【作者】 刘海春；

【导师】 张治国；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2008， 硕士

【摘要】 发展短波长固体激光器是稀土离子上转换发光的突出应用之一。Er3+离子具有丰富的长寿命亚稳态能级,并且能被大功率红外二极管激光器有效地激发,具有很强的上转换能力,是一种优良的上转换发光材料的激活离子。利用Er3+离子的上转换发光,获得短波长固体激光器,具有很大的研究价值,值得我们为之努力。研制Er3+离子短波长上转换激光器的前提条件是深入研究Er3+离子在红外激光激发下多光子上转换发光性质和提高其发光效率。在我们以前的工作中,发现在Er3+离子掺杂的Y2O3纳米晶中进一步掺杂Li+离子能极大地增强Er3+离子的可见上转换荧光强度。在本论文中采用溶胶-凝胶法制备出了以Er3+作激活离子的Y2O3:Er3+/Li+和Y2O3:Yb3+/Er3+/Li+纳米晶,并研究了在970nm二极管激光器的激发下,Li+离子掺杂对Er3+离子蓝、紫外上转换发光性质的影响。在Y2O3:Er3+/Li+体系中,观察到尽管Li+离子的加入没有引起Y2O3晶格晶相的改变,但是却使其晶胞参数发生了变化,这意味着Er3+离子周围的晶体场环境发生了改变。改变了的晶体场环境使Er3+离子的辐射性质发生了很大变化,Er3+离子中间亚稳态的寿命显著增长,这极大地促进了Er3+离子的上转换发光,使Er3+离子的蓝、紫外上转换发光强度增强了55-90倍。在Y2O3:Er3+/Li+纳米晶中,增强后的Er3+离子的蓝、紫外上转换发光强度能达到Y2O3:Er3+体材料中的50%。此外,在体材料中掺杂Li+离子对Er3+离子的蓝、紫外上转换发光也具有明显的促进作用。在Yb3+/Er3+/Li+体系中,发现在掺杂高浓度的敏化离子Yb3+后,掺杂Li+离子,能进一步增强Er3+离子的蓝、紫外上转换发光。掺杂15mol%的Li+离子时使Er3+离子的蓝、紫外上转换发光强度增加了约30倍。研究表明,这种增强同样得益于Li+离子掺杂引起的Er3+离子中间亚稳态能级寿命的增长。在Yb3+/Er3+/Li+体材料中,Li+离子的加入对Er3+离子的蓝、紫外上转换发光也具有明显的促进作用。另外,研究发现Li+离子的加入也引起了Er3+离子绿色和紫外上转换荧光光子过程的改变。在Y2O3:Yb3+10mol%/Er3+1mol%纳米晶中Er3+离子绿色和紫外上转换荧光分别表现为三光子和四光子过程;当加入15mol%的Li+离子后,Er3+离子的绿色和紫外上转换荧光分别表现为两光子和三光子过程。研究表明,这种光子过程的变化来源于Li+离子掺杂导致的Er3+离子之间的交叉弛豫过程2H9/2+4I15/2→4S3/2+4I13/2、4G7/2+4I15/2→4G11/2+4I13/2 ,以及合作敏化上转换过程22F5/2(Yb3+)+4F9/2(Er3+)→22F7/2(Yb3+)+4G7/2(Er3+)的弱化。更多还原

【Abstract】 Developing short-wave solid lasers is one of the most outstanding applications of rare earth ions’upconversion radiations. Er3+ ions are excellent activators of upconversion materials, because they have ample long-lived metastable energy levels and can be effectively pumped by high-power infrared diode lasers. Achieving Er3+ upconversion short-wave solid lasers is valuable and deserves our effort, and its final success must base on the deep investigation of Er3+ ions’multi-photon upconversion emissions and the great enhancement of Er3+ ions’upconversion emissions intensities. In our previous work, we reported that the visible upconversion emissions intensities of Er3+ ions in Y2O3 nanocrystals were dramatically enhanced by further doping with Li+ ions. In this thesis, Y2O3:Er3+/Li+ and Y2O3:Yb3+/Er3+/Li+ nanocrystals were synthesized by a complex precursor method and the effect of Li+ ions doping on Er3+ ions’blue and ultraviolet upconversion properties were investigated under 970 nm laser diode excitation.In Y2O3:Er3+/Li+ series, the changes of cell parameters of the same cubic Y2O3 lattice induced by Li+ ions doping were observed, which indicated the change of Er3+ ions’local environment. The changed local environment resulted in the distinct lengthening of the lifetimes of Er3+ ions’metastable states, which greatly benefited Er3+ ions’upconversion radiations. The blue and ultraviolet upconversion radiations were enhanced up to about 55-90 times by codoping with Li+ ions. The integrated intensity of enhanced upconversion blue and ultraviolet radiations in Y2O3:Er3+/Li+ nanocrystals can nearly reach half of that in Y2O3:Er3+ ceramic bulk. In addition, Li+ can also obviously facilitate Er3+ ions’blue and ultraviolet upconversion radiations in ceramic bulkIn Y2O3:Yb3+/Er3+/Li+ series, it was observed that further doping with Li+ ions after doping high-concentration sensitizers, Yb3+, could ulteriorly enhance Er3+ ions’blue and ultraviolet upconversion radiations. The blue and ultraviolet upconversion radiations of Er3+ ions was enhanced up to about 30 times after doping with Li+ ions of 15 mol%. The remarkable enhancement also benefited from the lengthening of the lifetimes of Er3+ ions’excited states according to investigation. In Y2O3:Yb3+/Er3+/Li+ ceramic bulk, Li+ ions can also facilitate Er3+ ions’blue and ultraviolet upconversion radiations. Additionally, the multiphoton processes of Er3+ ions’green and ultraviolet upconversion radiations were also changed after Li+ doping. In Y2O3:Yb3+10mol%/Er3+1mol% nanocrystals, Er3+ ions’green and ultraviolet upconversion radiations resulted from a three- and four-photon process respectively, while Li+ of 15 mol% were incorporated in, they presented a two- and three-photon process respectively. These changes originated from the weakening of CR processes between Er3+ ions: 2H9/2+4I15/2→4S3/2+4I13/2 and 4G7/2+4I15/2→4G11/2+4I13/2, as well as the CU process:22F5/2(Yb3+)+4F9/2(Er3+)→22F7/2(Yb3+)+4G7/2(Er3+), induced by Li+ ions’incorporating.更多还原