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. On February 1, 2013, he announced he would not serve for the President's second term and resigned on April 22, 2013.