Kenji Numata

Learn More
We evaluate thermal noise (Brownian motion) in a rigid reference cavity used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability(More)
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. The goal of DECIGO is to detect gravitational waves from various kinds of sources mainly between 0.1 Hz and 10 Hz and thus to open a new window of observation for gravitational wave astronomy. DECIGO will consist of three dragfree(More)
Masaki Ando, ∗ Koji Arai, Youichi Aso, Peter Beyersdorf, Kazuhiro Hayama, Yukiyoshi Iida, Nobuyuki Kanda, Seiji Kawamura, Kazuhiro Kondo, Norikatsu Mio, Shinji Miyoki, Shigenori Moriwaki, Shigeo Nagano, Kenji Numata, Shuichi Sato, Kentaro Somiya, Hideyuki Tagoshi, Hirotaka Takahashi, 10 Ryutaro Takahashi, Daisuke Tatsumi, Yoshiki Tsunesada, Zong-Hong Zhu,(More)
We present the application of a novel method of time-series analysis, the Hilbert-Huang Transform, to the search for gravitational waves. This algorithm is adaptive and does not impose a basis set on the data, and thus the time-frequency decomposition it provides is not limited by time-frequency uncertainty spreading. Because of its high time-frequency(More)
We directly measured mechanical thermal fluctuations in mirrors over three decades of frequency range using a short-length Fabry-Perot interferometer. This is the first such measurement at wide off-resonant frequency band that is much lower than mechanical resonant frequencies. Theoretically, the mechanical fluctuation in mirrors had been thought to become(More)
A 1542-nm planar-waveguide external cavity laser (PW-ECL) is shown to have a sufficiently low level of noise to be suitable for precision measurement applications. Its frequency noise and intensity noise was comparable or better than the non-planar ring oscillator (NPRO) and fiber laser between 0.1 mHz to 100 kHz. Controllability of the PW-ECL was(More)
Hideyuki Tagoshi, Nobuyuki Kanda, Takahiro Tanaka, Daisuke Tatsumi, Souichi Telada, Masaki Ando, Koji Arai, Akito Araya, Hideki Asada, Mark A. Barton, Masa-Katsu Fujimoto, Mitsuhiro Fukushima, Toshifumi Futamase, Gerhard Heinzel, Gen’ichi Horikoshi, Hideki Ishizuka, Norihiko Kamikubota, Keita Kawabe, Seiji Kawamura, Nobuki Kawashima, Yasufumi Kojima,(More)
0740-7475/99/$10.00 © 1999 IEEE 53 RECENTLY, RESEARCHERS have reported on many embedded DRAMs—large-scale integrated devices that merge dynamic RAM and logic.1-6 As embedded DRAMs find increasing applications, their testing has become a focus of attention. Embedded DRAMs have several features that distinguish them from commodity DRAMs, such as wider I/O(More)
We demonstrate a wavelength-locked laser source that rapidly steps through six wavelengths distributed across a 1572.335 nm carbon dioxide (CO(2)) absorption line to allow precise measurements of atmospheric CO(2) absorption. A distributed-feedback laser diode (DFB-LD) was frequency-locked to the CO(2) line center by using a frequency modulation technique,(More)
We developed an interferometric testbed to stabilize environmental motions over time scales of several hours and a length scale of 1 m. Typically, thermal and seismic motions on the ground are larger than 1 microm over these scales, affecting the precision of more sensitive measurements. To suppress such motions, we built an active stabilization system(More)