窄线宽半导体激光阵列外腔光谱合束的研究
文献类型：学位论文
| 作者 | 于娜 |
| 文献子类 | 硕士 |
| 导师 | 周常河 |
| 关键词 | 半导体激光阵列 Diode laser array 光束整形 beam shaping 光谱合束 Spectral beam combining 外腔反馈 external cavity feedback 衍射光栅 diffraction gratings |
| 其他题名 | Research on Narrow Wavelength Spread Spectral Beam Combining of Diode Laser Array with External Cavity Feedback |
| 英文摘要 | 高功率半导体激光器具备高电光转换效率、高稳定性、尺寸小和性价比高等优点，促进了很多领域的快速发展，可以用作固体激光器和光纤激光器的泵浦源以及用于材料加工、医学治疗和国防武器等领域。但是半导体激光器较差的光束质量和低亮度限制了其作为直接光源的应用。如何在保证光束质量的同时提高半导体激光器的输出功率一直是半导体激光器急需解决的问题。光谱合束已经被证明了是获得高光束质量、高亮度半导体激光器的最有效简单的方式，其最大的优点在于实现光束功率叠加的同时保证光束质量不会产生退化。本文将对如何得到窄线宽的半导体激光阵列的外腔光谱合束光源展开以下研究： 1. 对半导体激光阵列的输出特性和外腔光谱合束进行了理论分析，针对光谱合束中存在的几个问题提出了相应的解决办法，并提出了增加半导体激光器输出功率的几种主要方式： （1）引入光束整形系统，将光谱合束的方向由原本的慢轴方向变为快轴方向，改善smile现象对光谱合束的影响，均衡快慢轴的光束质量。 （2）可以通过更多的合束单元，更高的单元输出功率，以及更高的光谱合束效率等几种方式来提高半导体激光输出功率。 2. 经过分析得到，增加合束单元数量是提高半导体激光器输出功率最简单有效的途径。合束单元数量的增加会导致整体的光谱谱宽增加，而在有限的半导体激光器的增益带宽和有限的衍射光栅的高效率衍射范围内，合束光光谱过宽会导致合束功率下降。因此，压缩半导体激光阵列光谱合束后的光谱谱宽是提高输出功率的重要手段。所以提出用非平行双光栅结构代替单个光栅，将光谱谱宽压缩一半，可以实现在原本的光谱谱宽内增加一倍的合束单元，提高半导体激光阵列光谱合束功率。实验后得到光谱谱宽为7nm，输出功率为30.88W，光谱合束效率为71%，合束光的快轴和慢轴光束质量M2分别为1.2和6.6，验证了双光栅结构压缩谱宽的效果。 3. 在双光栅结构的基础上，提出利用单个光栅和反射元件实现两次衍射压缩谱宽的结构。该结构能够最大程度地利用光栅的色散能力，与单个光栅的光谱合束相比，在各元件参数一致时，光谱谱宽被压缩至一半，即可以在原本谱宽范围内增加一倍的合束单元数。最重要的是，在保证光谱谱宽与单光栅一致时，外腔的腔长可以减小一半，使合束系统更紧凑，激光模式会更稳定。最终实验得到谱宽为6.3nm，输出功率为26.1W，电光转换效率为23%，光谱合束效率为63.7%。快慢轴的光束质量M2分别为2.0和10.5。这种新的压缩谱宽的方式将会为实现高功率、高亮度的半导体激光器提供一个可行的解决方法。; High power diode laser significantly contribute to the rapid development of various fields, including optical pumping of solid-state lasers, materials processing, medical treatment, and national defense weapons, owing to their superior Electro-Optic efficiency, stability, small size, and low price. However, diode lasers are limited by their low beam quality and low brightness as direct sources. The improvement of their output power, while maintaining beam quality, is of key importance. Spectral beam combining (SBC) has been demonstrated as one of the most efficient approaches to achieve high beam quality and brightness for the development of high-efficiency diode lasers. In this thesis, on the aim of obtaining narrow wavelength spread diode lasers, mainly focus on the following aspects: 1. The output characteristics of the diode laser array and external cavity spectral beam combining are fully theoretical analyzed. In order to solve the problems existed in the SBC, we have proposed several solutions. Besides, we have proposed several methods to increase the output power of diode lasers. (1) A beam transformation system (BTS) as a beam shaping system is employed to rotate the beams by 90o, and the direction of spectral beam combining turns into fast axis direction from original slow axis direction. The smile effect of SBC is reduced and the beam quality is optimized. (2) We have proposed several types of method to increase the output power of diode lasers: increasing the number of combining emitters; enhancing the output power of a single emitter; and increasing the combining efficiency of SBC. 2. It has been learned that increasing the number of combining emitters is the most effective method to obtain high power diode lasers. Theoretically, more emitters correspond to a broader wavelength range. The number of combined emitters is limited as the gain bandwidth of diode lasers is usually tens of nanometers. Furthermore, the diffraction efficiency of a grating used in the SBC changes with the wavelength and the range of high efficiency is limited. It’s an important problem to compress the wavelength spread to achieve high power diode lasers. Hence, we have proposed d non-parallel double grating structure in SBC method to instead of a single grating. The most attractive advantage of this method is that it will compress the wavelength spread into a half of its original spectrum, which means the number of combined emitters can be doubled and the output power of diode lasers is improved. We achieved a power of 30.88W under continuous operation with a wavelength spread of 7 nm. The spectral beam combining efficiency was 71%, and the beam quality is M2 is 1.6 in fast axis and 6.6 in slow axis at a low current. 3. Based on the non-parallel double grating structure, we proposed a novel wavelength-spread compression technique for spectral beam combining of a diode laser array. A reflector, which is parallel to the grating, is introduced to achieve double pass with a single grating. The grating could be efficiently employed by double diffraction. This facilitated the reduction of the wavelength spread by half, and doubled the number of combined elements in the gain range of the diode laser. Furthermore, the cavity length could be decreased approximately by half, while maintaining a fixed wavelength spread. Finally, we achieved a power of 26W under continuous operation with a wavelength spread of 6.3 nm. The spectral beam combining efficiency was 63.7%, and the beam quality is M2 is 2.0 in fast axis and 10.5 in slow axis. This method shows significant potential for a more efficient spectral beam combining of diode laser arrays. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/31051]  |
| 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 | 于娜. 窄线宽半导体激光阵列外腔光谱合束的研究[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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