Design and Manufacturing Method of Fundamental Beam Mode Shaper for Adapted Laser Beam Profile in Laser Material Processing.

Christian Bischoff,Jana Schmitt,Udo Umhofer,Erwin Jäger,Friedemann Völklein,Ulrich Rädel,Andrés Fabián Lasagni

doi:10.3390/ma12142254

Abstract

Many laser material processing applications require an optimized beam profile, e.g., ring shape or Top-Hat profiles with homogeneous intensity distribution. In this study, we show a beam shaping concept leading to a phase shifting element with binary height profile as well as a very low periodicity with near diffraction limited spot size. Further advantages of so-called Fundamental Beam Mode Shaping (FBS) elements are the simplified handling, and a high efficiency and homogeneity. The calculated height profile of FBS elements are transferred in fused silica substrates using a combination of microlithography technologies, reactive ion etching (RIE) and ion beam etching (IBE). The experiments demonstrated a linear relation between the etching depth after RIE and IBE. The optical evaluation of the manufactured FBS beam mode shaper confirmed the presented concept design.

Highlights

Nowadays, pulsed solid-state lasers are well established for many micromachining processes.In general, picosecond and femtosecond laser sources deliver ultra-short pulses with low energies, causing low thermal effects, leading to high-precision micro structuring processes that enable the fabrication of structures in the micrometer range
The calculated height profile of fundamental beam mode shaper (FBS) elements are transferred in fused silica substrates using a combination of microlithography technologies, reactive ion etching (RIE) and ion beam etching (IBE)
The measured +/− first order Top-Hat profiles behind and in front of the focal plane are not described by the design concept

Summary

Introduction

Picosecond and femtosecond laser sources deliver ultra-short pulses with low energies, causing low thermal effects, leading to high-precision micro structuring processes that enable the fabrication of structures in the micrometer range. In addition to the pulse duration, the wavelength and the beam profile have a strong influence on the quality of the laser ablation process. A single-mode beam with a Gaussian intensity distribution is well-known to be the most convenient laser beam spatial distribution. It preserves its distribution while propagating, and even when focused. For many applications, the raw Gaussian beam profile of single-mode lasers does not lead to the best result

Methods

Results

Conclusion