John L. Hall
The Nobel Prize in Physics 2005
Born: 21 August 1934, Denver, CO, USA
Affiliation at the time of the award: University of Colorado, JILA, Boulder, CO, USA, National Institute of Standards and Technology, Boulder, CO, USA
Prize motivation: "for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique."
Prize share: 1/4
According to quantum physics, light and other electromagnetic radiation appear in the form of quanta, packets with fixed energies, which also correspond to energy transitions in atoms. Consequently, determining the frequency of light waves provides information about the atoms' properties, benchmarks for time and length, and the possibility of determining physical constants. Around the year 2000, John Hall and Theodor Hänsch developed the frequency comb technique, in which laser light with a series of equidistant frequencies is used to measure frequencies with great precision.