Surface error modeling of mounted large optics in high power laser system

The surface form of mounted large optics has a very important impact on the laser beam performance in high power laser system. To make the surface form to the minimized distortion and keep with the design specifications is always a difficult challenge in China's SG-III laser system which is made up of thousands meter-sized large optical units and requires to focus all 48 laser beams into nearly 600 μm-diameter spot better than 50 μm (RMS) within a few picoseconds. In this paper, a methodology integrated both 3D finite elements modeling method and nanometer-level precision metrology is proposed to evaluate the surface performance. According to various spatial frequencies, the wavefront characters of large aperture optical component are measured and provided to analyze its mounted surface characters. Assembly and mounting process will be adjusted to meet for the surface wavefront requirements both of with the data both of measured when pre-Alignment and predicted for installation. By a case study of large transport mirror, the proposed approach has shown a good performance on obtaining precise surface features and guiding the optical mounting.