Optical properties of Nd:Bi4Ge3O12 crystals grown by the micro-pulling-down method

Abstract

Nd3+-doped Bi4Ge3O12 (Nd:BGO) single crystals have been successfully grown by the micro-pulling-down (μ-PD) method. The absorption spectra, fluorescence spectra and fluorescence decay curve have been measured at room temperature. The absorption cross section is about 1.39 × 10–20 cm2 at around 808 nm for 0.3 at% Nd:BGO. The Judd–Ofelt theory has been applied to calculate the intensity parameters, and three spectroscopic parameter Ωt (t = 2,4,6), radiative transition probabilities, radiative lifetime and branching ratios were calculated. The stimulated emission cross-section of 4F3/2→4I11/2 transition at 1064 nm was obtained to be 3.29 × 10–20 cm2 for 0.3 at% Nd3+-doped BGO crystal. The fluorescence lifetimes of 0.3 at% and 1.0 at% neodymium-doped BGO crystals were measured to be 288 μs and 242 μs, respectively. Those results indicate that Nd3+-doped BGO crystal grown by the μ-PD method would be a potential laser medium.