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 (<i>f</i>), the input aperture size (<i>D</i>), the target spot size (<i>d</i>), and the number of segments (<i>s</i>). For a design case with <i>D</i>=49.5<i>m</i><i>m</i>, <i>f</i>=350<i>m</i><i>m</i>, <i>d</i>=20<i>m</i><i>m</i>, and <i>s</i>=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 20.39<i>m</i><i>m</i>×1.41<i>m</i><i>m</i> (1/<i>e</i>² 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.