NaYF_4:Tm^(3+)纳米棒中激光脉宽调控的荧光选择输出特性  

Luminescence selective output characteristics tuned by laser pulse width in Tm^(3+) doped NaYF_4 nanorods

作　　者：张翔宇[1] 王晋国[1] 徐春龙[1] 潘渊[1] 侯兆阳[1] 丁健[1] 程琳[1] 高当丽[2] 

机构地区：[1]长安大学理学院,西安710064 [2]西安建筑科技大学理学院,西安710055

出　　处：《物理学报》2016年第20期98-107,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51101022);陕西省青年科技新星项目(批准号:2015KJXX-33);陕西省自然科学基金(批准号:2014JQ1008;2014JM2-5066);中央高校基本科研业务费(2013G1121085;310812152001)资助的课题~~

摘　　要：基于频域和时域的光谱学分析,系统地研究了Tm^(3+)掺杂的NaYF_4纳米棒的荧光选择输出特性及荧光输出与激光脉冲宽度、激发波长、抽运功率及环境温度的依赖关系.结果表明:与其他因素相比,输出光色强烈地依赖于激光脉宽.通过合适的脉宽激光激发,在NaYF_4:0.5 mol%Tm^(3+)纳米棒中获得了强烈的单带近红外荧光发射,该波段荧光在深层组织成像方面具有极大应用优势.基于多声子无辐射弛豫理论和荧光动力学过程,揭示了脉冲宽度调控的单带近红外荧光的输出机理,其机理为多声子弛豫辅助的下转换荧光和激光脉宽调制的上转换荧光之间的竞争,该研究为光谱调控提供了新的理论依据和途径.The variations in material composition, phase and structure can provide a useful tool for tuning emission colour,but the controlling of the emission colour in a material, with a composition fixed, remains to be a daunting challenge. In this work, we systematically study the luminescence selective output characteristics of Tm^3＋doped NaYF4 nanorods,and also the dependences of fluerecence output on pulse duration, excitation wavelength, pump power, and ambient temperature. The results show that the color of output light is strongly dependent on laser pulse duration compared with other factors. The temperature dependent luminescence of the nanorods shows very different behaviors with shortpulse laser excitation from those of continuous wave（CW） laser. When the pulse laser at 656 nm is employed, the emission spectra from NaYF4：0.5 mol% Tm^3＋nanorods at the different temperatures are dominated by near-infrared（NIR） luminescence about 800 nm accompanied with weak blue luminescence, giving rise to nearly spectrally-pure NIR emissions at 20 K. When the pulse laser is replaced by CW laser, blue double emissions at 453 and 478 nm with the same order of magnitude of NIR luminescence can be clearly detected at room temperature. The key mechanism responsible for colour-tunable emission can be explained in terms of the population process of luminescence level, in which the different luminescence level populations need different time intervals. Considering excited-state absorption（ESA） for a particular ^1D2 energy level, there needs an extra step of ^3F2,3→^3H4 multiphonon nonradiation relaxation process to populate the ^3H4 state and subsequently pump its ^1D2 state for blue emission. Therefore, the pulse width should be longer than nonradiation relaxation time of ^3F（2,3）→^3H4 to comply with the ESA, while the nonradiation relaxation time can further be tuned by controlling ambient temperature. We show that the variation of the excitation power leads to interesting change in the upconversion（UC）

关 键 词：NaYF4:Tm^3+纳米棒 脉冲宽度 选择激发 光谱调控 

分 类 号：TB383.1[一般工业技术—材料科学与工程]