With the increase of Mg doping amount, the absorption edge in ultraviolet-visible absorption spectra of Mg:Mn:LiNbO_3 crystal shifts to the violet and then inversely to the red when Mg doping concentration is up to the threshold.

• 晶体的紫外-可见吸收光谱表明,当掺镁量没有达到阈值浓度时,Mg:Mn:LiNbO_3晶体的吸收边随掺镁量的增大发生紫移,当掺镁量达到阈值浓度后,晶体的基础吸收边又发生相对红移。