Fabrication of Aberration-corrected Diffraction Grating for Soft X-ray Grating Monochromator

In this work, we present the design and fabrication of an aberration corrected diffraction grating for soft X-ray monochromator. Spherical mirrors, which induce spherical, coma and astigmatic aberration, degrade the performance of a grating monochromator. These aberrations are often corrected by aspherical mirrors. however, aspherical mirrors with high surface accuracy are very difficult to fabricate. We proposed a new diffraction grating, by carefully adjust the positions of grating lines, the wavefront of the diffracted light can be modified and the aberrations can be corrected under certain conditions and the performance of the monochromator can be improved. The aberrations of a typical Czerny-Turner monochromator are discussed in detail and the grating design method is proposed in this work. A lamina type aberration corrected reflective grating for soft X-ray is fabricated using e-beam lithography, and the detailed process is elaborated.