An extreme ultraviolet interferometer suitable to generate dense interference pattern

摘要

It has been designed a new type of interferometer working in extreme ultraviolet (XUV) region and intended for direct imprinting of densest possible (for given wavelength) interference pattern into a substrate. The interferometer belongs to the wave-front division category: each of its two aspheric mirrors reflects approximately one half of incoming laser beam and focuses it into a point image. Both focused beams have to intersect each other, and in the intersection region an interference pattern is generated. The closer the intersection region is to the above-mentioned point images, the smaller the interference field is, but simultaneously the smaller the fringe-pitch is. This paper describes interferometer design (inclusive fringe-pitch calculation, and inclusive design of multilayer reflection coatings for the wavelength 46.9 ran (Ar~(8+) laser) - ensuring equal reflectivity at different reflection angles). The interferometer design is supplemented not only by ray-tracing verification of straight shape of interference fringes in ideal interferometer, but also by modelling of interference pattern of real interferometer with various misalignments as well as with random deformation of mirrors. These data enable to define necessary production as well as alignment tolerances.