advanced magnonic device functionalities.

Contribution

It introduces a method to locally tune spin wave dispersion via patterning, facilitating spatially localized second harmonic generation in magnonic devices.

Findings

Localized high-intensity magnons achieved in patterned YIG structures.

Second harmonic signals confirmed as nonlinear magnon scattering processes.

Potential for enhanced magnonic device sensitivity and logic operations.

Abstract

The anisotropic dispersion and inherent nonlinearity of magnetostatic spin waves in thin films and confined structures provide unique opportunities for implementation in next-generation magnonic devices for data and signal processing. A particular challenge is to establish an effective means to locally generate higher harmonics and subsequently exploit them while avoiding extraneous nonlinear losses. Here we demonstrate that deterministically and locally tuning the dispersion relation by geometric confinement through standard patterning processes, allows the creation spatially localized, high-intensity magnons hundreds of $\mu m$ or even further from the excitation source. The local intensity obtained in passive, lithographically patterned YIG funnel structures is sufficient to achieve second harmonic generation in localized regions via conventional magnon scattering processes. We verify these effects are truly nonlinear processes by direct measurement and comparison of the 1-$\omega$ and 2-$\omega$ magnon signals as determined by highly sensitive frequency- and spatially-resolved SNS-MOKE technique. This lays the foundation for using similar devices in future magnon-based infrastructures to localize and enhance sensitivity of readout, downstream magnon-based logic operations, and for other higher harmonic generation-related phenomena and low-power magnonics applications.