FAST OPTICAL SWITCHING AND OPTICAL DATA PROCESSING IN SEMICONDUCTOR PHOTOREFRACTIVE MATERIALS

FAST AND SENSITIVE NONLINEAR OPTICAL MATERIALS ARE THE KEY TO THE SUCCESSFUL IMPLEMENTATION OF OPTICAL SWITCHING AND OPTICAL DATA PROCESSING. NOVEL ARCHITECTURES INVOLVING FOUR-WAVE MIXING AND TWOBEAM COUPLING HAVE BEEN PROPOSED TO CONSTRUCT OPTICAL DATA PROCESSING ELEMENTS. FOR PRACTICAL APPLICATIONS, HOWEVER, MATERIALS SHOULD HAVE A REASONABLY FAST RESPONSE TIME, BUT AT THE SAME TIME SHOULD HAVE THE CAPABILITY OF EXHIBITING RELATIVELY LARGE NONLINEAR INDEX OF REFRACTION WITH DIODE LASER SOURCES. SEMICONDUCTOR PHOTOREFRACTIVE MATERIALS HAVE BEEN SHOWN TO HAVE RESPONSE TIME IN THE MICROSECOND REGIME FOR INTENSITY LEVELS OF WATTS/CM(2). MAINLY GAAS AND INP HAVE BEEN INVESTIGATED. THE TECHNICAL OBJECTIVES OF THIS PROPOSAL CALL FOR A DETAILED SURVEY OF SEMICONDUCTOR PHOTOREFRACTIVE MATERIALS TO IDENTIFY THE MATERIAL WITH OPTIMUM PROPERTIES. ONCE THE MATERIAL HAS BEEN IDENTIFIED, THEORETICAL PREDICTION OF ITS PERFORMANCE IN FOUR-WAVE MIXING AND TWO-BEAM COUPLING EXPERIMENTS WILL BE UNDERTAKEN UNDER DIFFERENT EXPERIMENTAL CONDITIONS. DARK AND PHOTOCONDUCTIVITY MEASUREMENTS WILL BE PERFORMED TO CONFIRM THE RESPONSE TIME AND TO EVALUATE THE SENSITIVITY OF THE MATERIAL AT LOW INCIDENT POWER LEVELS. ON THE BASIS OF THE INFORMATION OBTAINED FROM THE CALCULATIONS AND THE EXPERIMENTS PERFORMED APPROPRIATE DEVICE CONFIGURATIONS WILL BE SUGGESTED.