Noncollinear Interaction of Guided Optical Waves and Magnetostatic Forward Volume Waves Under Inclined Bias Magnetic Field

Coupled-mode equations for Stokes and anti-Stokes interactions of guided optical waves with magnetostatic forward volume waves under inclined magnetic field are given. Calculation results indicate that, only at normal magnetization, the diffraction efficiency (DE) is equal to the mode-conversion efficiency (MCE) in magnitude; by comparison to the case of normal magnetization, the DE and the MCE can be increased greatly under appropriate inclined magnetic field. For the YIG waveguide used, the DE for the Stokes interaction is much greater than that for the anti-Stokes interaction when the inclined angle |θ| < 25^o and the MCE is symmetrical about θ. For the Bi-doped YIG film, the MCE presents a rapid oscillation with θ. The obtained results tally with the experiments.