稀土离子的上转换发光通常具有发射带宽窄及峰位难以调节等问题。为了获得近红外光激发下的宽带上转换发光, 我们对Yb3+-Mn2+共掺杂CaF2材料的上转换发光性质进行了研究。将稀土离子Yb3+及过渡族金属离子Mn2+掺入到CaF2材料中作为发光中心, 利用高温固相反应法制备了Yb3+单独掺杂及不同浓度Yb3+及Mn2+离子共掺杂的CaF2体相材料。在980 nm近红外光激发下对不同样品的上转换发光进行了比较研究。实验结果表明, 与单独掺杂Yb3+离子的材料相比, CaF2∶Yb3+/Mn2+材料在980 nm激光激发下出现了一个位于620 nm附近的宽带发光, 我们认为这个发光来自于Yb3+团簇向Mn2+离子的合作敏化, 对应于Mn2+离子的 4T1 →6A1跃迁。因此, CaF2体系中存在Yb3+离子二聚体向Mn2+离子的合作能量传递过程。

Lanthanide-doped upconversion luminescence generally features in narrow emission band and fixed emission wavelength. In order to obtain photo upconversion with wide-spectrum emission characteristic upon near-infrared laser excitation, upconversion luminescence of CaF2∶Yb3+ and CaF2∶Yb3+/Mn2+ materials is investigated. Yb3+ and Mn2+ ions are codoped into CaF2 materials as activators. CaF2∶Yb3+ and CaF2∶Yb3+/Mn2+ bulky materials are synthesized using high-temperature solid state reactions. The upconversion luminescence properties of Yb3+ doped and Yb3+-Mn2+ codoped CaF2 materials are investigated upon 980 nm laser excitation. The experimental results indicate that compared with CaF2∶Yb3+ system, a new upconversion emission peaked at 620 nm is obtained in CaF2∶Yb3+/Mn2+ materials. The cooperative energy transfer from Yb3+-dimers to Mn2+ is considered to be the main reason for populating excited state of Mn2+ ions and the emission peaked at 620 nm comes from its4T1→6A1 transition. The cooperative energy transfer from Yb3+-dimers to Mn2+ is efficient in CaF2∶Yb3+/Mn2+ materials to populate excited Mn2+ and to obtain room-temperature upconversion emission of Mn2+ ions.