magnons in a small yttrium iron garnet (YIG) sphere are strongly but dispersively coupled to
the photons in a three-dimensional cavity. When the YIG sphere is pumped to generate
considerable magnons, the Kerr effect yields a perceptible shift of the cavity's central
frequency and more appreciable shifts of the magnon modes. We derive an analytical
relation between the magnon frequency shift and the drive power for the uniformly …