2.05 μm emission properties and energy transfer mechanism of germanate glass doped with Ho~(3+), Tm~(3+), and Er~(3+)

摘要

A new GeO_2-Ga_2O_3-Na_2O-BaO-La_2O_3 germanate glass doped with Ho_2O_3, Tm_2O_3, and Er_2O_3 has been investigated for application as a laser material at the 2 μm region. The spectroscopic properties and energy transfer mechanisms of Ho~(3+) sensitized by Tm~(3+) and Er~(3+) are analyzed. Based on the measurement of absorption spectra, the Judd-Ofelt intensity parameters, radiation emission probability, branching ratio, and lifetime of Ho~(3+) are calculated to evaluate the spectroscopic properties. The maximum value of emission cross section of Ho~(3+) around 2.05 μm is 8.003 × 10~(-21) cm~2, which indicates that the germanate glass may provide high gain as a good medium in high-power level laser system. It is also found that the 2.05 μm emission of Ho~(3+):~5I_7→5I_8 can be greatly enhanced by adding the proper amount of Er_2O_3 and Tm_2O_3 under excitation at 808 nm. With the large energy transfer coefficient, the high efficient energy transfer process among Ho~(3+), Tm~(3+), and Er~(3+) ions is proven.