【作者】 张云军；

【导师】 王月珠；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2006， 博士

【摘要】 采用包层泵浦技术,加上大功率多模半导体激光器工艺的快速发展与完善,光纤激光器在常温下获得了极高的输出功率。热问题是影响掺Tm³⁺晶体激光器阈值、效率和输出功率的主要因素,而掺Tm³⁺硅基光纤激光器的掺Tm³⁺光纤不需要复杂的主动冷却设备,在常温下即可获得高效率的大功率激光输出。本论文从理论和实验两个方面对掺Tm³⁺硅基双包层光纤激光器进行了研究工作。讨论了Tm³⁺掺在四种常用激光晶体里的吸收光谱、荧光发射谱和Tm³⁺掺在ZBLAN、silica光纤基质中的吸收光谱、荧光发射谱,Tm³⁺在两种光纤基质中的吸收光谱、荧光发射谱要明显宽于Tm³⁺在四种晶体里的光谱。概述了强泵浦光纤激光器的输出功率和阈值的解析表达式,分析了掺稀土离子双包层光纤吸收泵浦光有效吸收系数的理论模型和计算有效吸收系数的简化表达式。从Tm³⁺的稳态速率方程出发,结合谐振腔结构特点,在输出793nm的LD激光器作为泵浦源的情况下,给出了双包层光纤激光器的振荡阈值特性、激光输出特性和激光器谐振腔结构参数的关系。从理论上分析了3H6,3H4→3F4,3F4交叉弛豫过程降低掺Tm³⁺硅基光纤激光器的阈值、提高激光器斜率效率的机理。3H6,3H4→3F4,3F4交叉弛豫过程可以使激光器的量子效率达到2,分析了掺杂浓度与加强掺Tm³⁺硅基光纤激光器交叉弛豫过程的关系、掺杂浓度对光纤长度的影响。详细介绍了LD单端泵浦掺Tm³⁺硅基双包层光纤激光器的实验过程和实验结果。研究了光纤长度、腔型结构和光纤温度对激光器阈值、斜率效率以及输出激光光谱的影响。在实验上对比了单程泵浦和双程泵浦掺Tm³⁺双包层LMA光纤激光器的阈值、斜率效率的变化,用LD输出的807.5nm激光作为泵浦源泵浦掺Tm³⁺双包层LMA光纤获得了高效的连续波激光输出。从速率方程出发,模拟了在1.06μm脉冲激光作为泵浦源时掺Tm³⁺硅基光纤激光器增益开关弛豫振荡输出近2μm脉冲激光的波形振荡过程,模型中加入了Tm³⁺在1.06μm作为泵浦源时强的激发态吸收效应,而且Tm³⁺间存在的四个交叉弛豫效应也包含在速率方程中。计算并分析了Tm³⁺掺杂浓度对激光器阈值的影响。更多还原

【Abstract】 Using cladding-pumped method and high-power multimode laser diode as pumping sources, the fiber laser maximum output power has been increased greatly at room-temperature. The lasing threshold, slope efficiency and output scaling power of Tm³⁺-doped crystals host is sensitive to the host material temperature. The Tm³⁺-doped silica fiber laser can operate high efficiently with only passive cooling. The dissertation focuses on the Tm³⁺-doped double clad fiber laser.The absorption and fluorescent spectrums of Tm³⁺-doped four kind of popular laser crystals, ZBLAN fiber and silica fiber are reviewed and compared in the chapter 2. The absorption and fluorescent spectrums of Tm³⁺-doped in the fiber host are wider than those of crystals host. Based on a rate equation model, the lasing threshold and output power approximate analytical and quasi-analytical expression are present. The theory of mode analysis to calculate the absorption efficiency for the double-clad optical fibers is present, and the simplified expression of calculating the effective absorption coefficient is given. From the Tm³⁺ rates equations, pumped at CW 793nm laser, the Tm³⁺-doped silica fiber laser threshold characteristics, laser output characteristics, that correlated to parameters of cavity are discussed. The mechanics of 3H6,3H4→3F4,3F4 cross relaxation process due to low the lasing threshold and increase the slope efficiency. The 3H6,3H4→3F4,3F4 cross relaxation process can make the fiber laser quantum efficiency get to 2. The theoretical analysis results show that the heavily Tm³⁺-doped silica fiber can boost the cross relaxation probability. At the same time, relevant energy levels parameters are variable.The experimental courses and results of Tm³⁺-doped silica fiber laser are described in details using the single end-pumping method. It is also investigated that the fiber length, cavity structure and fiber temperature influence on the lasing threshold, slope efficiency and laser spectrum. The single-pass pump and double-pass pump results, including the lasing threshold and slope efficiency, are compared using the LMA Tm³⁺-doped silica fiber. Pumped the LMA Tm³⁺-doped silica fiber at 807.5nm output from LD,the fiber lasers acquire high efficient更多还原