Theory of mode coupling in a photorefractive crystal waveguide

The mode coupling among guided modes in a photorefractive crystal waveguide is investigated. coupled equations of guided modes in a photorefractive cr ystal waveguide. Analytical solutions of the couples equations are obtained for a two-mode photorefractive crystal waveguide. We also numerically anal yze the coupled equations of guided modes in a multimode photorefractive cr ystal fiber. As a result of the coupling, power may flow to the fundamental mode or the highest-order mode, depending on the direction of the crystal optical axis. In addition, we report an analytical solution of the modal po wer in core and cladding for all guided HEvm, and EHvm modes for cylindrica l fibers made of uniaxial crystals. (C) 2000 Optical Society of America [S0 740-3224(00)02406-1].