HOLOGRAPHIC DIFFRACTION GRATINGS

NEW TECHNIQUES ARE NEEDED IN THE FABRICATION OF HIGH-QUALITYDIFFRACTION GRATINGS OF THE TYPE REQUIRED FOR PLANNED AND ANTICIPATED SPACE ASTRONOMY INSTRUMENTS. GRATINGS WITH THE REQUIRED LOW LEVELS OF SPECTRALLY-SCATTERED LIGHT AND LARGE BLAZE ANGLES ARE NOT CURRENTLY AVAILABLE, AND IT IS DOUBTFULTHAT SUCH GRATINGS CAN BE PRODUCED BY THE TRADITIONAL METHODOF MECHANICAL RULING. A MORE PROMISING APPROACH IS TO USE AHOLOGRAPHIC INTERFERENCE PATTERN TO EXPOSE A PHOTORESIST COATING ON THE GRATING SURFACE. DURING PHASE I, SEVERAL PROMISING HOLOGRAPHIC METHODS ARE INVESTIGATED, INCLUDING: FABRY-PEROT METHODS, DIGITAL INTERFEROGRAM SYNTHESIS, AND SELECTIVE CHEMICAL ETCHING. THE FEASIBILITY OF USING THESE TECHNIQUES ARE ASSESSED BY LABORATORY TESTS OF CRITICAL ASPECTS OF THE FABRICATION TECHNOLOGY.