Quadratic power corrections to the dynamic magnetization using the transverse magnetostatic wave-optical interaction

Abstract

A microstrip T-transducer excites forward volume magnetostatic waves (MSWs) in a [BiLu]3Fe5O12 film. An optical beam is edge coupled into the film and the transverse MSW–optical interaction is observed at high microwave power levels. Using the coupled mode equations, we demonstrate that a T-transducer causes the intensity of the diffracted beam to be a product of terms involving the magneto-optic coupling coefficient (κ) and the phase mismatch between the optical guided modes and the MSWs. Taylor series expansions for κ and the MSW wave number (β) are used to obtain an analytic expression for the MSW–optical interaction. The dependence on β causes a shift in the interaction spectrum with increasing power. After correcting for this shift, the residual dependence on power is attributed to a quadratic correction to the dynamic magnetization which in turn affects κ. We demonstrate how the quadratic dependence plays an important role in accurately determining an expansion for the MSW dispersion relation.