Radially accelerating light waves

这个项目的目的是加深对所谓的径向自加速束（RABs）的了解。我们的研究将涵盖理论和实验方面，以应付这个非常多才多艺的研究领域。特别是，我们将回答以下问题：(1)强聚焦条件下光束的物理性质是如何变化的？(2)是否有可能高效地生成RABs ？(3)数值方法是否使光束裁剪成为可能，以获得特定的空间强度分布？(4)激光材料加工，特别是激光打孔和光刻的优势是什么？(5)是否有一种方法可以利用RABs来操纵纳米粒子，是否也可以控制活细胞？回答这些问题将促进RABs在各个研究和工业领域的直接应用。到目前为止，RABs仅在弱聚焦状态下产生。然而，对于几乎所有的应用，需要没有意外热沉积的高光强，因此，使用强聚焦物镜是不可避免的。然而，这是一种全新的物理机制，必须加以研究。此外，高能效的光束产生对于大多数应用是必不可少的。目前的技术只利用入射光的一小部分进行实际的光束整形，而丢弃其余部分。在这个项目中，我们将实施一种新的创新光学设计，这将极大地提高效率水平(2)。它可能需要生成相当复杂的光束轮廓。尽管RABs具有必要的自由度，但分析方法并不是特别有希望找到所需的光束参数。通过采用新的数值优化算法，如遗传算法，我们计划克服这一问题，并开发一种能够找到任何所需光束轮廓的光束参数的代码(3)。此外，RABs在螺旋孔钻孔和光刻结构生成方面的应用也将引起我们的注意(4)。之前获得的关于光束缩放(1)、节能发电(2)和优化(3)的知识将在这里发挥主要作用。由于在这方面将使用具有天然宽光谱范围的超短激光脉冲，我们还必须找到一个重要问题的答案，即如何充分塑造非单色光。在最后的项目阶段，我们将关注另一个创新的概念：螺旋光束轮廓应该被用来产生一个光学螺旋输送机，使纳米粒子能够以双向的方式运输(5)。有了这样的工具，可以实现连续的颗粒流，并且可以根据颗粒惯性对相同的颗粒进行排序。此外，由于生物细胞基本上只是小颗粒，控制它们也应该是可行的。

It is the aim of this project to deepen the knowledge on so called Radially Self-Accelerating Beams (RABs). Our studies will cover theoretical as well as experimental aspects in order to cope with this very versatile field of research. In particular, we are going to answer the following questions: (1) How do the physical beam properties change under strong focusing conditions? (2) Is it possible to generate RABs efficiently? (3) Do numerical methods render beam tailoring possible in order to achieve specific spatial intensity distributions? (4) What are the advantages for laser material processing, especially in regards to laser drilling and photo lithography? (5) Is there a way to employ RABs for nano-particle manipulation and is it viable to control living cells as well?Answering those questions will promote the direct application of RABs in various fields of research and industry. So far, RABs were solely generated in the weak focusing regime. For virtually all applications, however, high optical intensities without unintended heat deposition are required and, thus, the use of strong focusing objectives is unavoidable. However, this is an entirely new physical regime, which has to be investigated (1). Also energy-efficient beam generation is essential for most applications. Current techniques utilize only a minor fraction of the incident light for actual beam shaping while discarding the rest. Within this project we will implement a new and innovative optical design that will elevate the level of efficiency tremendously (2). In it might be required to generate rather complex beam profiles. Albeit RABs exhibit the necessary degrees of freedom, analytical methods are not particularly promising candidates to find the desired beam parameters. By employing new numerical optimization algorithms such as genetic ones we are planning to overcome this issue and develop a code that is capable finding the beam parameters to any desired beam profile (3). Moreover, the application of RABs for the drilling of spiral holes and for the generation of photo-lithographic structures will get our attention (4). The previously acquired knowledge about beam scaling (1), energy-efficient generation (2) and optimization (3) will play a major role here. Since ultrashort laser pulses with a naturally broad spectral range will be employed in this regard, we also have to find an answer to the important question how non-monochromatic light can be shaped adequately. In the final project stage we are going to concern ourselves with another innovative concept: The spiraling beam profile is supposed to be used to generate an optical screw-conveyor that enables transport of nano-particles in a bidirectional fashion (5). With such a tool, continues particle flows could be achieved and based on particle inertia sorting of the same should be possible. Moreover, since biological cells are basically just small particles, controlling them should viable as well.