Research of Ultra-High-Speed Optical Devices Using Multi Dimensional Quantum-Well Structure

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Multidimensional quantum-well structures, such as quantum wire and quantum box, are expected to operate with high speed due to their material properties different from conventional bulk crystals. The main purpose of this research is the development of fabrication technique of multidimensional quantum well structures and the application of these structures to devices for ultra-high capacity optical communication. Results obtained are summarized as follows.Optimal device structures were found theoretically for laser and optical switch/modulator with multidimensional quantum well structures by analyzing the structure dependence of the laser threshold and the insertion loss of optical switch/modulator precisely.Lasing action was obtained for the first time at 77K with pulsed current injection in GaInAs/GaInAsP/InP quantum-wire laser with 10nm-thick 30nm-wide wires fabricated by newly developed nanometer fabrication technology viz. Electron beam lithography for pattern writing, wet chemical etching and OMVPE regrowth for embedding process.GaInAs/GaInAsP/InP multi-quantum-film lasers with wire-like active region, Which were fabricated by two step OMVPE growth and wet chemical etching, operated at room temperature for the first time, An increase in the threshold current density in such lasers was drastically reduced by using a preheating process in hydrogen atmosphere and a thin InP covering layer growth prior to the regrowth of a GaInAsP optical confinement layer.A GaInAsP/InP quantum wire structure was fabricated by using a high vacuum electron-cyclotron-resonance reactive-ion-beam-etching system with very low acceleration voltage. Large refractive index variation (-4%) and low optical absorption under electric field application was observed in this structuure. This result indicates that multidimensional quantum well structures are suitable for high performance optical switches/modulators.