<title>Initital research of three-dimensional volumetric display based on di-frequency upconversion</title>

Three-dimensional display may be one of the most wonderful techniques attracting scientists to research on. But most of current approaches are fictitious ones. On the CLEO&apos;94, E. A. Downing and L. Hesselink et al. reported a virtual three-dimensional volumetric display using Pr doped fluoride glass upconversion luminescence which is evaluated as a new excellent physics achievement in 1996. The ZBLAN:Pr glass is proved by L. Hesselink to be a interesting material for three-dimensional volumetric display based on upconversion. In the processes of upconverting near-infrared radiation to visible, the 1G4 level of Pr3+ locates at an important position. But the transition probability of 3H4-1G4 proved to be one or two order of magnitude smaller than other strong transitions. So to improve the population on 1G4 has an practical significance. In this paper, we report a simple 3-D volumetric display experiment which has used the upconversion sensitization method. A bulk ZBLAN:Pr,Yb and ZBLAN:Pr glasses were selected as display medium. Just as the sensitized action of Yb3+ ion, the di-frequency upconversion luminescence intensity of Pr3+ ion is enhanced more than thirty times. So, the brightness of 3-D display is better than the work of E. A. Downing and L. Hesselink. Some technique consideration is discussed. In addition a conception of multilayer 3-D display device is also presented, which are thought having several advantages.EI