Novel Beam Shaping for Laser Micro Processing

“Flexible Beam Shaper” – high-power suitable beam shaping system for laser micromachining based on phase modulation (Source: Pulsar Photon.)

“Flexible Beam Shaper” – high-power suitable beam shaping system for laser micromachining based on phase modulation (Source: Pulsar Photon.)

Pulsar Photonics has developed a machine integrable beamforming system that opens up new possibilities in the laser process development, particularly with ultrashort pulse lasers. By using optical phase modulators, the laser radiation in the working plane can be shaped almost arbitrarily, which is the basis for novel laser processes. Tested with average laser power of up to 60 W using an ultrafast laser and a user-friendly software, the company offers a complete beam shaping system for laser micro processing for the first time.

The use of laser radiation as a tool in the production has been established in industry for many areas and has led to a transformation, in which classical manufacturing processes are replaced by laser-based processes. For several years now, ultrashort pulse lasers (USP) are on the market. Their pulses allow to evaporate almost any material, without taking harmful effect on the surrounding material. With these lasers, a high-precision tool for manufacturing has arrived, with the potential of a huge range of applications. So far, components of smartphone displays are already being processed with USP lasers. In areas such as stent-manufacturing, the drilling of injection nozzles and electronics manufacturing USP processes are industrially used for some time.

Beam shaping as a tool to increase the process efficiency

Although the distinct advantages of the ultrashort pulse laser have already been demonstrated in many applications, the often poor efficiency of the processes limit a widespread use of technology. With falling prices of laser sources and ever-increasing average power, the foundation for a wide dissemination of the USP technology from the laser side is increasingly given. For many laser processes, however, this is not sufficient, because usually only a fraction of the maximum available laser power can be used. A simple increase in the average power at constant focus geometries results in thermal effects, which greatly affect the process quality.

With the “Flexible Beam Shaper” and a USP laser generated QR code pattern on a steel surface (Source: Pulsar Photon.)

With the “Flexible Beam Shaper” and a USP laser generated QR code pattern on a steel surface (Source: Pulsar Photon.)

In addition, new applications require beam distributions that deviate from the classical Gaussian geometry. With currently used machining systems, the realization of these geometries is either not possible or difficult. Only through new and appropriate beam shaping and distribution concepts, the laser power can be fully used and thus the process efficiency can be increased.

With the Flexible Beam Shaper (FBS), Pulsar Photonics has now developed a machine-integrable beam shaping system for laser micromachining, that can generate almost any beam distribution. By combining an electronically controllable optical phase modulator and a classic galvanometer scanner, the intensity distributions can first be flexibly changed and then scanned over the workpiece. This enables novel laser processes. For example, any data matrix codes can be displayed with high process speed by generating 2D dot patterns in the working plane. The data matrix code can be loaded into the self-developed control software which calculates a corresponding phase image by using an adapted computer algorithm. The calculated phase image is then displayed on the phase modulator. If now a laser beam first passes the phase modulator and will be modified in such a way that after focusing on the workpiece, the intensity distribution will have the geometry of the desired data matrix code.

Parallel removal of pockets in steel with a flexible change of the spot distance in the software (Source: Pulsar Photon.)

Parallel removal of pockets in steel with a flexible change of the spot distance in the software (Source: Pulsar Photon.)

In addition to marking applications, the processing system also allows to generate other beam shapes: The phase modulator can also be used for beam splitting or to generate arbitrary beam shapes in the focus area. While the process acceleration by a parallel processing is in the foreground first, new laser processes can be studied with the beam forming of the focus. For example, by generating multiple foci along the optical beam axis it is possible to explore new processes for separating brittle materials. Furthermore, more complex beam distributions like Bessel beams could be generated using spatial light modulator systems, which allow completely new laser processes. This underlines the potential of the technology for the study of new laser processes.

Challenges in the development of Flexible Beam Shaper were mainly the use of the phase modulator at higher average laser power, and the calibration and control of the system. By a modification of the phase modulator display, the maximum laser power limit could be increased significantly. In experiments, a permanent irradiation of the display with up to 60 W average USP laser power could be carried out without a measurable change in the phase calibration of the system.

The goal of Pulsar Photonics with the Flexible Beam Shaper is to provide users and process developers a flexible and versatile tool with which allows them to develop new laser processes. The technology and potential applications of the Flexible Beam Shaper in laser micromachining will be presented by Dr. Stephan Eifel from Pulsar Photonics, in his talk on the LANE 2016 in Fürth.

Links: Pulsar Photonics GmbH, Herzogenrath, Germany“LANE 2016 – 9. International Conference on Photonic Technologies“, 19.-22. September 2016, Fürth, Germany; Bayerisches Laserzentrum GmbH, BLZ

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