Alternate Multilayer Gratings with Enhanced Diffraction Efficiency in the 500–5000 eV Energy Domain

An alternate multilayer (AML) grating is a 2 dimensional diffraction structure formed on an optical surface, having a 0.5 duty cycle in the in‐plane and in the in‐depth direction. It can be made by covering a shallow depth laminar grating with a multilayer stack. We show here that their 2D structure confer AML gratings a high angular and energetic selectivity and therefore enhanced diffraction properties, when used in grazing incidence. In the tender X‐ray range (500eV – 5000 eV) they behave much like blazed gratings. Over 15% efficiency has been measured on a 1200 lines/mm Mo/Si AML grating in the 1.2 – 1.5 keV energy range. Computer simulations show that selected multilayer materials such as Cr/C should allow diffraction efficiency over 50% at photon energies over 3 keV.