Potential candidate for new tunable solid-state laser between 1 and 2 μm: Ni²⁺-doped MgAl₂O₄ spinel grown by the micro-pulling-down method

Square-shaped blue single crystals of nickel-doped magnesium aluminum spinel have been pulled down from the melt, by the micro-pulling-down method. The absorption spectra of doped samples show three broad absorption bands. According to the absorption map and the chemical analysis of these crystals, the effective segregation coefficients of Ni²⁺ in MgAl₂O₄ at low doping concentration (C_Ni〈 2 mol%) were calculated to be less than the unity, due to the vaporization behavior of NiO. Strong infrared broad emission in the eye-safe region peaking at 1.3 μm have been systematically investigated under high-intensity pulsed Nd:YAG laser excitation in the red region. The suitable absorption for InGaAs laser-diode pumping combined with long decay time of the infrared emissions and the good thermal properties of MgAl₂O₄ make Ni²⁺-MgAl₂O₄ a promising laser crystal.