Hirofumi Shimomura

Growth of AlPSb and GaPSb on InP by gas-source molecular beam epitaxy

We have studied the growth conditions of AlPSb and GaPSb lattice match to InP substrates using gas-source molecular beam epitaxy. Mirror-like surface morphology was obtained under the lattice matching growth conditions. It was found that the solid compositions of AlPSb and GaPSb were sensitive to the relative flux ratio of the two group V elements (P,Sb) and to the growth temperature, respectively. The electrical properties of Be-doped and Si-doped GaPSb were characterized by Hall measurements at room temperature. In Si-doped GaPSb, electron concentration seems to saturate at 5 × 1017cm−3. For optical properties, the ellipsometically measured refractive indices at 1.55 μm were 3.037 for AlPSb and 3.579 for GaPSb showed larger refractive index difference than the InGaAsP (Eg = 1.45 μm)InP system. 20 paris of AlPSbGaPSb DBR reflectivity measurements demonstrate a stop-band width of 206 nm with the maximum reflectivity exceeding 99%. This result will promise to be useful for long-wavelength surface emitting lasers.

Network resource advantages of bidirectional wavelength-path switched ring

Wavelength-division-multiplexing (WDM) transport ring-network architectures analogous to conventional time-division multiplexing systems are disadvantageous in that they require either an increase in the necessary number of wavelengths, or long optical-transmission brought about by loop-back, thus raising costs. We have studied a transport WDM ring network in which the switching unit is wavelength and the standby resources are shared. Its advantages are confirmed by evaluation of the necessary number of wavelengths, the maximum circumference for a transparent ring, and the number of 3R-regenerators (3R: reshaping, regeneration, and retiming) for a large-sized opaque ring network.

Wavelength-division add/drop multiplexer using a single wavelength-filter and back-reflector switches

Summary form only given. The increase of the channels in wavelength-division multiplexing (WDM) in optical systems will make possible reconfigurable and transparent WDM networks, such as ring networks with wavelength-division add-drop multiplexer (WD-ADM). The most crucial issue for the WD-ADM system is the limitation of the cascaded-node count caused by passband-frequency misalignment of wavelength multiplexers/demultiplexers. For example, cascadability performance of an arrayed waveguide grating (AWG) spaced at 100-GHz interval is practically limited to several spans. In this paper, we propose a novel WD-ADM configuration using a single AWG and back-reflecting-type Er/sup 3+/-doped fiber amplifier (EDFA) gate switches, which improves the allowable cascaded-node count. The feasibility of the proposed WD-ADM configuration has been confirmed through experiments, and the cascadability of nodes has been estimated.

Growth studies on AlPSb, GaPSb new ternary III-V compounds for InP-based surface emitting lasers

The present paper describes studies of the growth of the AlPSb/GaPSb material system using gas source molecular beam epitaxy (GSMBE). The most remarkable feature revealed in this study is that alloy compositions strongly depend on group V supply ratio and growth temperature. We also investigated the optical and electrical properties of GaPSb. 20 pairs of AlPSb/GaPSb DBR reflectivity measurement demonstrates a stop-band width of 206 nn with maximum reflectivity exceeding 99% at approximately 1.66 /spl mu/m. We demonstrated that an AlPSb/GaPSb system has a large index difference, which is useful for Bragg reflectors in InP based VCSELs emitting near 1.55 /spl mu/m. The alloy composition of AlPSb is sensitive to the group V supply ratio, and that of GaPSb is sensitive to growth temperature. Precise control of growth conditions is therefore necessary with this material system. A highly reflective DBR was obtained in this growth study, its reflectivity near 1.6 /spl mu/m exceeded 99%. The possibility of doping control in GaPSb layers was also demonstrated. This thin DBR structure will be of great help in creating a low-threshold VCSEL for use at long wavelengths.