Lene V. Hau

Mallinckrodt Professor of Physics and of Applied Physics

Ph.D. Physics, M.Sc. Physics, B.Sc. Mathematics and Physics
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Professor Hau's current research centers on optics with cold atoms and Bose–Einstein condensates. Her group precools atoms using laser cooling to temperatures in the microkelvin range. The atoms are subsequently trapped in a 4-Dee electromagnet and cooled by evaporation to nanokelvin temperatures, resulting in the creation of Bose–Einstein condensates that typically contain millions of atoms. The condensates are formed in an ultrahigh vacuum system constructed for easy access to and manipulation of cold atom clouds using light probes and nano-mechanical structures. Professor Hau's group recently reduced the light speed to 17 meters per second (the speed of a racing bicycle) - and ultimately completely stopped a light pulse - by optically inducing a quantum interference in a Bose–Einstein condensate.

Ultraslow and stopped light is obtained by creating a new and unique optical medium: an entangled system of photons and atoms that exhibits extreme optical properties. Hau's group has demonstrated a nonlinear refractive index that is 14 orders of magnitude larger that in an optical fiber and, by a factor of a million, the largest ever measured. This work opened a new territory of nonlinear optics at extremely low light levels.

Interesting potential applications of the large nonlinearities include creation of optical switches that will work at the single-photon level, dynamically programmable optical delay lines, and controlled optical information storage and processing. A practical system might be based on atom cooling by diode lasers and micro-traps, a possibility related to another of Professor Hau's interests: atomic wave guides for cold atoms.

Professor Hau and her collaborators were the first to suggest a wave-guide for cold atoms based on a mechanical structure. This "Kapitza guide" involves dynamical stabilization of atom motion around a metallic wire with time-varying electric potentials; it is the atomic-matter wave analogue of the optical fibers used as guiding structures for light.


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