Temperature and concentration dependence of spectroscopic properties of Nd-doped yttrium aluminum garnet crystal

The optical absorption spectra of yttrium aluminum garnet (YAG) crystals doped with Nd³⁺ ions with different concentrations (0.6 at%, 1.0 at%, 1.2 at%) at the temperature range from 300 K to 500 K have been measured. The calculated Judd–Ofelt (JO) parameters Ω_t (t=2, 4, 6) based on the spectra have been used to predict the radiative transition probabilities, branching ratios and radiative lifetimes of the transitions from ⁴F_3/2 level to the lower levels (⁴I_13/2, ⁴I_11/2, ⁴I_9/2) at each concentration and temperature. The three JO parameters Ω_t (t=2, 4, 6), according to the calculation, decrease with the increasing doped concentration at each temperature. The JO parameters Ω₂ and Ω₄ increase, while the parameter Ω₆ decreases with the increasing temperature at each concentration. The branching ratios and radiative transition probabilities of the transitions from the ⁴F_3/2 level to ⁴I_13/2 and ⁴I_11/2 levels decrease, while the transition from the ⁴F_3/2 level to ⁴I_9/2 level increases with the increasing temperature. The obtained results at each concentration and temperature are discussed.