Beam coupling and spatial mode conversion in photorefractive planar waveguide

Beam coupling in photorefractive bulk crystals has been studied intensively and demonstrated for many application concepts, including coherent image amplification, image processing and parallel logic operations. In contrast, photorefractive beam coupling and spatial mode conversion in guided wave structures have attracted much less attention. The latter has potential application in facilitating the coupling of a free propagating laser beam to low-order guided modes in an appropriate waveguide structure. In this paper, we discuss this novel concept and present experimental demonstrations of beam coupling and spatial mode conversion in a thin plate of strontium barium niobate (SBN:75) crystal.<>