MANUFACTURE OF BLAZED ZONE PLATES IN GERMANIUM FOR USE IN THE 10-MU-M SPECTRAL REGION

Blazed zone plates have been manufactured in germanium. A suitable surface relief pattern was first generated by recording in photo-resist the circular fringes transmitted by a Fabry-Perot 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 10-mu-m for zone plates working in transmission and on axis.