Holographic exposure mosaic technology is a feasible solution to fabricate large-area pulse compression gratings, wherethe mosaic grating method of developing region by region is one of the mosaic approaches. In this method, an exposedarea of the substrate is firstly developed, and then the developed photoresist grating mask is put back into the previousexposure system. The next area grating mask is fabricated by aligning the interference fringes formed by the exposurebeam and the developed real grating. However, since the unequal exposure and inconsistent development, the grooveshapes of grating masks in two areas, including groove depth and duty cycle, will be different. When detecting themosaic grating error, the differences of the groove shapes will cause the dislocation in the -1-order reflected diffractionwavefront at gap of the mosaic grating. It will be superimposed on the phase change caused by the lateral displacementerror, so that the judgement of lateral displacement error will be seriously interfered. To solve this problem, themeasurement method of the 0-order diffraction wavefront under multiple incident angles is proposed to precisely judgethe lateral displacement error in the mosaic grating. In this paper, the grating diffraction analysis program based on therigorous coupled-wave analysis is firstly written, and then the initial phase of 0-order reflected diffraction wavefront ofmosaic grating mask is calculated. Subsequently, the sample is tested by atomic force microscopy and interferometer. Byimporting the measurement data into the searching program, the groove parameters of grating masks are obtained by thelibrary matching method. Then, the lateral displacement error of the mosaic grating is further deduced. Finally, thefeasibility of the proposed judgment method is confirmed by the experiment.
展开▼
