Periodically poled structures in doped lithium niobate crystals

Periodically poled lithium niobate crystals doped with transition-metal ions Cr3+ and Hf4+, and rare earth ions Er3+ and Yb3+ were grown by the Czochralski method. Periodic domain structures were obtained either by rotation-induced growth striations (during off-centered growth) or by the application of a periodic electric current passed through the crystal-melt system during growth. We achieved controlled formation of domains having a width from 4 to 50 μm. The influence of dopant ion concentrations and the type of these dopant impurities were investigated relative to the formation of the periodic domain structure. Methods that involve the use of scanning electron microscopy and single-pass second harmonic generation show a high degree of domain structure uniformity over a large section (∼3 mm) of the crystals grown. Samples doped with HfO2 show reasonable photorefractive resistance, an important feature in the application of these materials in photonic devices.