EFFICIENCY AND LONG-TERM STABILITY OF A MULTILAYER-COATED, ION-ETCHEDBLAZED HOLOGRAPHIC GRATING IN THE 125-133-ANGSTROM WAVELENGTH REGION

The efficiency of an ion-etched blazed holographic grating was measure d by the use of synchrotron radiation in the 125-133-Angstrom waveleng th range and at near-normal incidence. The grating had a Mo-Si multila yer interference coating that resulted in a peak normal-incidence effi ciency of 13% in the second grating order and at a wavelength of 128 A ngstrom. This is the highest efficiency obtained to date from a multil ayer-coated grating in this wavelength region and at normal incidence. These measurements are compared with similar measurements performed o n the same grating 4.5 years later. Over this time the peak grating ef ficiency decreased from 13% to 8%, and this result is attributed to th e decrease in the reflectance of the multilayer coating from 55% to 42 %. Oxidation and contamination of the multilayer with carbon appear to be the causes of these losses. The groove efficiency of the grating s ubstrate in the second order is 23%. (C) 1995 Optical Society of Ameri ca