Optical properties of Nd3+ in single crystal SrAl12O19

The spectroscopic characteristics of triply ionized neodymium in Sr1−xNdxAl12−xMgxO19 for x = 0.03 and 0.15 are presented; one Mg2+ ion per Nd3+ is required for charge compensation. Crystals of this composition are optically uniaxial, with absorption and emission depending strongly on polarization. The room-temperature fluorescence lifetime is 430 μs for x = 0.03 and 280 μs for x = 0.15. The main absorption and emission peaks can be fit by assuming the Nd3+ ion substitutes for Sr2+ in a site of D3h point-group symmetry. A crystal-field Hamiltonian of D3h symmetry is used to fit the data. A best-fit rms deviation of 4.2 cm−1 is obtained between 32 experimental and theoretical energy levels for the 13 lowest J-multiplets of the 4f3 electronic configuration of Nd3+ with the following crystal field parameters: B20 = −202.8 cm−1, B40 = 632.7 cm−1, B60 = −1752 cm−1, and B66 = −1180 cm−1. The stimulated emission in the 4F32 → 4I92, 4F32 → 4I112, and 4F32 → 4I132 channels peaks at 902, 1049.7, and 1306.5 nm, respectively, and in all cases it is σ-polarized. The respective spectroscopically determined stimulated emission cross sections for these wavelengths are 3.7 × 10−20, 1.1 × 10−19, and 2.6 × 10−20 cm2. The best absorption band for diode-laser pumping is centered at 798 nm, with an absorption coefficient of 14 cm−1 for x = 0.15 and a full-width at half-maximum of 2.5 nm.