Smooth and flat photoluminescence spectra of Nd3+ active ions in tri-doped CaF2 single crystals

Abstract

Spectroscopic properties of tri-doped Nd3+,R13+,R23+:CaF2 (R1, R2=Y, La, Gd, Lu) crystals were investigated, where R13+ and R23+ act as the lattice regulating ions. According to the spectra properties of co-doped Nd3+,R3+:CaF2 (R = Y, La, Gd, Lu) crystals, the regulating ions are classified into two categories, Y3+ and Lu3+ ions are in the same class while La3+ and Gd3+ are divided into the other. Attribute to the “combination effect” of the regulating ions, the absorption spectra can be regulated controllably in tri-doped CaF2 crystals, and the emission spectra of Nd3+ in CaF2 crystals become smoother and flatter by incorporating two different types of regulating ions. Preliminary CW laser experiment was conducted for Nd3+,Y3+,Gd3+:CaF2 crystal and Nd3+,Lu3+,Gd3+:CaF2 crystal. The slope efficiency and maximum output power of the former reached up to 49.4% and 2.1W, respectively. A CW wavelength tuning range of 34 nm (1043-1077 nm) was obtained for Nd3+,Y3+,Gd3+:CaF2 crystal. The spectra properties and CW tuning operation indicate that the tri-doped Nd3+,R13+,R23+:CaF2 crystals are suitable for the application of femtosecond mode-locked laser.