Theodor W. Hänsch

Theodor Wolfgang Hänsch (born 30 October 1941) is a German physicist. He received one fourth of the 2005 Nobel Prize in Physics for "contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique", sharing the prize with John L. Hall and Roy J. Glauber.

Hänsch is Director of the Max-Planck-Institut für Quantenoptik (quantum optics) and Professor of experimental physics and laser spectroscopy at the Ludwig-Maximilians University in Munich, Bavaria, Germany.

Hänsch received his secondary education at Helmholtz-Gymnasium Heidelberg and gained his Diplom and doctoral degree from Ruprecht-Karls-Universität Heidelberg in the 1960s.[1] Subsequently, he became a professor at Stanford University, California from 1975 to 1986. He was awarded the Comstock Prize in Physics from the National Academy of Sciences in 1983.[2] In 1986, he received the Albert A. Michelson Medal from the Franklin Institute.[3] In the same year Hänsch returned to Germany to head the Max-Planck-Institut für Quantenoptik. In 1989, he received the Gottfried Wilhelm Leibniz Prize of the Deutsche Forschungsgemeinschaft, which is the highest honour awarded in German research. In 2005, he also received the Otto Hahn Award of the City of Frankfurt am Main, the Society of German Chemists and the German Physical Society. In that same year, the Optical Society of America awarded him the Frederic Ives Medal and the status of honorary member in 2008.

One of his students, Carl E. Wieman, received the Nobel Prize in Physics in 2001.

In 1970 he invented a new type of laser which generated light pulses with an extremely high spectral resolution (i.e. all the photons emitted from the laser had nearly the same energy, to a precision of 1 part in a million). Using this device he succeeded to measure the transition frequency of the Balmer line of atomic hydrogen with a much higher precision than before. During the late 1990s, he and his coworkers developed a new method to measure the frequency of laser light to an even higher precision, using a device called the optical frequency comb generator. This invention was then used to measure the Lyman line of atomic hydrogen to an extraordinary precision of 1 part in a hundred trillion. At such a high precision, it became possible to search for possible changes in the fundamental physical constants of the universe over time. For these achievements he became co-recipient of the Nobel Prize in Physics for 2005.

Theodor Wolfgang Hänsch
Theodor Haensch
Theodor Hänsch at the 2012 Lindau Nobel Laureate Meeting
Born30 October 1941 (age 77)
Alma materUniversity of Heidelberg
Known forLaser-based precision spectroscopy
AwardsJames Joyce Award (2009)
Carl Friedrich von Siemens Prize (2006)
Rudolf Diesel Gold Medal (2006)
Ioannes Marcus Marci Medal (2006)
Bambi Award (2005)
Otto Hahn Prize (2005)
I. I. Rabi Award (2005)
Nobel Prize in Physics (2005)
Matteucci-Medal (2002)
SUNAMCO Medal (2001)
Philip Morris Research Prize (1998, 2000)
Arthur L. Schawlow Award (2000)
Stern-Gerlach Medal (2000)
Arthur L. Schawlow Prize (1996)
Einstein Prize for Laser Science (1995)
King Faisal International Prize (1989)
Gottfried Wilhelm Leibniz Prize(1989)
Italgas Prize for Research and Innovation (1987)
Michelson Medal (1986)
William F. Meggers Award (1985)
Herbert P. Broida Prize (1983)
Comstock Prize in Physics (1983)
Otto Klung Prize (1980)
Scientific career
InstitutionsLudwig-Maximilians University
Stanford University
European Laboratory for Non-Linear Spectroscopy (LENS), Università degli Studi di Firenze
Doctoral studentsCarl E. Wieman
Markus Greiner
Immanuel Bloch
Dietrich Leibfried
Tilman Esslinger
Theodor W. Hänsch

Background to Nobel Prize

The Nobel Prize was awarded to Professor Hänsch in recognition for work that he did at the end of the 1990s at the Max Planck Institute in Garching, near Munich, Germany. He developed an optical "frequency comb synthesiser", which makes it possible, for the first time, to measure with extreme precision the number of light oscillations per second. These optical frequency measurements can be millions of times more precise than previous spectroscopic determinations of the wavelength of light.

The work in Garching was motivated by experiments on the very precise laser spectroscopy of the hydrogen atom. This atom has a particularly simple structure. By precisely determining its spectral line, scientists were able to draw conclusions about how valid our fundamental physical constants are - if, for example, they change slowly with time. By the end of the 1980s, the laser spectroscopy of hydrogen had reached the maximum precision allowed by interferometric measurements of optical wavelengths.

The researchers at the Max Planck Institute of Quantum Optics thus speculated about new methods, and developed the optical frequency comb synthesizer. Its name comes from the fact that it generates a light spectrum out of what are originally single-colour, ultrashort pulses of light. This spectrum is made of hundreds of thousands of sharp spectral lines with a constant frequency interval.

Such a frequency comb is similar to a ruler. When the frequency of a particular radiation is determined, it can be compared to the extremely acute comb spectral lines, until one is found that "fits". In 1998, Professor Hänsch received a Philip Morris Research Prize for the development of this "measurement device".

One of the first applications of this new kind of light source was to determine the frequency of the very narrow ultraviolet hydrogen 1S-2S two-photon transition. Since then, the frequency has been determined with a precision of 15 decimal places.

The frequency comb now serves as the basis for optical frequency measurements in large numbers of laboratories worldwide. Since 2002, the company Menlo Systems, in whose foundation the Max Planck Institute in Garching played a role, has been delivering commercial frequency comb synthesizers to laboratories all over the world.

Laser development

Hänsch introduced intracavity telescopic beam expansion to grating tuned laser oscillators[4] thus producing the first narrow-linewidth tunable laser. This development has been credited with having had a major influence in the development of further narrow-linewidth multiple-prism grating laser oscillators.[5] In turn, tunable narrow-linewidth organic lasers, and solid-state lasers, using total illumination of the grating, have had a major impact in laser spectroscopy.[6]


  1. ^ Nobel Foundation. "Biographical: Theodor W. Hänsch". Retrieved 4 March 2019.
  2. ^ "Comstock Prize in Physics". National Academy of Sciences. Archived from the original on 29 December 2010. Retrieved 13 February 2011.
  3. ^ "Franklin Laureate Database - Albert A. Michelson Medal Laureates". Franklin Institute. Archived from the original on April 6, 2012. Retrieved June 16, 2011.
  4. ^ T. W. Hänsch, Repetitively Pulsed Tunable Dye Laser for High Resolution Spectroscopy, Appl. Opt. 11, 895-898 (1972).
  5. ^ F. J. Duarte, Tunable Laser Optics (Elsevier Academic, New York, 2003).
  6. ^ W. Demtröder, Laser Spectroscopy: Basic Principles, 4th Ed. (Springer, Berlin, 2008).

External links

Einstein Prize for Laser Science

The Einstein Prize for Laser Science was a recognition awarded by the former Society for Optical and Quantum Electronics and sponsored by the Eastman Kodak Company. The prize, awarded in the 1988–1999 period, consisted of a 3-inch brass medal including Einstein's image and a depiction of a two-level transition including the A and B coefficients. Recipients of the prize include:

Serge Haroche, 1988

Herbert Walther, 1988

H. Jeff Kimble, 1989

Richart E. Slusher, 1989

Carlton M. Caves, 1990

Daniel Frank Walls, 1990

S. E. Harris, 1991

L. M. Narducci, 1991

John L. Hall, 1992

Willis E. Lamb, 1992

Raymond Chiao, 1993

Norman F. Ramsey, 1993

G. S. Agarwal, 1994

Theodor W. Hänsch, 1995

Carl E. Wieman, 1995

David J. Wineland, 1996

Peter L. Knight, 1996

Paul Corkum, 1999In retrospect, the prize was mainly awarded for significant contributions in quantum optics. Two recipients of the Einstein Prize for Laser Science were already Nobel laureates in physics (W. E. Lamb and N. F. Ramsey) and five other recipients went on to win the Nobel Prize in Physics (S. Haroche, J. L. Hall, T. W. Hänsch, C. E. Wieman, and D. J. Wineland). Presentation of the prize was done at the Lasers'88 to Lasers'99 conferences.

Note: the official name of these conferences was The International Conference on Lasers and Applications, Lasers 'XX.

John L. Hall

John Lewis "Jan" Hall (born August 21, 1934) is an American physicist, and Nobel laureate in physics. He shared the 2005 Nobel Prize in Physics with Theodor W. Hänsch and Roy Glauber for his work in precision spectroscopy.


A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "Light Amplification by Stimulated Emission of Radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.

A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Alternatively, temporal coherence can be used to produce pulses of light with a broad spectrum but durations as short as a femtosecond ("ultrashort pulses").

Lasers are used in optical disk drives, laser printers, barcode scanners, DNA sequencing instruments, fiber-optic and free-space optical communication, laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. They have been used for car headlamps on luxury cars, by using a blue laser and a phosphor to produce highly directional white light.

Matteucci Medal

The Matteucci Medal is an Italian award for physicists, named after Carlo Matteucci. It was established to award physicists for their fundamental contributions. Under an Italian Royal Decree dated July 10, 1870, the Italian Society of Sciences was authorized to receive a donation from Carlo Matteucci for the establishment of the Prize.

Matteucci MedalistsSource: Italian Society of Sciences

2005 Nobel Prize laureates
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Physiology or Medicine

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