Luminescence properties of thin films prepared by laser ablation of Nd-doped potassium gadolinium tungstate

Optically active thin films on Si substrates have been produced by laser ablation of a Nd-doped potassium gadolinium tungstate (Nd:KGW) single crystal. Films grown at low oxygen pressures (< 0.6 mbar) are potassium-deficient and appear to be mainly disordered. They show a poor photoluminescence (PL) performance that improves upon annealing in air at temperatures in the range 700-1000 degreesC. Films grown at high oxygen pressure (1 mbar) show instead good stoichiometry and the presence of a dominant textured gadolinium-tungstate phase compared to KGW. These films have low absorption, a refractive index close to that of bulk KGW and good PL performance, the emission lifetimes being longer (tau > 150 mus) under certain conditions than those measured in the single-crystal material.