Direct imaging of strong photon-magnon coupling in a planar geometry*

Recently, photon-magnon (MP) coupling has attracted great attention due to the coherent information exchange, critical for quantum-information applications. Essential in this regard is the miniaturization of the microwave source and the magnetic medium for information transduction applications. 

Here, we reveal the strong interaction of microwave photons in a planar resonator with magnons in yttrium iron garnet (YIG) films with thicknesses 200~nm and 2.46~$\mu$m at room temperature using two complementary measurement techniques: microwave spectroscopy and Brillouin light scattering spectroscopy (BLS). BLS demonstrates an up-conversion from microwave to optical frequencies. In addition, although MP coupling can be clearly observed in both techniques, the BLS results reveal both magnonic and photonic characteristics, whereas the inductive measurements mainly probe the photonic character. We find coupling strengths of 37~MHz and 130~MHz in 200~nm and 2.46~$\mu$m thick YIG films, respectively.

This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-SC0020308.