Method for shaping Gaussian laser beam into rectangular beam with uniformly distributed energy, and application of method

The invention provides a method for shaping a Gaussian laser beam into a rectangular beam with uniformly distributed energy by using a polynomial freeform lens system, and application of the method. The method comprises the following steps: S1, according to the law of the conservation of energy, an energy corresponding relation of the Gaussian beam on an input plane and a rectangular light spot with uniformly distributed energy on an output plane is built; S2, the mapping function relation of the beams on the input plane and the output plane is obtained; and S3, a polynomial freeform equation of a lens is selected, based on the mapping function relation of the beams on the input plane and the output plane, optical design software is utilized for optimizing the coefficient of the polynomial freeform equation, and after the Gaussian beam on the input plane passes through the polynomial freeform lens system, the Gaussian beam is shaped into the rectangular light spot with uniformly distributed energy on the output plane. According to the method provided by the invention, a rectangular laser light spot with uniformly distributed energy can be obtained, and meanwhile, the method can be applied to tests and research needing to use the rectangular uniform laser light spot, for example, the research and industrial production of laser pulse shot blasting strengthening and forming which need a square uniform laser light spot.