Abstract:
Background In high-power coherent beam combining systems based on segmented-mirror-splitters (SMS), thermal effects arising from parasitic absorption in optical components are a critical factor that limits steady-state combining performance.
Purpose To address the limited understanding of the mechanisms underlying thermally induced performance degradation in high-power two-stage cascaded SMS systems,
Methods we established a 28-channel optical-thermal-mechanical multi-physics coupling model using the finite element method. Numerical simulations were performed to analyze the thermally induced wavefront distortion and the sequential coherent superposition of multiple beams within the zig-zag optical path.
Results The results indicate that the accumulation of laser power along the combining direction leads to a significantly higher thermal load on the second-stage segmented mirror than on the first stage. Consequently, an asymmetric temperature gradient induces substantial beam quality degradation along the combining direction.
Conclusions Furthermore, parametric optimization demonstrates that reducing the substrate thickness can effectively suppress thermal distortion, thereby enhancing combining efficiency and improving beam quality. Meanwhile, although increasing the sub-beam spacing reduces thermal effects and enhances combined power, it simultaneously intensifies the anisotropic beam quality degradation.
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