After obtaining his doctorate he remained at Berkeley as a postdoctoral researcher for two years before joining Bell Labs, where he and his several co-workers carried out his Nobel Prize-winning laser cooling work. He left Bell Labs and became a professor of physics at Stanford University in 1987, serving as the chair of its Physics Department from 1990 to 1993 and from 1999 to 2001. At Stanford, Chu and three others initiated the Bio-X program, which focuses on interdisciplinary research in biology and Medicine, and played a key role in securing the funding for the Kavli Institute for Particle Astrophysics and Cosmology. In August 2004, Chu was appointed as the Director of the Lawrence Berkeley National Laboratory, a U.S. Department of Energy National Laboratory, and joined UC Berkeley's Department of Physics and Department of Molecular and Cell Biology. Under Chu's leadership, the Lawrence Berkeley National Laboratory has been a center of research into biofuels and solar Energy. He spearheaded the laboratory's Helios project, an initiative to develop methods of harnessing solar power as a source of renewable Energy for transportation.