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

本计画包括（1）近红外光谱之光折变半导体元件之发展，（2）高强度宽面积雷射二极体之光束净化，及（3）光折变材料之三维光波导之制作。(1)我们已经制作了InGaAs/GaAs多量子阱光折变器件，在1 μ m左右的波长具有灵敏度。量子阱层外延生长后，通过质子注入引入深能级缺陷。我们可以通过这个过程使样品半绝缘高达10^5 OMEGAcm。然后利用二波混频测量了折射率光栅和吸收光栅的振幅。在<-1>930- 940 nm波长范围内测得耦合增益约为40 cm ↑ [2]。(2)为了提高大功率宽面阵半导体激光器的光束质量，利用光折变BaTiO_3双相位共轭器实现了半导体激光器的注入锁定，使光束耦合效率高，无需调节。最终实现了500 mW以上大功率半导体激光器的纵向单模运转，空间相干度优于80%。(3)为了实现高密度互连，我们研究了由高折射率点阵列构成的光折变LiNbO_3中的三维波导。我已经证明，点阵成功地引导波与低损耗。点阵列波导的优点之一是易于改变波导的结构。

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.