Alignment method for fabricating a parallel flat-field grating used in soft x-ray region

摘要

Parallel flat-field gratings consist of two flat-field gratings lying on one substrate, one for 5-20 nm and the other for 2 -5 nm spectral regions, and thus can be widely used in various fields to record broader spectra in the soft x-ray region. The alignment of two subgratings directly determines the resolving power of parallel flat-field gratings. The theoretical resolving power is evaluated by means of the ray-tracing method and the maximal allowable alignment error is 0.366 degrees. Alignment is based on diffraction patterns and moire fringes and the total alignment error in our experiment is within 0.234 degrees. The results demonstrate that this alignment method is an effective way for fabricating parallel flat-field gratings. (C) 2015 Optical Society of America