John L. Hall is a fellow and senior research associate at JILA, a joint institute of the University of Colorado at Boulder and the National Institute of Standards and Technology. He was awarded the 2005 Nobel Prize in Physics.
Hall is known as a pre-eminent laser experimentalist, concentrating on improving the precision and accuracy with which lasers can produce a specific, sharp frequency or color of light, and the stability to hold that frequency. His work has been essential to precision spectroscopy for physical and chemical analysis, new tests and measurements of fundamental physical laws and constants, time and length, metrology and fiber-optic communications.
In the 1960s he worked on the development of the methane-stabilized helium-neon laser, which became the cornerstone of a famous experiment at NIST to measure the speed of light at least 100 times better than any previous determination. The work ultimately led to a fundamental redefinition of the meter, the basic unit of distance measurement.
Hall shared the Nobel with Theodor W. Hänsch of the Max Planck Institute for Quantum Optics and a professor of physics at Ludwig Maximilians University in Munich, Germany, and Roy J. Glauber, a professor of physics at Harvard University. Hall and Hänsch were awarded half the Nobel Prize for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique. An optical frequency comb is generated by a laser specially designed to produce a series of extremely short -- a few billionths of a second -- equally spaced pulses of light. The other half of the prize was awarded to Glauber for his contribution to the quantum theory of optical coherence.
Hall has been affiliated with CU-Boulder's physics department since 1966, retired from NIST in 2004 and is a senior research associate at JILA, located on the CU-Boulder campus. Hall has been the thesis adviser of 15 physics doctoral students at CU-Boulder.
Nobel Prize lecture