The development of photorefractive semiconductor in near infrared region of spectrum and its application to the optical communication

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This project has involved (1) the development of photorefractive semiconductor devices at near infrared of spectrum, (2) the beam cleanup of high intensity broad area laser diodes, and (3) the fabrication of three dimensional wave guides in photorefractive material.(1) We have fabricated InGaAs/GaAs multiple quantum well photorefractive devices that have the sensitivity at the wavelength of around 1mum. After the epitaxial growth of quantum well layrs, the deep level defects are introduced by proton implantation. We can make the samples semi-insulating up to 10^5OMEGAcm by this process. Than we measured the amplitudes of refractive-index and absorption gratings by the two- wave mixing. The coupling gain of about 40cm^<-1> are measured at the wavelength of 930-940nm.(2) In order to improve the beam quality of high-power broad area laser diode, we carried out the injection locking of laser diodes through a double phase conjugator using photorefractive BaTiO_3, which make the beam coupling efficient and adjustment-free. We finally achieved the longitudinal single mode operation of high-power laser diode up to 500mW.The degree of spatial coherence is better than 80%.(3) In order to realize the high-density interconnection, we have investigated 3 dimensional waveguides in photorefractive LiNbO_3, which made of the array of high refractive index dots. I have proved that dot-array successfully guides the wave with low loss. One of the advantage of the dot-array is easy to change the structure of the waveguides.