Homogeneous and inhomogeneous spectrum broadening in Nd3+-doped mixed vanadate crystals

Homogeneous and inhomogeneous spectrum broadening in Nd:LuxGd1−xVO4 series crystals were directly measured for the first time, and compared with that in the Nd:LuxY1−xVO4 and Nd:GdxY1−xVO4 crystals. Spectroscopic properties including fluorescence lifetime, spectral line width, emission peak, and stimulated emission cross section had obvious changes with the temperature increased from 77 K to 300 K, owing to the thermal phonon vibration. Compared to the pure vanadate crystals, we found these changes were more sensitive to temperature in the case of mixed crystals, in which cations (Lu, Y, and Gd) are random replaced by each other at the same lattice site. At 77 K, the thermal phonon vibration effect can be ignored and the inhomogeneous spectrum broadening that caused by disordered structure in all samplers can be calculated with the line-width of pure vanadate crystals as reference point, the corresponding values (ΔΓ(T)′) were 2.2 nm-3.8 nm in 4F3/2 → 4I11/2 transition and 1.7 nm-2.8 nm in 4F3/2 → 4I13/2 transition. Compared to Nd:LuxY1−xVO4 and Nd:GdxY1−xVO4 series mixed crystals, the change in spectral line width with x is most obvious in the case of Nd:LuxGd1−xVO4 series crystals, which may be attributed to the larger ionic radius difference between Gd and Lu (RLu < RY < RGd).