OPTICAL CHARACTERISTICS INVESTIGATION ON COMPOUND SEMICONDUCTOR NATIVE DEFECTS AND RELATED MATERIALS

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Investigations have been carried out for luminescence as well as optical absorption characteristics of several interesting materials including semi-insulating GaAs, infrared emitting phosphors and Er-doped silica glass fiber.It has been previously demonstrated that the native defects in semi-insulating GaAs can be characterized by recovery characteristics as well as bleaching and absorption characteristics. These kinds of characterizing procedures are being extended for examining two dimensional, spatial distribution characteristics. This research work is being continued.Systematic investigations on rare earth-activated, infrared emitting phosphors have been carried out. It has been shown that Er-activated phosphors having flouride lattices present fairly intense luminescence at 2.6 to 2.8um wavelength region. It has been demonstrated that these phosphors present simple and convenient detecting device for atmospheric water vapor sensor, if combined with GaAs:Si infrared light emitting diode and PbS photoconductive detector. Research activity is still continued for exploring longer wavelength emitting light materials.Examinations have been performed on amplified spontaneous emission characteristics in Er-doped, silica glass fiber. The measurements were carried out by using Ar ion laser as excitation source. It has been fairly established that the wavelength conversion processes from higher levels are not solely nonradiative decay process as previously postulated but considerably due to intermediate radiative decay process.