Waveguide-light-spin-wave interaction in nonuniformly magnetized yttrium iron garnet films

Abstract

The magneto-optic interaction of waveguide light (WL) with spin waves (SW) in nonuniformly magnetized yttrium iron garnet (YIG) films was investigated both experimentally and theoretically. The measurements were carried out on YIG film of thickness 3.8 µm at the optical wavelength of 1.15 µm and in the SW frequency band of 3-4 GHz. It is shown that for collinear WL-SW interaction, a spatial nonuniformity of the magnetizing field can provide SW beam focusing and improve WL-SW interaction efficiency by a factor of an order of magnitude. Field nonuniformity in the transverse direction results in a spatial separation of regions of WL interaction with SW of different frequencies. For orthogonal geometry of the WL-SW interaction the artificial field nonuniformity leads to an increase in the Bragg diffraction angles.