Scientific Breakthroughs

Our group is exploring three major areas on the research frontiers of modern AMO physics: (1) the development of an optical atomic clock based on neutral ⁸⁷Sr atoms, together with improved methods for transferring clock signals across fiber networks; (2) magnetic trapping and cooling of simple molecules, with the goals of investigating fundamental constants and elucidating molecular structure and dynamics at the quantum mechanical level; and (3) the development of new optical frequency comb-based spectroscopy and the quantum control of matter, including devices for ultrasensitive detection and systems using vacuum ultraviolet (VUV) frequency combs. In the past three years, our group has made major breakthroughs in all three fields, as highlighted below.

Ultracold Polar Molecules

The Jin and Ye groups have crafted an entirely new form of matter — tens of thousands of ultracold polar molecules in their lowest energy state. The ground-state molecules of potassium and rubidium (⁴⁰K⁸⁷Rb) are too cold to exist anywhere else in the Universe. To make them, the researchers first lowered the magnetic field applied to an ultracold gas cloud containing both kinds of atoms. This process created large, fluffy, and loosely bound ⁴⁰K⁸⁷Rb molecules. Then they locked two lasers to different lines of the same femtosecond comb. They aimed two coherent beams of laser light into the cloud of large, fluffy molecules so that the two laser beams interfered with each other, producing a pulse of light perfectly tuned to coherently transfer the molecules into their lowest-energy ground state. The ground-state molecules are relatively long lived and have an uneven distribution of electric charge over the two nuclei in the molecules (i.e., an electric dipole moment). The creation of these molecules has opened the door to future studies of ultracold chemistry and novel quantum dynamics. It has also once again demonstrated the incredible power of frequency combs. NIST press release CU press release

Selected Journal Articles:

K.-K. Ni, S. Ospelkaus, M. H. G. de Miranda, A. Pe’er, B. Neyenhuis, J. J. Zirbel, S. Kotochigova, P. S. Julienne, D. S. Jin, and J. Ye, Science, published online Sept. 18, 2008.

S. Ospelkaus, A. Pe'er, K.-K. Ni, J. J. Zirbel, B. Neyenhuis, S. Kotochigova, P. S. Julienne, J. Ye, and D. S. Jin, Nature Physics 4, 622–626 (2008).

J. J. Zirbel, K.-K. Ni, S. Ospelkaus, T. L. Nicholson, M. L. Olsen, P. S. Julienne, C. E. Wieman, J. Ye, and D. S. Jin, Physical Review A 78, 013416/1–7 (2008).

Popular Articles:

Laura Sanders highlights the Jin and Ye groups research in the article, "Physicists Hot for Ultracold," Science News (December 20, 2008).

 

Ultracold Chemistry

The Jin and Ye groups have for the first time observed chemical reactions near absolute zero, demonstrating that chemistry is possible at ultralow temperatures and that reaction rates can be controlled using quantum mechanics, the peculiar rules of submicroscopic physics.

Selected Journal Articles:

S. Ospelkaus, K. K. Ni, D. Wang, M. H. G. de Miranda, B. Neyenhuis, G. Quemener, P. S. Julienne, J. L. Bohn, D. S. Jin, and J. Ye, "Quantum-State Controlled Chemical Reactions of Ultracold KRb Molecules,Science 327, no. 5967, 853-857 (February 2010).

Popular Articles:

NIST News Release, "Seeing the Quantum in Chemistry: JILA Scientists Control Chemical Reactions of Ultracold Molecules," (February 11, 2010).

CU News Release, "CU-NIST Scientists Observe Chemical Reactions Near Absolute Zero for the First Time," (February 11, 2010).

 

Strontium Atomic Clock

For the past two years, our group has been developing an ⁸⁷Sr optical lattice atomic clock. The overall systematic uncertainty has reached below the cesium (Cs)-fountain clock, the nation's primary standard, located at the National Institute of Standards and Technology (NIST). Our clock is currently undergoing comparisons with other optical atomic clocks at NIST to determine the best performing technology. We hope our clock will be a strong contender in this determination. In 2007, we reported a precise measurement of the frequency of the ⁸⁷Sr lattice clock transition as 429 228 004 229 874.0(1.1) Hz. This is the most accurate measurement of a neutral atom-based optical transition frequency ever made. We have also achieved the highest quality factor (Q) of a natural resonance for any form of coherent spectroscopy.

Selected Journal Articles:

G. K. Campbell, M. M. Boyd, J. W. Thomsen, M. J. Martin, S. Blatt, M. D. Swallows, T. L. Nicholson, T. Fortier, C. W. Oates, S. A. Diddams, N. D. Lemke, P. Naidon, P. Julienne, Jun Ye, A. D. Ludlow, "Probing Interactions Between Ultracold Fermions," Science 324, 360-363 (2009).

T. Zelevinsky, S. Blatt, M. M. Boyd, G. K. Campbell, A. D. Ludlow, and Jun Ye, "Highly Coherent Spectroscopy of Ultracold Atoms and Molecules in Optical Lattices," ChemPhysChem 9, 375-382 (2008).

A. D. Ludlow, T. Zelevinsky, G. K. Campbell, S. Blatt, M. M. Boyd, M. H. G. de Miranda, M. J. Martin, J. W. Thomsen, S. M. Foreman, Jun Ye, T. M. Fortier, J. E. Stalnaker, S. A. Diddams, Y. Le Coq, Z. W. Barber, N. Poli, N. D. Lemke, K. M. Beck, C. W. Oates, "Sr Lattice Clock at 1 x 10^-16 Fractional Uncertainty by Remote Optical Evaluation with a Ca Clock," Science 319, 1805 (2008).

S. Blatt, A. D. Ludlow, G. K. Campbell, J. W. Thomsen, T. Zelevinsky, M. M. Boyd, J. Ye, X. Baillard, M. Fouche, R. Le Targat, A. Brusch, P. Lemonde, M. Takamoto, F. L. Hong, H. Katori, and V. V. Flambaum, "New Limits on Coupling of Fundamental Constants to Gravity Using ⁸⁷Sr Optical Lattice Clocks," Physical Review Letters 100, 140801 (2008).

Martin M. Boyd, Andrew D. Ludlow, Sebastian Blatt, Seth M. Foreman, Tetsuya Ido, Tanya Zelevinsky, and Jun Ye, "⁸⁷Sr Lattice Clock with Inaccuracy below 10^-15," Physical Review Letters 98, 083002/1-4 (2007).

M. M. Boyd, T. Zelevinsky, A. D. Ludlow, S. Blatt, T. Zanon-Willette, S. S. Foreman, G. K. Campbell, and Jun Ye, "Nuclear spin effects in optical lattice clocks," Physical Review A 76, 022510 (2007).

A. D. Ludlow, X. Huang, M. Notcutt, T. Zanon-Willette, S. M. Foreman, M. M. Boyd, S. Blatt, and J. Ye, "Compact, thermal noise-limited optical cavity for diode laser stabilization at 1 x 10^-15," Optics Letters 32, 641 (2007).

Martin M. Boyd, Tanya Zelevinsky, Andrew D. Ludlow, Seth. M. Foreman, Sebastian Blatt, Tetsuya Ido, and Jun Ye, "Optical atomic coherence at the 1-second time scale," Science, 314, 1430 (2006).

T. Zanon-Willette, A. D. Ludlow, M. M. Boyd, S. Blatt, E. Arimondo, and J. Ye, "Dynamic cancellation of ac Stark shift for pulsed EIT/Raman optical lattice clocks," Physical Review Letters 97, 233001 (2006).

T. Zelevinsky, M. M. Boyd, A. D. Ludlow, T. Ido, J. Ye, R. Ciurylo, P. Naidon, and P. S. Julienne, "Narrow line photoassociation in an optical lattice," Physical Review Letters 96, 203201 (2006).

A. D. Ludlow, M. M. Boyd, T. Zelevinsky, S. M. Foreman, S. Blatt, M. Notcutt, T. Ido, and J. Ye, "Systematic study of the ⁸⁷Sr clock transition in an optical lattice," Physical Review Letters 96, 033003 (2006).

T. Ido, T. H. Loftus, M. Boyd, A. Ludlow, K. W. Holman, and J. Ye, "Precision spectroscopy and density-related frequency shifts in ultracold Sr," Physical Review Letter 94, 153001 (2005).

R. Santra, E. Arimondo, T. Ido, and C. H. Greene, and J. Ye, "A high-accuracy optical clock via three-level coherence in neutral bosonic ⁸⁸Sr," Physical Review Letters 94, 173002 (2005).

T. H. Loftus, T. Ido, A. Ludlow, M. Boyd, and J. Ye, "Narrow line cooling: finite photon recoil dynamics," Physical Review Letters 93, 073003 (2004).

Popular Articles:

NIST News Release, "JILA/NIST Scientists Get a Grip on Colliding Fermions to Enhance Atomic Clock Accuracy," (April 16, 2009).

National Science Foundation News from the Field, "Scientists Get a Grip on Colliding Fermions to Enhance Atomic Clock Accuracy," (April 16, 2009).

R & D Magazine, "Researchers solve fermion puzzle, fine-tune their clock," (April 15, 2009).

Jeff Hecht, "PHOTONIC FRONTIERS: FREQUENCY COMBS — Frequency combs achieve extreme precision," LaserFocusWorld (June 2007).

"Steadier lasers could make best atomic clock yet," New Scientist News Service (Nov.30, 2006).

"Strontium scheme enters atomic clock race," EE Times (Nov. 30, 2006).

"Optical Clocks: Beating the standard," Nature Photonics (April, 2008).

World's Most Stable Lasers

Red Orbit, "Scientists Create Most Stable Laser in the World," (September 15, 2012).

New Electronics, "Researchers develop 'most stable laser in the world'," (September 17, 2012).

Laser Focus World, "World's most stable laser created by NIST/JILA and German researchers," (September 14, 2012).

JILA Research Highlights, "Precision Measurement: The Next Frontier," (September 17, 2012).

Single-crystal silicon optical cavity has been developed to produce the world's most stable laser, which is needed for the next generation optical atomic clocks and precision interferometers. The properties of silicon (crystalline structure shown in background) enable high immunity to length fluctuations. The work results from a great collaborative effort between PTB Germany and JILA.

Time Transfer

Our group has been working on ways to transmit clock signals over a fiber optic network more accurately and precisely than optical atomic clocks can currently measure time. To do this, we devised a way to cancel fiber noise caused by road sounds, temperature changes, or other environmental conditions. Our new method not only makes it possible to remotely compare new clock designs, but also enables stable transmissions for connecting phase-coherent telescope arrays via optical carriers. In the future, it may figure in techniques for remotely synchronizing accelerator-based light sources for studies of ultrafast phenomena in physics, chemistry, biology, and materials science.

Journal Articles:

S. M. Foreman, A. D. Ludlow, M.H. G. De Miranda, J. Stalnaker, S. A. Didams, and J. Ye, "Coherent optical phase transfer over a 32-km fiber with 1-s instability <10^-17," Phys. Rev. Lett. 99, 153601 (2007) .

Seth M. Foreman, Kevin W. Holman, Darren D. Hudson, David J. Jones, and Jun Ye, "Remote transfer of ultrastable frequency references via fiber networks," Review of Scientific Instruments 78, 021101/1-25 (2007).

Magnetic Trapping of Cold OH Molecules

Our group has developed an innovative magneto-electrostatic trap as part of a system to cool and trap dipolar OH molecules. The new trap confines slowly moving cold molecule packets created in a Stark decelerator. It will allow us to conduct extensive studies of the dynamics of trapped cold molecules. Our goal is to learn to use electric fields to control cold molecule collisions and possibly even chemical reactions.

Journal Articles:

B. C. Sawyer, B. L. Lev, E. R. Hudson, B. K. Stuhl, M. Lara, J. L. Bohn, and J. Ye, "Magnetoelectrostatic trapping of ground state OH molecules," Physical Review Letters 98, 253002 (2007).

Fine Structure Constant

As part of our cold molecule research, our group has precisely measured four OH transition frequencies that will help physicists determine whether the fine structure constant has changed in the past 10 billion years. The fine structure constant is a measure of the strength of the electromagnetic force that governs how electrons, muons, and light interact. Determining whether it has changed over vast spans of cosmic time will help determine which model of the basic structure of matter is correct.

Journal Articles:

B. L. Lev, E. R. Meyer, E. R. Hudson, B. C. Sawyer, J. L. Bohn, and Jun Ye, "OH hyperfine ground state: From precision measurement to molecular qubits," Physical Review A 74, 061402 (R)/1-4 (2006).

Eric R. Hudson, H. J. Lewandowski, Brian C. Sawyer, and Jun Ye, "Cold Molecule Spectroscopy for Constraining the Evolution of the Fine Structure Constant," Physical Review Letters 96, 143004 (2006).

Popular Articles:

Robert C. Cowen, "Not-so-constants?" The Christian Science Monitor (May 4, 2006).

"Measurements may help show if constants are changing," PHYSORG.COM (April 28, 2006).

Frequency Comb Spectroscopy

Our group developed direct frequency comb spectroscopy (DFCS) in 2004. This technique allows researchers to explore fast dynamics in the time domain and high-resolution structural information in the frequency domain. The comb is also ideal for setting up a massive set of parallel detection channels (up to several million) to gather spectroscopic information. With this technique, we have measured electron energy levels in atoms, detected and controlled atomic energy level transitions in real time, investigated quantum coherence, studied atomic and molecular dynamics, and identified unknown substances by detecting characteristic energy-level transitions.

Journal Articles:

M. C. Stowe, M. J. Thorpe, A. Pe'er, J. Ye, J. E. Stalnaker, V. Gerginov, and S. A. Diddams, "Direct frequency comb spectroscopy," Advances in Atomic, Molecular, and Optical Physics, in press.

Adela Marian, Matthew C. Stowe, John R. Lawall, Daniel Felinto, and Jun Ye, "United Time-Frequency Spectroscopy for Dynamics and Global Structure," Science 306, 2063 (2004).

A. Marian, M. C. Stowe, D. Felinto, and J. Ye, "Direct frequency comb measurements of absolute optical frequencies and population transfer dynamics," Physical Review Letters 95, 023001 (2005).

M. C. Stowe, F. Cruz, A. Marian, and J. Ye, "High resolution atomic coherent control via spectral phase manipulation of an optical frequency comb," Physical Review Letters 96, 153001 (2006).

Journal Article:

K. C. Cossel, D. Gresh, L. C. Sinclair, T. Coffey, A. Petrov, A. Titov, R. W. Field, E. R. Meyer, E. A. Cornell, and J. Ye, "Velocity modulation spectroscopy of HfF+ with frequency comb and cw: towards a measurement of the electron electric diople moment" Chem. Phys. Lett. , 546, 1-11 (2012).

To enable efficient spectroscopic investigations of unexplored molecular ions, the Cornell and Ye groups have developed a powerful technique for broadband, high-resolution survey spectroscopy that combimes cavity-enhanced direct frequency-comb spectroscopy with velocity-modulation spectroscopy. This technique was used to determine the HfF+ molecular structure that is relevant to experimental search for the permanent electric dipole moment of the electron (eEDM).

 

 

 

 

We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity-modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF⁺ and achieved a fractional absorption sensitivity of 3 x 10^-7 recorded over 1500 simultaneous channels spanning 150 cm^-1 around 800 nm with an absolute frequency accuracy of 30 MHz (0:001 cm^-1). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 min.

Journal Articles:

L. C. Sinclair, K. C. Cossel, T. Coffey, J. Ye, and E. A. Cornell, "Frequency Comb Velocity-Modulation Spectroscopy" Physical Review Letters, 107, 093002 (2011).

Molecular Fingerprinting

Our group invented cavity-enhanced direct frequency comb spectroscopy in 2006 to perform ultrasensitive detection of unknown chemicals. Each atom or molecule placed inside the cavity will absorb photons of particular frequencies that are unique to each chemical. By analyzing light exiting the cavity, we can identify every constituent in a mixture. We recently developed a more sensitive, smaller, and less costly fiber laser for this system, bringing us closer to developing this technique for medical and homeland-security applications.

Journal Articles:

Thorpe, Michael J., Balslev-Clausen, David, Kirchner, Matthew S., and Jun Ye, "Cavity-enhanced optical frequency comb spectroscopy: application to human breath analysis," Optics Express 16:4, 2387 (2008).

Thorpe, Michael J., Hudson Darren D., Moll, Kevin D., Lasri, Jacob, and Jun Ye, "Cavity-ringdown molecular spectroscopy based on an optical frequency comb at 1.45-1.65 µm," Optics Letters 32, 307 (2007).

Thorpe, M. J., Moll, K. D., Jones, R. J., Safdi, B., and Ye, J., "Broadband cavity ringdown spectroscopy for sensitive and rapid molecular detection," Science 311, 1595 (2006).

M. J. Thorpe, R. J. Jones, K. D. Moll, J. Ye, and R. Lalezari, "Precise measurements of optical cavity dispersion and mirror coating properties via femtosecond combs," Optics Express 13, 882 (2005).

Popular Articles:

"'New Breath-Based Diagnostic: An innovative technique for detecting different biomarkers could result in a precise, easy-to-use diagnostic tool," An MIT Enterprise Technology Review, March 14, 2008; and "Frequency-comb spectroscopy detects disease via breath analysis", BioOptics World, March 2008

"'Collaboration Helps Make JILA Strontium Atomic Clock 'Best in Class' 'Crystal of Light' Clock Surpasses Accuracy of NIST-F1 Fountain Clock," United States Department of Commerce News, Feb. 14, 2008.

"'News Coverage of the JILA Breathalyzer February - March 2008," Compiled By: NIST Public Affairs Office."

"'Frequency comb' spectroscopy proves to be powerful chemical analysis tool," PHYSORG.COM (March 16, 2006).

"Optical 'Comb" Measures Finer Frequencies," photonics.com, News and Features (April 4, 2006).

VUV Frequency Comb

Recent demonstrations of high-harmonic generation (HHG) at very high repetition frequencies (~100 MHz) may allow for the revolutionary transfer of frequency combs to the vacuum-ultraviolet range. This advance necessitates unifying optical frequency-comb technology with strong-field atomic physics. Whereas strong-field studies of HHG have often focused on above-threshold harmonic generation (photon energy above the ionization potential), for vacuum-ultraviolet frequency combs an understanding of below-threshold harmonic orders and their generation process is crucial. Here, we present a new and quantitative study of the harmonics 7-13 generated below and near the ionization threshold in xenon gas with an intense 1,070 nm driving field. We show multiple generation pathways for these harmonics that are manifested as on-axis interference in the harmonic yield. This discovery provides a new understanding of the strong-field, below-threshold dynamics under the influence of an atomic potential and allows us to quantitatively assess the achievable coherence of a vacuum-ultraviolet frequency comb generated through below-threshold harmonics. We find that under reasonable experimental conditions, temporal coherence is maintained. As evidence, we present the first explicit vacuum-ultraviolet frequency-comb structure beyond the third harmonic.

In 2005, our group created one of the first two frequency combs in the vacuum ultraviolet (VUV). The VUV comb is a short-wavelength version of the optical frequency comb. It may one day make it possible to conduct coherent light-based experiments in the VUV. Our VUV comb generator uses an ultrafast mode-locked laser coupled to a high-finesse optical cavity equipped with custom-designed mirrors and filled with argon gas. We are currently working on increasing the power of our generator with enhanced cavity mirrors, a new fiber laser, and better methods for getting X-rays out of the cavity once they are created.

Journal Articles:

D. C. Yost, T. R. Schibli, J. Ye, J. L. Tate, J. Hostetter, M. B. Gaarde, and K. J. Schafer, "VUV frequency combs from below-threshold harmonics," Nature Physics 5, 815 (2009).

T. R. Schibli, I. Hartl, D. C. Yost, M. J. Martin, A. Marcinkevicius, M. E. Fermann, and J. Ye, "Optical frequency comb with sub-mHz linewidth and >10 W average power," Nature Photonics 2, 355-359 (2008).

D. C. Yost, T. R. Schibli, and J. Ye, "Novel geometry for output coupling of intracavity high harmonic generations," Opt. Lett. 33, 1099 - 1101 (2008).

E. E. Eyler, D. E. Chieda, M. C. Stowe, M. J. Thorpe, T. R. Schibli, and J. Ye, "Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy," Eur. Phys. J. D 48, 43 - 55 (2008).

I. Hartl, T. R. Schibli, A. Marcinkevicius, M. E. Fermann, D. C. Yost, D. D. Hudson, and J. Ye, "Cavity-enhanced similariton Yb-fiber laser frequency comb: 3 x 10¹⁴ W/cm² peak intensity at 136 MHz," Opt. Lett. 32, 2870 (2007).

R. Jason Jones, Kevin D. Moll, Michael J. Thorpe, and Jun Ye, "Phase-coherent Frequency Combs in the Vacuum Ultraviolet via High-Harmonic Generation inside a Femtosecond Enhancement Cavity," Physical Review Letters 94, 193901 (2005).

K. D. Moll, R. J. Jones, and J. Ye, "Output coupling methods for cavity-based high-harmonic generation," Optics Express 14, 8189 (2006).

K. D. Moll, R. J. Jones, and J. Ye, "Nonlinear dynamics inside femtosecond enhancement cavities," Optics Express 13, 1672 (2005).

R. J. Jones and J. Ye, "High-repetition rate, coherent femtosecond pulse amplification with an external passive optical cavity," Optics Letters 29, 2812 (2004).

R. J. Jones and J. Ye, "Femtosecond pulse amplification by coherent addition in a passive optical cavity," Optics Letters 27, 1848 (2002).

Popular Articles:

Phil Schewe & Ben Stein, "Ultraviolet Frequency Comb," Physics News Update 735 (June, 2005); also selected as Top Physics News Story, December 2005.

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