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Ultrashort Pulsed Laser Processing at 1 Kilowatt Using a Flexible Multi Beam Approach

Periodic Reporting for period 1 - MultiFlex (Ultrashort Pulsed Laser Processing at 1 Kilowatt Using a Flexible Multi Beam Approach)

Reporting period: 2019-01-01 to 2020-06-30

Ultrafast lasers can do something very unique: They ablate material of almost any kind without thermal load of the adjacent material. Their cuts are smooth and melt-free, even on a micron scale. This makes ultrafast lasers very interesting for many industry branches such as tool making, where hard materials must be processed very precisely. Unfortunately, such precise processes take time. Too much time for an efficient use of this technology for many industrial applications.
The MultiFlex project will overcome this obstacle and pave the way for a widespread, cost-effective application of ultrafast lasers in industrial manufacturing.
In the MultiFlex project, a consortium of six partners from industry and research is doing the next step in the development of the ultrafast laser process technology to make materials processing with ultrafast lasers up to a hundred times faster.

The basic idea behind MultiFlex is to setup a high power “USP laser-dot-matrix-printer”, which consists of a newly developed high power ultrashort pulsed laser with an output power of more than 1 kilowatt and a flexible multi beam optics concept.
In MultiFlex a highly stable high power laser with average power of more than 1 kilowatt and a pulse duration below 1 ps will be developed as pulse durations in the femtosecond range enable higher process efficiency, better quality and broader process windows. Special emphasis will be given to flexibility in pulse shaping, power stability as well as pulse modulation capability at high pulse energies.
The optical system converts the single laser beam into a pattern of more than 60 beamlets, where each single beamlet can be turned on and off separately. The resulting pattern can be directed onto the workpiece with a fast scanner. By enabling the flexible switching of the separated single beams and a control system for compensating field distortions, arbitrary surface structures can be generated with highest precision and throughput. The complex system will be accomplished by an industry grade control unit.
The “USP laser-dot-matrix-printer” developed within MultiFlex will be evaluated on several demonstrator parts as well as in two industrial use cases provided by associated industrial partners.
At the beginning of the MultiFlex project the requirements of all core components were defined. The basis of all definitions are the use cases provided by the associated industrial partners.
Based in the demands for fabricating the desired structures the requirements on system components like, machine, laser source and optical system were defined.
Different concepts and configurations to build up an ultrafast laser with more than 1 kW average output power have been investigated. Based on considerations about expectable performance, stability and risk in the development one approach was selected to be realized. The mechanical design up to the 3rd amplifier stage was finalized. Most of the parts have been ordered and the electrical rack is finalized. The amplifier setup was tested and in laboratory already 1.2 kW have been achieved. The flexible laser control option (“Femtotrig”) has been validated for the needed parameter set. A prototype laser with more than 100 W average output power was realized and the Femtotrig option was included.
Regarding the optical system for materials processing, a new design approach was developed.
A setup and alignment routine was prepared and a final design for the prototype optic was realized. The multi-channel modulators as key elements of the processing optics has been designed, manufactured and shipped. Optical components like the DOE, prism arrays and imaging lenses have been purchased and tested.
A basic version of the control system that controls all 64 beamlets in dependence on the galvanometer position has been developed and realized. The necessary hardware was selected, purchased and assembled and a first basic software to control the system is ready for application tests.
The parameters for the process and machine monitoring have been specified, sensors have been selected and a prototype version for the data acquisition system including a software solution was developed.
The design of the machine that integrates all components was finalised. Key components like granite, mechanical axis and housing have been purchased and the assembling has begun. Software adaptions to integrate the components are under development.
The MultiFlex project aims for a completely new dimension in ultrafast laser processing. By efficiently using twenty times higher laser power compared to conventional processes, a 20 times faster control system, an up to 100 times higher productivity will be reached.
With the developed technology opening up a new dimension of multi-beam processing, large area applications get feasible.
Ultrafast laser processing and especially surface structuring has numerous potential fields of application. The focus of MultiFlex is in the field of structuring of tool and molds, but the planned developments can be used for several other ultrafast laser applications as well. The developments of this project help to strengthening industrial manufacturing based on ultrashort pulse lasers and to extend its field of applications.
MultiFlex will deliver an enabling technology for the European industry in the field of mass production of functional and design surfaces in several fields, e.g. Automotive, Lighting, Consumer and Luxury Goods, Lightweight Construction and Filter Systems.
This helps to bring the advantages of ultrafast laser processing to a broader application and helps to replace environmental problematic technologies like chemical etching.
Due to the significant increase new field of applications like surface functionalization of large parts like ship hulls, wings or wind turbine blades get thinkable, helping to increase energy efficiency and reduce CO2 emission.

Up to now a laser source with a new power level for industrial ultrafast lasers has been demonstrated in laboratory. An advanced flexible control system with higher precision and lower jitter has been demonstrated. In the further project the beam source will be finalized and prepared for industrial environments. The control system will be transferred to the high power source and the pulse trains (bursts) will get shaped in their intensity.
The approach of the individually switchable multi-beam optics is completely new. In the further project this approach will be realized in a prototype optics and further extended to be used with 64 beams.
A completely new FPGA-based system to control the single beams in dependence on the current beam position has been developed. The basic version will be extended during the further project to include advanced processing strategies, higher accuracy and better easier usability. A multi-channel AOM as a device to switch multiple beamlets has been developed. To withstand high peak intensities and powers quartz as new material for these devices was used. The device is already finalized and ready for operation.
An FPGA-based system for acquiring sensor data was developed and realized in a basic version. In the future correlating sensor data with processing result using different algorithm will help to understand the processes and keep track on the status of key components of the overall system.
Sketch of the MultiFlex optical system.
Tasks within MultiFlex.
Concept of MultiFlex solution.