Nonspherical optomagnonic resonators for enhanced magnon-mediated optical transitions

We study magnon-mediated optical transitions in micrometer-sized axially symmetric yttrium iron garnet (YIG) particles, which act as optomagnonic cavities, by means of electromagnetic calculations, treating the magneto-optical coupling to first order in perturbation theory, in the framework of a fully dynamic approach. Such particles with engineered shape anisotropy exhibit high-quality-factor Mie resonances in the infrared part of the spectrum, with a separation of few gigahertz, which matches the typical frequencies of magnons. This allows for optical transitions mediated by spin waves, while the micrometer volume favors stronger overlap between the optical modes and the precessing magnetization. Our results predict that photon-magnon coupling strengths of tens of kilohertz could be realized with cylindrical or spheroidal particles, since mainly the reduced volume, but also shape anisotropy, can lead to strong, up to four orders of magnitude, enhancement of the coupling strengths compared to submillimeter YIG spheres.

Automated summary

This study investigates magnon-mediated optical transitions in micrometer-sized YIG particles, finding that their engineered shape anisotropy leads to high-quality-factor Mie resonances in the infrared spectrum. As a result, photon-magnon coupling strengths can be significantly enhanced compared to submillimeter YIG spheres.