HIGH SPEED GAAS/ALGAAS LASER DIODE MODULATOR

KEY REQUIREMENTS REMAIN IN THE DEVELOPMENT OF GALLIUM ARSENIDE (GAAS) MONOLITHIC MICROWAVE INTEGRATED CIRCUITS (MMICS) TO BE USED IN COMMUNICATION SYSTEMS, PARTICULARLY IN THE FREQUENCIES OF THE KA BAND OR HIGHER. SIGNAL DISTRIBUTION FOR CONTROLLING AND FEEDING SIGNALS TO EACH ELEMENT CAN BE QUITE COMPLEX FOR LARGE NUMBERS OF MMIC'S. FIBER OPTICS SHOW A LOT OF PROMISE FOR RELIEVING THE PROBLEMS ASSOCIATED WITH USING STANDARD TECHNIQUES SUCH AS MICROWAVE WAVEGUIDES AND COATEDCABLES. INTEGRATED OPTIC TRAVELING WAVE MODULATORS HAVE BEEN DEVELOP-ED FOR HIGH SPEED LASER DIODE MODULATION BUT HAVE BEEN LIMITED IN MODULATION SPEED DUE TO OPTICAL AND MICROWAVE VELOCITY MISMATCH. THE APPROACH OF AN INDIRECT MODULATION OF LASER DIODES IS BEING USED TO MATCH THE OPTICAL AND MICROWAVE PHASE VELOCITIES IN A GAAS/ALGAAS INTEGRATED OPTIC STRUCTURE. THE TECHNIQUE IS A MODIFIED DIRECTIONAL COUPLER TRAVELING WAVE STRUCTURE THAT MATCHES THE MICROWAVE AND OPTICAL PHASE VELOCITIES SUFFICIENT TO ACHIEVE MODULATION SPEEDS UP TO100 GHZ AND WOULD BE COMPATIBLE WITH MONOLITHIC INTEGRATION. WHEN SUCCESSFUL, COMMERCIAL APPLICATIONS EXIST IN COMPUTING, DATA PROCESSING AND SENSING WHERE HIGH SPEED OPTOELECTRONIC INTERFACES ARE NEEDED, INCLUDING VERY LARGE SCALE INTEGRATED/VERY HIGH SPEED INTEGRATED CIRCUIT BASED SYSTEMS.