Diffraction limited, EUV interference microscope with long working distance, using one spherical off-axis mirror and a Fresnel bimirror interferometer

Abstract
In some applications, microimaging in EUV requires a long working distance, i.e. a long distance between the object plane and the first optical surface. This is in particular the case when imaging hot plasmas, such as those produced by high energy pulsed lasers focused onto solid targets for X-ray laser production or plasma fusion studies. In this context, a working distance of several 10's cm is required, which makes even the usual Schwarzschild configurations not convenient. Other major requirements are a high resolution and phase detection capability, in order to allow a direct detection of the plasma density. The field should be millimetric. A System was build for diffraction limited (resolution 1  m) interferometric imaging at  nm, using an X-ray laser source. This System was first tested on a synchrotron beamline (LURE, Orsay). Also, the imaging part was used to obtain high resolution images of the lasing emission provided by a Ni-like, picosecond Ag plasma, at  nm. Such a System might be useful in other applications, e.g. phase-sensitive micro-inspection of reflecting surfaces in the field of EUV lithography.