Submicrometer surface structuring with a Bessel beam generated by a reflective axicon

Journal of Laser Applications, vol. 33

Abstract

In ultrashort pulse (USP) laser ablation, focus diameters in the range of >20 μm are common for microstructuring, but the demand for much smaller structure sizes is rising, especially in the fields of filter technology, surface functionalization, and electronics. However, strong focusing of a Gaussian beam near the diffraction limit is accompanied by a very limited depth of focus, which leads to an extreme increase in process sensitivity. It is often too challenging to meet the necessary precision requirements for the system technology. A potential solution to overcome the problem of the short focus depth is the usage of a nondiffracting Bessel beam that is well known for providing a depth of field in the mm range while allowing the diameter of the central processing spot to be below 1 μm. There are several ways to generate a Bessel beam, but only an axicon is suitable for efficient high-power USP ablation. However, even high-precision manufactured axicons have a round tip resulting in a highly oscillating intensity along the propagation axis. This characteristic is a major obstacle for reproducible and reliable laser nanostructuring of metals. For this reason, reflective axicons were newly introduced to the market. They generate a Bessel beam much closer to the ideal axial intensity distribution. In this paper, we compare the Bessel beam generated by a reflective axicon with that of a conventional axicon in an application-oriented setting. Furthermore, we demonstrate the enormous potential of Bessel beams for surface structuring.

Authors 5

1. Martin Osbild Aachen Fraunhofer Institute for Laser Technology 1 2Chair for Laser Technology LLT

   Fraunhofer Institute for Laser Technology · Cailabs (France) · RWTH Aachen University

   Affiliation as printed

   Fraunhofer Institute for Laser Technology 1 , Steinbachstr. 15, Aachen 52074, Germany

   2Chair for Laser Technology LLT, RWTH Aachen University, Steinbachstr. 15, Aachen 52074, Germany

   3Cailabs, 38 Boulevard Albert 1er, Rennes 35200, France

2. Elisabeth-Annemarie Gerhorst Aachen 2Chair for Laser Technology LLT 1Fraunhofer Institute for Laser Technology

   Fraunhofer Institute for Laser Technology · Cailabs (France) · RWTH Aachen University

   Affiliation as printed

   2Chair for Laser Technology LLT, RWTH Aachen University, Steinbachstr. 15, Aachen 52074, Germany

   1Fraunhofer Institute for Laser Technology, Steinbachstr. 15, Aachen 52074, Germany

   3Cailabs, 38 Boulevard Albert 1er, Rennes 35200, France

3. Siddharth Sivankutty Aachen 1Fraunhofer Institute for Laser Technology 2Chair for Laser Technology LLT

   Fraunhofer Institute for Laser Technology · Cailabs (France) · RWTH Aachen University

   Affiliation as printed

   Cailabs 3 , 38 Boulevard Albert 1er, Rennes 35200, France

   1Fraunhofer Institute for Laser Technology, Steinbachstr. 15, Aachen 52074, Germany

   2Chair for Laser Technology LLT, RWTH Aachen University, Steinbachstr. 15, Aachen 52074, Germany

4. Gwenn Pallier Aachen 1Fraunhofer Institute for Laser Technology 2Chair for Laser Technology LLT

   Fraunhofer Institute for Laser Technology · Cailabs (France) · RWTH Aachen University

   Affiliation as printed

   Cailabs 3 , 38 Boulevard Albert 1er, Rennes 35200, France

   1Fraunhofer Institute for Laser Technology, Steinbachstr. 15, Aachen 52074, Germany

   2Chair for Laser Technology LLT, RWTH Aachen University, Steinbachstr. 15, Aachen 52074, Germany

5. Guillaume Labroille Aachen 1Fraunhofer Institute for Laser Technology 2Chair for Laser Technology LLT

   Fraunhofer Institute for Laser Technology · Cailabs (France) · RWTH Aachen University

   Affiliation as printed

   Cailabs 3 , 38 Boulevard Albert 1er, Rennes 35200, France

   1Fraunhofer Institute for Laser Technology, Steinbachstr. 15, Aachen 52074, Germany

   2Chair for Laser Technology LLT, RWTH Aachen University, Steinbachstr. 15, Aachen 52074, Germany