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We experimentally study data suppression characteristics of a semiconductor optical amplifier with a Faraday rotator mirror used for wavelength-reuse WDM-PON. Bidirectional transmission over 10 km assisted by spectral trimming using a Fabry-Perot etalon is demonstrated.

The available data rate of wavelength reuse WDM-PON using gain saturation of semiconductor optical amplifier can be enhanced by spectral trimming through a Fabry-Perot etalon. Experiments on 10-Gbps bidirectional transmission reveal the condition on downstream signals required for system realization.

Red fluorescent molecules suffer from large, non-radiative internal conversion rates (k(IC)) governed by the energy gap law. To design efficient red thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs), a large fluorescence rate (k(F)) as well as a small energy difference between the lowest singlet and triplet excited states (ΔE(ST)) is necessary. Herein, we demonstrated that increasing the distance between donor (D) and acceptor (A) in intramolecular-charge-transfer molecules is a promising strategy for simultaneously achieving small ΔE(ST) and large k(F). Four D-Ph-A-Ph-D-type molecules with an anthraquinone acceptor, phenyl (Ph) bridge, and various donors were designed, synthesized, and compared with corresponding D-A-D-type molecules. Yellow to red TADF was observed from all of them. The k(F) and ΔE(ST) values determined from the measurements of quantum yield and lifetime of the fluorescence and TADF components are in good agreement with those predicted by corrected time-dependent density functional theory and are approximatively proportional to the square of the cosine of the theoretical twisting angles between each subunit. However, the introduction of a Ph-bridge was found to enhance k(F) without increasing ΔE(ST). Molecular simulation revealed a twisting and stretching motion of the N-C bond in the D-A-type molecules, which is thought to lower ΔE(ST) and k(F) but raise k(IC), that was experimentally confirmed in both solution and doped film. OLEDs containing D-Ph-A-Ph-D-type molecules with diphenylamine and bis(4-biphenyl)amine donors demonstrated maximum external quantum efficiencies of 12.5% and 9.0% with emission peaks at 624 and 637 nm, respectively.

著者人数: 59名, Accepted: 2014-08-26, 資料番号: SA1005030000

Organic light-emitting diodes (OLEDs) are attractive for next-generation displays and lighting applications because of their potential for high electroluminescence (EL) efficiency, flexibility and low-cost manufacture. Although phosphorescent emitters containing rare metals such as iridium or platinum produce devices with high EL efficiency, these metals are expensive and their blue emission remains unreliable for practical applications. Recently, a new route to high EL efficiency using materials that emit through thermally activated delayed fluorescence (TADF) was demonstrated. However, it is unclear whether devices that emit through TADF, which originates from the contributions of triplet excitons, are reliable. Here we demonstrate highly efficient, stable OLEDs that emit via TADF by controlling the position of the carrier recombination zone, resulting in projected lifetimes comparable to those of tris(2-phenylpyridinato)iridium(III)-based reference OLEDs. Our results indicate that TADF is intrinsically stable under electrical excitation and optimization of the surrounding materials will enhance device reliability.

A new blood flow measurement system using Laser Speckle Flowgraphy was developed to measure the blood flow easily. The measurement system loads a small display unit to view the results of the measurements without PC. In addition, the system consists of a microcontroller, line sensor, laser unit. We integrated these devices into the system so that the system was miniaturized. We made an experiment of measuring blood flow value by the system.

Trench-filling technology realizes an outstanding productivity for fabricating the Super Junction (SJ) structure of SJ-MOSFETs. However, crystal defects that occur during epitaxial growth are causing poor electrical characteristics. Our optimized process reduced the number of crystal defects from over 2000/mm2 to under 10/mm2. As a result, we have achieved both low loss and low leakage current and high ruggedness for the first time with the SJ-MOSFET fabricated by the trench filling epitaxial growth technique. The drain leakage current decreased from tens of micro amperes to tens of nano amperes. The improved SJ-MOSFET has achieved an avalanche current of 35 A, a specific on-resistance (RonA) of 13.5 mΩcm2, an output capacitance stored energy (Eoss) of 10.3 μJ, and a diode commutation speed (di/dt) of over 2000 A/μs, respectively.

Organic light-emitting diodes (OLEDs) are attractive for next-generation displays and lighting applications because of their potential for high electroluminescence (EL) efficiency, flexibility and low-cost manufacture. Although phosphorescent emitters containing rare metals such as iridium or platinum produce devices with high EL efficiency, these metals are expensive and their blue emission remains unreliable for practical applications. Recently, a new route to high EL efficiency using materials that emit through thermally activated delayed fluorescence (TADF) was demonstrated. However, it is unclear whether devices that emit through TADF, which originates from the contributions of triplet excitons, are reliable. Here we demonstrate highly efficient, stable OLEDs that emit via TADF by controlling the position of the carrier recombination zone, resulting in projected lifetimes comparable to those of tris(2-phenylpyridinato)iridium(III)-based reference OLEDs. Our results indicate that TADF is intrinsically stable under electrical excitation and optimization of the surrounding materials will enhance device reliability.

The three-dimensional structure of a complex of soybean beta-amylase [EC 3.2.1.2] with an inhibitor, alpha-cyclodextrin, has been determined at 3.0 A resolution by X-ray diffraction analysis. Preliminary chain tracing showed that the enzyme folded into large and small domains. The large domain has a (beta alpha)8 super-secondary structure, while the smaller one is formed from two long loops extending from the beta 3 and beta 4 strands of the (beta alpha)8 structure. The interface of the two domains together with shorter loops from the (beta alpha)8 structure form a deep cleft, in which alpha-cyclodextrin binds slightly away from the center. Two maltose molecules also bind in the cleft. One shares a binding site with alpha-cyclodextrin and the other is situated more deeply in the cleft.

The structure of soybean β-amylase has been determined by X-ray crystallography by using multiple isomorphous replacement technique. The low resolution analysis at 6 A revealed that the enzyme is composed of a large and a small domain. The difference Fourier synthesis for the enzyme-a-cyclodextrin complex and the enzyme-maltose complex showed that the substrate analogs bind to a deep cleft between the two domains. One maltose molecule is supposed to occupy the binding site of nonreducing ends of the substrate (subsite 1). The higher resolution analysis at 3 A of the enzyme-a-cyclodextrin complex clearly showsthat the large domain contains a (αβ)8 supersecondary structure. The chain following shows that the smaller domain is inserted in the loop region after β4. The structure of β-amylase is quite different from that of β-amylases except for the (αβ)8 barrel structure. The chain following also shows that the two SH groups, Cys95 and Cys343, are located in the edges of the active cleft. Cys95 is near the maltose specific binding site and Cys343 is near the α-cyclodextrin binding site. These two SH groups were demonstrated to be responsible for the inactivation of the enzyme by chemical modification.

A Super Junction (SJ) MOSFET with high aspect ratio p/n columns structure has been proposed to improve the trade-off relationship between breakdown voltage and specific on-resistance (Ron)- We have proposed a new trench filling epitaxial growth technique to fabricate this structure. In this work, we tried to apply this method to 600 V-class SJ-MOSFETs. We succeeded in fabricating p/n columns structure of which the aspect ratio is 25. It shows that its Ron is lower than that of IGBTs, and is the lowest in the reported 600 V-class Si devices.

A super junction (SJ) MOSFET which trench gates are orthogonal to p/n columns was fabricated to improve a tradeoff relationship between specific on-resistance (Ron) and gate-drain charge (Qgd). In this structure, a trench gate pitch and a p/n column pitch can be independently controlled. We experimentally demonstrated a dependence of Ron and Qgd on the orthogonal gate pitch. The experimental value of Ron*Qgd decreased with the increase of gate pitch, and this value of 0.16 OmeganC was achieved at the trench gate pitch of 10 mum and the p/n column pitch of 2.7 mum. This figure-of- merits (FOMs) value is about 36% lower than that of the previous reported for 200V SJ-MOSFETs. Moreover, the undamped inductive switching (UIS) endurance of this SJ- MOSFET was 24 mJ/mm2 and this result is 1.3 times stronger than that of conventional trench MOSFET.

In this paper, a new filling process using an anisotropic epitaxial growth was proposed as the fabrication method of a super junction (SJ) MOSFET. The anisotropic growth controlled with silicon (Si) and chlorine (Cl) source gases was applied to filling of the high-aspect-ratio trenches without voids. Using the process we succeeded in filling trenches with aspect ratio of 18, which is the highest aspect ratio works previously reported, and we fabricated a 200V SJ-MOSFET with a 2.7mum pitch trench gate structure. Consequently, the MOSFET showed electrical characteristics of the lowest on-resistance of 1.5 m-ohm-cm 2 and a breakdown voltage of 225V

A steady state of a binary mixture of hard‐sphere gases in the near continuum regime, where the Knudsen number is small, is considered in the case where the density and temperature variations are large, but the Mach number of the flow is as small as the Knudsen number. Thus, the flow vanishes in the continuum limit where the Knudsen number goes to zero. The set of fluid‐dynamic‐type equations in this case was derived by Takata and Aoki [Transp. Theor. Stat. Phys. 30, 205 (2001)] by means of a systematic asymptotic analysis of the Boltzmann equation. This set gives the correct behavior of the mixture in the continuum limit, i.e., it describes the ghost effect discovered by Sone et al. for a single‐component gas [Phys. Fluids 8, 628 (1996)]. The set contains various transport coefficients that depend on the local properties of the gas. In particular, their dependence on the local concentration of one of the components cannot be obtained explicitly. In this paper, this unknown dependence is established numerically by a direct numerical analysis of the basic integral equations, and a database that provides the numerical values of the transport coefficients immediately for an arbitrarily specified local state of the mixture is constructed. The database makes the fluid‐dynamic‐type equations applicable to practical problems.