Research Of Gaussian Beam Shaping

As the laser beam has the characteristic of Gaussian energy distribution, in the field such as laser processing, laser welding and laser medicine, the non-uniform distribution of energy will restrict the application of the laser technology. Therefore, in order to eliminate the negative effects of non-uniform energy distribution, Gaussian beam has to be converted to the flattened beam with uniformly distributed energy. Comparing with all other techniques, aspheric lens shaping is an effective method with the advantages of high energy utilization and high laser-induced damage threshold. So it has significant engineering application value. The traditional method is still a complicated work which needs a lot of calculation. So the research on the method of automatic optimization design which adapt to the software has practical significance to extension the laser beam shaping technology. Furthermore, to research the high-order Gaussian beam can perfect the theory of aspheric lens system.The propagation in the free space of flattened beam will induce the non-nuiform energy distribution because of the diffraction effects. So the research of the propagation of the flattened beam is also a hotspot of laser technology. By researching the propagation principles of the flattened beam, which can utilize the characteristic of the flattened beam effectively, and improve the capacity of laser beam shaping. The familiar physical models that have been used to describe flattened irradiance profiles are super-Gaussian, flattened Gaussian beam, Fermi-Dirac beam, super-Lorentzian beam and Flattened-Lorentzian beam. To choose the appropriate physical model play an important role in researching the beam shaping and the propagation of the flattened beam. While the different physical model must have the intrinsic relationship, to construct the equivalent relation between the different physical model of the flattened beam have the signification to research the propagation of the flattened beam.This thesis focus on the research to the method of Gaussian beam shaping by utilizing the aspherical lens and the propagation of the flattened beams. The major contents are following as:1) On the basic of analyzing the traditional method of fundamental-mode Gaussian beam shaping, the method of of automatic optimization design of Gaussian beam shaping by using the optical software is researched. Based on the law of conservation of energy, the flattened Lorentzian function(FL) is chosen as the distribution of flattened beam. The mapping function of arbitrary ray in incident plane and image plane was deduced. And then, according to the characteristics of this system, Zemax programming language (ZPL) was used to compile ZPL macro orders to optimize the Gaussian beam shaping automatically.2) Extend the application of the aspheric lens laser beam shaping. The beam shaping technology of high-order Hermit-Gaussian beam and Laguerre-Gaussian beam was researched. The flattened-Lorentzian beam and the Fermi-Dirac beam were selected for the distribution of flattened beam respectively. The mapping function was deduced.3) Research the propagation characteristic of the flattened beam and the equivalent relation between the different physical model of the flattened beam. Discuss the affecting factors of the propagation, and improve the capability of the Gaussian beam shaping system. Discuss the equivalent relation of different flattened beam by utilizing the matching profiles and the M2factors.4) Design the experiment system.