中红外拉曼光纤激光器研究
文献类型：学位论文
| 作者 | 姜华卫 |
| 文献子类 | 博士 |
| 导师 | 冯衍 |
| 关键词 | 光纤激光器 fiber laser 中红外 mid-infrared 拉曼 Raman 级联包层泵浦 Cascaded cladding pumping. |
| 其他题名 | Research on mid-infrared Raman fiber laser |
| 英文摘要 | 中红外波段的激光源在医疗、遥感、生物工程、污染监测等领域有着广泛的市场需求和应用前景。目前产生中红外光源的方法主要有光参量振荡器、固体激光器和光纤激光器等。其中光纤激光器因结构紧凑、效率高、光束质量好和热管理方便等优点而受到广泛关注，是目前激光技术研究的重要主题。 拉曼光纤激光器具有波长灵活的特性。只要有合适的泵浦源，便可以在增益介质透明波段范围内获得激光输出。目前用于中红外拉曼光纤激光器的增益介质主要有软玻璃光纤（氟化物，硫化物，碲酸盐玻璃光纤等）和高掺锗石英基光纤。本文主要针对高掺锗石英基光纤和硫化物光纤在中红外波段的输出特性展开了研究，内容如下： 1. 首先建立了级联自发拉曼光纤放大器模型。然后针对脉冲泵浦的高掺锗石英基光纤自发拉曼放大器，建立和求解了泵浦光和各阶斯托克斯频移光的耦合波方程。通过数值模拟确定了不同泵浦波长、泵浦峰值功率下的最佳增益光纤长度、输出波长范围和脉冲时域变化特性。模拟结果显示，利用高掺锗石英基光纤作为拉曼增益介质，在高峰值功率脉冲泵浦作用下，通过两级拉曼级联，可以在2.5μm获得激光输出。 2. 研究了高掺锗石英基光纤自发拉曼放大器的输出特性。对锁模和声光调Q种子源进行放大，获得高峰值功率的脉冲激光，然后泵浦合适长度的高掺锗石英基光纤，通过两级级联，在2.43μm和2.48μm分别获得了0.3W和0.15W的平均功率输出；通过一级拉曼，在2.2μm获得了3W的脉冲激光输出，是目前石英基光纤在该波长获得的最大输出功率。对波长可调谐声光调Q脉冲种子进行放大，然后泵浦8m高掺锗石英基光纤，通过一级拉曼，在2128.5-2236.2nm波段范围内获得了平均功率大于2W的脉冲激光输出。 3.为获得更长波长的中红外拉曼激光输出，建立了脉冲泵浦的硫化物光纤自发拉曼放大器模型。讨论了泵浦波长、泵浦峰值功率和光纤长度对输出激光特性的影响。根据高掺锗光纤自发拉曼放大器的输出参数，理论模型中采用波长在2.2μm波段，峰值功率数百瓦的脉冲激光泵浦硫化物光纤，经过5级或6级拉曼级联，可以在3.5μm-4μm波段产生激光输出。 4.验证了多包层光纤作为拉曼增益介质时，级联包层泵浦的拉曼光纤激光器可以克服普通双包层拉曼光纤激光器亮度提升的限制。在理论模型中，首先设计了一种新型多包层光纤，将其作为拉曼放大器的增益介质，通过改变包层数目和包层半径来观察拉曼放大器的输出特性。当包层2直径设定为105μm，纤芯直径设定为10μm时，通过数值模拟发现，包层数目为4，包层到纤芯半径分别为5/12.5/26/52.5μm时，斯托克斯光转化效率从13%提升到了59.6%，并且亮度提升从650增加到了2800。即利用此多包层光纤作为拉曼增益介质时，包层泵浦拉曼激光器可以在获得高转化效率的同时，还可以提升信号光的输出亮度。; Lasers operating at mid-infrared wave-band have a wide range of market demand and application prospects due to a large number of applications including LIDAR, gas sensing, optical communication and other fields. Nowadays, the methods of generating mid-infrared light source mainly cantain optical parametric oscillator, solid-state laser and fiber laser, etc. The fiber lasers are widely concerned because of their compact structure, high efficiency, good beam quality and easy heat management. It is an important subject of laser technology research. Raman fiber laser has the characteristic of wavelength flexibility. Under pumping of appropriate laser source, it can generating light at any wavelength within the fiber transmission window. At present, the main gain medium for medium-infrared Raman fiber lasers includes soft glass fiber (fluoride, sulfide, tellurite glass fiber, etc.) and highly Ge-doped silica fiber. In this paper, we investigate output characteristics of highly Ge-doped silica fiber and AsS fiber at wavelengths far beyond 2 μm. Details are as follow: 1. Firstly，a cascaded spontaneous Raman fiber amplifier model is established. Then with high Ge-doped silica fiber as gain medium，the coupled wave equations for pump and Stokes light is established and solved for pulse pumped spontaneous Raman amplifier. In the numerical model, we discuss the influencs of the pump wavelength and pump peak power on the optimal fiber length, output wavelength range and pulse shape. The simulation results reveals that 2.5 μm Stokes light can be generated by two order Raman frequency shifting in the highly Ge-doped silica fiber pumped by high peak power pulse source. 2. The output characteristics of high germanium-based silica fiber spontaneous Raman amplifiers are studied. The high peak power pulse laser is obtained by amplifying the mode-locked and acousto-optic Q-switched seed source, and then used to pump highly Ge-doped silica fiber with suitable length. By two cascaded Raman conversion, 0.30 W at 2.43 μm is achieved with an optical efficiency of 16.5 % and a peak power of 275 W. 0.15 W at 2.48 μm is achieved with an optical efficiency of 7.9 %. The output wavelength obtained is currently the longest produced in the silica fiber laser. By one cascaded Raman, 3 W 1st-order Raman Stokes light at 2.2 μm is obtained with an optical efficiency of 35.9%. By amplifying the wavelength tunable acousto-optic Q-switched pulse seed and then pumping the 8m highly Ge-doped fiber, the Raman fiber amplifier can produce > 2W power over the whole wavelength range from 2128.5 to 2236.2 nm. 3. In order to obtain the mid-infrared Raman laser output with longer wavelength, a pulsed pumped spontaneous Raman amplifier model was established with the AsS fiber as gain medium. The influence of pump wavelength, pump peak power and fiber length on the output laser characteristics are discussed。Based on the output parameters of highly Ge-doped fiber spontaneous Raman amplifier, in the numerical model, 3.5μm-4μm band Stokes light can be generated by 5 order or 6 order Raman frequency shifting in the AsS fiber pumped by several hundred watts peak power pulse laser operating at 2.2μm。 4. With the multi-cladding fiber used as Raman gain medium，we demonstrate that the cascaded pumped Raman fiber laser can overcome the limitation of the brightness enhancement of the ordinary double-clad Raman fiber laser. In the numerical model, a specially designed multi-cladding fiber is used as gain medium of the Raman amplifier, and the output characteristics of the Raman amplifier are studied by changing the number of cladding and the radius of the cladding. The diameter of the cladding2 and core are set as 105 μm and 10 μm, respectively. The numerical simulation reveals that when the number of cladding is set as 4 and the cladding to core radius is 5/12.5/26/52.5μm, the Stokes light conversion efficiency increase from 13% to 59%, and the brightness enhancement increases from 650 to 2800. So using this multi-clad fiber as the Raman gain medium, the cladding pumped Raman fiber laser can obtain the high conversion efficiency and improve the signal light output brightness. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30969]  |
| 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 | 姜华卫. 中红外拉曼光纤激光器研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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