Growth of 4-in diameter MgO-doped near-stoichiometric lithium tantalate single crystals and fabrication of periodically poled structures

Pure and MgO (0.5. 0.7 and 1 mol%)-doped near-stoichiometric lithium tantalate (near-SLT) crystals of 4-in diameter have been grown from off-stoichiometric melt using a double crucible. The grown crystals are free from cracks and twins. The addition of MgO increases the Curie temperature. SLT crystals with 0.7 mol% or more MgO doping concentrations showed enhanced optical damage resistance. The ordinary ray refractive indices in MgO-doped SLT crystals are slightly lower than the corresponding index of non-doped crystal. On the other hand, the extraordinary ray index of SLT is unaffected upon MgO doping. Periodically poled structures of 8 μm period have been fabricated over a length of 40 mm for 532 nm green generation through quasi phase matching.