GROWTH BY LHPG, STRUCTURE AND SPECTROSCOPY OF ND3-DOPED BA2NANB5O15 NONLINEAR SINGLE-CRYSTAL FIBERS()

The renewal of the second order nonlinear crystals is very strong in l aser materials optics. We are involved in the search for new systems b ased upon highly nonlinear niobate crystal family. Among these crystal s, Ba2NaNb5O15 is characterized by tile highest nonlinear parameters b ut, unfortunately, it is difficult to grow crackless samples. The obte ntion of good quality and crackless Ba2NaNb5O15 single crystals doped with different concentrations of Nd2O3 is reported. The crystals were grown as monocrystalline fibres by tile laser heated pedestal growth t echnique. A new determination of the crystallographic structure of Ba2 NaNb5O15 has been performed. The structure of fires doped with 1 at.% Nd3+ was found orthorhombic with the new space group Pba2 instead of C mm2. The well-known twinning of Ba2NaNb5O15 due to tile exchange of ti le a and b axes of tile unit cell, which disturbs the optical properti es, decreases as tile Nd3+ content of the fibre increases. Above 3% Nd 3+ ions, such monocrystalline fibres were found to be of tetragonal st ructure. Low temperature spectroscopy reveals that Nd3+ ions substitut e probably both Ba2+ and Na+ ions. The stimulated emission cross-secti on near 1060 nm of the F-4(3/2) --> I-4(11/2) channel and its branchin g ratios are determined with tile help of Judd-Ofelt analysis. This wo rk shows that b-axis grown monocrystalline fibres are potentially self -doubling laser materials.