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ABSTRACT: We propose a novel, high-performance, and practical laser source system for optical clocks. The laser linewidth of a fiber-based frequency comb is reduced by phase locking a comb mode to an ultrastable master laser at 1064 nm with a broad servo bandwidth. A slave laser at 578 nm is successively phase locked to a comb mode at 578 nm with a broad servo bandwidth without any pre-stabilization. Laser frequency characteristics such as spectral linewidth and frequency stability are transferred to the 578-nm slave laser from the 1064-nm master laser. Using the slave laser, we have succeeded in observing the clock transition of <sup>171</sup>Yb atoms confined in an optical lattice with a 20-Hz spectral linewidth.
Optics Express 04/2013; 21(7):7891-6. · 3.59 Impact Factor
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ABSTRACT: A narrow linewidth diode laser system at 689 nm is realized by phase-locking an extended cavity diode laser to one tooth of a narrow linewidth optical frequency comb. The optical frequency comb is phase-locked to a narrow linewidth laser at 1064 nm, which is frequency stabilized to a high-finesse optical cavity. We demonstrate the magneto-optical trapping of Sr using an intercombination transition with the developed laser system.
Optics Express 07/2012; 20(14):16010-6. · 3.59 Impact Factor
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ABSTRACT: The spectral resolution and accuracy of asynchronous-optical-sampling terahertz time-domain spectroscopy (ASOPS-THz-TDS) were evaluated by examining low-pressure gas-phase samples. Use of dual 56-MHz, erbium (Er)-doped, mode-locked femtosecond fiber lasers enhanced the spectral resolution to as low as 50.5 MHz and the spectral accuracy to as low as 6.2 × 10(-6). The results indicate that ASOPS-THz-TDS has the potential to achieve high spectral resolution, high spectral accuracy, and wide spectral coverage at the same time. ASOPS-THz-TDS will open a new door to gas-phase spectroscopy of multiple chemical species in the field of atmospheric gas analysis.
Optics Express 07/2012; 20(14):15071-8. · 3.59 Impact Factor
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ABSTRACT: We have developed an optical frequency comb using a mode-locked fiber ring laser with an intra-cavity waveguide electro-optic modulator controlling the optical length in the laser cavity. The mode-locking is achieved with a simple ring configuration and a nonlinear polarization rotation mechanism. The beat note between the laser and a reference laser and the carrier envelope offset frequency of the comb were simultaneously phase locked with servo bandwidths of 1.3 MHz and 900 kHz, respectively. We observed an out-of-loop beat between two identical combs, and obtained a coherent δ-function peak with a signal to noise ratio of 70 dB/Hz.
Optics Express 06/2012; 20(13):13769-76. · 3.59 Impact Factor
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ABSTRACT: Long-path pulse-to-pulse interferometers of two-color frequency combs are developed using fundamental and second harmonics of a mode-locked fiber laser. Interferometric phase difference between two-color frequency combs was precisely measured by stabilizing the fundamental fringe phase by controlling the repetition frequency of the comb, and a stability of 10(-10) for 1000 s was achieved in the measurement of an optical path length difference between two wavelengths. In long-term measurements performed for 10 h, results of phase variation of interferometric measurements were highly consistent with the fluctuations in the calculated difference of refractive indices of air at two wavelengths with an accuracy of 10(-10). The difference between the measured optical distances corresponding to two wavelengths and the optical distance corresponding to the fundamental wavelength were used in the two-color method; high-accuracy self-correction of the fluctuation of refractive index of air was performed with an uncertainty of 5 × 10(-8) for 10-h measurements when the maximum refractive index change was on the order of 10(-6).
Optics Express 12/2011; 19(27):26095-105. · 3.59 Impact Factor
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ABSTRACT: We constructed a widely and continuously tunable terahertz frequency synthesizer traceable to a hydrogen maser linked to coordinated universal time. Photomixing of two optical frequency synthesizers, linked to the hydrogen maser via dual optical frequency combs, gave this THz synthesizer frequency uncertainty of 10⁻¹². To demonstrate the potential of wide and continuous tunability in the THz synthesizer, we tuned its output frequency up to 50 GHz discretely and 1.26 GHz continuously in the F-band while maintaining the unprecedented frequency uncertainty by using a uni-traveling-carrier photodiode as a photomixer. This THz synthesizer will be a powerful tool for broadband, high-precision THz spectroscopy and THz frequency metrology.
Optics Express 02/2011; 19(5):4428-37. · 3.59 Impact Factor
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Michael Matus,
Petr Balling,
Petr Kren,
Pavel Mašika,
Feng-Lei Hong,
Jun Ishikawa, Hajime Inaba,
Kazumoto Hosaka,
Masami Yasuda,
Daisuke Akamatsu, [......],
Anusorn Tonmueanwai,
Siew Leng Tan,
Zhixia Chao,
Kew-Huat Yeoh,
Nazariah Mat Daud,
Tak Kin Chan,
Roman Fíra,
Oliver Stalder,
Kalman Tomanyiczka,
Lennart Robertsson
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ABSTRACT: Lasers from ten national metrology institutes (NMIs) plus the institutes responsible for Chinese Taipei and Hong Kong, China, were compared as part of the CCL-K11 ongoing key comparison, initiated by the 13th meeting of the Comité Consultative des Longueurs (CCL) in 2007. The absolute frequency of the f component of the R(127) 11-5 transition of molecular iodine was measured for these lasers following the technical protocol for CCL-K11. The results of these measurements are compiled in the present report. Main text. To reach the main text of this paper, click on Final Report [http://www.bipm.org/utils/common/pdf/final_reports/L/K11/CCL-K11_10.pdf] . Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/ [http://kcdb.bipm.org/] . The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
Metrologia 01/2011; 48(1A):04001. · 1.75 Impact Factor
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ABSTRACT: A frequency-stabilized light source emitting at 556 nm is realized by frequency-doubling a 1112-nm laser, which is phase-locked to a fiber-based optical frequency comb. The 1112-nm laser is either an ytterbium (Yb)-doped distributed feedback fiber laser or a master-slave laser system that uses an external cavity diode laser as a master laser. We have achieved the continuous frequency stabilization of the light source over a five-day period. With the light source, we have completed the second-stage magneto-optical trapping (MOT) of Yb atoms using the 1S0 - 3P1 intercombination transition. The temperature of the ultracold atoms in the MOT was 40 uK when measured using the time-of-flight method, and this is sufficient for loading the atoms into an optical lattice. The fiber-based frequency comb is shown to be a useful tool for controlling the laser frequency in cold-atom experiments. Comment: 18 pages, 6 figures, submitted to and accepted by J. Opt. Soc. Am. B (ID 125081)
05/2010;
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ABSTRACT: We constructed a fiber-based, hybrid terahertz (THz) spectrometer having two working modes, asynchronous-optical-sampling THz time-domain spectroscopy (AOS-THz-TDS) and multiple-frequency-heterodyning THz comb spectroscopy (MFH-THz-CS), by use of dual fiber-laser-based frequency combs. A spectral range of 2THz and dynamic range of 100 was achieved at the single sweep measurement of 200ms in the AOS-THz-TDS mode, whereas the detailed structure of the THz frequency comb was clearly observed in the MFH-THz-CS mode. The spectrometer features compactness, robustness, flexibility, and cost effectiveness, in addition to high spectral resolution in rapid data acquisition, and has the potential to become a powerful tool for practical applications.
Optics Letters 05/2010; 35(10):1689-91. · 3.40 Impact Factor
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ABSTRACT: A light source to drive the (1)S0-(3)P0 transition in Yb atoms is generated by 2 solid state lasers: a Nd:YAG laser and an Yb:YAG laser, using a sum-frequency generation (SFG) scheme. With a ridge waveguide (WG) periodically poled lithium niobate (PPLN) device, SFG power of about 150 mW is obtained at the required frequency. The zero-expansion temperature of a Fabry-Pérot etalon was determined by using a home-made fiber-based optical frequency comb running continuously for weeks. Frequency stabilization of the clock laser system was also evaluated by the optical frequency comb.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control 03/2010; 57(3):606-12. · 1.80 Impact Factor
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ABSTRACT: A continuously tunable, phase-locked, single-frequency, continuous-wave (cw) terahertz generator has been demonstrated around 120 GHz, corresponding to the spectral bandwidth of the F-band unitraveling-carrier photodiode (UTC-PD) used as a photomixer in this study. This cw-terahertz generator is based on photomixing of an accurately tunable cw laser and a tightly fixed cw laser in the optical frequency region, phase locked to two independent optical combs. The continuous tuning range of the presented method was three orders of magnitude around 0.1 THz and two orders around 1 THz broader than that of a previous photomixing method in which two cw lasers are phase locked to a single optical comb, and fully covered the available spectral bandwidth of the F-band UTC-PD. The spectral behavior of the tight locking and continuous tuning of 120 GHz cw-terahertz radiation was confirmed in real time by use of a terahertz-comb-referenced spectrum analyzer. This cw-terahertz generator shows promise as a terahertz clock and synthesizer for terahertz frequency metrology.
Journal of Applied Physics 03/2010; · 2.17 Impact Factor
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Yoshiaki Nakajima, Hajime Inaba,
Kazumoto Hosaka,
Kaoru Minoshima,
Atsushi Onae,
Masami Yasuda,
Takuya Kohno,
Sakae Kawato,
Takao Kobayashi,
Toshio Katsuyama,
Feng-Lei Hong
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ABSTRACT: We demonstrate that fiber-based frequency combs with multi-branch configurations can transfer both linewidth and frequency stability to another wavelength at the millihertz level. An intra-cavity electro-optic modulator is employed to obtain a broad servo bandwidth for repetition rate control. We investigate the relative linewidths between two combs using a stable continuous-wave laser as a common reference to stabilize the repetition rate frequencies in both combs. The achieved energy concentration to the carrier of the out-of-loop beat between the two combs was 99% and 30% at a bandwidth of 1 kHz and 7.6 mHz, respectively. The frequency instability of the comb was 3.7x10(-16) for a 1 s averaging time, improving to 5-8x10(-19) for 10000 s. We show that the frequency noise in the out-of-loop beat originates mainly from phase noise in branched optical fibers.
Optics Express 01/2010; 18(2):1667-76. · 3.59 Impact Factor
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ABSTRACT: We demonstrate a one-dimensional optical lattice clock with ultracold 171Yb atoms, which is free from the linear Zeeman effect. The absolute frequency of the 1S0(F = 1/2) - 3P0(F = 1/2) clock transition in 171Yb is determined to be 518 295 836 590 864(28) Hz with respect to the SI second. Comment: 11 pages, 5 figures, Appl. Phys. Express (Open Select Paper: open access)
06/2009;
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ABSTRACT: Distance measurements using the 821st-harmonic of the intermode beat frequency in an
optical comb with optical-sub-wavelength accuracy are demonstrated. Direct comparison with a laser interferometer for the same optical setup reveals good agreement to 20-nm.
Conference on Lasers and Electro-Optics; 05/2009
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Yoshiaki Nakajima, Hajime Inaba,
Kazumoto Hosaka,
Atsushi Ihara,
K-i Watabe,
Atsushi Onae,
Kaoru Minoshima,
Sakae Kawato,
Takao Kobayashi,
Toshio Katsuyama,
others
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ABSTRACT: We attempted to reduce a phase noise of an optical frequency comb by phase-locking a beat frequency between the comb and a narrow linewidth laser using a mode-locked fiber laser with an intracavity electro-optic modulator
Lasers and Electro-Optics, 2009 and 2009 Conference on Quantum electronics and Laser Science Conference. CLEO/QELS 2009. Conference on; 05/2009
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ABSTRACT: A stable light source obtained using sum-frequency generation (SFG) is developed for high-resolution spectroscopy at 578 nm. Hyperfine transitions of molecular iodine are observed by using the SFG light source with saturation spectroscopy. The light source is frequency stabilized to the observed hyperfine transition and achieves a stability of 2x10(-12) for a 1-s averaging time. The absolute frequency of the light source stabilized on the a1 component of the R(37)16-1 transition is determined as 518304551833 (2) kHz. This transition serves as a frequency reference for the (1)S(0)-(3)P(0) optical clock transition in neutral ytterbium (Yb).
Optics Express 03/2009; 17(3):1652-9. · 3.59 Impact Factor
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IEEE T. Instrumentation and Measurement. 01/2009; 58:1234-1240.
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Ken-ichi Watabe, Hajime Inaba,
K. Okumura,
Feng-Lei Hong,
John G. Hartnett,
Clayton R. Locke,
Giorgio Santarelli,
Shinya Yanagimachi,
Kaoru Minoshima,
Takeshi Ikegami,
Atsushi Onae,
Shin-ichi Ohshima,
Hirokazu Matsumoto
IEEE T. Instrumentation and Measurement. 01/2007; 56:632-636.
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ABSTRACT: A continuous-wave (cw) optical frequency synthesizer is demonstrated by using a monolithic-type cw optical parametric oscillator (cw-OPO) and an optical frequency comb. The cw-OPO is phase locked to an optical frequency comb that is phase locked to an atomic clock. The output frequency of the cw-OPO is frequency shifted with an electro-optic modulator, which makes it possible to tune the frequency continuously over 10 GHz. Furthermore, Doppler-free spectroscopy is performed using the optical frequency synthesizer for a cesium D1 line at 895 nm. The observed linewidth of 5 MHz is the natural linewidth of cesium. The center frequency of the line is consistent with a previous report.
Applied Optics 08/2006; 45(20):4910-5. · 1.41 Impact Factor
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Hajime Inaba,
Yuta Daimon,
Feng-Lei Hong,
Atsushi Onae,
Kaoru Minoshima,
Thomas R Schibli,
Hirokazu Matsumoto,
Masaaki Hirano,
Toshiaki Okuno,
Masashi Onishi,
Masataka Nakazawa
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ABSTRACT: We have developed a fiber-based frequency comb system consisting of a simple mode-locked fiber laser and a backward pumping amplifier combined with a highly nonlinear fiber with a short zerodispersion wavelength. As a result, the signal to noise ratio of the obtained carrier-envelope-offset frequency beat is larger than 45 dB at a bandwidth of 100 kHz. Furthermore, we have succeeded in measuring the optical frequencies of a 1542-nm acetylene-stabilized laser and a 532-nm iodinestabilized Nd:YAG laser continuously for more than one week using the fiber-based comb system. The long-term measurement revealed that the frequency stability of the iodine-stabilized laser was 5.7 x 10(-15) with 100 000 s averaging.
Optics Express 07/2006; 14(12):5223-31. · 3.59 Impact Factor
