Holographically recorded ion-etched variable-line-space gratings

Variable line space (VLS) diffraction gratings present interesting solutions to design high resolution monochromators for synchrotrons. The problem is to be able to record holographically the desired grooves distribution in order to take advantage of the holographic recording and ion etching process: low stray light, absence of ghosts and second order reduction. We will review the method of calculation of VLS diffraction gratings recorded holographically by using spherical and aspherical laser wavefronts. Then the manufacture of these gratings (accuracy of recording and ion etching process) will be described. We will give an example. And finally, the theory and the accuracy of a checking method will be presented.