Magneto-Optic Coupling Theory for Guided Optical Waves andMagnetostatic Waves Using an Arbitrarily Tilted Bias Magnetic Field

Abstract

We report the magneto-optic (MO) coupling interaction of guided opticalwaves (GOWs) with magnetostatic waves (MSWs) in MO film waveguidesusing arbitrarily tilted bias magnetic fields. The universal MOcoupled-mode equations are obtained and can be applied to the collinearor noncollinear interactions of the GOWs with magnetostatic forwardvolume wave (MSFVW), magnetostatic backward volume wave (MSBVW) andmagnetostatic surface wave (MSSW). As a typical example, thenoncollinear diffraction interaction of the GOW with the MSFVW excitedby single-element microstrip line transducer in the yttrium-iron-garnet(YIG) film is analysed in detail. For the case of normal magnetization,the calculated plot is consistent with the experimental results in thefirst passband. By comparison, the diffraction efficiency (DE) canfurther be improved by optimizing the magnetization direction. Themaximum DE gain can reach 5.7 dB under the appropriately inclined biasmagnetic field at φ = 180 degrees and θ = 9 degrees.