A5080553016- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Photonic and Optical Devices
- Semiconductor Lasers and Optical Devices
- Semiconductor Quantum Structures and Devices
- Particle Detector Development and Performance
- Optical Network Technologies
- Neutrino Physics Research
- Nuclear physics research studies
- Dark Matter and Cosmic Phenomena
- Spectroscopy and Laser Applications
- Advanced Photonic Communication Systems
- Particle Accelerators and Free-Electron Lasers
- Advanced Fiber Laser Technologies
- Advanced Semiconductor Detectors and Materials
- Atomic and Subatomic Physics Research
- Semiconductor materials and interfaces
- Atomic and Molecular Physics
- Medical Imaging Techniques and Applications
- Semiconductor materials and devices
- Advanced Chemical Physics Studies
- Superconducting Materials and Applications
- Black Holes and Theoretical Physics
- Molecular Junctions and Nanostructures
Osaka University
2004-2023
The University of Tokyo
2011-2020
Akita University
2020
High Energy Accelerator Research Organization
2020
Japan Proton Accelerator Research Complex
2020
Uppsala University
2015
University of Belgrade
2015
NTT (Japan)
2003-2014
Ludwig-Maximilians-Universität München
2013
Northwestern University
2008-2009
We demonstrate 50-Gb/s direct modulation by using 1.3-μm distributed-feedback lasers with a ridge waveguide structure. employed InGaAlAs material for multiple-quantum well to obtain low damping factor <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> , and fabricated structure buried in benzocyclobutene realize parasitic capacitance. In addition, high maximum frequency relaxation oscillations fr, we designed the cavity length...
We present a series of measurements based on ${K}_{L,S}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${K}_{L,S}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ decays collected in 1996--1997 by the $\mathrm{KTeV}$ experiment (E832) at Fermilab. compare these four $\stackrel{\ensuremath{\rightarrow}}{K}\ensuremath{\pi}\ensuremath{\pi}$ decay rates to measure direct $\mathrm{CP}$ violation parameter...
The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay KL→π0e+e− . This mode is expected to have a significant CP violating component. measurement of its branching ratio could support standard model or indicate existence new physics. Letter reports results from 1999–2000 data set. One event observed with an background 0.99±0.35 events. We set limit on 3.5×10−10 90% confidence level. Combining previous result based taken in 1997 yields final KTeV result:...
This paper describes the wide temperature range operation of an electroabsorption modulator (EAM) integrated with DFB laser diodes (LDs) (EML) designed to reduce power consumption and size optical transmitters. We optimized multiquantum wells (MQWs) for LD EAM separately realize uncooled operation. employed a conduction band offset (¿ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ec</i> ) around 250 meV 150 EAM. The number well layers was set at...
This paper has demonstrated a 40-Gb/s low-driving-voltage electroabsorption modulator (EAM) having InGaAlAs/InAlAs multiquantum-well active core. A narrow core buried with polyimide provides strong optical and electrical confinement, resulting in maintained large extinction ratio (ER) an increased 3-dB down frequency. The fabricated EAM shows frequency as 46 GHz, even for the active-core length long 200 /spl mu/m. operates at 40 Gb/s RF ER of 10.5 dB driving voltage low 0.79 V.
The Fermilab KTeV experiment has searched for lepton-flavor-violating decays of the KL meson in three decay modes. We observe no events signal region any modes studied, and we set following upper limits their branching ratios at 90% C.L.: BR(KL→π0μ±e∓)<7.6×10−11; BR(KL→π0π0μ±e∓)<1.7×10−10; BR(π0→μ±e∓)<3.6×10−10. This result represents a factor 82 improvement ratio limit KL→π0μ±e∓ is first reported KL→π0π0μ±e∓.Received 21 November 2007DOI:https://doi.org/10.1103/PhysRevLett.100.131803©2008...
The pure effects of both strain and quantum confinement on differential gain InGaAsP/InP strained-layer quantum-well lasers (SL-QWL's) are studied the basis valence band structures calculated by k/spl middot/p theory. Using an InGaAsP quaternary compound as active layer makes it possible to distinguish effect (both tensile compressive) from quantum-confinement when keeping emission wavelength constant. essential features strain-induced changes in extracted results four characterization...
A high-performance 1.3 µm InGaAlAs electroabsorption modulator integrated with a DFB laser for the metro-area 100 Gbit/s Ethernet system (100GBASE-LR4 and -ER4) has been developed. 40 km transmission under 25 operation on singlemode fibre that is required 100GBASE-ER4 application at 40°C demonstrated first time.
We report the first observation of a manifestly CP violating effect in K(L)-->pi(+)pi(-)e(+)e(-) decay mode. A large asymmetry was observed distribution these decays CP-odd and T-odd angle straight phi between planes e(+)e(-) pi(+)pi(-) pairs K(L) center mass system. After acceptance corrections, overall is found to be [13.6+/-2. 5(stat)+/-1.2(syst)]%. This largest CP-violating yet when integrating over entire phase space mode such an angular variable.
Low-chirp lasing operation in semiconductor lasers is addressed a theoretical investigation of the possibility reducing linewidth enhancement factor ( alpha factor) quantum-well (QW) to zero. It shown that it essential oscillation be around peak differential gain spectrum, not vicinity peak. The condition for such analytically derived. wavelength dependence material gain, and are calculated detail taking into account effects compressive strain band mixing on valence subband structure. effect...
We present new measurements of the six largest branching fractions ${K}_{L}$ using data collected in 1997 by KTeV experiment (E832) at Fermilab. The results are $B({K}_{L}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{\mathrm{e}}^{\ensuremath{\mp}}\ensuremath{\nu})=0.4067\ifmmode\pm\else\textpm\fi{}0.0011$,...
Isospin is a good quantum number under the assumption that nuclear interaction charge independent. An analogous structure of excited states expected for nuclei with same mass $A$ but different $z$ components ${T}_{z}$ isospin $T$, where ${T}_{z}=(N\ensuremath{-}Z)/2$. The has been studied isobaric $^{58}\mathrm{Ni}$ and $^{58}\mathrm{Cu}$ by comparing transitions from ground state (initial ${T}_{i}=1$ ${J}^{\ensuremath{\pi}}={0}^{+}$) to $M1$ Gamow-Teller (GT)...
We demonstrated a 25-Gb/s direct modulation up to 85degC with 1.3- mum InGaAlAs ridge-waveguide multiple-quantum-well distributed-feedback laser. The dependence of the relaxation oscillation frequency on current was 3.3 GHz/mA <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> , and this is highest value ever reported for 200-mum-long lasers in 1.3-mum wavelength region. alpha parameter around 2.7 at 25degC, an error-free operation after...
Spin-isospin excitations in $^{13}\mathrm{N}$ have been studied by means of the $(^{3}\mathrm{He},t)$ and $(^{3}\mathrm{He},tp)$ reactions at a bombarding energy $E(^{3}\mathrm{He})=450\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. The zero-degree spectrum is found to be similar those from $(p,n)$ intermediate energies, suggesting simple direct reaction mechanism Gamow-Teller $(\mathrm{GT})$ states with ${J}^{\ensuremath{\pi}}=1∕{2}^{\ensuremath{-}}$ $3∕{2}^{\ensuremath{-}}$ strongly excited...
We present the uncooled operation of a 1.55- mum 40-Gb/s InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser within temperature range 95degC (-15degC to 80degC ). To best our knowledge, this is largest reported so far for such EAM DFB laser. designed operate at high speed by reducing electrical parasitics, and we achieved 3-dB frequency bandwidth over 39 GHz an length less than 150 mum. demonstrated 2-km single-mode fiber (SMF) transmission wide -15degC...
The Gamow-Teller transition strengths, $B$(GT), in $pf$-shell nuclei are of interest nuclear physics as well astrophysics. A high-resolution (${}^{3}\mathrm{He},t$) charge-exchange (CE) reaction was performed on the ${T}_{z}=+1$ nucleus ${}^{54}$Fe at 0${}^{\ensuremath{\circ}}$ and an intermediate incident energy 140 MeV/nucleon for study precise GT strengths to final ${T}_{z}=0$ ${}^{54}$Co. By applying dispersion matching techniques a high-quality ${}^{3}$He beam RCNP, resolution 21 keV...
We report on a new measurement of the decay ${K}_{L}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}\ensuremath{\gamma}$ by KTeV experiment at Fermilab. determine branching ratio to be $(1.68\ifmmode\pm\else\textpm\fi{}0.07\ifmmode\pm\else\textpm\fi{}0.08)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. Our data show first evidence for low-mass $\ensuremath{\gamma}\ensuremath{\gamma}$ signal as predicted recent $O({p}^{6})$ chiral perturbation calculations which...
The linewidth enhancement factor alpha in InGaAsP-InP modulation-doped strained multiple-quantum-well (MQW) lasers has been evaluated theoretically and experimentally. A reduction of the -parameter due to modulation doping is demonstrated. small less than 1 obtained not at wavelength for gain peak but within certain range where positive. smaller MQW should result performance improvements that are advantageous optical communication system applications.< <ETX...
We present results of a search for new form hadronic matter, six-quark, dibaryon state called the H0, predicted to exist in several theoretical models. Analyzing data collected by experiment E799-II at Fermilab, we searched decay H0-->Lambdappi(-) and found no candidate events. place an upper limit on [B(H0-->Lambdappi(-))dsigma(H)/dOmega]/(dsigma(Xi)/dOmega) and, context published models, exclude region lightly bound mass states just below LambdaLambda threshold, 2.194<M(H)<2.231 GeV/c(2),...
Reduction of the linewidth enhancement factor /spl alpha/ is studied in InP-based strained multiple-quantum-well (MQW) lasers. Theoretical analysis shows that alpha/-parameter greatly reduced modulation-doped MQW lasers and may be zero while keeping positive gain. The experimental evaluation exhibits a very small around 1 InGaAsP/InP As result alpha/-parameter, linewidth-power product effectively 1.5-/spl mu/m DFB with structure. A narrow spectral 100 kHz was also obtained reproducibly...
We consider the problem of charge transport and recombination in semiconductor quantum well infrared photodetectors quantum-dot-in-a-well detectors. The photoexcited carrier relaxation is calculated using rigorous random-walk diffusion methods, which take into account finiteness cross sections, if necessary memory generation point. In present application, bias fields are high it sufficient to drift limited regime. photoconductive gain discussed a quantum-mechanical language, making more...
Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction 450 MeV and 0 degrees. For 176Yb, two low-lying states are observed, setting thresholds Q(nu) = 301 445 keV for neutrino nu) capture. Capture rates estimated from GT strengths, simple two-state structure, in Yb-Lu indicate that Yb-based nu detectors well suited a direct measurement of sub-MeV solar electron-neutrino nu(e)) spectrum including pp neutrinos.
We demonstrate the 50-Gb/s operation of a 1.3-μm InGaAlAs directly modulated laser (DML) for first time. Clear eye openings were achieved 60-km SMF transmission.