基于内腔走离效应的Nd:YVO4柱状矢量激光器研究
文献类型：学位论文
| 作者 | 王宁 |
| 学位类别 | 硕士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 李建郎 |
| 关键词 | 圆柱矢量偏振光束 横向模式 单轴晶体 腔内透镜 |
| 其他题名 | Cylindrical Vector Nd:YVO4 Laser Based on Intracavity Walk-off Effect |
| 中文摘要 | 径向偏振和切向偏振光束都属于圆柱矢量偏振光束，它们具有空间圆对称偏振特性以及环形强度分布特性。圆柱矢量光束具有许多优于线偏振光束和圆偏振光束的性能，比如它经过高数值孔径透镜聚焦后在焦点具有更小的光斑点和更强的纵向电场强度。在材料加工领域，金属材料对圆柱矢量偏振光束具有更高的吸收率。这些特点使得圆柱矢量偏振光束在粒子捕获、原子导引、各类材料加工以及超分辨技术等领域具有很大的应用潜力和应用价值。 已经有很多获得矢量偏振的被动及主动方法。被动法在激光器谐振腔外利用某些元件实现空间偏振模式转换，比如空间相位延迟器、衍射光栅等。然而被动方法难以获得高质量以及高功率的矢量偏振光束。与此相反，主动方法通过在激光器谐振腔内引入双折射元件直接获得矢量偏振光束，比如单轴晶体、布儒斯特轴椎体、激光晶体热致双折射等。同时利用光子晶体光栅作为腔镜也能从激光器谐振腔内直接获得矢量偏振光束。 本论文将腔内透镜和单轴晶体的走离效应相结合，分别从平行平面腔结构和平凹腔结构的Nd:YVO4激光器获得了径向偏振及切向偏振激光输出，且腔内透镜可以调节激光器谐振腔内的横向模式。基于此种方法的矢量激光器具有结构紧凑，成本低，易于实现大规模生产应用的优势。同时，我们的实验结果表明：与平行平面腔结构的Nd:YVO4激光器相比，平凹腔结构的Nd:YVO4激光器能够获得更高斜效率、更高功率的径向偏振及切向偏振激光输出。 本论文的主要内容如下： 第一章，简要介绍了圆柱矢量偏振光的相关背景，包括圆柱矢量偏振光束的数学描述、与线偏光和圆偏光相比圆柱矢量偏振光的一些优异性质以及圆柱矢量偏振光束相关应用领域。最后我们列举了常见的获得矢量偏振光束的被动方法及主动方法。 第二章，介绍了谐振腔的相关理论。首先分析了c切单轴晶体的走离效应。其次利用光线传输矩阵数值模拟了激光器谐振腔的稳定性。最后利用激光速率方程理论模拟了激光器的阈值功率及斜效率。 第三章，搭建了基于平平腔结构的矢量光Nd:YVO4激光器。我们将单轴晶体的走离效应与腔内透镜相结合进行偏振模式以及谐振腔内横向模式的选择。通过调节腔内透镜的位置以及腔长，获得了最高斜效率和最高功率分别为0.415%、14mW的径向偏振激光输出以及最高斜效率和最高功率分别为0.226%、7mW的切向偏振激光输出。此外，激光器谐振腔内的横向模式可调。 第四章，搭建了基于平凹腔结构的矢量光Nd:YVO4激光器。我们将单轴晶体的走离效应与腔内透镜相结合进行偏振模式以及谐振腔内横向模式的选择。通过调节腔内透镜的位置以及腔长，获得了最高斜效率和最高输出功率分别为10.4%、430mW，偏振纯度92.1%的切向偏振激光输出以及最高斜效率和最高输出功率分别为5.1%、220mW，偏振纯度89.9%的径向偏振激光输出。激光器谐振腔内的横向模式同样可调。 第五章，对本论文的研究结果进行了总结，指出实验中的不足之处，并提出了可能的解决方案。 |
| 英文摘要 | Radially and azimuthally polarized light beams? known as two eminent members of the family of the cylindrical vector light, are characterized by spatially axis-symmetrical polarizations and ring-shaped intensity distribution. The cylindrical vector beam has shown particular properties, including the tight focusing and the existence of longitudinal electric field at the focal spot in the presence of a high numeric-aperture lens. Futhermore, in the field of material processing, the metal materials exhibit about two-times high absorption efficiency to clindrical vector beam, when compared that to linearly or circularly polarized beams. These features of cylindrical vector light enable its wide application in optical trapping, particle acceleration, high-resolution microscopy and etc. To generate such beams, a number of methods, including passive and active ways, were developed. The former refers to spatiall polarization conversion to an incoming beam by using various optical elements like spatially veariable waveplate and difrractive grating. However, most of passive methods had a problem in dealing with the beam quality and somehow the high beam power. On the contrary, the active methods can directly generate the cylindrical vector beams inside the laser cavity by using intra-cavity elements, including birefringent elements, an intra-cavity axicon and thermally induced birefringence to the laser rods, as well as polarization-selective elements such as photonic crystal grating and diffraction mirror. In this thesis, we demonstrated the achievement of vector laser output in a laser-diode end-pumped Nd:YVO4 laser by combining a birefringent crystal and a lens inside the two different resonator types (plan-plano cavity and plano-concave cavity). In this investigation, the walk-off effect in the birefringent crystal was used for intracavity polarization discrimination, and the lens was used to adjust the transverse mode parameters inside the laser cavity. This three-element compact cavity was low-cost and easy to mass production. Our results showed that, in the Nd:YVO4 laser with plano-concave cavity, radially- or azimuthally-polarizied modes could be obtained with high slope efficiency and high output power, when compared to the those of Nd:YVO4 laser with plan-plano cavity. The main contents of the thesis are as follows: In chapter one, we briefly overviewed the background of cylindrical vector beam, including its mathematical description, its particular advantages over linearly or circularly polarized beams and its promising applications. Futhermore, passive and active methods to generate cylindrical vector beams were summarized. In chapter two, we numerically simulated the design to a vector laser cavity by using ABCD matrix theory in the presence of a c-cut birefringent crystal for the discrimination of radially- or azimuthally-polarizied modes. We also used laser rate equations to simulate the threshold pump power and slope efficiency of our laser resonator. In chapter three, a vector Nd:YVO4 laser with plan-plano cavity was demonstrated. In this investigation, both the birefringent walk-off effect in the laser crystal and the intracavity lens were used for polarization discrimination and transverse mode discrimination. By adjust the position of lens and also cavity length, this laser emitted radially-polarizied modes with the maximum slope efficiency of 0.415% and the maximum output power of 14mW, or azimuthally-polarizied modes with the maximum slope efficiency of 0.226% and the maximum output power of 7mW. The transverse mode parameters inside the laser cavity were adjustable. In chapter four, a vector Nd:YVO4 laser with plano-concave cavity was demonstrated . In this investigation, both the birefringent walk-off effect in the laser crystal and the intracavity lens were used for polarization discrimination and transverse mode discrimination. By adjust the position of both the lens and output coupler, this laser emitted radially-polarizied modes with the maximum slope efficiency of 5.1% and the maximum output power of 220mW, or azimuthally-polarizied modes with the maximum slope efficiency of 5.1% and the maximum output power of 220mW. The polarization purities of radially- or azimuthally-polarizied modes were 92.1% and 89.9%, respectively. In chapter five, the results were summarized, and the prospect of our laser resonator was discussed. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16953]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 王宁. 基于内腔走离效应的Nd:YVO4柱状矢量激光器研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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