Spectroscopic study of neodymium-doped sodium-yttrium double fluoride Nd3+: Na0.4Y0.6F2.2 crystals

Nd3+:Na0.4Y0.6F2.2 (Nd3+:NYF) crystals are grown by the Stockbarger-Bridgma n method for a stoichiometric mixture prepared by the solid-phase method an d containing neodymium up to 20 at. %. The absorption spectrum of Nd3+:NYF crystals exhibits bands located in the emission region of laser diodes. The peak absorption cross section of the 796.8-nm band is sigma (a) = 0.96 x 1 0(-20) cm(2) and the bandwidth is Delta lambda = 17.5 nm. The most intense luminescence band is located at 1.05 mum and the radiative rime of the F-4( 3/2) level is to = tau (exp) similar to 60 mus. It is shown that the P-2(3/ 2) and D-4(3/2) levels of Nd3+:NYF crystals are also radiative with lifetim es tau (exp) equal to similar to 110 and 9.5 mus, respectively. However, th ese radiative transitions are partially quenched due to nonradiative relaxa tion. The intensity parameters Omega (t) are determined by the Judd-Ofelt m ethod to be Omega (2) = 1.18 x 10(-20), Omega (4) = 1.55 x 10(-20), and Ome ga (6) = 2.85 x 10(-20) cm(2). Using these parameters, the probabilities of radiative transitions and branching ratios are calculated, and the probabi lities of nonradiative transitions are estimated. A conclusion is made that Nd3+:NYF crystals are promising as active media for diode-pumped tunable l asers, in particular, up-conversion-pumped lasers. (C) 2000 MAIK "Nauka/Int erperiodica".