飞秒矢量光束生成及其微纳加工应用研究

GENERATION OF FEMTOSECOND VECTOR BEAMS AND THEIR APPLICATION ON MICRO-/NANO FABRICATION

郑健

11849223

硕士

机械电子工程

徐少林

2020-06-02

2020-07-20

哈尔滨工业大学

深圳

在自然界中，具备从纳米到微米多尺度特征的微纳复合结构赋予了生物表面独特的光学、力学、润湿性等性能。通过仿生学手段，制备与生物表面具有相似或更加优异功能的人造织构具有广阔的应用前景，但如何实现跨尺度表面织构的设计与高效制造仍然具有挑战性。飞秒激光加工技术是最为前沿和最具潜力的微纳加工技术之一，但利用传统的高斯光束直写加工方式难以形成多样化、多尺度的微纳复合结构。因此，本课题从材料表面多尺度微纳复合结构的制备方法出发，旨在利用飞秒激光直写微纳加工的优点，致力于开发一种通过偏振态调控丰富激光诱导形成表面微纳结构的多样性的新工艺，并通过矢量光束的动态调控拓展加工的自由度。在矢量光束的基本原理及其描述方法的研究基础上，利用波片和基于空间缓变结构的超表面偏振转换器的偏振调制实现了高阶庞加莱球光束与杂化偏振矢量光束，分析了波片级联方式对偏振的影响及偏振态的演化规律。基于对标量光束和矢量光束的斯托克斯参量测试，分析了不同偏振态光束的偏振特性，验证了矢量光束的实验生成结果。以单晶SiC材料为研究对象，对飞秒激光诱导表面微纳结构进行了实验研究，并对其形成过程中激光与材料的相互作用机理进行了分析。通过与线偏振飞秒激光进行对比，着重探究了偏振态和脉冲重叠率对周期性微纳结构形成与演化的作用规律，研究了包括杂化偏振光束在内的新型矢量光束微纳加工过程中的现象。结果表明，通过对矢量偏振态的设计和动态调控可以制备具有不同几何轮廓特征和亚波长结构分布特征的复合织构表面。为了提高制备的多尺度微纳复合结构的多样化程度，利用反射式空间光调制器和超表面偏振转换器，设计并实现了一种飞秒矢量光束腔外生成系统，理论分析了液晶分子相位延迟与高阶庞加莱球上坐标的对应关系，并实现了多种矢量光束的产生及动态调控，提高了原有系统的灵活性。在此基础上，改变空间光调制器上加载的相位掩模及其切换频率，实现了不同分布方式的表面微纳结构阵列的动态加工，验证了矢量光束动态调控应用于多尺度微纳织构加工的可行性。

In nature, the hierarchical micro-/nanostructures with multi-scale characteristics ranging from nanoscale to micron scale endows the biological surface with unique optical, mechanical, wettability and other properties. By means of bionics, it has prospective application to obtain artificial texture with similar or better performance with biological surface. However, how to realize the design and efficient manufacture of multiscale surface textures is still challenging.Femtosecond laser processing technology is one of the most advanced and promising micro-nano processing technologies, but it is difficult to form diversified and multiscale micro-/nanostructures by using the traditional direct writing processing method of Gaussian beam. Therefore, starting with the preparation method of multiscale hybrid micro-/nano structures on the surface of materials and using the advantage of femtosecond laser direct micro-nano machining, this research project is committed to developing a new technology to increase the degree of freedom of laser-induced surface structures through the manipulation of polarization states.On the basis of the basic principle of vector beams and their description method, the high-order Poincaré sphere beams and hybrid vector beams were realized by using the polarization modulation of wave plates and metasurface polarization converter based on spatially slowly varying structures. The influence of cascade mode of wave plate on polarization and the evolution law of polarization states were also analyzed. Based on the Stokes parameters measurements of scalar and vector beams, the polarization characteristics of different polarized beams were analyzed, and the experimental results of vector beams generation were verified.The micro-/nanostructures induced by femtosecond laser on the surface of single crystal SiC were experimentally studied, and the interaction mechanism between laser and material was analyzed. By comparing with the structures fabricated by linearly polarized laser, the effects of polarization states and pulse overlap rate on the formation and evolution of periodic surface structures were studied emphatically, and the phenomena in the micro-nano processing of new vector beams including hybrid vector beams were revealed. The results show that the hierarchical surface textures with different geometric characteristics and distribution characteristics of subwavelength structure can be prepared by the design and dynamic manipulation of the vector polarization states.In order to improve the diversity of the prepared multiscale micro-/nano structures, a femtosecond vector beam outside-cavity generation system was designed and implemented by using a reflective spatial light modulator and a metasurface polarization converter. The corresponding relationship between phase delay of liquid crystal molecules and coordinates on high-order Poincaré sphere was derived theoretically, and the generation and flexible manipulation of multiple vector beams were also realized, which improved the flexibility of the original maching system. On this basis, the phase masks loaded on the spatial light modulator and their switching frequency were changed to realize the surface structures arrays with different arrangements, which verified the feasibility of applying the vector beam dynamic manipulation to the multiscale micro-/nano structures processing.

飞秒激光 偏振态 矢量光束 单晶SiC 多尺度微纳结构

femtosecond laser polarization states vector beam single crystal SiC multiscale micro-/nanostructures

中文

联合培养

南方科技大学

郑健. 飞秒矢量光束生成及其微纳加工应用研究[D]. 深圳. 哈尔滨工业大学,2020.