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题名	超短脉冲激光诱导透明材料发光现象研究
作者	钱静
文献子类	博士
导师	赵全忠
关键词	超短脉冲激光 ultrashort laser pulse 上转换发光 upconversion luminescence 长磷光 long persistent luminescence 黑体辐射 black-body radiation
其他题名	Ultrashort pulsed laser induced luminescence in transparent solids
英文摘要	超短脉冲激光与掺杂活性离子的透明材料作用，不仅能诱导多光子吸收的上转换荧光，也可在材料内部诱导长磷光。超短脉冲激光作用下，即使是不掺杂任何活性离子的透明材料，也会辐射出光谱，这是由超短脉冲激光在材料内部引起的高温高压产生的黑体辐射谱。本文的主要工作包括以下三个方面： 1.超短脉冲激光与Na2O–Ga2O3–GeO2 ：x Mn2+玻璃体系相互作用，诱导Mn2+的上转换发光（4T1→6A1）。通过荧光积分强度与激光功率密度的Ln-Ln关系，判定该上转换过程为双光子吸收；超短脉冲激光对Mn2+实现价态操作，部分Mn2+被氧化成Mn3+，玻璃由透明变成紫色，常温下该色心稳定；除了诱导Mn2+荧光，超短脉冲激光还诱导两个缺陷中心发光：非桥氧空穴中心以及与Ge相关的Eδ′心，与此同时，玻璃的本征缺陷—氧空穴中心被破坏。 2.对比超短脉冲激光诱导掺杂Mn2+的Na2O–Ga2O3–GeO2玻璃以及微晶玻璃体系长磷光。玻璃热处理之后，出现纳米晶相，晶粒尺寸在60 nm左右，部分Mn2+从八配位转为四配位，荧光谱也从只有八配位的红光波段延伸到四配位的绿光波段； 微晶玻璃的长磷光光谱中并未出现四配位的Mn2+对应的短波光谱，根据这种荧光光谱与长磷光光谱不一致的现象，我们提出了一种长磷光发光模型；对比同组分玻璃以及微晶玻璃中Mn2+长磷光的发光性能，发现微晶玻璃体系并没有提高长磷光的强度和发光时间，反而降低了其发光性能，猜想这可能与超短脉冲激光在玻璃体内引起局域晶化有关。 3.我们提出了用黑体辐射法在纳秒尺度内测量电解质内部被超短脉冲激光加工后的温度。测量不同延时条件下的黑体辐射谱，用普朗克公式拟合得到温度随时间的衰减趋势，计算出透明电介质内部温度下降到室温的时间，再反推出热累积效应出现时对应的激光重复频率。以石英玻璃为例，激光脉冲的宽度在600 fs时，单脉冲能量在110 μJ到270 μJ范围内变化，单脉冲作用后5 ns和20 ns其对应的温度在5000 K和 4500 K附近波动。而当脉冲宽度增加到0.83 ns时，单脉冲激光作用后5 ns和20 ns 其对应的温度分别为6659 K和5109 K。可以发现，脉冲宽度对温度的影响要远远高于单脉冲能量对温度的影响。根据温度的衰减趋势，得到600 fs和0.83 ns的激光脉冲，热累积效应产生时对应的重复频率分别为0.42~0.47 MHz 以及0.25 MHz。这种方法同样适用于其他透明的电介质材料。; Ultrashort laser pulses can not only induced upconversion luminescence but also long persistent luminescence (LPL) in transition metal or rear earth metal doped trasparent solids. A structureless broad continuum emission can also be initiated in transparent materials by a single ultrashort laser pulse, which is proved to be black-body radiation in nature. The three reselts are as follows: 1. A strong upconversion luminescence with a central wavelength longer than 600 nm, can be induced by an ultrashort laser. The upconversion luminescence was originated from the 4T1→6A1 transition of Mn2+ ions and was proven to be a two-photon process. The absorption band around 500 nm was extensively enhanced and was probably ascribed to the 5E→5T2 transition of Mn3+. Two extrinsic defects with photoluminescence bands peaking at 1.85 and 2.2 eV were also induced, which were attributed to non-bridging oxygen hole centers (≡Ge?O?, NBOHC) and Ge-related Eδ', respectively. While at the same time, the intrinsic defect -of Ge-related oxygen deficient centers [≡ Ge…Ge ≡, GODC (II)] was destroyed by a ultrashort laser. 2. A distinct long persistent luminescencewas obtained both from home-made Mn2+-activated sodium gallium germanate glass and glass-ceramics, which were excited by an ultrashort laser. In Mn2+-activated glass-ceramics, an obvious green emission band appeared in PL spectra while absent in LPL spectra , which indicated a process distinguished from traditional heat-assisted tunneling effect. A new mechanism is proposed to elucidate the generation of LPL. In addition, the maximum intensity of glass-ceramics was much less than that of glass. However, the UV-induced LPL was more efficient in crystalline structure than in glassy network. We thought that ultrashort laser pulses gave rise to the localized crystallization of glassy structure while the already crystalline structure of glass ceramics was destroyed upon laser irradiation. 3. The nanoscale measurement of temperature in the bulk of dielectrics initiated by a single ultrashort laser pulse was first investigated by black-body radiation. A structureless broad continuum emission has been recorded.The temporally resolved emission spectrum was proved to be blackbody radiation in nature, and temperature was obtained by fitting the radiation with the Planckian formula. Pulse energy was varied from 110 to 270 μJ at 600 fs and a pulse duration of 0.83 ns was also used. The temperature was about 5000 K and 4500 K at 5 and 20 ns when pulse energy was at 600 fs. However, due to the energy transfer from heated electrons to lattice, the corresponding temperature was sharply increased to 6659 and 5109 K at 270 μJ when pulse duration was increased to 0.83 ns. It was estimated that heat accumulation started at 0.42–0.47 MHz for a laser pulse at 600 fs, while it was 0.25 MHz for a laser pulse at 0.83 ns.
学科主题	光学
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31009]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	钱静. 超短脉冲激光诱导透明材料发光现象研究[D].

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