Crystal growth, thermal and laser properties of neodymium-doped strontium fluorapatite

In this paper, the neodymium-doped strontium fluorapatite crystal has been grown by the Czochralski method. The data of thermal expansion and specific heat of the crystal have been measured. The thermal expansion coefficients along X and Z direction are α₁ = 11.4×10^-6/K and α₃ = 12.3×10^-6/K respectively. The specific heat is 110 cal/mol·K at 330K. The measured absorption spectra from 400 nm to 850 nm show that the crystal has absorption peaks around 805.5 nm, and the absorption coefficients at 805.5 nm are 16.05 cm^-1 and 5.59 cm^-1 for π and σ polarization respectively. The polarization fluorescence spectra at room temperature show that the strongest fluorescence is centered at 1058.8 nm. The lifetime of ⁴F_3/2 is 175 μs for 1 at. % Nd³⁺ doped in the crystal. The laser at 1058.8 nm is demonstrated pumped by a 3W cw laser diode at 805.5 nm, and the slope efficiency is 31.7%.