Optical Parameters of Nd‐Doped Gadolinium Aluminium Tetraborate Crystals

Nd‐doped gadolinium aluminium tetraborate, Nd_xGd_1‐xAl₃(BO₃)₄ (NGAB), crystallizes with x = 0.1 in the trigonal system with point group 32, conforming space group R32. They were grown using flux method, of large sizes and good optical quality. The unit cell constants were a = 0.93057 (6) and c = 0.72481 (3) nm, and z = 1. The measured absorption of the NGAB is compared to Judd‐Ofelt (JO) theory. When applied, the JO theory of parity‐forbidden electric‐dipole transitions of rare earth ions on noncentrosymmetric sites demonstrates good agreement. A measured band gap of the eigentransition was about 4.00 eV. The fitted intensity parameters Ot (t = 2, 4, and 6) were 2.446 × 10^‐20, 2.266 × 10^‐20 and 2.598 × 10^‐20 cm². Both the emission properties of the sub‐stable ⁴F_3/2 state with the level lifetime of 506.20 μs and a fluorescence spectrum corresponding to the transition ⁴F_3/2 → ⁴I_11/2 were studied. The results indicate the pass band of laser for potential applications in practice.