QUASI-PHASE-MATCHED PARAMETRIC INTERACTIONS IN PROTON-EXCHANGED LITHIUM-NIOBATE WAVE-GUIDES

We present a review of parametric fluorescence with bulk. and guided g eometries in quasi-phase matched lithium niobate. Whereas bulk experim ents have yielded results close to theoretical predictions, waveguided versions have shown strongly reduced efficiencies. Attributing the ob served conversion efficiency reductions to a loss of the material nonl inearity, to a destruction of the inverted domains during the waveguid e fabrication, or to both, we carefully studied the influence of the p roton-exchange process on the nonlinear and structural properties of t he periodically poled lithium niobate. We found that an annealed proto n-exchange process can essentially conserve the nonlinearity but will erase the periodic domain structure. This erasure can be avoided by us e of a highly diluted proton-exchange melt. This direct proton-exchang e process perfectly preserves all the nonlinear optical and structural properties of periodically poled LiNbO3. (C) 1997 Optical Society of America.