Broadband multilayer-coated normal incidence blazed grating with approximately 10% diffraction efficiency through the 13-16 nm wavelength region.

Diffraction gratings used in extreme UV are typically coated with periodic multilayer thin films. These coatings have a small bandwidth, thus leading to a narrow usable spectral region of multilayer gratings. Well-designed aperiodic multilayer coatings could provide high reflectivity over a much broader wavelength region, so they could broaden the usable spectral region of multilayer gratings. We designed and deposited an aperiodic Mo/Si multilayer coating onto a blazed grating substrate. At an incidence angle of 10 degrees, the -2nd-order diffraction efficiency of the multilayer grating is approximately 10% through the wavelength range of 13-16 nm.