BLUE-LIGHT GENERATION USING BULK SINGLE-CRYSTALS OF NIOBIUM-DOPED KTIOPO4

We report here new solid-solution KTiOPO4 (KTP) isomorphs, namely K1-xNbxTi1-xOPO4 and K1-xTaxTi1-xOPO4, suitable for the second-harmonic generation (SHG) of blue light. Aliovalent substitution of the Ti4+-K+ pair in KTP with Nb5+ or Ta5+ increases substantially the optical birefringence (n(2)-n(y,x)) of KTP, and blueshifts the SHG cutoff wavelengths for propagation along the x and y axes. A birefringence increase of similar to 70%, and a SHG cutoff wavelength as short as 892 nm have been experimentally observed in crystals of K1-xNbxTi1-xOPO4. Detailed single-crystal x-ray structure determination reveals that the Nb substitution is ordered, with Nh strongly favoring the cis-Ti(l) sites. We discuss possible correlation between this preferential substitution and the observed compositional dependence of nonlinear susceptibilities d(24), and d(15). Optimal solid-solution compositions for the noncritically phase-matched frequency doubling of the 1.064 and 0.946 mu m lines of Nd:YAG lasers are presented, and potential applications for these new materials are outlined.