Research progress on rare earth doped fluoride multiband upconversion laser

Upconversion laser has the characteristics of anti-stokes displacement, monochromatism, and high stability. It has been widely used in many fields, such as medicine, projector, data storage, laser headlamp, laser teletype visible light communication, microscope, and new generation display technology, which has gained major progress in both basic research and application exploration after more than ten years of development. But there arc still problems and bottlenecks. The research status of the upconversion laser is reviewed. As for different band and different pump sources, the main progress in recent years is specifically introduced. In addition, as for this topic, the critical issues at present arc commented and the future development is prospected.