Replication of a holographic ion-etched spherical blazed grating for use at extreme-ultraviolet wavelengths: efficiency

摘要

Using synchrotron radiation, we have measured the efficiency at an angle of incidence of 10 deg of a holographic ion-etched spherical blazed grating and three of its fourth-generation replicas. The measured efficiency profile of replicas 1 and 3 prior to multilayer coating oscillated from thin-film interference produced by the replicas' Al/Al_(2)O_(3)/SiO_(2) structure. A Mo_(2)C/Si multilayer coating was applied to the master grating and replicas 1 and 2. After coating, the maximum grating efficiency occurred in the -2nd order and the maximum values were 12.4percent at 143.8 A for the master and 11.6percent at 145.2 A for replicas 1 and 2. On the basis of measurements obtained after coating, the derived groove efficiency was 22.2percent for the master, 19.4percent for replica 1, and 19.3percent for replica 2. The groove efficiency of the uncoated replica 3 was 24.3percent at 142.5 A. We find that the replicas are reasonably faithful copies of the ion-etched master, and models based on measured atomic force microscope groove profiles are in general agreement with measured results. However, subtle issues remain regarding the widths of the peak order profile and the location of its maximum wavelength.