Kuninori Otsubo

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China is a developing country with a vast areas affected by desertification. Especially in northern China, sandy desert has been spreading rapidly over a vast surface. From the end of the 1950s to the middle of the 1970s about 39 000 km of sandy land suffered from desertification at a speed of 1560 km /year. The phenomenon then increased by 25 200 km from(More)
This paper presents the lasing properties and their temperature dependence for 1.3-/spl mu/m semiconductor lasers involving self-assembled InGaAs-GaAs quantum dots as the active region. High-density 1.3-/spl mu/m emission dots were successfully grown by the combination of low-rate growth and InGaAs-layer overgrowth using molecular beam epitaxy. 1.3-/spl(More)
1.3-µm-wavelength AlGaInAs distributed reflector lasers were investigated for uncooled high-speed direct modulation. 40-Gbps modulation under low driving current of 50 mA up to 50°C and 40-Gbps eye opening at 85°C are demonstrated.
The novel technique for completely transparent wavelength conversion using replicas by dual pump nearly-degenerated FWM in a Mach-Zehnder interferometer SOA has enabled 16-nm conversion of a 10-Gb/s signal with high efficiency of -6.0 dB.
This paper describes 1.3-mum AlGaInAs multiple-quantum-well semi-insulating buried-heterostructure distributed-feedback lasers for high-speed direct modulation. Combination of large differential gain AlGaInAs quantum wells and semi-insulating buried-heterostructure for reduction of active region achieved 25 and 40 Gb/s direct modulation with the device(More)
We demonstrate the first 1.3-/spl mu/m continuous-wave (CW) lasing at room temperature of self-assembled InGaAs-GaAs quantum dots. High-density 1.3-/spl mu/m emission dots were successfully formed by the combination of low-rate growth and InGaAs-layer overgrowth methods of molecular beam epitaxy. The 1.3-/spl mu/m ground-level CW lasing occurred at up to(More)
This paper reports recent developments of our self-assembled InGaAs quantum-dot (QD) lasers and their unique physical properties. We achieved a low-threshold current of 5.4 mA at room temperature with our originally designed columnar-shaped QD's, and also, room-temperature 1.3-/spl mu/m continuous-wave (CW) lasing with self-assembled dots grown at a(More)
1.3-μm semi-insulating buried-heterostructure AlGaInAs-MQW distributed reflector lasers have shown very high slope value of relaxation oscillation frequency of 4.0 GHz/mA½. 25- and 40-Gb/s direct modulation has been achieved with low driving current.
Long-wavelength InGaAs-InAlGaAs strained quantum-well lasers have been fabricated on In/sub 0.22/Ga/sub 0.78/As ternary substrates grown by the Bridgman method. The threshold current density and lasing wavelength at 20/spl deg/C are 245 A/cm/sup 2/ and 1.226 /spl mu/m, respectively. The device has lased up to 210/spl deg/C, which is the highest operating(More)
High relaxation oscillation frequency of 20.5 GHz and its slope of 3.2 GHz/mA<sup>1/2</sup> were obtained by SI-BH 1.3-mum AlGaInAs MQW DFB lasers. Eye-opening up to 50degC was demonstrated as a result of 40-Gb/s direct modulation.