MG-ION INDIFFUSION OF LITHIUM-NIOBATE SINGLE-CRYSTAL FIBER

A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by us ing an Mg-ion indiffusion process; The propagation loss of the cladded crystal fiber is measured to be 14 times as low as that of the unclad ded crystal fibers. Mechanisms of Mg-ion indiffusion and reasons of la ttice distortion are analyzed and discussed. It is found by X-ray diff raction analysis as well as scanning electron microscopy that MgO-rich layer in the magnesium diffused surface exhibits the crystal structur e of a new compound From the Li-Mg-Nb-O ternary system. It is proposed , for the first time, that this new compound in MgO-rich layer is the real source of Mg-ion indiffusion lithium niobate.