Radially accelerating light waves

• Applicant: Professor Alexander Szameit, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 329130931

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.

• DFG Programme: Research Grants