PHOTOETCHED ECHELLE GRATINGS IN SILICON

ECHELLE DIFFRACTION GRATINGS ARE CRITICAL COMPONENTS IN MANY OF NASA'S SPACE MISSIONS FOR THE PURPOSE OF SPECTRAL ANALYSIS OF LIGHT FROM STELLAR AND ALBEDO SOURCES. FOR EXAMPLE, THE SPACE TELESCOPE IMAGING SPECTROGRAPH (STIS) INCORPORATES SEVERAL ECHELLE SPECTROSCOPIC GRATINGS INTO ITSOPTICAL DESIGN. PHOTOELECTROCHEMICAL ETCHING (PEC) IS A PROCESS FOR PRODUCING DIFFRACTION GRATINGS DIRECTLY INTO SEMICONDUCTING MATERIALS WITH A HIGH DEGREE OF CONTROL OF REACTION RATE, LATERAL UNIFORMITY AND GROOVE ANGLE. SILICON POSSESSES THE CRYSTALLOGRAPHIC PROPERTIES WHICH WOULD ALLOW THE DIRECT FABRICATION BY THE PEC METHOD OF DEEP, LOW PITCH ECHELLE GRATINGS FOR USE IN HIGH ORDERS IN NASA SPECTROSCOPIC INSTRUMENTATION. THE PRODUCTION OF GRATINGS GREATER THAN 3" X 3" IN SIZE IS POSSIBLE, SINCE SI IS AVAILABLE IN BOTH HIGH QUALITY AND LARGE AREA (>6" DIAM). THE PHASE I PROPOSAL ENTAILS THE DEMONSTRATION OF THE FEASIBILITY OF MAKING ECHELLE DIFFRACTION GRATINGS IN SI BY THE PEC METHOD. THE EFFECTS OF PHOTOETCHANT COMPOSITION, EXPOSURE TIMES, LIGHT INTENSITY, MASKING PROCEDURE AND DOPING DENSITY OF THE SI WILL BE EXAMINED. THE ANTICIPATED RESULTS OF THE PHASE I AND II PROGRAMS IS THE PRODUCTION OF PRACTICAL SIZED ECHELLE GRATINGS FOR EVALUATION BY NASA.