Design, simulation, and experimental validation of a segmented beam-shaping integrator mirror

Achieving uniform intensity distribution is essential for various laser applications such as material processing. This paper presents the design, simulation, and experimental validation of a segmented beam-shaping integrator mirror aimed at transforming an incident laser beam into a uniform line-shaped spot. The mirror surface is composed of multiple connected parabolic segments. A geometric optics computational method, implemented using Python code, was developed to determine the unique parameters and boundaries for each segment, based on input specifications including the working distance (f), the input aperture size (D), the target spot size (d), and the number of segments (s). For a design case with D=49.5mm, f=350mm, d=20mm, and s=7, the segment parameters were calculated. The calculated design was modeled in SolidWorks, and its performance was simulated using Zemax ray tracing, predicting a shaped spot closely matching the 20 mm target size in the segmented direction and an expected size (approx. 1.4 mm) in the orthogonal direction. Experimental validation was conducted using a 4 kW fiber laser equipped with a fiber core diameter of 400 µm and a numerical aperture of 0.15, along with a collimating lens with a 100 mm focal length. The measured spot size at the target plane was 20.39mm×1.41mm (1/e² width), showing excellent agreement with both the design specification and the simulation results. This work successfully demonstrates the effectiveness of the integrator mirror design method and fabrication process for creating high-performance beam-shaping integrator optics for high-power laser systems.