Steven Chu ( Chinese: 朱棣文; pinyin: Zhū Dìwén, born February 28, 1948 ) is an American physicist who served as the 12th United States Secretary of Energy from 2009 to 2013. Chu is known for his research at Bell Labs in cooling and trapping of atoms with laser light, which won him the Nobel Prize in Physics in 1997, along with his scientific colleagues Claude Cohen-Tannoudji and William Daniel Phillips. At the time of his appointment as Energy Secretary, he was a professor of physics and molecular and cellular biology at the University of California, Berkeley, and the director of the Lawrence Berkeley National Laboratory, where his research was concerned primarily with the study of biological systems at the single molecule level. Previously, he had been a professor of physics at Stanford University. He is a vocal advocate for more research into renewable energy and nuclear power, arguing that a shift away from fossil fuels is essential to combating climate change. For example, he has conceived of a global "glucose economy", a form of a low-carbon economy, in which glucose from tropical plants is shipped around like oil is today. On February 1, 2013, he announced he would not serve for the President's second term and resigned on April 22, 2013.