Kiyohisa Hiramoto

Protonic Conduction in the Single Crystals of SrZr0.95M0.05O3 (M=Y,Sc,Yb,Er).

The protonic conductivities of SrZr0.95M0.05O3 doped with four acceptor ions (M3+=Y3+, Sc3+, Yb3+, Er3+) have been studied in the single crystal form. The protonic conductivity is found in four acceptor ions, indicating that protons migrate by hopping from site to site. The Yb-doped crystal has the lowest activation energy and the highest conductivity amongst the four acceptor ions. This is considered to be due to the difference in strength of the O–H bond with different acceptor doping.

Protonic Conduction in the Single Crystal of Sc-Doped SrZrO3

The protonic conduction of Sc-doped SrZrO3 (SrZr1-xScxO3) in the single crystal form is investigated. The SrZr1-xScxO3 crystals exhibit significantly higher conductivity than the pure ones, and the crystal with x=0.05 exhibits the highest conductivity of those masured. The activation energy of the SrZr1-xScxO3 crystal decreases rapidly with increasing Sc3+ concentration when x≤0.05, and increases when x>0.05. The activation energy of SrZr0.95Sc0.05O3 agrees with the energy separation between hole states at the top of the valence band and the Fermi level.

Highly reliable and stable-lateral-mode operation of high-power 0.98-/spl mu/m InGaAs-InGaAsP lasers with an exponential-shaped flared stripe

A 0.98-/spl mu/m InGaAs-InGaAsP-GaAs strained quantum-well (QW) laser with an exponential-shaped flared stripe is proposed for high-power, highly reliable operation. The stripe width is wider at the front facet to reduce the optical density by widening the spot size. The stripe width is narrower at the rear facet for stable lateral-mode operation. The stripe width in the transient region is varied exponentially along the cavity for smooth mode transformation. We showed that this structure expands the spot size effectively without any deterioration in stable lateral-mode operation. The kink-occurrence output power is determined only by the stripe width at the rear facet, and the spot size at the front facet is a function only of the stripe width at the front facet. The maximum output power is 40-60% higher than that of ordinary straight-stripe lasers for the same kink-occurrence output power. Testing at 150 mW showed stable operation with an estimated lifetime of more than 200000 h at 25/spl deg/C.

Protonic Conduction in the Single Crystal of SrTi1-xScxO3

The proton conduction of Sc-doped SrTiO3 (SrTi1-xScxO3) has been studied in the single crystal form. The SrTi1-xScxO3 crystals exhibit significantly higher conductivities than the pure ones, and the crystal with x=0.02 exhibits sufficiently higher conductivity than any other. The activation energy of SrTi1-xScxO3 crystals decreases rapidly with increasing Sc3+ concentration at x≤0.02, then increases slightly when x≥0.02. These results indicate that the protonic conduction of SrTi1-xScxO3 depends on the Sc3+ dopant concentration.

High-Reflectivity InGaP/GaAs Multilayer Reflector Grown by MOCVD for Highly Reliable 0.98-μm Vertical-Cavity Surface-Emitting Lasers

We report an InGaP/GaAs multilayer grown by low-pressure MOCVD for highly reliable 0.98-µ m InGaAs vertical-cavity surface-emitting lasers. High reflectivity of over 99% is obtained for the 45-period multilayer. The stability of the layer thickness over the entire multilayer is discussed from the viewpoint of the asymmetrical reflectivity spectrum. Our results indicate that the layer thickness slightly decreases during epitaxial growth.

Strain-Compensation Effect on the Reduction of Lattice Distortion in InGaAs/(In)GaAs(P) Strained Quantum-well Structures on GaAs Substrates

InGaAs/InGaAsP strained quantum-well (QW) structures grown by metal-organic vapor phase epitaxy on (001) GaAs substrates were investigated using photoluminescence measurement and transmission electron microscopy. The lattice distortion in and near the QW structures caused by compressive strain in the InGaAs wells was reduced far below that of ordinary InGaAs/GaAs QW structures and the maximum number of QWs without cross-hatched patterns on the samples can be increased when tensile-strain InGaAsP barriers were introduced.

Demonstration of world-first 103 Gbit/s transmission over 40 km single mode fiber by 1310 nm LAN-WDM optical transceiver for 100GbE

4 ch × 25.8 Gbit/s WDM transmission over 40 km single mode fiber was demonstrated. Minimum receiver sensitivity each lane after 40 km transmission was less than −26.0 dBm, proving the transceiver will meet IEEE 100GBASE-ER4 specifications.

Lasing operation of InGaAsP-Based InGaAs/GaAs vertical-cavity surface-emitting lasers with a strain-compensated active region

We demonstrate the first lasing operation of InGaAsP-based 0.98-µm-range vertical-cavity surface-emitting lasers (VCSELs). The laser consists of a high reflectivity 45.5-pair InGaP/GaAs multilayer reflector, a strain-compensated InGaAs/InGaAsP triple-quantum-well active region, and a 10-pair SiO2/ TiO2 multilayer reflector. The 11-µm-diameter VCSEL exhibited a threshold current of 1.7 mA and a low threshold voltage of 1.6 V under pulsed operation at room temperature. Continuous-wave operation was also obtained with a threshold current of 2.8 mA.