Study On Beam Shaper Based On High-power Fiber Lasers

Laser quenching is widely used in industrial processing areas. The lasers with energy distribution of gaussian are often used during quenching processes, which retards the further development of this technology for not obtainting uniform deepth hardened layer. The quality of laser quenching can be improved by using the shaped laser beam in therory. However, a few research results are used in laser quenching experiments for potential applications.In this thesis, a laser beam shaper used in high-power fiber laser quenching system was designed and assembled based on our laboratory conditions. The main aim is to change the distribution of the fiber laser beam from gaussian to approximately flat-top. The main studies include: (1) the even aspheric lens was selected as the lens of beam shaping system based on the geometric optics and energy conservation law. In addition, the initial data (including the thickness of the lens, distance and diameter) were determined. (2) The ZEMAX optical design software was used to simulate the beam shaper. Then the system was optimized according to the merit function to make the energy density of the laser beam homogenize. (3) The assembled shaper was used in the fiber laser quenching experiments to verify the effect of shaping.The results show that the energy distribution of the spot is basically uniform except for a bright ring near the center black spot. When the center black spot is not considered and the laser spot locates near the working distance, the change of the spot size with the working distance is consistent with that of the simulation results. In experiment, the working distance is reduced by a value of 90 mm in comparison with the theoretical value. But the real spot size has increased 1 mm than the theoretical value. Finally, the laser quenching experiments based on the designed shaper can obtaint hardened layer with uniform depth, which demonstrates that the designed shaper has met the design requirements for high-power fiber laser quenching system.