Spectroscopic properties of Tm:Bi4Ge3O12 crystals grown by the micro-pulling-down method

Tm3+-doped bismuth germanate crystals (Tm:BGO) with various doping concentrations of 0.5, 0.75, 1.0, 1.5, and 2.0 at.% were grown by the micro-pulling-down method (mu-PD). The effect of thulium concentration on the growth, structure, absorption spectra, emission spectra and fluorescence lifetime of H-3(4) and F-3(4) state was studied. Under excitation of 792 nm, Tm:BGO crystals exhibit two fluorescence bands corresponding to the H-3(4) -) F-3(4) and th(e 3)F(4) -) H-3(6) transitions. The fluorescence lifetime of H-3(4) state decreased strongly as the thulium concentration increased, while the lifetime of F-3(4) state was relatively constant for all thulium concentrations.