Manufacture of blazed zone plates in germanium for use in the 10 micrometer spectral region

Abstract

Blazed zone plates have been manufactured in germanium. A suitable surface relief pattern was first generated by recording in photoresist the circular fringes transmitted by a Fabry-Pérot interferometer. By scanning the fringe pattern and recording a series of exposures, we were able to generate a triangular groove profile. This was then transferred to the germanium substrate by ion-beam etching. By this means, diffraction efficiencies in excess of 80% have been achieved at 10μm for zone plates working in transmission and on axis.