WIDEBAND MULTI-CHANNEL ACOUSTO-OPTIC SPECTROMETER FOR RADIO ASTRONOMY APPLICATIONS

WE PROPOSE TO DEVELOP A COMPACT, RUGGED 4-CHANNEL ACOUSTO-OPTIC SPECTROMETER FOR RADIO ASTRONOMY SIGNAL PROCESSING APPLICATIONS. THE SPECTROMETER EMPLOYS A MULTI-CHANNEL BRAGG CELL THAT UTILIZES A SPECIAL ACOUSTIC MODE IN GALLIUM PHOSPHIDE THAT ALLOWS MULTIPLE CHANNELS TO BE FABRICATED ON A SINGLE SUBSTRATE WHILE MAINTAINING AT LEAST 40 DB ISOLATION BETWEEN ADJACENT CHANNELS THROUGHOUT THE OPTICAL APERTURE. THIS NEW CELL USES A SELF-COLLIMATING ACOUSTIC MODE AS WELL AS APODIZED ELECTRODES TO MINIMIZE CHANNEL-TO-CHANNEL CROSSTALK. THE SYSTEM WILL HAVE A BANDWIDTH OF 1 GHZ AND A FREQUENCY RESOLUTION OF 1 MHZ. THE CURRENT DEVELOPMENT OF WIDEBAND ACOUSTO-OPTIC SPECTROMETERS IS LIMITED TO SINGLE-CHANNEL SYSTEMS. IN ADDITION, MULTI-CHANNEL ACOUSTO-OPTIC BRAGG CELLS HAVE HERETOFORE NOT BEEN DESIGNED TO OPERATE AT THESE BANDWIDTHS AND TIME APERTURES WITH 40 DB CHANNEL-TO-CHANNEL ISOLATION ACROSS THE ENTIRE OPTICAL APERATURE. ALSO, LONG TERM STABILITY HAS NOT BEEN AN IMPORTANT PERFORMANCE PARAMETER IN MOST CURRENT SINGLE-CHANNEL SYSTEMS. DURING PHASE I THE MULTI-CHANNEL BRAGG CELL WILL BE DESIGNED WITH RIGOROUS CROSSTALK AND THERMAL MODELING TO ASSURE ADEQUATE PERFORMANCE IN THE SPECTROMETER SYSTEM. OPTICAL AND ELECTRONIC COMPONENTS WILL BE SPECIFIED AND EVALUATED AND AN OPTICAL AND OPTO-MECHANICAL DESIGN COMPLETED WITH ATTENTION TO LONG TERM STABILITY.