Student LIL system for pressurized environment processingThursday (25.06.2020) 14:30 - 14:50 Room 2
Laser processing system will be presented and different approaches are evaluated for processing different materials in pressurized conditions. Elevated pressure environment is used to enable material reactions. The goal is to modify material surface or change conditions so that desired material reaction or modification is implemented. The usefulness of LIL compared to traditional way is 'ordered structures' that can be small. Advantage is also possibility to synthesize numerous kinds of structures by choosing 2,3,4 or more beams as well as by changing polarization.
LIL patterns cover large area with single exposure or with multiple pulses in short time, which is advantage compared to conventional laser processing. In LIL system the pattern is generated depending of the number of beams, incident angle, azimuth angle, and laser beam wavelength. Typically, beam can be divided with beam splitters, Floyd mirror or diffractive optical elements. Floyd configuration is a good and easy solution for two beam configurations, generating lines. However, multiple beams are commonly implemented with the DOE, gratings or beam splitters.
Beam source will also have effect on the result, and source that meets the requirements was developed in the project. The main requirements of this laser were long coherence length, flat-top intensity distribution in the beam profile with low wave-front distortion, pulse energies of 300 mJ / 200 mJ / 100 mJ at 1064nm / 532nm / 355nm respectively and 5-7 ns pulse duration.
Two systems were developed; mirror based system and lens based system. In the mirror based LIL system the beam is divided in four beam with the DOE element, producing 4 beams. These beams are steered with 4 symmetrical beam lines in two mirrors per line, and the last mirror function is to define incident angle. In the second concept, the beams are split similarly with the DOE, but instead of mirrors, lens system is used to produce interference pattern. In this configuration, each beam is in same optical path, which makes it easier to implement and the system is compact. However, as all beam paths are close together, manipulating polarization and laser power for each path individually is harder to implement. Both concepts are feasible, but after careful alignment the results and versatility of the system is better with the mirror based system, as modifying the beam properties is easier and more accurate.
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