Jun-ichi Hashimoto

Long-Wavelength GaInNAs Vertical-Cavity Surface-Emitting Laser With Buried Tunnel Junction

A long-wavelength GaInNAs vertical-cavity surface-emitting laser with a buried tunnel junction (BTJ) has been demonstrated in this paper. It has been shown that a combination of a GaAs-based BTJ for a current confinement, GaInNAs multi-quantum wells for an active region, a dielectric distributed Bragg reflector (DBR) for a top mirror, and an AlGaAs/GaAs DBR for a bottom mirror is desirable to realize high-speed operation at high temperature. The maximum output power of 4.2 mW with a low resistance of 65 Omega has been obtained at 25degC. Operations of 10 Gb/s have been achieved over the temperature range of 25degC-85degC, with operation current of 6.9 mA and extinction ratio of 5.0 dB.

InP Etching by HI/Xe Inductively Coupled Plasma for Photonic-Crystal Device Fabrication

We investigated the inductively coupled plasma etching of InP-based materials for photonic-crystal (PC) device fabrication. By optimizing bias power and gas pressure, circular holes with a diameter of <0.2 µm, a depth of 2.0 µm and a maximum aspect ratio of 13 were formed with an e-beam resist mask. This technique was applied to the fabrication of PC-slab devices, and a single-point-defect PC laser was demonstrated at room temperature.

Eight-channel wavelength multiplexing with 200-GHz spacing using uncooled coaxial fiber Bragg grating external-cavity semiconductor laser module

As a low-cost light source for wavelength-division-multiplexing networks, the authors develop an uncooled coaxial fiber Bragg grating external-cavity semiconductor laser (FGL). To realize high-wavelength stability, an FGL structure is adopted, and to reduce the cost of light source itself, a coaxial pigtail module structure is selected. High-wavelength stabilities of 2 pm/mA and 12 pm/K against current and ambient temperature variation are realized. Using the FGLs, successive eight-channel wavelength multiplexing with 200-GHz spacing and with almost the same peak power is realized between -30/spl deg/C to 70/spl deg/C. For each channel, the wavelength difference from the corresponding ITU grid is only within /spl plusmn/0.1 nm at 25/spl deg/C.

Surface Treatment by Ar Plasma Irradiation in Electron Cyclotron Resonance Chemical Vapor Deposition

To reduce the surface states of GaAs and related semiconductors which originate from native oxides on a surface, we developed a simple surface treatment method in which the surface oxides could be physically sputtered by Ar plasma irradiation in an electron cyclotron resonance chemical vapor deposition (ECR-CVD) apparatus. In the experiment of Ar irradiation of a GaAs surface, we were able to determine the optimum irradiation time at which the native-oxide-related surface states were almost removed without damaging the irradiated surface. Then, we applied this method to an actual 0.98-µm semiconductor laser in which catastrophic optical damage (COD) failure occurred due to the surface states of the output facet. By irradiating Ar plasma to the output facet of the laser and removing the oxide-related surface states there, tolerance to COD was remarkably improved compared with that of a conventional non-Ar-irradiated one.

Electric Property Control of Carbon Nanotubes by Defects

Effects of local low-energy irradiation on the electric properties of metallic single-walled carbon nanotubes were studied. Defects formed by 20 keV-electron irradiation in an electron beam lithography system converted the room-temperature electric properties to p-type or ambipolar semiconducting. Coulomb oscillation was also observed at room temperature. The results also suggest that electric measurements are inconclusive for distinguishing whether a nanotube is metallic or semiconducting.

Coaxial fiber-Bragg-grating external-cavity semiconductor laser module without temperature control

An uncooled coaxial fiber-Bragg-grating external-cavity semiconductor laser module was fabricated for the first time. A single mode operation without mode-hopping was obtained up to 100 mA and between -30/spl deg/C and 70/spl deg/C. The lasing wavelength dependencies on temperature and current were as small as 11 pm/K and 2 pm/mA, respectively.

GaInNAs Distributed Feedback (DFB) Laser Diode

First successful operation of a buried-ridge-type GaInNAs-DFB laser was realized. Under CW condition, it oscillated with a threshold current of 18 mA at 25degC, and it could oscillate up to 110degC with good I-L linearity and with SMSR > 40 dB.

1.3 um travelling-wave GaInNAs semiconductor optical amplifier

Travelling-wave GaInNAs-SOA was realized for the first time. The peak chip gain of 14dB and 3-dB gain bandwidth of 49 nm were obtained. The Gain dependence of the GaInNAs-SOA on temperature was much smaller than that of the conventional InP-based-SOA.

100°C, 10 Gbps operation of buried tunnel junction GaInNAs VCSELs

10 Gbps operation of BTJ GaInNAs VCSELs is achieved over temperature range of 25degC to 100degC with operation current of 5.6 mA and extinction ratio of 4.2 dB.

GaInNAs DFB Laser with Buried GaAs Grating

We for the first time fabricated a GaInNAs DFB laser having a buried GaAs grating in the center current injection region. A successful DFB laser oscillation with the threshold current of 34 mA was obtained