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ABSTRACT: We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".
Optics Express 07/2012; 20(14):15589-609. · 3.59 Impact Factor
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ABSTRACT: We report a precision and fast wavelength tuning technique demonstrated for a digital-supermode distributed Bragg reflector laser. The laser was dynamically offset-locked to a frequency-stabilized master laser using an optical phase-locked loop, enabling precision fast tuning to and from any frequencies within a ~40-GHz tuning range. The offset frequency noise was suppressed to the statically offset-locked level in less than ~40 μs upon each frequency switch, allowing the laser to retain the absolute frequency stability of the master laser. This technique satisfies stringent requirements for gas sensing lidars and enables other applications that require such well-controlled precision fast tuning.
Optics Express 06/2012; 20(13):14234-43. · 3.59 Impact Factor
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ABSTRACT: 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, limiting its peak-to-peak frequency drift to 0.3 MHz at 0.8 s averaging time over 72 hours. Four online DFB-LDs were then offset locked to this laser using phase-locked loops, retaining virtually the same absolute frequency stability. These online and two offline DFB-LDs were subsequently amplitude switched and combined. This produced a precise wavelength-stepped laser pulse train, to be amplified for CO(2) measurements.
Applied Optics 03/2011; 50(7):1047-56. · 1.41 Impact Factor
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ABSTRACT: Using an iodine cell with fixed gas pressure, we built a simple frequency reference at 1064 nm with 10 MHz absolute accuracy and used it to demonstrate deterministic phase locking between two single-frequency lasers. The reference was designed to be as simple as possible, and it does not use a cooler or frequency modulator. This system should be useful, especially for space interferometric missions such as the Laser Interferometer Space Antenna.
Applied Optics 11/2010; 49(32):6264-7. · 1.41 Impact Factor
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ABSTRACT: 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 demonstrated by stabilizing its frequency to acetylene ((13)C(2)H(2)) at 10(-13) level of Allan deviation. The PW-ECL also has the advantage of the compactness of a standard butterfly package, low cost, and a simple design consisting of a semiconductor gain media coupled to a planar-waveguide Bragg reflector.
Optics Express 10/2010; 18(22):22781-8. · 3.59 Impact Factor
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Masaki Ando,
Seiji Kawamura,
Naoki Seto,
Shuichi Sato,
Takashi Nakamura,
Kimio Tsubono,
Takeshi Takashima,
Ikkoh Funaki, Kenji Numata,
Nobuyuki Kanda, [......],
Yaka Wakabayashi,
Kent Yagi,
Hiroshi Yamakawa,
Kazuhiro Yamamoto,
Toshitaka Yamazaki,
Jun'ichi Yokoyama,
Chul-Moon Yoo,
Shijun Yoshida,
Taizoh Yoshino,
Ke-Xun Sun
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ABSTRACT: A space gravitational-wave antenna, DECIGO (DECI-hertz interferometer Gravitational wave Observatory), will provide fruitful insights into the universe, particularly on the formation mechanism of supermassive black holes, dark energy and the inflation of the universe. In the current pre-conceptual design, DECIGO will be comprising four interferometer units; each interferometer unit will be formed by three drag-free spacecraft with 1000 km separation. Since DECIGO will be an extremely challenging mission with high-precision formation flight with long baseline, it is important to increase the technical feasibility before its planned launch in 2027. Thus, we are planning to launch two milestone missions. DECIGO pathfinder (DPF) is the first milestone mission, and key components for DPF are being tested on ground and in orbit. In this paper, we review the conceptual design and current status of DECIGO and DPF.
Classical and Quantum Gravity 04/2010; 27(8):084010. · 3.32 Impact Factor
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ABSTRACT: We have developed a linearly-polarized Ytterbium-doped fiber ring laser with single longitudinal-mode output at 1064nm for LISA and other space applications. Single longitudinal-mode selection was achieved by using a fiber Bragg grating (FBG) and a fiber Fabry-Perot (FFP). The FFP also serves as a frequency-reference within our ring laser. Our laser exhibits comparable low frequency and intensity noise to Non-Planar Ring Oscillator (NPRO). By using a fiber-coupled phase modulator as a frequency actuator, the laser frequency can be electro-optically tuned at a rate of 100kHz. It appears that our fiber ring laser is promising for space applications where robustness of fiber optics is desirable. Comment: Proceedings for 8th Edoardo Amaldi Conference on Gravitational Waves, New York, (2009). To be published in Journal of Physics Conference Series.
03/2010;
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ABSTRACT: 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 composed of interferometric sensors, a hexapod actuator, and a frequency-stabilized laser. With this stabilized testbed, environmental motions were suppressed down to the nanometer level. This system will allow us to perform sensitive measurements, such as ground testing of the Laser Interferometer Space Antenna, in the presence of environmental noise.
Applied Optics 01/2009; 47(36):6832-41. · 1.41 Impact Factor
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Kazuhiro Yamamoto,
Shinji Miyoki,
Takashi Uchiyama,
Hideki Ishitsuka,
Masatake Ohashi,
Kazuaki Kuroda,
Takayuki Tomaru,
Nobuaki Sato,
Toshikazu Suzuki,
Tomiyoshi Haruyama,
Akira Yamamoto,
Takakazu Shintomi, Kenji Numata,
Koichi Waseda,
Kazuhiko Ito,
Koji Watanabe
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ABSTRACT: We have measured the mechanical loss of a dielectric multilayer reflective coating (ion-beam sputtered SiO$_2$ and Ta$_2$O$_5$) in cooled mirrors. The loss was nearly independent of the temperature (4 K $\sim$ 300 K), frequency, optical loss, and stress caused by the coating, and the details of the manufacturing processes. The loss angle was $(4 \sim 6) \times 10^{-4}$. The temperature independence of this loss implies that the amplitude of the coating thermal noise, which is a severe limit in any precise measurement, is proportional to the square root of the temperature. Sapphire mirrors at 20 K satisfy the requirement concerning the thermal noise of even future interferometric gravitational wave detector projects on the ground, for example, LCGT.
02/2006;
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ABSTRACT: 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 achieved with a rigid frequency-reference cavity of order 1 Hz/ square root Hz (0.01 Hz/ square root Hz) at 10 mHz (100 Hz) at room temperature. This level coincides with the world-highest level stabilization results.
Physical Review Letters 01/2005; 93(25):250602. · 7.37 Impact Factor
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Masaki Ando,
Koji Arai,
Youichi Aso,
Peter Beyersdorf,
Kazuhiro Hayama,
Yukiyoshi Iida,
Nobuyuki Kanda,
Seiji Kawamura,
Kazuhiro Kondo,
Norikatsu Mio, [......],
Shigeo Nagano, Kenji Numata,
Shuichi Sato,
Kentaro Somiya,
Hideyuki Tagoshi,
Hirotaka Takahashi,
Ryutaro Takahashi,
Daisuke Tatsumi,
Yoshiki Tsunesada,
Zong-Hong Zhu
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ABSTRACT: 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 gravitational waves, the detection and fake-reduction schemes are different from well-investigated ones for a chirp-wave analysis, because precise waveform templates are not available. We used an excess-power filter for the extraction of gravitational-wave candidates, and developed two methods for the reduction of fake events caused by non-stationary noises of the detector. These analysis schemes were applied to real data from the TAMA300 interferometric gravitational wave detector. As a result, fake events were reduced by a factor of about 1000 in the best cases. The resultant event candidates were interpreted from an astronomical viewpoint. We set an upper limit of 2.2x10^3 events/sec on the burst gravitational-wave event rate in our Galaxy with a confidence level of 90%. This work sets a milestone and prospects on the search for burst gravitational waves, by establishing an analysis scheme for the observation data from an interferometric gravitational wave detector.
11/2004;
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Hirotaka Takahashi,
Hideyuki Tagoshi,
Masaki Ando,
Koji Arai,
Peter Beyersdorf,
Nobuyuki Kanda,
Seiji Kawamura,
Norikatsu Mio,
Shinji Miyoki,
Shigenori Moriwaki, [......],
Ken-ichi Ueda,
Fumihiko Usui,
Koichi Waseda,
Yuko Watanabe,
Hiromi Yakura,
Kazuhiro Yamamoto,
Akira Yamamoto,
Toshitaka Yamazaki,
Tatsuo Yoda,
Zong-Hong Zhu
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ABSTRACT: Japanese laser interferometric gravitational wave detectors, TAMA300 and LISM, performed a coincident observation during 2001. We perform a coincidence analysis to search for inspiraling compact binaries. The length of data used for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors are operated simultaneously. TAMA300 and LISM data are analyzed by matched filtering, and candidates for gravitational wave events are obtained. If there is a true gravitational wave signal, it should appear in both data of detectors with consistent waveforms characterized by masses of stars, amplitude of the signal, the coalescence time and so on. We introduce a set of coincidence conditions of the parameters, and search for coincident events. This procedure reduces the number of fake events considerably, by a factor ∼10-4 compared with the number of fake events in single detector analysis. We find that the number of events after imposing the coincidence conditions is consistent with the number of accidental coincidences produced purely by noise. We thus find no evidence of gravitational wave signals. We obtain an upper limit of 0.046 [1/h] (C.L.=90%) to the galactic event rate within 1 kpc from the Earth. The method used in this paper can be applied straightforwardly to the case of coincidence observations with more than two detectors with arbitrary arm directions.
Phys. Rev. D. 08/2004; 70(4).
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ABSTRACT: 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 the principal noise in precise interferometry, such as in gravitational wave detection. We identified the thermally induced noises in the interferometer, the so-called substrate Brownian noise, substrate thermoelastic noise, and coating Brownian noise.
Physical Review Letters 01/2004; 91(26 Pt 1):260602. · 7.37 Impact Factor
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ABSTRACT: We systematically measured the intrinsic mechanical quality factors of 13 kinds of bulk fused silica from four companies using a nodal support system. Some of them have actually been adopted as mirror substrates in interferometric gravitational wave detectors. The measured quality factors widely ranged from 7 × 105 to 4 × 107. They turned out to be independent of one specific property, such as the amount of OH content, suggesting that the loss mechanism has several origins. We found that many of the samples showed smaller losses at lower frequency. From the viewpoint of the mirror thermal noise, it would be fortunate if the loss continued to decrease with decreasing frequency. We also found that an annealing process increases their quality factors.
Classical and Quantum Gravity 03/2002; 19(7):1697. · 3.32 Impact Factor
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ABSTRACT: We measured the mechanical loss of crystalline anisotropic samples (silicon and sapphire) using a nodal support. The measured quality factor of the silicon sample reached 1.0×108 at room temperature. The sapphire sample showed lower quality factors, 6.4×107 at most, which were analytically confirmed to be dominated by surface loss.
Physics Letters A.
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Seiji Kawamura,
Masaki Ando,
Takashi Nakamura,
Kimio Tsubono,
Takahiro Tanaka,
Ikkoh Funaki,
Naoki Seto, Kenji Numata,
Shuichi Sato,
Kunihito Ioka, [......],
Yoshiki Tsunesada,
Ken-Ichi Ueda,
Masayoshi Utashima,
Hiroshi Yamakawa,
Kazuhiro Yamamoto,
Toshitaka Yamazaki,
Jun'ichi Yokoyama,
Chul-Moon Yoo,
Shijun Yoshida,
Taizoh Yoshino
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ABSTRACT: DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future
Japanese space gravitational wave antenna. DECIGO is expected to open a new window of
observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing
various mysteries of the universe such as dark energy, formation mechanism of supermassive
black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of
three drag-free spacecraft, whose relative displacements are measured by a differential Fabry–
Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre-
DECIGO first and finally DECIGO in 2024.
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Masaki Ando,
Seiji Kawamura,
Shuichi Sato,
Takashi Nakamura,
Kimio Tsubono,
Akito Araya,
Ikkoh Funaki,
Kunihito Ioka,
Nobuyuki Kanda,
Shigenori Moriwaki, [......],
Ken-Ichi Ueda,
Masayoshi Utashima,
Yaka Wakabayashi,
Hiroshi Yamakawa,
Kazuhiro Yamamoto,
Toshitaka Yamazaki,
Jun’ichi Yokoyama,
Chul-Moon Yoo,
Shijun Yoshida,
Taizoh Yoshino
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ABSTRACT: 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 fruitful insights into the universe, particularly about dark energy, the formation mechanism of supermassive black holes and the inflation of the universe. Since DECIGO will be an extremely challenging mission, which will be formed by three drag-free spacecraft with 1000 km separation, it is important to increase the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. In this paper, we review the conceptual design and current status of the first milestone mission, DPF.
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ABSTRACT: We measured the mechanical loss of cylindrical samples made of fused silica. The loss due to the support was excluded by using a nodal support technique. We evaluated separately the intrinsic loss of the material and the loss due to the surface roughness by systematically analyzing the measured losses.
Physics Letters A.
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Phys. Rev. Lett. 93(25):250602.
