Hall, John L (1934– )

US physicist, who with German physicist Theodor W Hänsch and US physicist Roy J Glauber shared the Nobel Prize in Physics in 2005 for his contributions to the development of laser-based precision spectroscopy. Hall's research group initially worked independently of that led by Hänsch in the development of the frequency comb technique for the precision measurement of the frequency of light. However, in the late 1990s the two groups collaborated to produce the first working system.

This system was used to measure the accuracy of the Lyman spectral line of hydrogen to an accuracy of fifteen digits. The technique can be used to measure light of all colours with extreme accuracy, forming the foundation for the development of laser-based precision spectroscopy. The technique can also be used over a range of applications, from the improvement of global positioning system (GPS) technology to the measurement of unusual phenomena such as gravity waves.

Hall was born in Denver, Colorado. He received a Bachelor of Science degree, a Master of Science degree, and a doctorate from the Carnegie Institute of Technology, Pittsburgh, Pennsyvania, in 1956, 1958, and 1961 respectively. He worked at the National Bureau of Standards of the US Department of Commerce from 1962 to 1971. In 1967 he became physics lecturer at the University of Colorado, Boulder. He was elected a member of the National Academy of Sciences in 1986.