The diffraction efficiency of echelle gratings increased by ion-beam polishing of groove surfaces

The efficiency of first-order diffraction on F1 glass echelle gratings for soft X-ray and extreme UV radiation can be significantly increased (by up to ten times) by etching the groove surface with a beam of neutralized Ar ions at 1250-eV energy. The processing was performed at normal incidence of ion beam on the surface of gratings, and the material thickness removed was on a level of 80–300 nm. A principle of optimization of the ion-beam etching process is proposed for solving particular tasks related to the planarization of microstructures with various lateral dimensions.