Tsuguo Fukuda

K2NbAlO2[(As,Nb)O4]2, isostructural with KTiOPO4

The title compound, potassium niobium aluminium arsenate (KNAA), is isostructural with KTiOPO 4 (KTP). In KNAA, the site corresponding to the Ti1 sites of KTP is occupied mostly by Nb atoms, the Ti2 site is occupied predomipantly by Al atoms, and the As1 and As2 tetrahedral sites are occupied mostly by As atoms. The M1O 6 octahedron is more distorted and the M2O 6 octahedron is less distorted than that of KTP.

Growth and Optical Properties of Nd3+ doped MGd(WO4)2 (M=K,Na) Single Crystal Fibers for Multicolor Laser

We have successfully grown Nd:MGd(WO4)2 (M=K,Na) single crystal fibers by micro pulling-down method. High concentration Nd3+ ions doped NaGd(WO4)2 single crystal fibers were possible to grow with controlled diameter. Their absorption coefficients increased with concentration of Nd3+ ions. The radiative lifetime of the lasing transition shortened with increasing Nd3+ ions. Stimulated Raman scattering spectra was also measured, and the Raman shift was larger than that of KGW. Nd3+ doped NaGd(WO4)2 single crystal fibers showed superior optical properties such as high doping level and large stimulated Raman scattering shift for efficient multicolor laser.

Laser performance of neodymium-doped lanthanum tungstate crystals

We demonstrated the laser oscillation of neodymium-doped lanthanum tungstate (Nd:LWO) crystals. The crystals with Nd concentration up to 20 at. % were grown using the micro-pulling-down method. Oscillation was observed using uncoated samples under pulsed laser pumping. Minimum threshold of 5.9 mW was exhibited for 1.8 at. %-doped sample. Maximum slope efficiency of 35 % was achieved for 3.2 at. %-doped sample. This crystal had high receptivity for Nd and low concentration quenching.

Fiber-like Lanthanum Tungstate Single Crystals for Efficient Stimulated Raman Scattering

We have grown fiber-like lanthanum tungstate crystals for efficient stimulated Raman conversion. Selective conversion to the first Stokes wave is demonstrated by doping the crystal with an impurity which absorbs higher order Stokes.