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Search Publications by: Andrew Ludlow (Fed)

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Displaying 51 - 75 of 89

Ultra-low-noise Regenerative Frequency Divider for High Spectral Purity RF Signal Generation

May 24, 2012
Author(s)
Archita Hati, Craig W. Nelson, Corey A. Barnes, Danielle G. Lirette, Jason A. DeSalvo, Tara M. Fortier, Franklyn J. Quinlan, Andrew D. Ludlow, Till P. Rosenband, Scott A. Diddams, David A. Howe
We implement an ultra-low-noise frequency divider chain from 8 GHz to 5 MHz that utilizes custom-built regenerative frequency divide-by-2 circuits. The single-sideband (SSB) residual phase noise of this regenerative divider at 5 MHz output is -163 dBc/Hz

High-Accuracy Measurement of Atomic Polarizability in an Optical Lattice Clock

April 13, 2012
Author(s)
Jeffrey A. Sherman, Nathan D. Lemke, Nathan M. Hinkley, M. Pizzocaro, Richard W. Fox, Andrew D. Ludlow, Christopher W. Oates
Presently, the Stark effect contributes the largest source of uncertainty in a ytterbium optical atomic clock through blackbody radiation. By employing an ultracold, trapped atomic ensemble and high stability optical clock, we characterize the quadratic

Cold-collision-shift cancelation and inelastic scattering in a Yb optical lattice clock

November 28, 2011
Author(s)
Andrew D. Ludlow, Nathan D. Lemke, Jeffrey A. Sherman, Christopher W. Oates, G. Quemener, J. von Stecher, A.M. Rey
Recently, ρ-wave cold collisions were shown to dominate the density-dependent shift of the clock transition frequency in a 171Yb optical lattice clock. Here we demonstrate that by operating such a system at the proper excitation fraction, the cold

p-Wave Cold Collisions in an Optical Lattice Clock

September 2, 2011
Author(s)
Nathan D. Lemke, Andrew D. Ludlow, J. von Stecher, Jeffrey A. Sherman, A.M. Rey, Christopher W. Oates
State-of-the-art optical clocks with neutral atoms employ an optical lattice to tightly confine the atoms, enabling high-resolution spectroscopy and the potential for high-accuracy timekeeping. Interrogating many atoms simultaneously facilitates high

Ultralow phase noise microwave generation with an Er:fiber-based optical frequency divider

August 15, 2011
Author(s)
Franklyn J. Quinlan, Tara M. Fortier, Matthew S. Kirchner, Jennifer A. Taylor, Michael J. Thorpe, Nathan D. Lemke, Andrew D. Ludlow, Yanyi Jiang, Christopher W. Oates, Scott A. Diddams
We present an optical frequency divider based on a 200 MHz repetition rate Er:fiber mode-locked laser that, when locked to a stable optical frequency reference, generates microwave signals with absolute phase noise that is equal to or better than cryogenic

Improving the stability and accuracy of the Yb optical lattice clock

July 31, 2011
Author(s)
Andrew D. Ludlow, Yanyi Jiang, Nathan D. Lemke, Jeffrey A. Sherman, J. von Stecher, Richard W. Fox, Long-Sheng Ma, A.M. Rey, Christopher W. Oates
We report results for improving the stability and uncertainty of the NIST $^{171}$Yb lattice clock. The stability improvements derive from a significant reduction of the optical Dick effect, while the uncertainty improvements focus on improved

Generation of Ultrastable microwaves via optical frequency division

June 26, 2011
Author(s)
Tara Fortier, Matthew S. Kirchner, Jennifer A. Taylor, James C. Bergquist, Yanyi Jiang, Andrew Ludlow, Christopher W. Oates, Till P. Rosenband, Scott Diddams, Franklyn Quinlan, Nathan D. Lemke
A frequency-stabilized femtosecond laser optical frequency comb serves as a source of microwave signals having very low close-to-carrier phase noise. Comparison of two independent systems shows combined absolute phase noise of -100 dBc/Hz at an offset of 1

Making optical atomic clocks more stable with 10 -16 level laser stabilization

January 23, 2011
Author(s)
Andrew D. Ludlow, Yanyi Jiang, Nathan D. Lemke, Richard W. Fox, Jeffrey A. Sherman, Long-Sheng Ma, Christopher W. Oates
The superb precision of an atomic clock is derived from its stability. Atomic clocks based on optical (rather than microwave) frequencies are attractive because of their potential for high stability, which scales with operational frequency. Nevertheless

Hyper-Ramsey spectroscopy of optical clock transitions

July 22, 2010
Author(s)
Christopher W. Oates, V. I. Yudin, A. V. Taichenachev, Zeb Barber, Nathan D. Lemke, Andrew D. Ludlow, U Sterr, Ch. Lisdat, F Riehle
We present nonstandard optical Ramsey schemes that use pulses individually tailored in duration, phase and frequency to cancel spurious frequency shifts related to the excitation itself. In particular, the field shifts and their uncertainties can be

Compensation of Field-Induced Frequency Shifts in Ramsey Spectroscopy of Optical Clock Transitions

December 10, 2009
Author(s)
A. V. Taichenachev, V. I. Yudin, Christopher W. Oates, Barber W. Zeb, Nathan D. Lemke, Andrew Ludlow, U Sterr, Ch. Lisdat, F Reihle
We develop a modified version of Ramsey spectroscopy that uses an additional frequency shift to compensate frequency shifts induced by the excitation itself. In its simplest realization, this method uses a small step of the probe frequency during the two

A Spin-1/2 Optical Lattice Clock

August 7, 2009
Author(s)
Nathan D. Lemke, Andrew D. Ludlow, Zeb Barber, Tara M. Fortier, Scott A. Diddams, Yanyi Jiang, Steven R. Jefferts, Thomas P. Heavner, Thomas E. Parker, Christopher W. Oates
We experimentally investigate an optical clock based on 171Yb (I = 1/2) atoms confined in an optical lattice. We have evaluated all known frequency shifts to the clock transition, including the density-dependent collision shift, with an uncertainty of 0.19

Probing interactions between ultracold fermions

April 17, 2009
Author(s)
G K. Campbell, M M. Boyd, J W. Thomsen, M J. Martin, S Blatt, M D. Swallows, Travis L. Nicholson, Tara Fortier, Christopher W. Oates, Scott Diddams, Nathan D. Lemke, Pascal Naidon, Paul S. Julienne, Jun Ye, Andrew Ludlow
At ultracold temperatures, the Pauli exclusion principle suppresses collisions between identical fermions. This has motivated the development of atomic clocks using fermionic isotopes. However, by probing an optical clock transition with thousands of

Yb Optical Lattice Clock

November 23, 2008
Author(s)
Nathan D. Lemke, Andrew Ludlow, Zeb Barber, N Poli, C.W. Hoyt, Long-Sheng Ma, Jason Stalnaker, Christopher W. Oates, Leo Hollberg, James C. Bergquist, A. Brusch, Tara Fortier, Scott Diddams, Thomas P. Heavner, Steven R. Jefferts, Tom Parker
We describe the development and latest results of an optical lattice clock based on neutral Yb atoms, including investigations based on both even and odd isotopes. We report a fractional frequency uncertainty below 10 -15 for 171Yb.