Thin-film interference effects on the efficiency of a normal-incidence grating in the 100-350-angstrom wavelength region

Thin-film interference effects were observed in the normal-incidence effici ency of a 2400-groove/mm replica grating. The efficiency was measured in th e 100-350-Angstrom wavelength range and had an oscillatory behavior that re sulted from the presence of a thin SiO2, coating. The thicknesses of the Si O2, and the underlying oxidized aluminum layers were inferred from computer modeling of the zero-order efficiency. The efficiencies in the diffracted orders were calculated with the modified integral approach and accounting f or the multilayer coating and the groove profile derived from atomic force microscopy. The calculated and measured efficiencies were in good agreement . (C) 1999 Optical Society of America. OCIS codes: 050.1950, 050.1960, 260. 3160, 260.7200, 310.6860.