Beam shaping of ultrashort laser pulses by means of acousto-optic deflection and refraction

• Applicant: Professor Dr.-Ing. Michael Schmidt
• Subject Area: Production Automation and Assembly Technology
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278658739

Ultrashort pulsed lasers with repetition rates of several MHz and an average power of more than 50 W are commercially available. In theory such lasers do allow for microstructuring at increased ablation rates. However in current practice, the beam guiding and shaping technology provoke severe limitations. Concurrent machinery, for example, does not allow the user to efficiently use the available pulse energy or repetition rate in the micro production technology.Primary objective of the project is to found the basis of a new generation of novel beam guiding and shaping methods of ultrashort laser pulses by the use of acoustooptical deflection and refraction technologies, experimental analysis and theoretical advances. Particularily, we seek to significantly reduce limitations in microstructuring caused by concurrent beam guiding and beam shaping systems.Our preliminary research shows, that fast and cylinder lens free beam guiding and basic beam shaping is possible by synchronizing the control signal of the acoustooptical deflector with the emission of the ultrashort laser pulse. Our findings strongly indicate, that the primary objective of the project can be achieved by developing control signals, which allow for beam guiding, beam shaping and beam splitting using diffractive mode of operation. With such methods fractions of a beam can be guided and shaped independently from other fractions of the same beam while beam shape and beam splitting are alterable from one laser pulse to the next one. Furthermore we intend to develop control signals that can be used to allow acoustooptic deflectors to operate by refraction instead of diffraction. Then, diffractive power losses due to diffraction can be prevented.To achieve the aim of this research proposal analytical models need to be developed and an experimental setup has to be planned, realized and characterized. To demonstrate the effectiveness of the new methods we also intend to carry out experiments in microstructuring. Prototypical implementation and application is forseen to identify and solve practical challenges of transferring the novel technology to the application. By practical demonstration we intend to make the high degree of innovation concrete, obvious and striking. In microstructuring, geometric structures may be produced using less pulses and higher repetition rates enforcing desirable ablation rates that are far higher than those possible today.

• DFG Programme: Research Grants