采用高温二次化料的方法制备一种多梯度折射率芯光纤所用掺镱锂硅酸盐玻璃，测量了玻璃样品的吸收光谱、荧光光谱和荧光寿命，利用McCumber理论计算了该玻璃系统中镱离子的2F5/2→2I7/2能级跃迁受激发射截面。研究表明锂硅酸盐玻璃中Yb3+在1006 nm处的σemi为0.38×10-20 cm2，荧光有效线宽为82.4 nm，荧光寿命为1.31 ms。在530 ℃高温硝酸钠熔盐中，对玻璃Li+-Na+离子交换到达中心轴前后制作的梯度折射率透镜的成像和折射率分布特性进行了研究。光谱分析和离子交换实验结果表明，该玻璃是制作梯度折射率光纤的理想材料，可用于多梯度折射率芯光纤的制作，是大模场光纤的候选材料。

An Yb3+-doped lithium silicate glass for multi-graded-index-core fiber is prepared by a two-step melting process. Absorption, emission spectra and fluorescence-lifetime of the samples are measured, and the stimulated emission cross-section σemi of Yb3+2F5/2→2I7/2 transition in samples is calculated by McCumber theory. It is found that σemi of Yb3+ ions in lithium silicate glass at 1006 nm is 0.38×10-20 cm2, and its fluorescence effective line-width is about 82.4 nm, its fluorescence lifetime is 1.31 ms. The Li+-Na+ ion-exchange properties of Yb3+ doped lithium silicate glasses are investigated in molten sodium nitrate at 530 ℃. Imaging properties and radial refractive index profile of gradient index lens made by ytterbium-doped lithium silicate glass before and after central-axis of Yb3+-doped lithium silicate glass rod Li+-Na+-ion-exchanged is studied. Spectral analysis and ion-exchange experimental results show that the glass is an ideal material for production of gradient index laser optical fiber. It can be used for multiple gradient index core fiber. A combination of good lasing and ion-exchange properties enables a new approach to large-mode-area fiber laser.