Multilayer-coated laminar grating with 16% normal-incidence efficiency in the 150-angstrom wavelength region

We characterized a laminar grating with a Mo/Si multilayer coating by using synchrotron radiation and atomic force microscopy. The grating substrate had 2400 grooves/mm, 40-Angstrom groove depth, and 2080-Angstrom groove width. The microroughness of the grating substrate was 5 Angstrom rms. The multilayer coating was optimized to have peak normal-incidence reflectance at a wavelength near 150 Angstrom. For an angle of incidence of 10 degrees the peak grating efficiency was 16.3% in the +1 order and 15.0% in the -1 order. The efficiency in the zero order was lower by a factor of 40 owing to the excellent matching of the groove depth and groove width to the wavelength of the incident radiation. By dividing the grating efficiencies by the measured reflectance of the multilayer coating, we obtained inferred groove efficiencies of 34% and 32% in the +1 and -1 orders, respectively. (C) 1991 Optical Society of America.