Bio


How can we make optimal use of quantum systems (atoms, lasers, and electronics) to test fundamental physics principles, enable precision measurements of space-time and when feasible, develop useful devices, sensors, and instruments?

Professor Hollberg’s research objectives include high precision tests of fundamental physics as well as applications of laser physics and technology. This experimental program in laser/atomic physics focuses on high-resolution spectroscopy of laser-cooled and -trapped atoms, non-linear optical coherence effects in atoms, optical frequency combs, optical/microwave atomic clocks, and high sensitivity trace gas detection. Frequently this involves the study of laser noise and methods to circumvent measurement limitations, up to, and beyond, quantum limited optical detection. Technologies and tools utilized include frequency-stabilized lasers and chip-scale atomic devices. Based in the Hansen Experimental Physics Laboratory (HEPL), this research program has strong, synergistic, collaborative connections to the Stanford Center on Position Navigation and Time (SCPNT). Research directions are inspired by experience that deeper understanding of fundamental science is critical and vital in addressing real-world problems, for example in the environment, energy, and navigation. Amazing new technologies and devices enable experiments that test fundamental principles with high precision and sometimes lead to the development of better instruments and sensors. Ultrasensitive optical detection of atoms, monitoring of trace gases, isotopes, and chemicals can impact many fields. Results from well-designed experiments teach us about the “realities” of nature, guide and inform, occasionally produce new discoveries, frequently surprise, and almost always generate new questions and perspectives.

Academic Appointments


Administrative Appointments


  • Professor, Dept. of Physics, Stanford University (2011 - Present)
  • Lecturer, University of Colorado, Department of Physics (1988 - Present)
  • Postdoctoral position, A.T.&T. Bell Labs (1984 - 1985)
  • Postdoctoral position, Joint Institute for Laboratory Astrophysics (1984 - 1984)
  • Teaching assistant, Undergraduates Dept. Physics, Stanford University (1975 - 1975)
  • Fellow, Optical Society of America (2003 - 2003)
  • Fellow, American Physical Society (2003 - 2003)

Honors & Awards


  • Gold Medal Award, Department of Commerce (2001)
  • Silver Medal Award, Department of Commerce (2005)
  • I.I. Rabi award, IEEE-UFFC, International Frequency Control Symposium (2007)
  • William F. Meggers Award, Optical Society of America (2009)
  • Rank Prize for Optoelectronics, Rank Prize Funds (2013)

Boards, Advisory Committees, Professional Organizations


  • Chief Technical Officer, AOSense (2008 - 2011)
  • Staff scientist, National Institute of Standards and Technology, Time and Frequency Division (1985 - 2008)
  • Group Leader, National Institute of Standards and Technology, Time and Frequency Division (1985 - 2008)
  • Research Assistant, Joint Institute for Laboratory Astrophysics (JILA) (1977 - 1984)
  • Research Assistant, United States Geological Survey (1976 - 1977)
  • Member, American Physical Society (APS)
  • Member, Optical Society of America (OSA)
  • Member, International IEEE
  • Deputy Director, Stanford Center for Position Navigation and Time, SCPNT (2012 - 2013)
  • Member, Physics Dept. Graduate Admissions Committee, Stanford University (2012 - 2013)
  • Member, NASA Review Committee on Cold Atom Laboratory for Space (2013 - 2013)

Professional Education


  • B.S., Stanford University, Physics (1976)
  • Ph.D., University of Colorado, Boulder, Physics (1984)

Patents


  • Leo Hollberg, J. Kitching, R. Wynands, S. Knappe. "United States Patent 10/175,324 Method of minimizing the short-term frequency instability of laser-pumped atomic clocks"
  • Leo Hollberg, J. Kitching. "United States Patent 10/175,498 Miniature frequency standard based on all-optical containment vessel"
  • Leo Hollberg, J. Kitching, L-A. Liew, S. Knappe, J. Moreland, V.L. Velichansky, H.G. Robinson. "United States Patent 10/821,236 Micromachined alkali-atom vapor cells and method of microfabrication"
  • Leo Hollberg, Ma Lang-sheng, Jon H. Shirley, John L. Hall. "United States Patent 4,590,597. Modulation Transfer Spectroscopy for Stabilizing Lasers"
  • Leo Hollberg, B. Dahmani. "United States Patent 4,907,237. Optical Feedback Locking of Semiconductor Lasers"

All Publications


  • Femtosecond frequency comb measurement of absolute frequencies and hyperfine coupling constants in cesium vapor PHYSICAL REVIEW A Stalnaker, J. E., Mbele, V., Gerginov, V., Fortier, T. M., Diddams, S. A., Hollberg, L., Tanner, C. E. 2010; 81 (4)
  • Optical frequency stabilization of a 10 GHz Ti:sapphire frequency comb by saturated absorption spectroscopy in (87)rubidium PHYSICAL REVIEW A Heinecke, D. C., Bartels, A., Fortier, T. M., Braje, D. A., Hollberg, L., Diddams, S. A. 2009; 80 (5)
  • Brillouin-Enhanced Hyperparametric Generation of an Optical Frequency Comb in a Monolithic Highly Nonlinear Fiber Cavity Pumped by a cw Laser PHYSICAL REVIEW LETTERS Braje, D., Hollberg, L., Diddams, S. 2009; 102 (19)

    Abstract

    We demonstrate self-seeded generation of a broadband comb in a highly nonlinear fiber resonator. When pumped with a cw laser, the fiber cavity generates a comb with two characteristic spacings. Hyperparametric modes spaced by approximately 2 THz create the base structure of the comb, while commensurate Brillouin modes spaced by approximately 10 GHz populate the intermediate frequency gaps. The frequency modes are coherent, and the repetition rate of the comb has been locked to a microwave standard.

    View details for DOI 10.1103/PhysRevLett.102.193902

    View details for Web of Science ID 000266207700026

    View details for PubMedID 19518952

  • Generation of 20 GHz, sub-40 fs pulses at 960 nm via repetition-rate multiplication OPTICS LETTERS Kirchner, M. S., Braje, D. A., Fortier, T. M., Weiner, A. M., Hollberg, L., Diddams, S. A. 2009; 34 (7): 872-874

    Abstract

    Optical filtering of a stabilized 1 GHz optical frequency comb produces a 20 GHz comb with approximately 40 nm bandwidth (FWHM) at 960 nm. Use of a low-finesse Fabry-Pérot cavity in a double-pass configuration provides a broad cavity coupling bandwidth (Deltalambda/lambda approximately 10%) and large suppression (50 dB) of unwanted modes. Pulse durations shorter than 40 fs with less than 2% residual amplitude modulation are achieved.

    View details for Web of Science ID 000265429100004

    View details for PubMedID 19340155

  • Improved signal-to-noise ratio of 10 GHz microwave signals generated with a mode-filtered femtosecond laser frequency comb OPTICS EXPRESS Diddams, S. A., Kirchner, M., Fortier, T., Braje, D., Weiner, A. M., Hollberg, L. 2009; 17 (5): 3331-3340

    Abstract

    We use a Fabry-Perot cavity to optically filter the output of a Ti:sapphire frequency comb to integer multiples of the original 1 GHz mode spacing. This effectively increases the pulse repetition rate, which is useful for several applications. In the case of low-noise microwave signal generation, such filtering leads to improved linearity of the high-speed photodiodes that detect the mode-locked laser pulse train. The result is significantly improved signal-to-noise ratio at the 10 GHz harmonic with the potential for a shot-noise limited single sideband phase noise floor near -168 dBc/Hz.

    View details for Web of Science ID 000264090900033

    View details for PubMedID 19259170

  • Low-noise synthesis of microwave and millimetre-wave signals with optical frequency comb generator ELECTRONICS LETTERS Xiao, S., Hollberg, L., Diddams, S. A. 2009; 45 (3): 170-171
  • Generation of a 20 GHz train of subpicosecond pulses with a stabilized optical-frequency-comb generator OPTICS LETTERS Xiao, S., Hollberg, L., Diddams, S. A. 2009; 34 (1): 85-87

    Abstract

    With a modulator-based 10 GHz optical-frequency-comb generator at 1.55 microm, we report a 20 GHz repetitive train of optical pulses as short as 450 fs. The timing stability of the 20 GHz pulses, in addition to the phase for optical-comb modes, shows a strong dependence on the relative frequency detuning between the comb generator's cavity and the seed cw laser. With a new and simple scheme, the comb generator's cavity resonance was locked to a narrow-linewidth seed laser within an estimated optical-frequency range < or = 6 MHz, enabling high-fidelity 20 GHz subpicosecond pulses and stable optical-frequency-comb generation for indefinite periods.

    View details for Web of Science ID 000262889300029

    View details for PubMedID 19109648

  • Laser noise cancellation in single-cell CPT clocks IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT Gerginov, V., Knappe, S., Shah, V., Hollberg, L., Kitching, J. 2008; 57 (7): 1357-1361
  • Toward a low-jitter 10 GHz pulsed source with an optical frequency comb generator OPTICS EXPRESS Xiao, S., Hollberg, L., Newbury, N. R., Diddams, S. A. 2008; 16 (12): 8498-8508

    Abstract

    We demonstrate low residual timing jitter of 10 GHz pulses from a 1.55 ?m optical frequency comb generator based on a doubly-resonant electro-optic modulator. The comb spectral phase is shown to be linear but of different slopes for the two sides of the optical spectrum. The linear phase delay predicts well the measured timing delay of the two pulse trains from the comb generator. The pulse timing jitter is analyzed, and we illustrate that the pump laser's linewidth plays a dominant role in the timing jitter. For Fourier frequencies from 1 Hz to 10 MHz, integrated residual timing jitter at 10 GHz was reduced from approximately 94 fs to approximately 8 fs when the pump laser's linewidth was reduced from approximately 10 MHz to approximately 1 kHz. An electronic servo was then used to stabilize the Fabry-Pérot cavity in the comb generator. Integrated residual timing jitter was further reduced to approximately 6 fs, and the corresponding residual phase noise power density is -105 dBc/Hz at 1 Hz frequency offset from the 10 GHz pulse carrier.

    View details for Web of Science ID 000256859900019

    View details for PubMedID 18545564

  • Frequency evaluation of the doubly forbidden S-1(0)-> P-3(0) transition in bosonic Yb-174 PHYSICAL REVIEW A Poli, N., Barber, Z. W., Lemke, N. D., Oates, C. W., Ma, L. S., Stalnaker, J. E., Fortier, I. M., Diddams, S. A., Hollberg, L., Bergquist, J. C., Brusch, A., Jefferts, S., Heavner, I., Parker, I. 2008; 77 (5)
  • Optical lattice induced light shifts in an Yb atomic clock PHYSICAL REVIEW LETTERS Barber, Z. W., Stalnaker, J. E., Lemke, N. D., Poli, N., Oates, C. W., Fortier, T. M., Diddams, S. A., Hollberg, L., Hoyt, C. W., Taichenachev, A. V., Yudin, V. I. 2008; 100 (10)

    Abstract

    We present an experimental study of the lattice-induced light shifts on the (1)S(0) --> (3)P(0) optical clock transition (nu(clock) approximately 518 THz) in neutral ytterbium. The "magic" frequency nu(magic) for the 174Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p(3)P(0) --> 6s8p(3)P(0), 6s8p(3)P(2), and 6s5f(3)F(2) two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 microK deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10(-17).

    View details for DOI 10.1103/PhysRevLett.100.103002

    View details for Web of Science ID 000254024500019

    View details for PubMedID 18352181

  • The Yb Optical Lattice Clock Proc. 2008 Symp. on Freq. Stds. Metrology Lemke, N., Ludlow, A., Barber, Z., Poli, N., Hoyt, C. W., Ma, L. S., Stalnaker, J. E., Oates, C. W., Hollberg, L., Bergquist, J. C., Brusch, A., Fortier, T., Diddams, S. A., Heavner, T. P., Jefferts, S. R., Parker, T. E. 2008: 200–208
  • Chip-scale atomic devices: precision atomic instruments based on MEMS Proc. 2008 Symp. Freq. Stds. Metrology Kitching, J., Knappe, S., Gerginov, V., Shah, V., Schwindt, P. D., Lindseth, B., Donley, E. A., Wang, Y. J., Hodby, E., Eardley, M., Jimenez, R., Griffith, W. C., Geraci, A., Preusser, J., Liebisch, T. C., Robinson, H. G., Hollberg, L. 2008: 445–453
  • Optical-to-microwave frequency comparison with fractional uncertainty of 10(-15) APPLIED PHYSICS B-LASERS AND OPTICS Stalnaker, J. E., Diddams, S. A., Fortier, T. M., Kim, K., Hollberg, L., Bergquist, J. C., Itano, W. M., DELANY, M. J., Lorini, L., Oskay, W. H., Heavner, T. P., Jefferts, S. R., Levi, F., Parker, T. E., Shirley, J. 2007; 89 (2-3): 167-176
  • Demonstration of high-performance compact magnetic shields for chip-scale atomic devices REVIEW OF SCIENTIFIC INSTRUMENTS Donley, E. A., Hodby, E., Hollberg, L., Kitching, J. 2007; 78 (8)

    Abstract

    We have designed and tested a set of five miniature nested magnetic shields constructed of high-permeability material, with external volumes for the individual shielding layers ranging from 0.01 to 2.5 cm(3). We present measurements of the longitudinal and transverse shielding factors (the ratio of external to internal magnetic field) of both individual shields and combinations of up to three layers. The largest shielding factor measured was 6 x 10(6) for a nested set of three shields, and from our results we predict a shielding factor of up to 1 x 10(13) when all five shields are used. Two different techniques were used to measure the internal field: a chip-scale atomic magnetometer and a commercially available magnetoresistive sensor. Measurements with the two methods were in good agreement.

    View details for DOI 10.1063/1.2767533

    View details for Web of Science ID 000249156700003

    View details for PubMedID 17764308

  • High-contrast coherent population trapping resonances using four-wave mixing in Rb-87 OPTICS LETTERS Shah, V., Knappe, S., Hollberg, L., Kitching, J. 2007; 32 (10): 1244-1246

    Abstract

    We demonstrate very high-contrast coherent population trapping(1) (CPT) resonances by using four-wave mixing in (87)Rb atoms. In the experiment, we take advantage of the spectral overlap between F=2-->F(?) and F=3-->F(?) optical resonances on the D1 line of (87)Rb and (85)Rb atoms, respectively, to eliminate the DC-light background from the CPT resonance signal. We observe a CPT resonance with a contrast in the range of 90%, compared with a few percent achieved by alternative methods.

    View details for Web of Science ID 000246121000016

    View details for PubMedID 17440548

  • Microfabricated saturated absorption laser spectrometer OPTICS EXPRESS Knappe, S. A., Robinson, H. G., Hollberg, L. 2007; 15 (10): 6293-6299

    Abstract

    We demonstrate a miniature microfabricated saturated absorption laser spectrometer. The system consists of miniature optics, a microfabricated Rb vapor cell, heaters, and a photodetector, all contained within a volume of 0.1 cm(3). Saturated absorption spectra were measured with a diode laser at 795 nm. They are comparable to signals obtained with standard table-top setups, although the rubidium vapor cell has an interior volume of only 1 mm(3). We discuss the performance and prospects for using such systems as a miniature optical wavelength reference, compatible with transportable instruments.

    View details for Web of Science ID 000246474300042

    View details for PubMedID 19546933

  • Low-noise optical injection locking of a resonant tunneling diode to a stable optical frequency comb APPLIED PHYSICS LETTERS Ramond, T. M., Hollberg, L., Juodawlkis, P. W., Calawa, S. D. 2007; 90 (17)

    View details for DOI 10.1063/1.2734368

    View details for Web of Science ID 000246568600024

  • Absolute frequency measurement of the neutral Ca-40 optical frequency standard at 657nm based on microkelvin atoms METROLOGIA Wilpers, G., Oates, C. W., Diddams, S. A., Bartels, A., Fortier, T. M., Oskay, W. H., Bergquist, J. C., Jefferts, S. R., Heavner, T. P., Parker, T. E., Hollberg, L. 2007; 44 (2): 146-151
  • Measurement of excited-state transitions in cold calcium atoms by direct femtosecond frequency-comb spectroscopy PHYSICAL REVIEW A Stalnaker, J. E., Le Coq, Y., Fortier, T. M., Diddams, S. A., Oates, C. W., Hollberg, L. 2007; 75 (4)
  • Precision atomic spectroscopy for improved limits on variation of the fine structure constant and local position invariance PHYSICAL REVIEW LETTERS Fortier, T. M., Ashby, N., Bergquist, J. C., Delaney, M. J., Diddams, S. A., Heavner, T. P., Hollberg, L., Itano, W. M., Jefferts, S. R., Kim, K., Levi, F., Lorini, L., Oskay, W. H., Parker, T. E., Stalnaker, J. E. 2007; 98 (7)

    Abstract

    We report tests of local position invariance and the variation of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground state hyperfine splitting in 133Cs. Analysis of the frequency ratio of the two clocks, extending over 6 yr at NIST, is used to place a limit on its fractional variation of <5.8x10(-6) per change in normalized solar gravitational potential. The same frequency ratio is also used to obtain 20-fold improvement over previous limits on the fractional variation of the fine structure constant of |alpha/alpha|<1.3x10(-16) yr-1, assuming invariance of other fundamental constants. Comparisons of our results with those previously reported for the absolute optical frequency measurements in H and 171Yb+ vs other 133Cs standards yield a coupled constraint of -1.5x10(-15)

    View details for DOI 10.1103/PhysRevLett.98.070801

    View details for Web of Science ID 000244250300012

    View details for PubMedID 17359009

  • Molecular fingerprinting with the resolved modes of a femtosecond laser frequency comb NATURE Diddams, S. A., Hollberg, L., Mbele, V. 2007; 445 (7128): 627-630

    Abstract

    The control of the broadband frequency comb emitted from a mode-locked femtosecond laser has permitted a wide range of scientific and technological advances--ranging from the counting of optical cycles for next-generation atomic clocks to measurements of phase-sensitive high-field processes. A unique advantage of the stabilized frequency comb is that it provides, in a single laser beam, about a million optical modes with very narrow linewidths and absolute frequency positions known to better than one part in 10(15) (ref. 5). One important application of this vast array of highly coherent optical fields is precision spectroscopy, in which a large number of modes can be used to map internal atomic energy structure and dynamics. However, an efficient means of simultaneously identifying, addressing and measuring the amplitude or relative phase of individual modes has not existed. Here we use a high-resolution disperser to separate the individual modes of a stabilized frequency comb into a two-dimensional array in the image plane of the spectrometer. We illustrate the power of this technique for high-resolution spectral fingerprinting of molecular iodine vapour, acquiring in a few milliseconds absorption images covering over 6 THz of bandwidth with high frequency resolution. Our technique for direct and parallel accessing of stabilized frequency comb modes could find application in high-bandwidth spread-spectrum communications with increased security, high-resolution coherent quantum control, and arbitrary optical waveform synthesis with control at the optical radian level.

    View details for DOI 10.1038/nature05524

    View details for Web of Science ID 000244039400039

    View details for PubMedID 17287805

  • Optical frequency standards based on mercury and aluminum ions Proc. 2007 SPIE Conf. Itano, W. M., Bergquist, J. C., Brusch, A., Diddams, S. A., Fortier, T. M., Heavner, T. P., Hollberg, L., Hume, D. B., Jefferts, S. R., Lorini, L., Parker, T. E., Rosenband, T., Stalnaker, J. E. 2007: 11
  • A proposed laser frequency comb based wavelength reference for high resolution spectroscopy Proc. 2007 SPIE Conf. Osterman, S., Diddams, S. A., Beasley, M., Froning, C., Hollberg, L., MacQueen, P., Mbele, V., Weiner, A. 2007: 9
  • Self-Injection Locking of a Low-Power Microwave Oscillator by Using Four-Wave Mixing in an Atomic Vapor Proc. 2007 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and EFTF Conf. Brannon, A., Shah, V., Popovic, Z., Gerginov, V., Knappe, S., Hollberg, L., Kitching, J. 2007: 275–278
  • Generation of coherent population trapping resonances with nearly 100% transmission contrast Joint IEEE International Frequency Control Symposium/21st European Frequency and Time Forum Shah, V., Knappe, S., Hollberg, L., Kitching, J. IEEE, ELECTRON DEVICES SOC & RELIABILITY GROUP. 2007: 1339–1341
  • Lattice-based optical clock using an even isotope of Yb Proc. 2007 SPIE Conf. Barber, Z., Hoyt, C., Stalnaker, J., Lemke, N., Oates, C. W., Fortier, T., Diddams, S. A., Hollberg, L. 2007: 9
  • Advances in Chip-Scale Atomic Frequency References at NIST Proc. 2007 SPIE Conf. Knappe, S., Shah, V., Brannon, A., Gerginov, V., Robinson, H. G., Popovic, Z., Hollberg, L., Kitching, J. 2007: 10
  • Improved limits on variation of the fine structure constant and violation of local position invariance Joint IEEE International Frequency Control Symposium/21st European Frequency and Time Forum Fortier, T. M., Ashby, N., Bergquist, J. C., Delaney, M. J., Diddams, S. A., Heavner, T. P., Hollberg, L., Itano, W. M., Jefferts, S. R., Kim, K., Oskay, W. H., Parker, T. E., Shirley, J., Stalnaker, J. E., Levi, F., Lorini, L. IEEE, ELECTRON DEVICES SOC & RELIABILITY GROUP. 2007: 663–665
  • Frequency uncertainty for optically referenced femtosecond laser frequency combs IEEE JOURNAL OF QUANTUM ELECTRONICS Ma, L., Bi, Z., Bartels, A., Kim, K., Robertsson, L., Zucco, M., Windeler, R. S., Wilpers, G., Oates, C., Hollberg, L., Diddams, S. A. 2007; 43 (1): 139-146
  • Long-term Stability of the NIST Chip-Scale Atomic Clock Physics Packages Proc. 2007 SPIE Conf. Knappe, S., Gerginov, V., Shah, V., Brannon, A., Robinson, H. G., Hollberg, L., Kitching, J. 2007: 9
  • Stable laser system for probing the clock transition at 578 nm in neutral ytterbium Joint IEEE International Frequency Control Symposium/21st European Frequency and Time Forum Oates, C. W., Barber, Z. W., StaInaker, J. E., Hoyt, C. W., Fortier, T. M., Diddams, S. A., Hollberg, L. IEEE, ELECTRON DEVICES SOC & RELIABILITY GROUP. 2007: 1274–1277
  • Magnetic resonance in an atomic vapor excited by a mechanical resonator PHYSICAL REVIEW LETTERS Wang, Y., Eardley, M., Knappe, S., Moreland, J., Hollberg, L., Kitching, J. 2006; 97 (22)

    Abstract

    We demonstrate a direct resonant interaction between the mechanical motion of a mesoscopic resonator and the spin degrees of freedom of a sample of neutral atoms in the gas phase. This coupling, mediated by a magnetic particle attached to the tip of the miniature mechanical resonator, excites a coherent precession of the atomic spins about a static magnetic field. The novel coupled atom-resonator system may enable development of low-power, high-performance sensors, and enhance research efforts connected with the manipulation of cold atoms, quantum control, and high-resolution microscopy.

    View details for DOI 10.1103/PhysRevLett.97.227602

    View details for Web of Science ID 000242538700064

    View details for PubMedID 17155843

  • Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb PHYSICAL REVIEW LETTERS Fortier, T. M., Le Coq, Y., Stalnaker, J. E., ORTEGA, D., Diddams, S. A., Oates, C. W., Hollberg, L. 2006; 97 (16)

    Abstract

    We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity.

    View details for DOI 10.1103/PhysRevLett.97.163905

    View details for Web of Science ID 000241405400025

    View details for PubMedID 17155398

  • Continuous light-shift correction in modulated coherent population trapping clocks APPLIED PHYSICS LETTERS Shah, V., Gerginov, V., Schwindt, P. D., Knappe, S., Hollberg, L., Kitching, J. 2006; 89 (15)

    View details for DOI 10.1063/1.2360921

    View details for Web of Science ID 000241247900024

  • Improved uncertainty budget for optical frequency measurements with microkelvin neutral atoms: Results for a high-stability Ca-40 optical frequency standard APPLIED PHYSICS B-LASERS AND OPTICS Wilpers, G., Oates, C. W., Hollberg, L. 2006; 85 (1): 31-44
  • Compact phase delay technique for increasing the amplitude of coherent population trapping resonances in open Lambda systems OPTICS LETTERS Shah, V., Knappe, S., Schwindt, P. D., Gerginov, V., Kitching, J. 2006; 31 (15): 2335-2337

    Abstract

    We propose and demonstrate a novel technique for increasing the amplitude of coherent population trapping (CPT) resonances in open Lambda systems. The technique requires no complex modifications to the conventional CPT setup and is compatible with standard microfabrication processes. The improvement in the CPT resonance amplitude as a function of intensity of the excitation light agrees well with the theory based on ideal open and closed Lambda systems.

    View details for Web of Science ID 000239173300031

    View details for PubMedID 16832477

  • Single-atom optical clock with high accuracy PHYSICAL REVIEW LETTERS Oskay, W. H., Diddams, S. A., Donley, E. A., Fortier, T. M., Heavner, T. P., Hollberg, L., Itano, W. M., Jefferts, S. R., Delaney, M. J., Kim, K., Levi, F., Parker, T. E., Bergquist, J. C. 2006; 97 (2)

    Abstract

    For the past 50 years, atomic standards based on the frequency of the cesium ground-state hyperfine transition have been the most accurate time pieces in the world. We now report a comparison between the cesium fountain standard NIST-F1, which has been evaluated with an inaccuracy of about 4 x 10(-16), and an optical frequency standard based on an ultraviolet transition in a single, laser-cooled mercury ion for which the fractional systematic frequency uncertainty was below 7.2 x 10(-17). The absolute frequency of the transition was measured versus cesium to be 1,064,721,609,899,144.94 (97) Hz, with a statistically limited total fractional uncertainty of 9.1 x 10(-16) the most accurate absolute measurement of an optical frequency to date.

    View details for DOI 10.1103/PhysRevLett.97.020801

    View details for Web of Science ID 000239057200007

    View details for PubMedID 16907426

  • Microfabricated atomic clocks and magnetometers 10th IEEE/LEOS International Conference on Optical MEMs and Their Applications Knappe, S., Schwindt, P. D., Gerginov, V., Shah, V., Liew, L., Moreland, J., Robinson, H. G., Hollberg, L., Kitching, J. IOP PUBLISHING LTD. 2006: S318–S322
  • Atomic-based stabilization for laser-pumped atomic clocks OPTICS LETTERS Gerginov, V., Shah, V., Knappe, S., Hollberg, L., Kitching, J. 2006; 31 (12): 1851-1853

    Abstract

    We describe a novel technique for stabilizing frequency shifts in laser-interrogated vapor-cell atomic clocks. The method suppresses frequency shifts due to changes in the laser frequency, intensity, and modulation index as well as atomic vapor density. The clock operating parameters are monitored by using the atoms themselves, rather than by using conventional schemes for laser frequency and cell temperature control. The experiment is realized using a chip-scale atomic clock. The novel atomic-based stabilization approach results in a simpler setup and improved long-term performance.

    View details for Web of Science ID 000238156800025

    View details for PubMedID 16729092

  • Long-term frequency instability of atomic frequency references based on coherent population trapping and microfabricated vapor cells JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Gerginov, V., Knappe, S., Shah, V., Schwindt, P. D., Hollberg, L., Kitching, J. 2006; 23 (4): 593-597
  • Magnetic field-induced spectroscopy of forbidden optical transitions with application to lattice-based optical atomic clocks PHYSICAL REVIEW LETTERS Taichenachev, A. V., Yudin, V. I., Oates, C. W., Hoyt, C. W., Barber, Z. W., Hollberg, L. 2006; 96 (8)

    Abstract

    We develop a method of spectroscopy that uses a weak static magnetic field to enable direct optical excitation of forbidden electric-dipole transitions that are otherwise prohibitively weak. The power of this scheme is demonstrated using the important application of optical atomic clocks based on neutral atoms confined to an optical lattice. The simple experimental implementation of this method--a single clock laser combined with a dc magnetic field--relaxes stringent requirements in current lattice-based clocks (e.g., magnetic field shielding and light polarization), and could therefore expedite the realization of the extraordinary performance level predicted for these clocks. We estimate that a clock using alkaline-earth-like atoms such as Yb could achieve a fractional frequency uncertainty of well below 10(-17) for the metrologically preferred even isotopes.

    View details for DOI 10.1103/PhysRevLett.96.083001

    View details for Web of Science ID 000235736200021

    View details for PubMedID 16606175

  • Direct excitation of the forbidden clock transition in neutral Yb-174 atoms confined to an optical lattice PHYSICAL REVIEW LETTERS Barber, Z. W., Hoyt, C. W., Oates, C. W., Hollberg, L., Taichenachev, A. V., Yudin, V. I. 2006; 96 (8)

    Abstract

    We report direct single-laser excitation of the strictly forbidden (6s2)1S0 <--> (6s6p)3P0 clock transition in 174Yb atoms confined to a 1D optical lattice. A small (approximately 1.2 mT) static magnetic field was used to induce a nonzero electric dipole transition probability between the clock states at 578.42 nm. Narrow resonance linewidths of 20 Hz (FWHM) with high contrast were observed, demonstrating a resonance quality factor of 2.6 x 10(13). The previously unknown ac Stark shift-canceling (magic) wavelength was determined to be 759.35 +/- 0.02 nm. This method for using the metrologically superior even isotope can be easily implemented in current Yb and Sr lattice clocks and can create new clock possibilities in other alkaline-earth-like atoms such as Mg and Ca.

    View details for DOI 10.1103/PhysRevLett.96.083002

    View details for Web of Science ID 000235736200022

    View details for PubMedID 16606176

  • Optical frequency measurements of 6s S-2(1/2)-6p P-2(1/2) (D-1) transitions in Cs-133 and their impact on the fine-structure constant PHYSICAL REVIEW A Gerginov, V., Calkins, K., Tanner, C. E., McFerran, J. J., Diddams, S., Bartels, A., Hollberg, L. 2006; 73 (3)
  • Chip-scale atomic devices at NIST Proc. 2006 SPIE Conf. Knappe, S., Schwindt, P. D., Gerginov, V., Shah, V., Brannon, A., Lindseth, B., Liew, L., Robinson, H. G., Moreland, J. M., Popovic, Z., Hollberg, L., Kitching, J. 2006: 8
  • Stable Isotopic Analysis of Atmospheric Methane by Infrared Spectroscopy Using Difference Frequency Generation in Periodically Poled Lithium Niobate Appl. Opt. Trudeau, M. E., Chen, P., Garcia, G. A., Hollberg, L. W., Tans, P. P. 2006; 45: 4136-4141
  • Absolute Optical Frequency Measurements with a Fractional Uncertainty at 1 x 10-15 Proc. 2006 IEEE Intl. Freq. Cont. Symp. Stalnaker, J., Diddams, S. A., Kim, K., Hollberg, L., Donley, E. A., Heavner, T. P., Jefferts, S. R., Levi, F., Parker, T. E., Bergquist, J. C., Itano, W. M., Jensen, M. J., Lorini, L., Oskay, W. H., Fortier, T. 2006
  • Spectral phase dependence of phase noise of stabilized optical frequency combs Proc. 2006 Ultrafast Phenomena Conf. Quraishi, Q., Diddams, S. A., Hollberg, L. 2006: 3
  • Atom-based stabilization for laserpumped atomic clocks Proc. 2006 EFTF Conf. Gerginov, V., Shah, V., Knappe, S., Hollberg, L., Kitching, J. 2006: 224–228
  • Stability measurements of the Ca and Yb optical frequency standards IEEE International Frequency Control Symposium and Exposition Oates, C. W., Hoyt, C. W., Le Coq, Y., Barber, Z. W., Fortier, T. M., Stalnaker, J. E., Diddams, S. A., Hollberg, L. IEEE. 2006: 74–79
  • Active light shift stabilization in modulated CPT clocks IEEE International Frequency Control Symposium and Exposition Shah, V., Schwindt, P. D., Gerginov, V., Knappe, S., Hollberg, L., Kitching, J. IEEE. 2006: 699–701
  • High-resolution spectral fingerprinting with a stabilized femtosecond laser frequency comb Proc. 2006 Ultrafast Phenomena Conf. Diddams, S. A., Hollberg, L., Mbele, V. 2006: 3
  • Spectroscopy of neutral ^174^Yb in a One-Dimensional Optical lattice Proc. 2006 EFTF Conf. Hoyt, C., Barber, Z., Oates, C. W., Taichenachev, A. V., Yudin, V. I., Hollberg, L. 2006: 324–328
  • A local oscillator for chip-scale atomic clocks at NIST IEEE International Frequency Control Symposium and Exposition Brannon, A., Jankovic, M., Breitbarth, J., Popovic, Z., Gerginov, V., Shah, V., Knappe, S., Hollberg, L., Kitching, J. IEEE. 2006: 443–447
  • A Compact High Stability Optical Clock Based on Laser-Cooled Ca Proc. 2006 EFTF Conf. Oates, C. W., LeCoq, Y., Wilpers, G., Hollberg, L. 2006: 346–349
  • Wavelength references for interferometry in air APPLIED OPTICS Fox, R. W., Washburn, B. R., Newbury, N. R., Hollberg, L. 2005; 44 (36): 7793-7801

    Abstract

    Cavity-mode wavelengths in air are determined by measuring a laser's frequency while it is locked to the mode in vacuum during a calibration step and subsequently correcting the mode wavelength for atmospheric pressure compression, temperature difference, and material aging. Using a Zerodur ring cavity, we demonstrate a repeatability of +/- 2 x 10(-8) (3sigma), with the wavelength accuracy limited to +/- 4 x 10(-8) by knowledge of the absolute helium gas temperature during the pressure calibration. Mirror cleaning perturbed the mode frequency by less than deltav/v approximately 3 x 10(-9), limited by temperature correction residuals.

    View details for Web of Science ID 000234078200016

    View details for PubMedID 16381529

  • Self-oscillating rubidium magnetometer using nonlinear magneto-optical rotation REVIEW OF SCIENTIFIC INSTRUMENTS Schwindt, P. D., Hollberg, L., Kitching, J. 2005; 76 (12)

    View details for DOI 10.1063/1.2136885

    View details for Web of Science ID 000234340500048

  • Atomic vapor cells for chip-scale atomic clocks with improved long-term frequency stability OPTICS LETTERS Knappe, S., Gerginov, V., Schwindt, P. D., Shah, V., Robinson, H. G., Hollberg, L., Kitching, J. 2005; 30 (18): 2351-2353

    Abstract

    A novel technique for microfabricating alkali atom vapor cells is described in which alkali atoms are evaporated into a micromachined cell cavity through a glass nozzle. A cell of interior volume 1 mm3, containing 87Rb and a buffer gas, was made in this way and integrated into an atomic clock based on coherent population trapping. A fractional frequency instability of 6 x 10(-12) at 1000 s of integration was measured. The long-term drift of the F=1, mF=0-->F=2, mF=0 hyperfine frequency of atoms in these cells is below 5 x 10(-11)/day.

    View details for Web of Science ID 000231964600001

    View details for PubMedID 16196316

  • Observation and absolute frequency measurements of the S-1(0)-P-3(0) optical clock transition in neutral ytterbium PHYSICAL REVIEW LETTERS Hoyt, C. W., Barber, Z. W., Oates, C. W., Fortier, T. M., Diddams, S. A., Hollberg, L. 2005; 95 (8)

    Abstract

    We report the direct excitation of the highly forbidden (6s2) 1S0 <--> (6s6p) 3P0 optical transition in two odd isotopes of neutral ytterbium. As the excitation laser frequency is scanned, absorption is detected by monitoring the depletion from an atomic cloud at approximately 70 microK in a magneto-optical trap. The measured frequency in 171Yb (F=1/2) is 518,295,836,591.6 +/- 4.4 kHz. The measured frequency in 173Yb (F=5/2) is 518,294,576,847.6 +/- 4.4 kHz. Measurements are made with a femtosecond-laser frequency comb calibrated by the National Institute of Standards and Technology cesium fountain clock and represent nearly a 10(6)-fold reduction in uncertainty. The natural linewidth of these J=0 to J=0 transitions is calculated to be approximately 10 mHz, making them well suited to support a new generation of optical atomic clocks based on confinement in an optical lattice.

    View details for DOI 10.1103/PhysRevLett.95.083003

    View details for Web of Science ID 000231310900020

    View details for PubMedID 16196856

  • High-resolution spectroscopy with a femtosecond laser frequency comb OPTICS LETTERS Gerginov, V., Tanner, C. E., Diddams, S. A., Bartels, A., Hollberg, L. 2005; 30 (13): 1734-1736

    Abstract

    The output of a mode-locked femtosecond laser is used for precision single-photon spectroscopy of 133Cs in an atomic beam. By changing the laser's repetition rate, the cesium D1 (6s 2S(1/2)-->6p 2P(1/2)) and D2 (6s 2S(1/2)-->6p 2P(3/2)) transitions are detected and the optical frequencies are measured with accuracy similar to that obtained with a cw laser. Control of the femtosecond laser repetition rate by use of the atomic fluorescence is also implemented, thus realizing a simple cesium optical clock.

    View details for Web of Science ID 000230193000046

    View details for PubMedID 16075554

  • The measurement of optical frequencies METROLOGIA Hollberg, L., Diddams, S., Bartels, A., Fortier, T., Kim, K. 2005; 42 (3): S105-S124
  • Microfabricated atomic frequency references METROLOGIA Kitching, J., Knappe, S., Liew, L., Moreland, J., Schwindt, P. D., Shah, V., Gerginov, V., Hollberg, L. 2005; 42 (3): S100-S104
  • Low-noise synthesis of microwave signals from an optical source ELECTRONICS LETTERS McFerran, J. J., Ivanov, E. N., Bartels, A., Wilpers, G., Oates, C. W., Diddams, S. A., Hollberg, L. 2005; 41 (11): 650-651
  • Optical frequency/wavelength references JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Hollberg, L., Oates, C. W., Wilpers, G., Hoyt, C. W., Barber, Z. W., Diddams, S. A., Oskay, W. H., Bergquist, J. C. 2005; 38 (9): S469-S495
  • Stabilized frequency comb with a self-referenced femtosecond Cr : forsterite laser OPTICS LETTERS Kim, K., Washburn, B. R., Wilpers, G., Oates, C. W., Hollberg, L., Newbury, N. R., Diddams, S. A., Nicholson, J. W., Yan, M. E. 2005; 30 (8): 932-934

    Abstract

    A frequency comb is generated with a Cr:forsterite femtosecond laser, spectrally broadened through a highly nonlinear optical fiber to span from 1.0 to 2.2 ,m, and stabilized using the f-to-2f self-referencing technique. The repetition rate and the carrier-envelope offset frequency are stabilized to a hydrogen maser, calibrated by a cesium atomic fountain clock. Simultaneous frequency measurement of a 657-nm cw laser by use of the stabilized frequency combs from this Cr:forsterite system and a Ti:sapphire laser agree at the 10(-13) level. The frequency noise of the comb components is observed at 1064, 1314, and 1550 nm by comparing the measured beat frequencies between cw lasers and the supercontinuum frequency combs.

    View details for Web of Science ID 000228235800041

    View details for PubMedID 15865403

  • International comparisons of femtosecond laser frequency combs 24th Conference on Precision Electromagnetic Measurements (CPEM2004) Ma, L. S., Bi, Z. Y., Bartels, A., Robertsson, L., Zucco, M., Windeler, R. S., Wilpers, G., Oates, C., Hollberg, L., Diddams, S. A. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 2005: 746–49
  • Femtosecond-laser-based synthesis of ultrastable microwave signals from optical frequency references OPTICS LETTERS Bartels, A., Diddams, S. A., Oates, C. W., Wilpers, G., Bergquist, J. C., Oskay, W. H., Hollberg, L. 2005; 30 (6): 667-669

    Abstract

    We use femtosecond laser frequency combs to convert optical frequency references to the microwave domain, where we demonstrate the synthesis of 10-GHz signals having a fractional frequency instability of < or =3.5 x 10(-15) at a 1-s averaging time, limited by the optical reference. The residual instability and phase noise of the femtosecond-laser-based frequency synthesizers are 6.5 x 10(-16) at 1 s and -98 dBc/Hz at a 1-Hz offset from the 10-GHz carrier, respectively. The timing jitter of the microwave signals is 3.3 fs.

    View details for Web of Science ID 000227515100027

    View details for PubMedID 15792011

  • A chip-scale atomic clock based on Rb-87 with improved frequency stability OPTICS EXPRESS Knappe, S., Schwindt, P. D., Shah, V., Hollberg, L., Kitching, J., Liew, L., Moreland, J. 2005; 13 (4): 1249-1253

    Abstract

    We demonstrate a microfabricated atomic clock physics package based on coherent population trapping (CPT) on the D1 line of 87Rb atoms. The package occupies a volume of 12 mm3 and requires 195 mW of power to operate at an ambient temperature of 200 degrees C. Compared to a previous microfabricated clock exciting the D2 transition in Cs [1], this 87Rb clock shows significantly improved short- and long-term stability. The instability at short times is 4 x?10-11 / tau?/2 and the improvement over the Cs device is due mainly to an increase in resonance amplitude. At longer times (tau?> 50 s), the improvement results from the reduction of a slow drift to ?5 x 10-9 / day. The drift is most likely caused by a chemical reaction of nitrogen and barium inside the cell. When probing the atoms on the D1 line, spin-exchange collisions between Rb atoms and optical pumping appear to have increased importance compared to the D2 line.

    View details for Web of Science ID 000227252700027

    View details for PubMedID 19494996

  • Nonlinear-resonance line shapes: Dependence on the transverse intensity distribution of a light beam (vol A 69, art non 024501, 2004) PHYSICAL REVIEW A Taichenachev, A. V., Tumaikin, A. M., Yudin, V. I., Stahler, M., Wynands, R., Kitching, J., Hollberg, L. 2005; 71 (2)
  • Generation of Microwaves with Ultra-low Phase-Noise from an Optical Clock Proc. 2004 IEEE Microwave Photonics Conf. Hollberg, L., Diddams, S. A., Bartels, A., McFerran, J. J., Ivanov, E. N., Wilpers, G., Oates, C. W., Oskay, W. H., Bergquist, J. C. 2005: 9–12
  • Observations of large atomic-recoil-induced asymmetries in cold atom spectroscopy Phys. Rev. A Oates, C. W., Wilpers, G., Hollberg, L. 2005; 71 (6): 023404
  • Microwave transitions and nonlinear magneto-optical rotation in anti-relaxation-coated cells PHYSICAL REVIEW A Budker, D., Hollberg, L., Kimball, D. F., Kitching, J., Pustelny, S., Yashchuk, V. V. 2005; 71 (1)
  • Study of Excess Noise Associated with Demodulation of Ultra-Short Infrared Pulses IEEE T. Ultrason. Ferr. Ivanov, E. N., Diddams, S. A., Hollberg, L. 2005; 52: 1068-1074
  • Component-level demonstration of a microfabricated atomic frequency reference IEEE International Frequency Control Symposium and Exposition Gerginov, V., Knappe, S., Schwindt, P. D., Shah, V., Liew, L., Moreland, J., Robinson, H. G., HOLBERG, L., Kitching, J., Brannon, A., Breitbarth, J., Popovic, Z. IEEE. 2005: 758–766
  • Microfabricated atomic clocks and magnetometers 17th International Conference on Laser Spectroscopy Knappe, S., Schwindt, P. D., Gerginov, V., Shah, V., Robinson, H. G., Hollberg, L., Kitching, J. WORLD SCIENTIFIC PUBL CO PTE LTD. 2005: 337–345
  • A Measurement of the Absolute Frequency of the 199Hg Single-ion Optical Clock Proc. 2005 EFTF Conf. Oskay, W. H., Jensen, M. J., Jefferts, S. R., Donley, E. A., Heavner, T. P., Parker, T. E., Kim, K., Fortier, T., Bartels, A., Diddams, S. A., Hollberg, L., Itano, W. M., Bergquist, J. C. 2005
  • Noise properties of microwave signals synthesized with femtosecond lasers IEEE International Frequency Control Symposium and Exposition Ivanov, E. N., McFerran, J. J., Diddams, S. A., Hollberg, L. IEEE. 2005: 932–936
  • Chip-Scale Atomic Frequency References: Fabrication and Performance Proc. 2005 EFTF Conf. Kitching, J., Knappe, S., Liew, L., Moreland, J., Robinson, H. G., Schwindt, P., Shah, V., Gerginov, V., Hollberg, L. 2005: 575–580
  • Optical frequency measurements with the global positioning system: tests with an iodine-stabilized He-Ne laser APPLIED OPTICS Fox, R. W., Diddams, S. A., Bartels, A., Hollberg, L. 2005; 44 (1): 113-120

    Abstract

    Global positioning system- (GPS-) referenced optical frequency combs based on mode-locked lasers offer calibrations for length metrology traceable to international length standards through the SI second and the speed of light. The absolute frequency of an iodine-stabilized He-Ne laser [127I2 R(127) 11-5 f component] was measured with a femtosecond comb referenced to a multichannel GPS timing receiver. The expected performance and limitations of GPS-referenced comb measurements are discussed.

    View details for DOI 10.1364/AO.44.000113

    View details for Web of Science ID 000226323200015

    View details for PubMedID 15662892

  • Femtosecond Lasers for Optical Clocks and Low Noise Frequency Synthesis Femtosecond Optical Frequency Comb: Principle, Operation, and Applications Femtosecond Optical Frequency Comb: Principle, Operation, and Applications Diddams, S. A., Ye, J., Hollberg, L. edited by Ye, J., Cundiff, S. T. Springer. 2005: 38
  • The optical calcium frequency standards of PTB and NIST COMPTES RENDUS PHYSIQUE Sterr, U., Degenhardt, C., Stoehr, H., Lisdat, C., Schnatz, H., Helmcke, J., Riehle, F., Wilpers, G., Oates, C., Hollberg, L. 2004; 5 (8): 845-855
  • Optical frequency measurements of 6s S-2(1/2)-6p P-2(3/2) transition in a Cs-133 atomic beam using a femtosecond laser frequency comb PHYSICAL REVIEW A Gerginov, V., Tanner, C. E., Diddams, S., Bartels, A., Hollberg, L. 2004; 70 (4)
  • A microfabricated atomic clock APPLIED PHYSICS LETTERS Knappe, S., Shah, V., Schwindt, P. D., Hollberg, L., Kitching, J., Liew, L. A., Moreland, J. 2004; 85 (9): 1460-1462

    View details for DOI 10.1063/1.1787942

    View details for Web of Science ID 000223555000004

  • Stabilization of femtosecond laser frequency combs with subhertz residual linewidths OPTICS LETTERS Bartels, A., Oates, C. W., Hollberg, L., Diddams, S. A. 2004; 29 (10): 1081-1083

    Abstract

    We demonstrate that femtosecond laser frequency combs (FLFCs) can have a subhertz linewidth across their entire emission spectra when they are phase locked to a reference laser with a similarly narrow linewidth. Correspondingly, the coherence time of the comb components relative to the reference laser can be of the order of a few seconds. Thus we are able to detect high-contrast spectral interferograms at up to 10-s integration time between two FLFCs locked to a common optical reference.

    View details for Web of Science ID 000221189400013

    View details for PubMedID 15181992

  • Microfabricated alkali atom vapor cells APPLIED PHYSICS LETTERS Liew, L. A., Knappe, S., Moreland, J., ROBINSON, H., Hollberg, L., Kitching, J. 2004; 84 (14): 2694-2696

    View details for DOI 10.1063/1.1691490

    View details for Web of Science ID 000220586800075

  • Optical frequency synthesis and comparison with uncertainty at the 10(-19) level SCIENCE Ma, L. S., Bi, Z. Y., Bartels, A., Robertsson, L., Zucco, M., Windeler, R. S., Wilpers, G., Oates, C., Hollberg, L., Diddams, S. A. 2004; 303 (5665): 1843-1845

    Abstract

    A femtosecond laser-based optical frequency synthesizer is referenced to an optical standard, and we use it to demonstrate the generation and control of the frequency of electromagnetic fields over 100 terahertz of bandwidth with fractional uncertainties approaching 1 part in 10(19). The reproducibility of this performance is verified by comparison of different types of femtosecond laser-based frequency synthesizers from three laboratories.

    View details for Web of Science ID 000220281600048

    View details for PubMedID 15031498

  • Absolute-frequency measurements with a stabilized near-infrared optical frequency comb from a Cr : forsterite laser OPTICS LETTERS Corwin, K. L., Thomann, I., Dennis, T., FOX, R. W., Swann, W., Curtis, E. A., Oates, C. W., Wilpers, G., Bartels, A., Gilbert, S. L., Hollberg, L., Newbury, N. R., Diddams, S. A., Nicholson, J. W., Yan, M. F. 2004; 29 (4): 397-399

    Abstract

    A frequency comb is generated with a chromium-doped forsterite femtosecond laser, spectrally broadened in a dispersion-shifted highly nonlinear fiber, and stabilized. The resultant evenly spaced comb of frequencies ranges from 1.1 to beyond 1.8 microm. The frequency comb was referenced simultaneously to the National Institute of Standards and Technology's optical frequency standard based on neutral calcium and to a hydrogen maser that is calibrated by a cesium atomic fountain clock. With this comb we measured two frequency references in the telecommunications band: one half of the frequency of the d/f crossover transition in 87Rb at 780 nm, and the methane v2 + 2v3 R(8) line at 1315 nm.

    View details for Web of Science ID 000188703300025

    View details for PubMedID 14971765

  • Broadband phase-coherent optical frequency synthesis with actively linked Ti : sapphire and Cr : forsterite femtosecond lasers OPTICS LETTERS Bartels, A., Newbury, N. R., Thomann, I., Hollberg, L., Diddams, S. A. 2004; 29 (4): 403-405

    Abstract

    We link the output spectra of a Ti:sapphire and a Cr:forsterite femtosecond laser phase coherently to form a continuous frequency comb with a wavelength coverage of 0.57-1.45 microm at power levels of 1 nW to 40 microW per frequency mode. To achieve this, the laser repetition rates and the carrier-envelope offset frequencies are phase locked to each other. The coherence time between the individual components of the two combs is 40 micros. The timing jitter between the lasers is 20 fs. The combined frequency comb is self-referenced for access to its overall offset frequency. We report the first demonstration to our knowledge of an extremely broadband and continuous, high-powered and phase-coherent frequency comb from two femtosecond lasers with different gain media.

    View details for Web of Science ID 000188703300027

    View details for PubMedID 14971767

  • Dark-line atomic resonances in submillimeter structures OPTICS LETTERS Knappe, S., Hollberg, L., Kitching, J. 2004; 29 (4): 388-390

    Abstract

    We present measurements of dark-line resonances excited in cesium atoms confined in submillimeter cells with a buffer gas. The width and contrast of the resonances were measured for cell lengths as low as 100 microm. The measured atomic Q factors are reduced in small cells because of frequent collisions of atoms with the cell walls. However, the contrast of coherent population trapping resonances measured in the small cells is similar in magnitude to that obtained in centimeter-sized cells, but substantially more laser intensity is needed to excite the resonance fully when increased buffer-gas pressure is used. The effect of the higher intensity on the linewidth is reduced because the intensity broadening rate decreases with buffer-gas pressure.

    View details for Web of Science ID 000188703300022

    View details for PubMedID 14971762

  • Nonlinear-resonance line shapes: Dependence on the transverse intensity distribution of a light beam PHYSICAL REVIEW A Taichenachev, A. V., Tumaikin, A. M., Yudin, V. I., Stahler, M., Wynands, R., Kitching, J., Hollberg, L. 2004; 69 (2)
  • Absolute Optical Frequency Metrology Encyclopedia of Modern Optics Cundiff, S. T., Hollberg, L. 2004: 82–90
  • Highcontrast dark resonances in sigma+ - sigma- optical field Laser Phys. Lett. Kargapoltsev, S., Kitching, J., Hollberg, L., Taichenachev, A. V., Velichanski, V. L., Yudin, V. I. 2004; 1: 495-499
  • Chip-scale atomic magnetometers Appl. Phys. Lett. Schwindt, P., Knappe, S., Shah, V., Hollberg, L., Kitching, J., Liew, L., Moreland, J. 2004; 85: 6409-6411
  • Stable Optical Cavities for Wavelength References NIST Tech. Note 1533, National Institute of Standards and Technology Fox, R. W., Crowin, K. L., Hollberg, L. 2004: 30
  • Optical clocks with cold atoms and stable lasers 16th International Conference on Laser Spectroscopy Hollberg, L., Oates, C. W., Wilpers, G., Curtis, E. A., Hoyt, C. W., Diddams, S. A., Bartels, A., Ramond, T. M. WORLD SCIENTIFIC PUBL CO PTE LTD. 2004: 14–21
  • The Era of Coherent Optical Frequency References NIST Spec. Publ. Hollberg, L., Oates, C. W., Diddams, S. A., Wilpers, G., Bartels, A., Hoyt, C., Barber, Z. 2004: 6
  • Microfabricated Atomic Frequency References Proc. 2004 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and UFFC Conf. Knappe, S. A., Schwindt, P., Shah, V., Hollberg, L., Kitching, J., Liew, L., Moreland, J. 2004: 87–91
  • Power dissipation in a vertically-integrated chip-scale atomic clock Proc. 2004 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and UFFC Conf. Kitching, J., Knappe, S., Liew, L., Schwindt, P., Shah, V., Moreland, J., Hollberg, L. 2004: 781–784
  • Microfabricated Atomic Clocks NIST Proc. 2004 PTTI Mtg. Knappe, S., Schwindt, P., Gerginov, V., Shah, V., Hollberg, L., Kitching, J., Liew, L., Moreland, J. 2004: 383–392
  • 420-MHz Cr : forsterite femtosecond ring laser and continuum generation in the 1-2-mu m range OPTICS LETTERS Thomann, I., Bartels, A., Corwin, K. L., Newbury, N. R., Hollberg, L., Diddams, S. A., Nicholson, J. W., Yan, M. F. 2003; 28 (15): 1368-1370

    Abstract

    We demonstrate a chromium-doped forsterite femtosecond ring laser that generates 30-fs pulses at a 420-MHz repetition rate with nearly 500 mW of average power. The compact solid-state design and broad spectral output make this laser attractive for telecommunications applications in the 1.3-1.5-micrometre region. Additional spectral broadening of the laser output in highly nonlinear optical fiber leads to octave-spanning spectra ranging from 1.06 to 2.17 micrometre. The octave is reached at a level of 18 dB below the peak. The underlying optical frequency comb can be linked to existing optical frequency standards.

    View details for Web of Science ID 000184256400026

    View details for PubMedID 12906092

  • Optical frequency combs: From frequency metrology to optical phase control IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS Ye, J., Schnatz, H., Hollberg, L. W. 2003; 9 (4): 1041-1058
  • Delivery of high-stability optical and microwave frequency standards over an optical fiber network JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Ye, J., Peng, J. L., Jones, R. J., Holman, K. W., Hall, J. L., Jones, D. J., Diddams, S. A., Kitching, J., Bize, S., Bergquist, J. C., Hollberg, L. W., Robertsson, L., Ma, L. S. 2003; 20 (7): 1459-1467
  • Analysis of noise mechanisms limiting the frequency stability of microwave signals generated with a femtosecond laser IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS Ivanov, E. N., Diddams, S. A., Hollberg, L. 2003; 9 (4): 1059-1065
  • Design and control of femtosecond lasers for optical clocks and the synthesis of low-noise optical and microwave signals IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS Diddams, S. A., Bartels, A., Ramond, T. M., Oates, C. W., Bize, S., Curtis, E. A., Bergquist, J. C., Hollberg, L. 2003; 9 (4): 1072-1080
  • Compact atomic vapor cells fabricated by laser-induced heating of hollow-core glass fibers REVIEW OF SCIENTIFIC INSTRUMENTS Knappe, S., Velichansky, V., Robinson, H. G., Kitching, J., Hollberg, L. 2003; 74 (6): 3142-3145

    View details for DOI 10.1063/1.1575925

    View details for Web of Science ID 000183124100031

  • Quenched narrow-line second- and third-stage laser cooling of Ca-40 JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Curtis, E. A., Oates, C. W., Hollberg, L. 2003; 20 (5): 977-984
  • Testing the stability of fundamental constants with the Hg-199(+) single-ion optical clock PHYSICAL REVIEW LETTERS Bize, S., Diddams, S. A., Tanaka, U., Tanner, C. E., Oskay, W. H., Drullinger, R. E., Parker, T. E., Heavner, T. P., Jefferts, S. R., Hollberg, L., Itano, W. M., Bergquist, J. C. 2003; 90 (15)

    Abstract

    Over a two-year duration, we have compared the frequency of the 199Hg+ 5d(10)6s (2)S(1/2)(F=0)<-->5d(9)6s(2) (2)D(5/2)(F=2) electric-quadrupole transition at 282 nm with the frequency of the ground-state hyperfine splitting in neutral 133Cs. These measurements show that any fractional time variation of the ratio nu(Cs)/nu(Hg) between the two frequencies is smaller than +/-7 x 10(-15) yr(-1) (1sigma uncertainty). According to recent atomic structure calculations, this sets an upper limit to a possible fractional time variation of g(Cs)(m(e)/m(p))alpha(6.0) at the same level.

    View details for DOI 10.1103/PhysRevLett.90.150802

    View details for Web of Science ID 000182320200004

    View details for PubMedID 12732024

  • Mode-locked laser pulse trains with subfemtosecond timing jitter synchronized to an optical reference oscillator OPTICS LETTERS Bartels, A., Diddams, S. A., Ramond, T. M., Hollberg, L. 2003; 28 (8): 663-665

    Abstract

    We independently phase lock the repetition rates of two femtosecond lasers at their approximately 456, 000th harmonic to a common optical oscillator. The timing jitter of each individual laser relative to the optical reference is only 0.45 fs in a 100-Hz bandwidth. Our method takes advantage of the tremendous leverage that is possible when stability is transferred from the optical to the microwave domain. The low timing jitter is commensurate with the independently measured fractional frequency instability in the repetition rates of < or = 2.3 x 10(-15) in 1-s averaging time, limited by the measurement system. The microwave signals at 1 GHz that are extracted by photodetection of the pulse trains have a 10-times-greater instability, confirming the presence of excess noise in the photodetection.

    View details for Web of Science ID 000181989100026

    View details for PubMedID 12703934

  • Experimental study of noise properties of a Ti : Sapphire femtosecond laser IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Ivanov, E. N., Diddams, S. A., Hollberg, L. 2003; 50 (4): 355-360

    Abstract

    The fidelity of a coherent link between optical and microwave frequencies is largely determined by noise processes in a mode-locked femtosecond laser. This work presents an experimental study of the noise properties of a Ti:sapphire femtosecond laser. It includes measurements of pulse repetition rate fluctuations and shot noise exhibited by the Ti:sapphire femtosecond laser. Based on the results of noise measurements, the fractional frequency stability of a microwave signal produced by the femtosecond laser has been evaluated.

    View details for Web of Science ID 000182674700001

    View details for PubMedID 12744390

  • Chromium-doped forsterite: dispersion measurement with white-light interferometry APPLIED OPTICS Thomann, I., Hollberg, L., Diddams, S. A., Equall, R. 2003; 42 (9): 1661-1666

    Abstract

    Using a Michelson white-light interferometer, we measure the group-delay dispersion and third-order dispersion coefficients, d2(phi)/d(omega)2 and d3(phi)/d(omega)3, of chromium-doped forsterite (Cr:Mg2SiO4) over wavelengths of 1050-1600 nm for light polarized along both the c and b crystal axes. In this interval, the second-order dispersion for the c axis ranges from 35 fs2/mm to -14 fs2/mm, and the third-order dispersion ranges from 36 fs3/mm to 142 fs3/mm. For the b axis the second-order dispersion ranges from 35 fs2/mm to -15 fs2/mm and the third-order from 73 fs3/mm to 185 fs3/mm. Our data are relevant for the development of optimized dispersion compensation tools for Cr:Mg2SiO4 femtosecond lasers. These measurements help to clarify previously published results and show some significant discrepancies that existed, especially in the third-order dispersion. Our results should furthermore be useful to build up an analytic expression for the index of refraction of chromium forsterite.

    View details for Web of Science ID 000181708400011

    View details for PubMedID 12665096

  • Atomic clocks of the future: using the ultrafast and ultrastable 13th International Conference on Ultrafast Phenomena Hollberg, L., Diddams, S., Oates, C., Curtis, A., Bize, S., Bergquist, J. SPRINGER-VERLAG BERLIN. 2003: 170–174
  • Role of spurious reflections in ring-down spectroscopy OPTICS LETTERS Fox, R. W., Hollberg, L. 2002; 27 (20): 1833-1835

    Abstract

    Spurious coherent reflections from optical elements that re-enter an exit port of a two-mirror ring-down cavity can significantly change the effective reflectivity of the cavity mirrors, thus altering the cavity decay time. For a 25-cm-long Fabry-Perot cavity with a decay constant of 40 mus , we find that a specular reflection of only 10(-4) of the transmitted ring-down power that is mode matched back toward the cavity could change the decay time by as much as +/-0.4 mus , depending on the phase of the returning reflection. The perturbation of the decay time is proportional to the electric field, so a decrease in the spurious reflected power of 100 times will result in a perturbation that is only 10 times smaller. We demonstrate the effect with a cw system by purposely introducing a spurious reflection.

    View details for Web of Science ID 000178561300029

    View details for PubMedID 18033378

  • Phase-coherent link from optical to microwave frequencies by means of the broadband continuum from a 1-GHz Ti : sapphire femtosecond oscillator OPTICS LETTERS Ramond, T. M., Diddams, S. A., Hollberg, L., Bartels, A. 2002; 27 (20): 1842-1844

    Abstract

    An optical clockwork is created with a compact 1-GHz repetition-rate laser and three nonlinear crystals. The broadband continuum output of the laser covers sufficient bandwidth to provide direct access to its carrier-envelope offset frequency without the use of a microstructure fiber. We phase lock the femtosecond comb to a Ca optical standard and monitor the stability of the repetition rate, f(r) , at 1 GHz. We demonstrate that the short-term stability of the microwave output of the optical clock is at least as good as that of a high-performance hydrogen maser.

    View details for Web of Science ID 000178561300032

    View details for PubMedID 18033381

  • Miniature vapor-cell atomic-frequency references APPLIED PHYSICS LETTERS Kitching, J., Knappe, S., Hollberg, L. 2002; 81 (3): 553-555

    View details for DOI 10.1063/1.1494115

    View details for Web of Science ID 000176599600055

  • Efficient frequency up-conversion in resonant coherent media PHYSICAL REVIEW A Zibrov, A. S., Lukin, M. D., Hollberg, L., Scully, M. O. 2002; 65 (5)
  • Wavelength references for 1300-nm wavelength-division multiplexing JOURNAL OF LIGHTWAVE TECHNOLOGY Dennis, T., Curtis, E. A., Oates, C. W., Hollberg, L., Gilbert, S. L. 2002; 20 (5): 776-782
  • Resonant enhancement of refractive index in a cascade scheme Conference on the Physics of Quantum Electronics Zibrov, A. S., Matsko, A. B., Hollberg, L., Velichansky, V. L. TAYLOR & FRANCIS LTD. 2002: 359–65
  • Temperature dependence of coherent population trapping resonances APPLIED PHYSICS B-LASERS AND OPTICS Knappe, S., Kitching, J., Hollberg, L., Wynands, R. 2002; 74 (3): 217-222
  • Locking Diode Lasers to Optical Cavities Cavity-Enhanced Spectroscopies Fox, R. W., Oates, C. W., Hollberg, L. edited by Zee, R. v., Looney, J. P. Academic Press, Boston MA. 2002: 1–46
  • Optical Frequency Standards Based on the 199Hg+ Ion IEEE Trans. Instrumen.Meas. Tanaka, U., Bergquist, J. C., Bize, S., Diddams, S. A., Drullinger, R. E., Hollberg, L., Itano, W. M., Tanner, C. E., Wineland, D. J. 2002; 52: 245-249
  • A Single 199Hg+ Optical Clock Proceedings of the XV International Conf. on Laser Spectroscopy Bergquist, J., Diddans, S., Oates, C., Curtis, E., Hollberg, L., Drullinger, R., Itano, W., Wineland, D., Udem, T. edited by Chu, S., Vuletic, V., Kerman, A. J., Chen, C. 2002: 106–114
  • Coherent Population Trapping Resonances in Thermal 85Rb Vapor: D1versus D2 Line Excitation Optics Letts. Stahler, M., Wynands, R., Knappe, S., Kitching, J., Hollberg, L., Taichenachev, A., Yudin, V. 2002; 27: 1472-1474
  • Femtosecond-laser-based optical clockwork with instability <= 6.3 x 10(-16) in 1 s OPTICS LETTERS Diddams, S. A., Hollberg, L., Ma, L. S., Robertsson, L. 2002; 27 (1): 58-60
  • A Femtosecond-Laser-Based Optical Clockwork Proceeds. of the 6th Symposium Diddams, S. A., Udem, T., Vogel, K. R., Ma, L. S., Robertsson, L., Oates, C. W., Curtis, E. A., Itano, W. M., Drullinger, R. E., Wineland, D. J., Bergquist, J. C., Hollberg, L. edited by Gill, P. 2002: 419–26
  • A 40Ca Optical Frequency Standard at 657 nm: Frequency Measurements and Future Prospects Proceeds. of the 6th Symposium Curtis, E. A., Oates, C. W., Diddams, S. A., Vogel, K. R., Hollberg, L., Udem, T. edited by Gill, P. 2002: 331–38
  • PARCS: A Laser-Cooled Atomic Clock in Space Proceeds. of the 6th Symposium Heavner, T. P., Hollberg, L. W., Jefferts, S. R., Robinson, H. G., Sullivan, D. B., Walls, F. L., Ashby, N., Klipstein, W. M., Maleki, L., Seidel, D. J., Thompson, R. J., Wu, S., Young, L., Mattison, E. M., Vessot, R. C., DeMarchi, A. edited by Gill, P. 2002: 253–60
  • Compact Microwave Frequency Reference Based on Coherent Population Trapping Proceeds. of the 6th Symposium Kitching, J. E., Robinson, H. G., Hollberg, L. W., Knappe, S., Wynands, R. edited by Gill, P. 2002: 167–74
  • A Mercury-Ion Optical Clock Proceeds. of the 6th Symposium Bergquist, J. C., Tanaka, U., Drullinger, R. E., Itano, W. M., Wineland, D. J., Diddams, S. A., Hollberg, L., Curtis, E. A., Oates, C. W., Udem, T. edited by Gill, P. 2002: 99–106
  • Optical frequency standards and measurements IEEE JOURNAL OF QUANTUM ELECTRONICS Hollberg, L., Oates, C. W., Curtis, E. A., Ivanov, E. N., Diddams, S. A., Udem, T., Robinson, H. G., Bergquist, J. C., Rafac, R. J., Itano, W. M., Drullinger, R. E., Wineland, D. J. 2001; 37 (12): 1502-1513
  • Compact atomic clock based on coherent population trapping ELECTRONICS LETTERS Kitching, J., Hollberg, L., Knappe, S., Wynands, R. 2001; 37 (24): 1449-1451
  • Optical-pumping noise in laser-pumped, all-optical microwave frequency references JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Kitching, J., Robinson, H. G., Hollberg, L., Knappe, S., Wynands, R. 2001; 18 (11): 1676-1683
  • Characterization of coherent population-trapping resonances as atomic frequency references JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Knappe, S., Wynands, R., Kitching, J., Robinson, H. G., Hollberg, L. 2001; 18 (11): 1545-1553
  • Frequency-dependent optical pumping in atomic A-systems OPTICS LETTERS Kitching, J., Hollberg, L., Knappe, S., Wynands, R. 2001; 26 (19): 1507-1509

    Abstract

    We consider the effects of optical pumping on the conversion of laser-frequency modulation into intensity modulation by an atomic absorption line in a vapor of alkali atoms driven in a ?-configuration. It is found that, due to optical pumping in combination with the excited-state hyperfine structure, the absorption line shape is distorted substantially as the Fourier frequency of the FM is changed. The most significant effect of the distortion is a shift of the apparent line center, which depends on how the frequency of the modulation compares with the optical pumping rate. This shift has implications for locking lasers to atomic transitions and also for FM-AM noise conversion in atomic vapors.

    View details for Web of Science ID 000171173700016

    View details for PubMedID 18049650

  • Quenched narrow-line laser cooling of Ca-40 to near the photon recoil limit PHYSICAL REVIEW A Curtis, E. A., Oates, C. W., Hollberg, L. 2001; 64 (3)
  • An optical clock based on a single trapped Hg-199(+) ion SCIENCE Diddams, S. A., Udem, T., Bergquist, J. C., Curtis, E. A., Drullinger, R. E., Hollberg, L., Itano, W. M., Lee, W. D., Oates, C. W., Vogel, K. R., Wineland, D. J. 2001; 293 (5531): 825-828

    Abstract

    Microwave atomic clocks have been the de facto standards for precision time and frequency metrology over the past 50 years, finding widespread use in basic scientific studies, communications, and navigation. However, with its higher operating frequency, an atomic clock based on an optical transition can be much more stable. We demonstrate an all-optical atomic clock referenced to the 1.064-petahertz transition of a single trapped 199Hg+ ion. A clockwork based on a mode-locked femtosecond laser provides output pulses at a 1-gigahertz rate that are phase-coherently locked to the optical frequency. By comparison to a laser-cooled calcium optical standard, an upper limit for the fractional frequency instability of 7 x 10(-15) is measured in 1 second of averaging-a value substantially better than that of the world's best microwave atomic clocks.

    View details for DOI 10.1126/science.1061171

    View details for Web of Science ID 000170241000035

    View details for PubMedID 11452082

  • Absolute frequency measurements of the Hg+ and Ca optical clock transitions with a femtosecond laser PHYSICAL REVIEW LETTERS Udem, T., Diddams, S. A., Vogel, K. R., Oates, C. W., Curtis, E. A., Lee, W. D., Itano, W. M., Drullinger, R. E., Bergquist, J. C., Hollberg, L. 2001; 86 (22): 4996-4999

    Abstract

    The frequency comb created by a femtosecond mode-locked laser and a microstructured fiber is used to phase coherently measure the frequencies of both the Hg+ and Ca optical standards with respect to the SI second. We find the transition frequencies to be f(Hg) = 1 064 721 609 899 143(10) Hz and f(Ca) = 455 986 240 494 158(26) Hz, respectively. In addition to the unprecedented precision demonstrated here, this work is the precursor to all-optical atomic clocks based on the Hg+ and Ca standards. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of the absolute value of( partial differential f(Ca)/ partial differential t)/f(Ca) < or =8 x 10(-14) yr(-1) and the absolute value of(partial differential f(Hg)/ partial differential t)/f(Hg) < or =30 x 10(-14) yr(-1).

    View details for Web of Science ID 000169013600004

    View details for PubMedID 11384404

  • Direct comparison between two cold-atom-based optical frequency standards using a femtosecond-laser comb Optics Lett. Vogel, K. R., Diddams, S. A., Oates, C. W., Curtis, E. A., Rafac, R. J., Itano, W. M., Bergquist, J. C., Fox, R. W., Lee, W. D., Wells, J. S., Hollberg, L. 2001; 26: 102-104
  • Optical frequency standards for clocks of the future Conference on Harnessing Light: Optical Science and Metrology at NIST Hollberg, L., Diddams, S. A., Curtis, E. A., Oates, C. W., FOX, R. W. SPIE-INT SOC OPTICAL ENGINEERING. 2001: 54–59
  • A compact femtosecond-laser-based optical clockwork Conference on Laser Frequency Stabilization, Standards, Measurement, and Applications Diddams, S. A., Udem, T., Vogel, K. R., Oates, C. W., Curtis, E. A., Windeler, R. S., Bartels, A., Bergquist, J. C., Hollberg, L. SPIE-INT SOC OPTICAL ENGINEERING. 2001: 77–83
  • Destruction of darkness: Optical coherence effects and multi-wave mixing in rubidium vapor XVIIth International Conference on Atomic Physics Zibrov, A. S., Hollberg, L., Velichansky, V. L., Scully, M. O., Lukin, M. D., Robinson, H. G., Matsko, A. B., Taichenachev, A. V., Yudin, V. I. AMER INST PHYSICS. 2001: 204–217
  • A microwave frequency reference based on VCSEL-driven dark line resonances in Cs vapor IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT Kitching, J., Knappe, S., Vukicevic, N., Hollberg, L., Wynands, R., Weidmann, W. 2000; 49 (6): 1313-1317
  • Improved short-term stability of optical frequency standards: approaching 1 Hz in 1 s with the Ca standard at 657 nm OPTICS LETTERS Oates, C. W., Curtis, E. A., Hollberg, L. 2000; 25 (21): 1603-1605

    Abstract

    For a neutral (40)Ca-based optical frequency standard we report a fractional frequency instability of 4 x 10(-15) in 1 s, which represents a fivefold improvement over existing atomic frequency standards. Using the technique of optical Bordé-Ramsey spectroscopy with a sample of 10(7) trapped atoms, we have resolved linewidths as narrow as 200 Hz (FWHM). With colder atoms this system could potentially achieve an instability as low as 2 x 10(-16) in 1 s. Such low instabilities are important for frequency standards and precision tests of fundamental physics.

    View details for Web of Science ID 000089988100013

    View details for PubMedID 18066290

  • Compact diode-laser based rubidium frequency reference Joint Meeting of the European-Frequency-and-Time-Forum/IEEE International Frequency Control Symposium Vukicevic, N., Zibrov, A. S., Hollberg, L., Walls, F. L., Kitching, J., Robinson, H. G. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 2000: 1122–26

    Abstract

    The performance of a simple microwave frequency reference based on Raman scattering in an atomic vapor is examined. This reference has the potential to be compact, low-power, and insensitive to acceleration. Several design architectures have been evaluated with a table-top experiment in order to guide the future development of a compact system. Fractional frequency deviations of

    View details for Web of Science ID 000089372500007

    View details for PubMedID 18238650

  • Performance evaluation of an optoelectronic oscillator Joint Meeting of the European-Frequency-and-Time-Forum/IEEE International Frequency Control Symposium Romisch, S., Kitching, J., Ferre-Pikal, E., Hollberg, L., Walls, F. L. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 2000: 1159–65

    Abstract

    Phase noise measurements of an optoelectronic oscillator (OEO) at frequencies less than 10 Ha from the carrier (10.6 GHz) as well as the measured Allan variance are presented for the first time. The system has a measured single-side-band (SSB) phase-noise of -123 dB/Hz at 10 kHz from the carrier and a sigma(y)(tau)=10(-10) for an integration time between 1 and 10 seconds. The importance of amplifier phase-noise and environmental fluctuations in determining the noise of the oscillator at these low Fourier frequencies is verified experimentally and analyzed using a generalized model of noise sources in the OEOs. This analysis then allows prediction of the oscillator performance from measured parameters of individual components in the system.

    View details for Web of Science ID 000089372500013

    View details for PubMedID 18238656

  • Difference-frequency generation in PPLN at 4.25 mu m: an analysis of sensitivity limits for DFG spectrometers APPLIED PHYSICS B-LASERS AND OPTICS Mazzotti, D., De Natale, P., Giusfredi, G., Fort, C., Mitchell, J. A., Hollberg, L. W. 2000; 70 (6): 747-750
  • Sub-systems for optical frequency measurements: application to the 282-nm Hg-199(+) transition and the 657-nm Ca line Joint Meeting of the European-Frequency-and-Time-Forum/IEEE International Frequency Control Symposium Frech, B., Wells, J. S., Oates, C. W., Mitchell, J., Lan, Y. P., Kurosu, T., Zink, L., Hollberg, L., Zibrova, T., YOUNG, B. C., Bergquist, J. C. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 2000: 513–17

    Abstract

    We are developing laser frequency measurement technologies that should allow us to construct an optical frequency synthesis system capable of measuring optical frequencies with a precision limited by the atomic frequency standards. The system will be used to interconnect and compare new advanced optical-frequency references (such as Ca, Hg(+ ), and others) and eventually to connect these references to the Cs primary frequency standard. The approach we are taking is to subdivide optical frequency intervals into smaller and smaller pieces until we are able to use standard electronic-frequency-measurement technology to measure the smallest interval.

    View details for Web of Science ID 000085926400031

    View details for PubMedID 18238575

  • Cavity-enhanced absorption spectroscopy of molecular oxygen JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Gianfrani, L., FOX, R. W., Hollberg, L. 1999; 16 (12): 2247-2254
  • A diode-laser optical frequency standard based on laser-cooled Ca atoms: Sub-kilohertz spectroscopy by optical shelving detection EUROPEAN PHYSICAL JOURNAL D Oates, C. W., Bondu, F., FOX, R. W., Hollberg, L. 1999; 7 (3): 449-460
  • Ultraslow group velocity and enhanced nonlinear optical effects in a coherently driven hot atomic gas PHYSICAL REVIEW LETTERS Kash, M. M., Sautenkov, V. A., Zibrov, A. S., Hollberg, L., Welch, G. R., Lukin, M. D., Rostovtsev, Y., Fry, E. S., Scully, M. O. 1999; 82 (26): 5229-5232
  • Interference-induced optical gain without population inversion in cold, trapped atoms PHYSICAL REVIEW A Kitching, J., Hollberg, L. 1999; 59 (6): 4685-4689
  • Tunable UV generation at 283 nm by frequency doubling and sum frequency mixing of two semiconductor lasers for the detection of Pb SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY Franzke, J., FOX, R. W., Hollberg, L. 1998; 53 (14): 1951-1955
  • Narrow-line-width diode laser with a high-Q microsphere resonator OPTICS COMMUNICATIONS Vassiliev, V. V., Velichansky, V. L., Ilchenko, V. S., Gorodetsky, M. L., Hollberg, L., Yarovitsky, A. V. 1998; 158 (1-6): 305-312
  • Extended-cavity grating-tuned operation of mid-infrared InAsSb diode lasers APPLIED PHYSICS B-LASERS AND OPTICS Murtz, M., Wells, J. S., Hollberg, L., Zibrova, T., Mackie, N. 1998; 66 (3): 277-281
  • Spectroscopy in dense coherent media: Line narrowing and interference effects PHYSICAL REVIEW LETTERS Lukin, M. D., Fleischhauer, M., Zibrov, A. S., Robinson, H. G., Velichansky, V. L., Hollberg, L., Scully, M. O. 1997; 79 (16): 2959-2962
  • Continuous-wave frequency tripling and quadrupling by simultaneous three-wave mixings in periodically poled crystals: application to a two-step 1.19-10.71-mu m frequency bridge OPTICS LETTERS Pfister, O., Wells, J. S., Hollberg, L., Zink, L., VANBAAK, D. A., Levenson, M. D., Bosenberg, W. R. 1997; 22 (16): 1211-1213

    Abstract

    We observed cw third-harmonic generation in a periodically poled LiNbO(3) crystal by cascading optimally phase-matched second-harmonic and sum-frequency generation. Other processes, such as fourth-harmonic generation, are allowed by the flexibility of quasi-phase matching. We demonstrate a divide-by-nine (1.19- 10.71-microm) frequency chain that uses only two lasers.

    View details for Web of Science ID A1997XP16700003

    View details for PubMedID 18185797

  • Precise measurement of methane in air using diode-pumped 3.4-mu m difference-frequency generation in PPLN APPLIED PHYSICS B-LASERS AND OPTICS Petrov, K. P., Waltman, S., Dlugokencky, E. J., Arbore, M., Fejer, M. M., Tittel, F. K., Hollberg, L. W. 1997; 64 (5): 567-572
  • Toward Extended-Cavity Grating-Tuned Mid-Infrared Diode Laser Operation NIST Technical Note 1388 Mürtz, M., Wells, J. S., Hollberg, L., Zibrova, T., Mackie, N. U.S. Gov. Printing Off.. 1997
  • An all-diode-laser optical frequency reference using laser-trapped calcium 1997 IEEE International Frequency Control Symposium Oates, C. W., Stephens, M., Hollberg, L. IEEE. 1997: 219–224
  • Semiconductor Diode Lasers Experimental Methods in the Physical Sciences Fox, R. W., Zibrov, A. S., Hollberg, L. Academic Press. 1997: 77–102
  • Experimental demonstration of enhanced index of refraction via quantum coherence in Rb PHYSICAL REVIEW LETTERS Zibrov, A. S., Lukin, M. D., Hollberg, L., Nikonov, D. E., Scully, M. O., Robinson, H. G., Velichansky, V. L. 1996; 76 (21): 3935-3938
  • Nonlinear Optics for Optical Frequency Synthesis and an Optical Divide by 3 Mürtz, M., Pfister, O., Marquardt, J. H., Stephens, M., Wells, J. S., Waltman, S., Hollberg, L., Robinson, H. G., Fox, R. W. edited by Bergquist, J. C. 1996
  • Two Laser Differential Absorption for Wide Molecular Bands Proceed. SPIE conf. Fox, R. W., Rudich, Y., Talukdar, R. K., Ravishankara, A. R., Hollberg, L. 1996: 364–368
  • Demonstration of Phase-lockable Microwave to Submillimeter-wave Sweeper Proceed. SPIE conf. Waltman, S. B., Hollberg, L. W., McIntosh, K. A., Brown, E. R. 1996: 55–58
  • Population- and Coherence-Induced Gain and Self-Oscillations in Alkali Vapor Zibrov, A. S., Robinson, H. G., Velichansky, V. L., Vasiliev, V. V., Hollberg, L., Arimondo, E., Lukin, M. D., Scully, M. O. edited by Bergquist, J. C. 1996
  • Grating-tuned semiconductor MOPA lasers for precision spectroscopy Conference on the Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring Marquardt, J. H., Cruz, F. C., Stephens, M., Oates, C. W., Hollberg, L. W., Bergquist, J. C., Welch, D. F., Mehuys, D., Sanders, S. SPIE - INT SOC OPTICAL ENGINEERING. 1996: 34–40
  • Highcoherence diode laser with optical feedback via a microcavity with whispering gallery modes Quantum Electronics Vasiliev, V. V., Velichianskii, V. L., Gorodetskii, M. L., Ilchenko, V. S., Hollberg, L., Yarovitskii, A. . 1996; 26: 657-658
  • Lineshapes of Cascade Two-Photon Transitions in a Cesium Magneto-Optic Trap J. Opt. Soc. Am. B Marquardt, J. H., Robinson, H. G., Hollberg, L. 1996; 13: 1384-1393
  • A 1 GHz Diode Laser-driven Optical Delay-Line Oscillator Proceed. of IEEE International Frequency Control Symposium Kitching, J., Hollberg, L., Walls, F. L. 1996: 807–814
  • High Accuracy Spectroscopy with Semiconductor Lasers: with Application to Laser Frequency Stabilization Frequency Control of Semiconductor Lasers Hollberg, L., Velichansky, V. L., Weimer, C. S., Fox, R. W. edited by Ohtsu, M. J. Wiley and Sons. 1996
  • Division by Three of Optical Frequencies Using Difference Frequency Generation in Non-Critically Phase-Matched RTA Opts. Lett. Pfister, O., Mürtz, M., Wells, J. S., Hollberg, L. 1996; 21: 1387
  • EXPERIMENTAL DEMONSTRATION OF LASER OSCILLATION WITHOUT POPULATION-INVERSION VIA QUANTUM INTERFERENCE IN RB PHYSICAL REVIEW LETTERS Zibrov, A. S., Lukin, M. D., Nikonov, D. E., Hollberg, L., Scully, M. O., Velichansky, V. L., Robinson, H. G. 1995; 75 (8): 1499-1502
  • SUB-DOPPLER FREQUENCY MEASUREMENTS ON OCS NEAR 1689 AND 1885 CM(-1) JOURNAL OF MOLECULAR SPECTROSCOPY Wells, J. S., Dax, A., Hollberg, L., Maki, A. G. 1995; 170 (1): 75-81
  • Transient Molecular Spectroscopy with a Frequency-Doubled Diode Laser OSA technical digest Fox, R. W., Hunter, M., Hollberg, L. 1995
  • Tunable Infrared Source by Difference Frequency Mixing Diode Lasers and Diode Pumped YAG, and Application to Methane Detection OSA technical digest Waltman, S., Petrov, K., Simon, U., Hollberg, L., Tittel, F., Curl, R. 1995
  • Diode lasers for frequency standards and precision spectroscopy 49th Annual IEEE International Frequency Control Symposium Hollberg, L., Aman, J., Waltman, S., Marquardt, J. H., Stephens, M., FOX, R. W., VANBAAK, D. A., WEIMER, C. S., Robinson, H. G., Zibrov, A. S., Mackie, N., Zibrova, T. P., Pendrill, L. I E E E. 1995: 185–189
  • Detection of Methane in Air Using Diode-Laser-Pumped Difference-Frequency Generation near 3.2 μm J. Opt. Soc. Am. B Petrov, K. P., Waltman, S., Simon, U., Curl, R. F., Tittel, F. K., Dlugokencky, E. J., Hollberg, L. 1995; 61: 553-558
  • AMPLITUDE MODULATION ON FREQUENCY-LOCKED EXTENDED-CAVITY DIODE LASERS Conference on Laser Frequency Stabilization and Noise Reduction/Photonics West 95 FOX, R. W., DEVELYN, L., Robinson, H. G., WEIMER, C. S., Hollberg, L. SPIE - INT SOC OPTICAL ENGINEERING. 1995: 58–62
  • External Cavity Difference-Frequency Source in the Mid-Infrared based on AgGaS2 and Diode Lasers J. Opt. Soc. Am. B Simon, U., Waltman, S., Loa, I., Tittel, F. K., Hollberg, L. 1995; 12: 323-327
  • SUB-DOPPLER FREQUENCY MEASUREMENTS ON OCS AT 87 THZ (3.4-MU-M) WITH THE CO OVERTONE LASER JOURNAL OF MOLECULAR SPECTROSCOPY Dax, A., Wells, J. S., Hollberg, L., Maki, A. G., Urban, W. 1994; 168 (2): 416-428
  • PROPOSED SUM-AND-DIFFERENCE METHOD FOR OPTICAL-FREQUENCY MEASUREMENT IN THE NEAR-INFRARED OPTICS LETTERS VANBAAK, D. A., Hollberg, L. 1994; 19 (19): 1586-1588

    Abstract

    We propose a method for the determination of optical frequencies in the near infrared that is based on the nonlinear generation of the optical sum and difference frequencies of two near-infrared lasers followed by the comparison of the sum and difference frequencies with standards in the visible and in the far infrared, respectively. We also address questions of practicability and discuss some examples open to the method.

    View details for Web of Science ID A1994PJ26500028

    View details for PubMedID 19855592

  • HIGH-RESOLUTION DIODE-LASER SPECTROSCOPY OF CALCIUM APPLIED PHYSICS B-LASERS AND OPTICS Zibrov, A. S., FOX, R. W., Ellingsen, R., WEIMER, C. S., Velichansky, V. L., Tino, G. M., Hollberg, L. 1994; 59 (3): 327-331
  • A CPW PHASE-LOCKED LOOP FOR DIODE-LASER STABILIZATION 1994 IEEE MTT-S International Microwave Symposium DEVELYN, L., Hollberg, L., Popovic, Z. B. IEEE. 1994: 65–68
  • OPTICAL PROBING OF COLD TRAPPED ATOMS OPTICS LETTERS FOX, R. W., Gilbert, S. L., Hollberg, L., Marquardt, J. H., Robinson, H. G. 1993; 18 (17): 1456-1458

    View details for Web of Science ID A1993LU85100025

    View details for PubMedID 19823413

  • THE DIODE-LASER AS A SPECTROSCOPIC TOOL SPECTROCHIMICA ACTA REVIEWS FOX, R. W., WEIMER, C. S., Hollberg, L., Turk, G. C. 1993; 15 (5): 291-299
  • Diode Lasers and Metrology Proc. of NATO ASI Fox, R., Turk, G., Mackie, N., Zibrova, T., Waltman, S., Marquardt, J., Zibrov, A., Weimer, C., Hollberg, L., Sassi, M. P. 1992
  • Precise Optical Frequency References and Difference Frequency Measurements with Diode Lasers Proc. of SPIE Conference on Frequency Stabilized Lasers & Their Applications Waltman, S., Romanovsky, A., Wells, J., Fox, R. W., Hollberg, L. W., Sassi, M. P., Robinson, H. G. 1992: 386
  • High-Sensitivity Spectroscopy with Diode Lasers Proc. of SPIE Conference on Frequency Stabilized Lasers & Their Applications Fox, R. W., Robinson, H. C., Zibrov, A. S., Mackie, N., Marquardt, J., Magyar, J., Hollberg, L. W. 1992: 360
  • A FREQUENCY-STABILIZED LNA LASER AT 1.083 MU-M - APPLICATION TO THE MANIPULATION OF HELIUM 4 ATOMS JOURNAL DE PHYSIQUE II Vansteenkiste, N., GERZ, C., Kaiser, R., Hollberg, L., Salomon, C., Aspect, A. 1991; 1 (12): 1407-1428
  • Diode Lasers and Spectroscopic Applications Proc. of Tenth Int'l Conf. on Laser Spectroscopy (TENICOLS) Hollberg, L., Fox, R., Mackie, N., Zibrov, A. S., Velichansky, V. L., Ellingsen, R., Robinson, H. G. edited by Ducloy, M., Giacobino, E., Camy, G. 1991: 347–352
  • USING DIODE-LASERS FOR ATOMIC PHYSICS REVIEW OF SCIENTIFIC INSTRUMENTS Wieman, C. E., Hollberg, L. 1991; 62 (1): 1-20
  • HYPERFINE-STRUCTURE OF THE METASTABLE S-2(5) STATE OF O-17 USING AN ALGAAS DIODE-LASER AT 777 NM PHYSICAL REVIEW LETTERS Tino, G. M., Hollberg, L., Sasso, A., Inguscio, M., Barsanti, M. 1990; 64 (25): 2999-3002
  • Cw Dye Lasers Dye Laser Principles with Applications Hollberg, L. edited by Duarte, F., Hillman, L. Academic Press. 1990: 185–238
  • DIODE-LASERS AND THEIR APPLICATION TO SPECTROSCOPY NATO ADVANCED STUDY INST ON APPLIED LASER SPECTROCOPY Hollberg, L. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1990: 117–125
  • CHARACTERISTICS OF AN OPTICALLY PUMPED CS FREQUENCY STANDARD AT THE NRLM IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT Ohshima, S., Nakadan, Y., Ikegami, T., Koga, Y., Drullinger, R., Hollberg, L. 1989; 38 (2): 533-536
  • The Effect of Laser Line-Narrowing on the Performance of Optically Pumped Cesium Atomic Beam Frequency Standards Proc. of 2nd European Frequency and Time Forum Ohshima, S., Koga, Y., Nakadan, Y., Hollberg, L., Drullinger, R. 1989: 531–532
  • MODULATABLE NARROW-LINEWIDTH SEMICONDUCTOR-LASERS APPLIED PHYSICS LETTERS Hollberg, L., Ohtsu, M. 1988; 53 (11): 944-946
  • An Optically Pumped Primary Frequency Standard Proc. of Fourth Symposium on Frequency Standards and Metrology Drullinger, R. E., Shirley, J. H., Glaze, D. J., Hollberg, L. 1988: 116–119
  • Optical Stabilization of Semiconductor Lasers Proc. of Fourth Symposium on Frequency Standards and Metrology Hollberg, L. 1988: 231–235
  • FREQUENCY STABILIZATION OF SEMICONDUCTOR-LASERS BY RESONANT OPTICAL FEEDBACK OPTICS LETTERS Dahmani, B., Hollberg, L., Drullinger, R. 1987; 12 (11): 876-878

    Abstract

    With simple optical geometries a separate resonant Fabry-Perot cavity can serve as an optical feedback element that forces a semiconductor laser automatically to lock its frequency optically to the cavity resonance. This method is used to stabilize laser frequencies and reduce linewidths by a factor of 1000 from 20 MHz to approximately 20 kHz.

    View details for Web of Science ID A1987K531500008

    View details for PubMedID 19741901

  • PROPOSAL FOR OPTICALLY COOLING ATOMS TO TEMPERATURES OF THE ORDER OF 10-6 K OPTICS LETTERS Chu, S., Bjorkholm, J. E., Ashkin, A., Gordon, J. P., Hollberg, L. W. 1986; 11 (2): 73-75

    View details for Web of Science ID A1986AYQ3600005

    View details for PubMedID 19730537

  • Cooling and Trapping of Atoms with Laser Light Methods of Laser Spectroscopy Chu, S., Bjorkholm, J., Ashkin, A., Hollberg, L., Cable, A. edited by Prior, Y., Reuven, A. B., Rosenbluh, M. Plenum Press. 1986: 41–49
  • Progress Toward an Optically Pumped Cesium Beam Frequency Standard Proc. of 40th Frequency Control Symposium Drullinger, R. E., Shirley, J., Glaze, D. J., Hollberg, L. W., DeMarchi, A. 1986: 428–431
  • SQUEEZED STATES IN OPTICAL CAVITIES - A SPONTANEOUS-EMISSION-NOISE LIMIT PHYSICAL REVIEW A Slusher, R. E., Hollberg, L., Yurke, B., MERTZ, J. C., Valley, J. F. 1985; 31 (5): 3512-3515
  • Observation of Squeezed States Generated by Four-Wave Mixing in an Optical Cavity Phys. Rev. Lett. Slusher, R. E., Hollberg, L. W., Yurke, B., Mertz, J. C., Valley, J. F. 1985; 55: 2409-2412
  • Three Dimensional Viscous Confinement and Cooling of Atoms by Resonance Radiation Pressure Phys. Rev. Lett. Chu, S., Hollberg, L., Bjorkholm, J. E., Cable, A., Ashkin, A. 1985; 55: 48 - 51
  • DYE-LASER FREQUENCY STABILIZATION USING OPTICAL RESONATORS APPLIED PHYSICS B-PHOTOPHYSICS AND LASER CHEMISTRY Hough, J., Hils, D., Rayman, M. D., Ma, L. S., Hollberg, L., Hall, J. L. 1984; 33 (3): 179-185
  • MEASUREMENT OF THE SHIFT OF RYDBERG ENERGY-LEVELS INDUCED BY BLACKBODY RADIATION PHYSICAL REVIEW LETTERS Hollberg, L., Hall, J. L. 1984; 53 (3): 230-233
  • PRECISION-MEASUREMENTS BY OPTICAL HETERODYNE TECHNIQUES PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS Hollberg, L., Ma, L. S., HOHENSTATT, M., Hall, J. L. 1983; 426: 91-98
  • PROGRESS TOWARD PHASE-STABLE OPTICAL FREQUENCY STANDARDS JOURNAL DE PHYSIQUE Hall, J. L., Hollberg, L., Ma, L. S., Baer, T., Robinson, H. G. 1981; 42 (NC8): 59-71
  • OPTICAL HETERODYNE SATURATION SPECTROSCOPY APPLIED PHYSICS LETTERS Hall, J. L., Hollberg, L., Baer, T., Robinson, H. G. 1981; 39 (9): 680-682