Study On Tiling Theory Of Large-area Grating

In Recent years, many optical engineering need large-area grating urgently,such as ICF (Inertial Confinement Fusion) which is significant in solving the worldenergy crisis, whether can get the meter-sized gratings has became the key factor toits success or not. Presently, restricted by technology and high cost, it is difficult tomanufacture large-area grating directly, so it is proposed that large grating can beachieved by grating tiling. Grating tiling can reduce the cost and moreover get highquality grating, which has attracted world-wide attention.In order to get high-performance tiled grating, the alignment errors must bestrictly controlled. The alignment of several small gratings to form a large gratingcan be achieved in comparison with one standard grating, so it is important todiscuss two grating tiling. In this paper, according to the five basic alignment errorsin the process of tiling, based on the scalar diffraction theory, a theoretical modalwhich can reveal the misalignment from far-field pattern distribution is built, theanalytical equation of the far-field intensity is obtained.We numerically analyzed the far-field pattern when different error exists and setup an alignment tolerance criterion which is according to whether the maximumintensity is greater than 0.9. The calculated results indicate that far-field patternsvary with different kinds of error; the far-field pattern presents periodical variationwith the longitudinal and transverse translation errors which can be compensatedwith each other if they satisfy certain condition; the influence of rotating error on theperformance of tiled grating is relatively severe, the far-field pattern will distortwhen the rotating error is greater than 1.7μrad and the maximum intensity willdecrease to 0.9. When both the translational and rotating error exists, the tolerance ofthe alignment error is stricter than only one existing. According to the theoreticalanalysis, we give some advice to monitor and control the alignment error during thetiling process.The results will be helpful for evaluating and controlling the misalignmentsduring the tiling process, which provides reference to grating tiling in the "fastignition".