Physical Society Colloquium

Steven Chu's investigations range over a wide range of topics in atomic physics, quantum electronics, polymer science and bio-physics.

His did his thesis and postdoctoral work at Berkeley. His observation of parity non-conservation in atomic transitions, in 1978, was one of the early confirmations of the Weinberg-Salam-Glashow theory that unifies the weak and electromagnetic forces.

In 1982, while at Bell Laboratories, Allen Mills and he did the first laser spectroscopy of positronium, the bound state of an electron and positron. They went on to measure the 1s-2s energy level splitting of that atom to an accuracy of a few parts per billion. They followed this with up the first measurement of the corresponding transition in muonium, an atom which has an electron bound to a muon.

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. The first optical trapping was followed by the demonstration of the magneto-optic trap, the most commonly used atom trap.

In 1987, after joining the Stanford Physics Department, Chu (and independently, Dalibard and Cohen-Tannoudji) explained how multi-level atoms can be cooled far below the minimum temperature predicted by the theory of two-level atoms. His group also demonstrated the first "atomic fountain" and then made the first atomic fountain frequency standard which exceeds the short term stability of atomic clocks. They developed a novel atom interferometer that has already exceeded the accuracy of the most accurate commercial inertial sensors.

Using the optical tweezers, Chu developed methods to simultaneously visualize and manipulate single bio-molecules. Using this new technique, his group has used single DNA molecules to address a number of long standing problems in polymer science. He is currently developing methods to study the interactions of individual bio-molecules.

Other contributions include the study of exciton energy transfer in solids, anomalous pulse propagation in absorbing medium, and the development of a transmission line, near-field microscope.

For these pioneering research activities, Steven Chu has been awarded many prizes and awards- to mention a few:the Herbert Broida Prize for Spectroscopy (American Physical Society, 1987), Richtmyer Memorial Prize Lecturer (APS/AAPT, 1990), Arthur Schawlow Prize (APS, 1994), William Meggers Award (Optical Society of America, 1994), the Science for Art Prize (Louis Vitton - M�et Hennesey,1995). He was awrded the Nobel Prize in Physics (1997).