Phase characterization of multilayer coatings by photoemission measurements

Attosecond science, photolithography, synchrotron, and free electron laser physics are new frontiers research and technological areas, where the properties of the beam play a fundamental role in the light-matter interaction. To fully control the properties of a propagating beam, knowledge and control of the efficiency and phase introduced by the optical components upon reflection is mandatory. In this letter, an original method based on photoemission measurements useful to determine the phase shift upon reflection of extreme ultraviolet multilayer mirrors working in a near Brewster's condition has been developed. The method has been also successfully applied to test two different innovative samples specifically designed and proposed for the FERMI@ELETTRA free electron laser beam transport system.