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Excitonic dephasing is investigated in InAs self-assembled quantum dots fabricated by the strain-compensation technique. The exciton ground-state emission is centered at the wavelength of 1420 nm at 5 K. Transient four-wave mixing measurements under resonant excitation clearly demonstrate a long dephasing time of 1.09 ns at 5 K, corresponding to the homogeneous broadening of 1.2 μeV. The extrapolated zero-temperature homogeneous broadening is limited only by the population lifetime of the exciton ground state. At slightly increased temperatures, the acoustic-phonon broadening becomes dominant on dephasing. [ABSTRACT FROM AUTHOR]

Nb3Ga and Nb3Al superconductors were successfully fabricated by continuous CO2 laser beam irradiation of a moving material. Transition temperatures after the irradiation are 17.0 and 16.5 K, respectively. These temperatures are increased by ∼2 K by the subsequent annealings. Critical current density Jc (for the reacted area) of 3×104 A/cm2 at 15 T and 4.2 K is obtained for Nb3Al tape with small magnetic field dependence up to 23 T. The results indicate that the continuous laser beam irradiation is a very attractive method for fabricating advanced superconductors, such as Nb3Ga, Nb3Al, Nb3(Al,Ge), etc. [ABSTRACT FROM AUTHOR]

AlGaAs/GaAs multiquantum well lasers and GaAs metal-semiconductor field-effect transistors have been monolithically integrated on a semi-insulating GaAs substrate by using molecular beam epitaxy. This integrated laser has exhibited cw operation with the low threshold current of 20 mA at room temperature. The laser/field-effect transistor (FET) characteristics, such as a linear control of laser output power by changing the FET gate voltage, have been confirmed. A conversion ratio of laser output power to FET gate voltage has been measured to be as high as 3.3 mW/V. Rise and fall times of 1 ns have been demonstrated. [ABSTRACT FROM AUTHOR]

Examines the molecular beam epitaxy technique for growing oxides using low-energy and high-density oxygen-ion beams. Simultaneous deposition of copper metal on magnesium oxide(100); Potential of oxygen beams for oxidation; Formation of copper oxide.