3μm以上中红外可调谐激光用的Dy3+:LnF3晶体的制备与性能系统研究

Mid-infrared laser has many important applications in the domains, such as environmental monitoring, medicine and cosmetology, scientific research and military affairs, etc. The mid-infrared all solid state laser has many advantages, such as the compact structure, the higher quality of beam of light, the better stability, etc. At present, the report of the research on the mid-infrared all solid state laser at the wavelength above 3μm is a fat lot. It is always the blank space and the shortage of light... Dy3+ can realize the broadband transmission at the wavelength above 3μm effectively. The new laser matrix of LnF3 crystal has many advantages, such as the good physical and chemical properties, higher mechanical strength, the lower maximum phonon energy, the higher laser induced damage threshold, etc. Their lower maximum phonon energy (350cm-1) can reduce the non-radiative decay rates of the excited states of Dy3+ and thus increase the fluorescence quantum efficiency. The rare earth ions such as Y,Gd,La,Lu can occupy the crystal lattice of Ln to form misch-crystal with local disordered structure. Multi-luminous center can thus be produced when Dy3+ doped in crystal and thus broaden and red shift the fluorescence spectral lines at the wavelength above 3μm, which will benefit to the tunable laser. Therefore, Dy:LnF3 crystals should be an excellent class of mid-infrared tunable laser crystals at the wavelength above 3μm. .. In this project, based on the structure-function relationship, the optimization crystal structure and elements of Dy:LnF3 crystals will be designed to obtain 2~3 kinds mid-infrared tunable laser crystals at the wavelength above 3μm firstly. Then, the research on their crystal growth, physical and chemical properties, spectra and laser characteristics will be developed. The study on the adjustment of mischcrystal with local disordered structure and the energy levels coupling with co-dopant sensitization ions theoretically and experimentally and the optimization of doping concentration of Dy and sensitization ions will be also performed to further broaden their mid-IR emission spectral width and make the emission spectrum red-shift. Finally, 1~2 kinds of Dy:LnF3 crystals will be optimized to carry on Nd:YAG laser or the suitable LD pumping to achieve the high efficiency and stable tunable laser output at the wavelength above 3μm.

中红外激光在环境监测、医疗、科研、国防等领域有着极其重要的应用。中红外全固态激光具有结构紧凑、光束质量好、稳定性高等优点。目前3μm以上全固态激光的研究报道很少，是紧缺光源。. Dy3+在3μm以上可实现宽带发射，而LnF3晶体具有机械强度大、光损伤阈值高等优势，其较低的声子能量可降低Dy3+激发态无辐射跃迁几率，提高量子效率。Y,Gd,La,Lu可占据Ln格位形成混晶局部无序结构, Dy掺杂可形成多发光中心而进一步拓宽荧光谱线，因此是一类优秀的3μm以上中红外可调谐激光晶体。.项目将从构效关系出发，在Dy:LnF3体系中优化结构组成设计出2~3种晶体，系统研究晶体生长、物化、光谱和激光性能，研究混晶调控和共掺敏化离子能级耦合机理，优化离子掺杂浓度，进一步拓宽、红移荧光谱线，优化出1~2种优质晶体，采用Nd:YAG激光或合适LD泵浦，实现高效、稳定的3μm以上可调谐激光输出。

~3μm以上中红外波段激光在环保、医疗、军事等诸多领域有重要的应用价值。Dy3+离子拥有丰富的能级结构，可以产生中红外荧光发射（6H13/2→6H15/2）。LaF3晶体具有良好的物化性能和低声子能量，是优秀的中红外激光的基质晶体材料。项目以Dy3+作为激活离子和LaF3作为基质晶体，深入研究了晶体生长、光谱与激光性能。为了克服Dy3+严重的浓度淬灭效应，选择了共掺无光学活性离子（Gd3+，Y3+，Sr2+，和Ca2+）来增加Dy3+离子之间的距离，从而减弱Dy3+的浓度淬灭效应；为了克服Dy3+对泵浦源的弱吸收，选择了共掺杂Nd3+和Tm3+离子，通过一系列交叉驰豫过程把能量有效传递给Dy3+离子，从而增强Dy3+对泵浦源的吸收。.首先，合成了一系列不同敏化离子及其不同浓度和不同Dy3+浓度掺杂的粉体材料，进行了物化性能和光谱性能的测试表征，对掺杂离子及其浓度进行了初步的优化，然后采用坩埚下降法生长了一系列Dy3+单掺、Dy3+与无光学活性离子（Gd3+，Y3+，Sr2+，和Ca2+）共掺的LaF3晶体和Nd3+和Tm3+离子共掺的Dy:LaF3晶体。测试研究了晶体的光谱性能，探索了Dy3+掺杂浓度荧光效应、无光学活性离子（Gd3+，Y3+，Sr2+，和Ca2+）对于Dy3+发光性能的影响和Nd3+和Tm3+离子的敏化机理，研究结果表明：.（1）共掺杂Y3+离子效果最佳，用1280nm激发2at%Dy3+/3at%Y3+:LaF3晶体，获得了半高宽240nm和峰值波长2840nm的中红外荧光发射谱，发射截面为3.9×10-21cm2，荧光寿命为6.66ms，量子效率为20.8%。当粒子数反转大于0.4时，有望得到2930-3200nm范围内的可调谐激光。.（2）共掺杂敏化离子Nd3+和Tm3+不仅可以增加LaF3晶体对泵浦源能量的吸收效率，还可以通过一系列交叉驰豫过程把能量有效传递给Dy3+离子，并发出中红外荧光，790nm-LD泵浦的Dy/Nd:LaF3和Dy/Tm:LaF3晶体有望实现3μm中红外激光输出。.最后，加工出尺寸为3×3×20 mm3和3×3×5 mm3的1at%Dy:LaF3和1at%Dy/5at%Y:LaF3晶体器件，采用1280 nm LD作为泵浦源，LD的光纤芯径200 μm，数值孔径0.22，激光谐振腔的输入镜IM采用平面镜（T≧80