Steven Chu
Laser Cooling and Trapping of Atoms

Resources with Additional Information · Interviews, Speeches, and Presentations · Patents

Steven Chu
Photo Credit:
Lawrence Berkeley National Laboratory
Roy Kaltschmidt, Photographer

Steven Chu was appointed by President Barack Obama to be the 12th Secretary of Energy and served in this capacity until April 22, 2013.  He was previously Director of Lawrence Berkeley National Laboratory (LBNL), Professor in the Physics Department at the University of California, Berkeley, and 'the Theodore and Frances Geballe Professor of Physics and Applied Physics at Stanford University. Professor Chu's research is in atomic physics, polymer and biophysics.

His thesis and postdoctoral work at Berkeley …  was the observation of parity non-conservation in atomic transitions in 1978. This experiment was one of the earliest atomic physics confirmations of the Weinberg-Salam-Glashow theory that unifies the weak and electromagnetic forces.

While at Bell Laboratories he and Allen Mills did the first laser spectroscopy of positronium, the most fundamental atom (consisting of an electron and its anti-particle) in 1982. They went on to measure the 1s-2s energy difference of that atom to an accuracy of a few parts per billion, at that time, one of the most precise tests of quantum electrodynamics. They also made the first measurement of the corresponding transition in muonium, an atom consisting of m+ and an electron. Chu demonstrated that light pulses are able to propagate in absorbing medium where the velocity of the pulse can reach infinity and even become negative. (A negative velocity is defined where the peak of the pulse exits the sample before it enters the sample.) In 1985, he led the group that showed how to first cool and then trap atoms with light. The optical trap was also used to trap microscopic particles in water: these so-called "optical tweezers" are widely used in biology. …  Using the optical tweezers, Chu invented methods to simultaneously visualize and manipulate individual bio-molecules in 1989.' 1

Steve Chu has been Director of Lawrence Berkeley National Laboratory since August, 2004. Chu, an early advocate for finding scientific solutions to climate change, has guided Berkeley Lab on a new mission to become the world leader in alternative and renewable energy research, particularly the development of carbon-neutral sources of energy. 'Dr. Chu understands the significance of our energy and environmental challenges, and more importantly, understands the technical solutions necessary to address them.' 2

Chu was co-winner of the 1997 Nobel Prize in Physics "for development of methods to cool and trap atoms with laser light".

1 Edited excerpt from Steven Chu (when Director at Lawrence Berkeley National Laboratory)
2 Edited excerpt from Statement by U.S. Energy Secretary Samuel W. Bodman Regarding Selection of Steven Chu as Successor


Resources with Additional Information

Additional information about Steven Chu, laser cooling, atom trapping, optical tweezers, and atom interferometry is available in electronic documents and on the Web.


Observation of the Forbidden Magnetic Dipole Transition 62P½ --> 72P½ in Atomic Thallium, DOE Technical Report, 1976

Three-dimensional Viscous Confinement and Cooling of Atoms by Resonance Radiation Pressure Physical Review Letters, Vol. 55, Issue 1; July 1985

Experimental Observation of Optically Trapped Atoms; Physical Review Letters, Vol. 57, Issue 3; July 1986

Atom-Interferometry Tests of the Isotropy of Post-Newtonian Gravity; Physical Review Letters, Vol. 100, Issue 3; January 2008

Atom Interferometry with up to 24-Photon-Momentum-Transfer Beam Splitters; Physical Review Letters, Vol. 100, Issue 18; May 2008


Additional Web Pages:

Landmarks: Laser Cooling of Atoms, Physical Review Focus, April 2, 2008

Steven Chu: Uncovering the Secret Life of Molecules, Stanford [online] Report, Stanford University

Growing Energy: Berkeley Lab's Steve Chu on What Termite Guts Have To Do with Global Warming

Steven Chu, Director, Lawrence Berkeley National Laboratory (LBNL)

Steven Chu, Stanford University


Interviews, Speeches, and Presentations

Chu: 'I am not a billionaire, but at least I am a nerd'; Harvard Commencement Address; June 4, 2009;

Statement of Steven Chu, Secretary of Energy-Designate, before the Committee on Energy and Natural Resources, U.S. Senate, January 13, 2009

Interview with Steven Chu; August 26, 2008;

Interview: Steven Chu, American Scientist, January - February 1998

Energy Nominee Steven Chu on Climate Change, National Public Radio (NPR)

A Scientist's Random Walk: Conversation with Steven Chu, Institute of International Studies, UC Berkeley

Laser Cooling - From Atomic Clocks to Watching Biomolecules (video)

What Can Physics Say About Life? (video)

Energy@Berkeley: Solutions for Global Warming (video)

Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science (video)


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