Effect of doping on crystalline quality of rubidium titanyl phosphate (RTP) crystals grown by the TSSG method
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Effect of doping on crystalline quality of rubidium titanyl phosphate (RTP) crystals grown by the TSSG method Jianqiu Guo1, Balaji Raghothamachar1, Michael Dudley1, Joan J. Carvajal2, Ali Butt2, Maria Cinta Pujol2, Rosam M Sole2, Jaume Massons2, Magdalena Aguilo2, Francesc Diaz2 1
Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY 11794, USA 2 Physics and Crystallography of Materials and Nanomaterials (FiCMA-FiCNA), Universitat Rovira i Virgili (URV), Campus Sescelades, c/MarcelΒ·lΓ Domingo s/n, E-43007 Tarragona, Spain ABSTRACT Defect structures in Rubidium Titanyl Phosphate (RTP) crystals (non-doped and doped) grown by the Top Seeded Solution Growth (TSSG) method were characterized using Synchrotron White Beam X-ray Topography. Main defects observed in non-doped crystals are growth sector boundaries while both growth sector boundaries and growth striations are observed in the Nb single doped and (Nb,Yb)-codoped crystals with relatively few linear defects such as dislocations. Results show that the overall crystalline quality is lowered as more doping elements are incorporated. Details of defect distributions are correlated with the growth process to facilitate high quality growth of doped RTP. INTRODUCTION Rubidium titanyl phosphate, RbTiOPO4, often referred as RTP, is a relatively new material in the field of nonlinear optics. RTP is one of the isostructurals in the well-known KTP (Potassium Titanyl Phosphate or KTiOPO4) family, which was initially reported back in 1976 by Zumsteg et al. [1] for the great potential use as nonlinear optical materials for laser applications. KTP family crystals show the combination of high non-linear optical coefficients and high laser damage threshold as well as chemical and mechanical stability. [2] With proper doping of lanthanides ions (Ln3+) which would enable laser effect, these crystals are able to give high intensity second harmonic generation (SHG) with good phase matching properties, providing a new material for potential self-frequency doubling (SFD). As one of the important isostructurals in this family structure, RTP was grown with Rubidium ions completely substituting Potassium ions in the structure, ending up with a bigger lattice parameter. RTP crystalizes in orthorhombic system with lattice parameters ππ = 12.93π΄π΄Μ, ππ = 6.49π΄π΄Μ, ππ = 10.56π΄π΄Μ and belongs to the acentric point group mm2 (space group Pna21). The structure of RTP (Fig. 1(a)) is identified by chains of TiO6 octahedra linked at two corners with alternating long and short bonds, in which the Ti-O chains are partially responsible for the large nonlinear optical (NLO) effects [1]. Theoretically, KTP family crystals with Ln3+ doping make good candidates for inducing SFD in laser generation. However the real problem exists where the doping level of Ln3+ elements is too low to induce the laser effect. Over years, efforts have been made on the possibility to increase the distribution coefficient of Ln3+ ions. In 2001, J. J. Carvajal and his coworkers [3] reported the succ
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