Jan Hall

2005 Nobel Prize in Physics

NIST Senior Fellow Emeritus John L. “Jan” Hall received the 2005 Nobel Prize in Physics for “contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique.” 

The optical frequency comb can be considered the biggest revolution in precision measurements since the introduction of the laser in 1960. It’s used in atomic clocks, medical diagnostics, remote chemical analysis, communications and even potentially to detect the atmospheres of planets outside our solar system.

Hall split half of the 2005 Nobel Prize with Theodor Hänsch of the Max Planck Institute for Quantum Optics in Garching, Germany. The other half went to Harvard University physicist Roy J. Glauber for developing a theory of coherent light—the kind produced by the lasers to which Jan Hall dedicated his career. 

Lasers have created an explosion of knowledge and discoveries in science through the technique of spectroscopy. Spectroscopy is the study of the rainbow of light and other electromagnetic radiation given off by objects such as atoms and stars. Analyzing these rainbows, or spectra, enables scientists to understand the interplay of matter with electromagnetic radiation. Scientists also can use electromagnetic radiation to measure phenomena in a vast range of systems, from atoms to the largest objects in the universe. The use of lasers, which deliver light in a much more controlled way than other light sources, has made spectroscopy far more precise and powerful. 

Hall’s work for NIST began in 1961, just a year after scientists first demonstrated laser technology. During the next four decades, Hall specialized in making lasers increasingly stable—that is, better able to produce light that maintains a constant color for longer and longer periods of time. Such work greatly advanced the laser as a tool of science and commerce and helped scientists redefine the speed of light, and, as a result, the meter—one of the most basic units of measurement. 

Late in his career, Hall realized that the technology was in place to make a device that would measure colors of light far more accurately than was previously possible. His team’s work would yield the optical frequency comb—a ruler for light. Within a few years of its invention, the optical frequency comb enabled scientists to develop the world’s most precise atomic clocks, and they have many other potential uses in fields from manufacturing to communications to health.

These pages consider Jan Hall’s 2005 Nobel Prize in more depth by exploring the following questions:

• Who is Jan Hall, and how did he get involved with the science that led to the Nobel Prize? 
• What is a frequency comb and why is it important?
• How did the discovery unfold? Was there a “eureka” moment?
• What has been the legacy of the Nobel Prize-winning effort?