Control scheme for optimizing the interferometer phase bias in a symmetric-Mach-Zehnder-type all-optical switch

A control scheme for accurately optimizing (and also automatically stabilizing) the interferometer phase bias of symmetric-Mach-Zehnder (SMZ)-type ultrafast all-optical switches is proposed. In this control scheme, weak continuous-wave light is used as supervisory input light and its spectral power ratio at the switch output is used as a bipolar error signal. Our experimental results for 168-Gb/s 16:1 demultiplexing with a hybrid-integrated SMZ switch indicate the feasibility and the sensitivity of this control scheme.     

A low-impedance open-bitline array for multigigabit DRAM

The noise-generating mechanisms inherent in the open-bitline DRAM array using the 6F² (F: feature size) memory cells and techniques for reducing the noise are described. The sources of differential noise coupled to the paired bitlines laid out in two arrays are the p-well, cell plate, and the group of nonselected wordlines. It was found, by simulation and by experiment with a 0.13-μm 256-Mb test chip, that the level of noise is dramatically reduced by using a low-impedance array with careful layout featuring low-resistivity materials, tight bridging between pairs of adjacent arrays, and a small array, achieving a comparable level of noise to that seen in the twisted and folded-bitline array. On basis of these results, it turns out that the open-bitline array has a strong chance of revival in the multigigabit generation, as long as these noise reduction techniques are applied     

Standardization activities in the ITU for a QoE assessment of IPTV

This article gives an overview of the state of the art of objective quality assessment of audio and visual media and its standardization activities in the ITU. IPTV services are becoming one of the most promising applications over next generation networks. To provide end users with comfortable, stable, and economical services, QoE assessment methodologies for quality design and management are indispensable.     

Optical response of tin nitride thin films prepared by halide chemical vapor deposition under atmospheric pressure

Optical response of tin nitride (SnN_x) films, which were deposited onto quartz substrates by means of atmospheric pressure, halide chemical vapor deposition (AP-HCVD), were examined by pulsed irradiation of a YAG laser (532 nm). It was observed that the transmittance of a light of a He-Ne laser (633 nm) through the SnN_x film decreases after the film is irradiated with a YAG laser. The atomic force microscopy (AFM) micrograph observation confirmed that spot-like humps appeared on the SnN_x film surface in the regions spotted by the YAG laser. This phenomenon was explained in terms of the laser-assisted thermal decomposition of SnN_x to β-tin.     

Properties of the peptides liberated from rice protein in sokujo-moto

In the supernatant of sokujo-moto, a high level of acid carboxypeptidase (ACP) activity and a large amount of peptides were observed, however, the amount of free amino acids liberated was small. In order to determine why these peptides were not hydrolyzed to any significant degree by the ACP, the properties of the peptides in sokujo-moto were investigated in this study. Peptides were fractionated from sokujo-moto by ion exchange column chromatography. ACP purified from rice-koji (rice overgrown with Aspergillus oryzae) was allowed to react with the peptides, and it was found that they were not hydrolyzed to any significant degree by the enzyme. Gel filtration chromatography was performed to ascertain the molecular size distribution of the peptides in sokujo-moto, and it was revealed that they were of low molecular sizes; molecular size: mainly in the range of 200-400, and chain length: 2-3. ACP purified from rice-koji was also allowed to react with various synthetic peptides, and it was found that ACP of rice-koji could not rapidly hydrolyze low-molecular-size peptides, such as dipeptides or tripeptides. Acid protease (AP) purified from rice-koji released peptides of molecular sizes mainly in the range of 300-600 or above from rice protein under acidic conditions (pH 3.6; the pH of sokujomoto). When AP and ACP were allowed to act at the same time on rice protein, mainly low-molecular-size peptides (molecular sizes mainly in the range of 200-400) were produced. From these results, it was estimated that AP released peptides with molecular sizes mainly in the range of 300-600 or above from rice protein and ACP degraded the relatively higher molecular size peptides among them to lower molecular size peptides; consequently only low-molecular-size peptides with molecular sizes mainly in the range of 200-400 were released in the supernatant of sokujo-moto.     

Classification and identification of strains of Lactobacillus brevis based on electrophoretic characterization of D-lactate dehydrogenase: relationship between D-lactate dehydrogenase and beer-spoilage ability

The cell-free extracts of 60 strains which were identified phenotypically as being those of Lactobacillus brevis, including 48 isolates from the environment and 12 reference strains, were applied to polyacrylamide gel electrophoresis for extracting their NAD-dependent D- and L-lactate dehydrogenases (LDH). These strains were divided into 5 groups, i.e., Groups A, B, C, D, and E, on the basis of the electrophoretic mobilities of their D-LDH. The strains showed variations in their carbohydrate fermentation patterns. No relationship between the profile of D-LDH and the carbohydrate fermentation pattern was recognized. However, there appeared to be a relationship between the D-LDH profile and the beer-spoilage ability, because 40 out of 44 beer-spoilage strains identified as L. brevis were classified to Group B. We purified D-LDHs from the so-called complete beer-spoilage strain SBC 8002 of LDH Group B and from the non beer-spoilage strains JCM 1059T of LDH Group A and AHU 1508 of LDH Group C. Although the purified D-LDHs had the same molecular weight (84 kDa), each possessed a different optimum pH, optimum temperature, and isoelectric point. The aforementioned parameter values for the enzyme from the so-called complete beer-spoilage strain SBC 8002 of LDH Group B were 10.0, 50 degrees C, and 4.1, respectively; this strain was discriminated from the D-LDHs of the other two non beer-spoilage strains especially by its optimum temperature (50 degrees C).     

Polarization-, Wavelength-, and Filter-Free All-Optical Clock Recovery in a Passively Mode-Locked Laser Diode With Orthogonally Pumped Polarization-Diversity Configuration

We proposed and demonstrated all-optical clock recovery system using a monolithic mode-locked laser diode (MLLD) that operated with less sensitivity to the polarization and the wavelength of the input data signals also with no bandpass filter to eliminate the input signal-components. The keys to this new technique are the MLLD integrated with a tensile-strained quantum-well saturable absorber and a new polarization-diversity setup by signal input orthogonally polarized to the lasing polarization of the MLLD. This approach was experimentally validated in the 40 Gbps clock recovery experiments. The results exhibited excellent performance of the clock recovery with low timing jitters (<0.3 ps) remaining small dependence on the wavelength and the polarization of the input data signals and input-signal suppression less than -30 dB with no use of the bandpass filter. We also succeeded in the stable clock recovery for the input of polarization-scrambled data signals.     

Light modulator using piezoelectric films with waveguides

A light modulator using piezoelectric films based on optical interference of the Mach-Zehnder type has been proposed and demonstrated. The modulator is constructed with two optical waveguides joined to each other at both ends to divide the incident light and to recombine them, and each waveguide is fabricated on a polyvinylidene fluoride (PVDF) film to serve as a voltage-driven phase-shifter.     

Lithium Phenolate Complexes with a Pyridine‐Containing Polymer for Solution‐Processable Electron Injection Layers in PLEDs

A series of (vinylphenyl)pyridine‐based polymer binders, PVPh2Py, PVPh3Py, and PVPh4Py, are designed and synthesized and it is found that mixtures of Liq and the polymers exhibit superior electron injection characteristics as ultrathin (1.6 nm) electron injection layer (EIL) films. They are comparable to those of EILs composed only of Liq. The addition of the polymers does not deteriorate the performance of Liq EILs. Additionally, when the EIL thickness is increased from 1.6 nm to 16 nm, the driving voltages increase and the external quantum efficiencies decrease. The increase in the voltage and decrease in the EQE are suppressed in the device with mixed EILs compared to those observed for the device composed of 100 wt% Liq. Furthermore, the position of the nitrogen in the pyridine ring is considered to influence the electron transport properties of the EILs. The mixing PVPh4Py with Liq improves the driving voltage of the fabricated devices, even with a thick mixed EIL. This reduced dependence of the performance of EILs on their thickness will be advantageous for the coating of large areas using solution processes.     

a-SiC:H/SiO2 Laminated Polarization Splitter for the Wavelength Region Longer Than 1.3 μm Prepared by Plasma-Enhanced Chemical Vapor Deposition

A laminated polarization splitter for the wavelength region longer than 1.3 μm is fabricated for the first time. It is composed of a-SiC:H/SiO₂ alternative multilayers prepared by plasma-enhanced chemical vapor deposition. Splitting behavior is also verified experimentally. It has low absorption loss even for the wavelength region around λ = 1.3 μm because the band-gap energy of a-Sic is larger than that of a-Si. The measured splitting angle is 13.8°, which is 2.4 times larger than the 5.7° splitting angle of rutile. The absorption loss of the multilayer is reduced to 1 × 10^-3 dB/μm at λ = 1.3 μm. The magnitude of the residual stress is 9.45 × 10⁸ dyn/cm², which is about one-third of that prepared by the rf bias sputtering equipment which is used for another project of our group. The deposition rate of SiO₂, is increased to 135 nm/min, which is 27 times larger than that prepared by the sputtering equipment.