Low-loss fibre-pigtailed 256 channel arrayed-waveguide gratingmultiplexer using cascaded laterally-tapered waveguides

A fibre-pigtailed 25 GHz-spacing 256 channel arrayed-waveguide grating (AWG) module has been fabricated. The module was composed of an AWG chip with a Δ of 1.5%, a fan-out planar lightwave circuit (PLC) with a A of 0.75%, an input fibre and two 128 fibre arrays. To improve the coupling loss of the 256 output fibres, a new PLC-fibre connection using cascaded laterally-tapered waveguides was developed. The fibre-pigtailing loss is reduced to only 1.1 dB and a multiplexer with a low insertion loss of 1.9-3.9 dB is realised     

Continuous-wave operation of 1.30μm GaAsSb/GaAs VCSELs

1.30 μm VCSELs using GaAsSb quantum wells, which operate continuous-wave at and above room temperature (RT), are reported. A threshold current as low as 1.2 mA at RT and a maximum CW operating temperature of 70°C are demonstrated     

Low-threshold operation of 1.3-μm GaAsSb quantum-well lasersdirectly grown on GaAs substrates

GaAsSb quantum-well (QW) edge-emitting lasers grown on GaAs substrates were demonstrated. The optical quality of the QW was improved by optimizing the growth conditions and introducing a multi-QW to increase the gain. As a result, 1.27-μm lasing of a GaAs_0.66 Sb_0.34-GaAs double-QW laser was obtained with a low-threshold current density of 440 A/cm², which is comparable to that in conventional InP-based long-wavelength lasers. 1.30 μm lasing with a threshold current density of 770 A/cm² was also obtained by increasing the antimony content to 0.36. GaAsSb QW was found to be a suitable material for use in the active layer of a 1.3-μm vertical-cavity surface-emitting lasers     

Evaluation of implementation of thorium fuel cycle with LWR and MSR

In order to construct a sustainable society, it is necessary to consider fairness beyond generations and between countries. It is expected that Asian countries continue growing their economy and will result consuming more energy. More CO₂ emission is not acceptable.Nuclear power has many advantages for reducing CO₂ emission. However, it still has concerns of nuclear proliferation, radioactive waste and safety. It is necessary to overcome these concerns if nuclear power is expanded to Asian countries. Thorium utilization as nuclear fuel will be an opening key of these difficulties because thorium produces less plutonium, less radioactive waste. Safety will also be enhanced. The use of molten-salt reactor (MSR) triggered by plutonium supply from ordinary light water reactor (LWR) with uranium fuel will allow implementation of thorium fuel cycle with electricity capacity of about 446 GWe around at 2050.The other important sector in a view of sustainability is transportation. Transportation is essential for economy growth. Therefore it is inevitable to reduce CO₂ emission from transportation sector. Electric vehicle (EV) will be used as a major mobility instead of gasoline engine cars. Rare-earth materials such as neodymium and dysprosium are necessary for producing EV. These materials are expected to be mined from Asian countries. It is often obtained with thorium as by-product. Thorium has not been used as nuclear fuel because it is not good for nuclear weapon and it does not have fissionable isotopes. Recent global trend of nuclear disarmament and accumulation of plutonium from uranium fuel cycle can support starting the use of thorium.Thorium utilization will help both to provide clean energy and to produce rare-earth for clean vehicle. These will create new industries in developing Asian countries. An international collaborative framework can be established by supplying resource from developing countries and supplying technology from developed countries. “THE Bank (THorium Energy Bank)” is proposed here as one part of such a framework.     

Optical Property Analyses of Plant Cells for Adaptive Optics Microscopy

In astronomy, adaptive optics (AO) can be used to cancel aberrations caused by atmospheric turbulence and to perform diffraction-limited observation of astronomical objects from the ground. AO can also be applied to microscopy, to cancel aberrations caused by cellular structures and to perform high-resolution live imaging. As a step toward the application of AO to microscopy, here we analyzed the optical properties of plant cells. We used leaves of the moss Physcomitrella patens, which have a single layer of cells and are thus suitable for optical analysis. Observation of the cells with bright field and phase contrast microscopy, and image degradation analysis using fluorescent beads demonstrated that chloroplasts provide the main source of optical degradations. Unexpectedly, the cell wall, which was thought to be a major obstacle, has only a minor effect. Such information provides the basis for the application of AO to microscopy for the observation of plant cells.     

Double-passed arrayed waveguide grating for 500-GHz pulse burst generation

500-GHz repetition rate pulse bursts on multiple wavelength shifted channels are generated via femtosecond readout of an arrayed waveguide grating (AWG). These bursts are combined onto a single channel by double-passing the AWG, resulting in a substantially increased number of output pulses.     

Phosphorylation of alphaB-crystallin in mitotic cells and identification of enzymatic activities responsible for phosphorylation

The immunofluorescence localization of alphaB-crystallin in U373 MG human glioma cells with an antibody specific for alphaB-crystallin that had been phosphorylated at Ser-45 revealed an intense staining of cells in the mitotic phase of the cell cycle. Phosphorylated forms of alphaB-crystallin in mitotic cells were detected in all cell lines examined and in tissue sections of mouse embryos. Increases in the levels of alphaB-crystallin that had been phosphorylated at Ser-45 and Ser-19, but not at Ser-59, were detected biochemically by isoelectric focusing or SDS-polyacrylamide gel electrophoresis and a subsequent Western blot analysis of extracts of cells collected at the mitotic phase. When we estimated the phosphorylation activity specific for alphaB-crystallin in extracts of mitotic U373 MG cells, using the amino-terminal 72-amino acid peptide derived from unphosphorylated alphaB2-crystallin as the substrate, we found that the activities responsible for the phosphorylation of Ser-45 and Ser-19 were markedly enhanced but that the activity responsible for the phosphorylation of Ser-59 was suppressed. The protein kinases responsible for the phosphorylation of Ser-45 and Ser-59 in the amino-terminal 72-amino acid peptide were partially purified from extracts of cells that had been stimulated by exposure to H2O2 in the presence of calyculin A. The activities responsible for the phosphorylation of Ser-45 and Ser-59 were eluted separately from a column of Superdex 200 at fractions corresponding to about 40 and 60 kDa, respectively, while the kinase for Ser-19 was unstable. p44/42 mitogen-activated protein (MAP) kinase and MAP kinase-activated protein (MAPKAP) kinase-2 were concentrated in the Ser-45 kinase fraction and Ser-59 kinase fraction, respectively. Recombinant human p44 MAP kinase and MAPKAP kinase-2 purified from rabbit muscle selectively phosphorylated Ser-45 and -59, respectively. The Ser-45 kinase fraction and Ser-59 kinase fraction phosphorylated myelin basic protein and hsp27, respectively. These results suggest that the phosphorylations of Ser-45 and Ser-59 in alphaB-crystallin are catalyzed by p44/42 MAP kinase and MAPKAP kinase-2, respectively, in cells and that the phosphorylation of Ser-45 by p44/42 MAP kinase is enhanced while the phosphorylation of Ser-59 by MAPKAP kinase-2 is suppressed during cell division.     

8-channel×2.5 Gbit/s hybrid integrated multiwavelengthphotoreceiver module with arrayed-waveguide grating demultiplexer

A compact 8-channel hybrid integrated multiwavelength photoreceiver module has been fabricated. The module, which consists of an arrayed-waveguide grating demultiplexer with a 100 GHz spacing, a photodiode array using a planar lightwave circuit platform, and preamplifier integrated circuits, successfully operated at 2.5 Gbit/s with good receiver sensitivity better than -17.5 dBm at a bit error rate of 10^-9 for all channels