Masatake Ohashi

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We present data-analysis schemes and results of observations with the TAMA300 gravitational-wave detector, targeting burst signals from stellar-core collapse events. In analyses for burst grav-itational waves, the detection and fake-reduction schemes are different from well-investigated ones for a chirp-wave analysis, because precise waveform templates are(More)
The thermal fluctuation of mirror surfaces is the fundamental limitation for interferometric gravitational wave (GW) detectors. Here, we experimentally demonstrate for the first time a reduction in a mirror's thermal fluctuation in a GW detector with sapphire mirrors from the Cryogenic Laser Interferometer Observatory at 17 and 18 K. The detector(More)
We evaluated the performance of polished mirror surfaces for the TAMA interferometric gravitational wave detector by comparing the experimental results with a wave-front tracing simulation. The TAMA mirror surfaces were polished to a roughness of a few nanometer rms. We confirmed that these polished mirrors do not limit the present TAMA sensitivity and that(More)
We have achieved a direct measurement of the thermal fluctuation of a pendulum in an off-resonant and wide frequency region using a laser interferometric gravitational-wave detector. These measurements have been well identified for over one decade by an agreement with a theoretical prediction, which is derived by a fluctuation-dissipation theorem. Thermal(More)
The bending-loss and dispersion-sensitivity characteristics of a dispersion-shifted dual-shape core fiber with an alpha index center core are described. Calculations show that these characteristics can be improved by decreasing a and that a bend-optimized, dual-shaped core fiber exhibits a small bending loss and a large mode field diameter.
DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected to provide us fruitful insights into the universe, in particular about dark energy, a formation mechanism of supermassive black holes, and the inflation of the(More)
We have developed and built a highly accurate laser strainmeter for geophysical observations. It features the precise length measurement of a 100-m optical cavity with reference to a stable quantum standard. Unlike conventional laser strainmeters based on simple Michelson interferometers that require uninterrupted fringe counting to track the evolution of(More)
Waveguide-dispersion characteristics are discussed experimentally and numerically. The waveguide dispersions of both dual-shape-core (DSC) and graded-index types of dispersion-shifted fibers are evaluated from the measured wavelength dependence of the mode field radius. It is shown that the dispersion sensitivity to core-radius change of a bend-optimized(More)
2 We evaluated the performance of polished mirror surfaces for the TAMA interfer-ometric gravitational wave detector by comparing the experimental results with a wave-front tracing simulation. The TAMA mirror surfaces were polished to a roughness of a few nanometer rms. We confirmed that these polished mirrors do not limit the present TAMA sensitivity, and(More)