Doping effects in polarization switching of lithium niobates

Summary form only given. Quasi-phase-matching (QPM) of ferroelectric nonlinear optical crystals with periodically 180/spl deg/ inverted domain structures has merged as an important technology for nonlinear frequency generation. A plethora of research activity in nonlinear optics has benefited from the availability of periodically poled lithium niobate (PPLN) and lithium tantalate (PPLT) as the source for infrared optical parametric and harmonic generation. Great challenge, however, resides in manipulating the coercive field required for polarization switching such that high fidelity of fine QPM structure can be maintained in the course of frequency conversion. We report an investigation of the zinc oxide (ZnO) doping effects on the periodical poling process of congruent grown LiNbO/sub 3/ crystals. It is found by increasing the ZnO doping level up to 8 mol.%, the polarization switching field in ZnO:LiNbO/sub 3/ can drop down to 2.5 kV/mm with an internal field strength reduced to /spl sim/0.5 kV/mm. We thereby are able to not only reduce the polarization switching field in congruent grown LiNbO/sub 3/ crystals by one order of magnitude, but also minimize the corresponding axial anisotropy in the periodical poling process for the first time to our knowledge.