Mode spectroscopy of double-layer magnetic garnet films

We report here theory and experiment on modes of propagating light waves in double-layer magnetic garnet films on garnet substrates. The double-layer garnet waveguides were prepared hy standard isothermal liquid phase epitaxy. The plane-wave expansion approach is used to derive a phase equation that predicts the guided modes of double-layer system. The experiment is based on measuring coupling angles using a converging laser beam and a prism coupler. From the propagation constants the thickness and refractive indices of the films were computed. We also discuss in detail numerical analysis of the equation of the guided modes.