Theodor Wolfgang Hänsch (; born 30 October 1941) is a German

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

. He received one-fourth of the 2005

Nobel Prize in Physics The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...

for "contributions to the development of

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

-based precision

spectroscopy Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...

, including the optical

frequency comb A frequency comb or spectral comb is a spectrum made of discrete and regularly spaced spectral lines. In optics, a frequency comb can be generated by certain laser sources. A number of mechanisms exist for obtaining an optical frequency comb, i ...

technique", sharing the prize with John L. Hall and Roy J. Glauber. Hänsch is Director of the

Max-Planck-Institut für Quantenoptik The Max Planck Society for the Advancement of Science (; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes. Founded in 1911 as the Kaiser Wilhelm Society, it was renamed to the M ...

(

quantum optics Quantum optics is a branch of atomic, molecular, and optical physics and quantum chemistry that studies the behavior of photons (individual quanta of light). It includes the study of the particle-like properties of photons and their interaction ...

) and

Professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other tertiary education, post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin ...

of experimental physics and laser spectroscopy at the Ludwig-Maximilians University in

Munich Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...

Bavaria Bavaria, officially the Free State of Bavaria, is a States of Germany, state in the southeast of Germany. With an area of , it is the list of German states by area, largest German state by land area, comprising approximately 1/5 of the total l ...

, Germany.

Biography

Hänsch received his secondary education at Helmholtz-Gymnasium Heidelberg and gained his

Diplom A ''Diplom'' (, from ) is an academic degree in the German-speaking countries Germany, Austria, and Switzerland and a similarly named degree in some other European countries including Albania, Bulgaria, Belarus, Bosnia and Herzegovina, Croatia ...

and

doctoral degree A doctorate (from Latin ''doctor'', meaning "teacher") or doctoral degree is a postgraduate academic degree awarded by universities and some other educational institutions, derived from the ancient formalism '' licentia docendi'' ("licence to teach ...

from

Heidelberg University Heidelberg University, officially the Ruprecht Karl University of Heidelberg (; ), is a public research university in Heidelberg, Baden-Württemberg, Germany. Founded in 1386 on instruction of Pope Urban VI, Heidelberg is Germany's oldest unive ...

in the 1960s.

Nobel Foundation The Nobel Foundation () is a private institution founded on 29 June 1900 to manage the finances and administration of the Nobel Prizes. The foundation is based on the last will of Alfred Nobel, the inventor of dynamite. It also holds Nobel Sym ...

"Biographical: Theodor W. Hänsch"
Retrieved 4 March 2019. Subsequently, he was a NATO postdoctoral fellow at

Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...

with Arthur L. Schawlow from 1970 to 1972. Hänsch became an assistant professor at

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

from 1975 to 1986. He was awarded the Comstock Prize in Physics from the

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

in 1983. In 1986, he received the Albert A. Michelson Medal from the

Franklin Institute The Franklin Institute is a science museum and a center of science education and research in Philadelphia, Pennsylvania. It is named after the American scientist and wikt:statesman, statesman Benjamin Franklin. It houses the Benjamin Franklin ...

. 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 The German Research Foundation ( ; DFG ) is a German research funding organization, which functions as a self-governing institution for the promotion of science and research in the Federal Republic of Germany. In 2019, the DFG had a funding bu ...

, 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 Frankfurt am Main () is the most populous city in the States of Germany, German state of Hesse. Its 773,068 inhabitants as of 2022 make it the List of cities in Germany by population, fifth-most populous city in Germany. Located in the forela ...

, the Society of German Chemists and the German Physical Society. In that same year, the

Optical Society of America Optica, founded as the Optical Society of America (later the Optical Society), is a professional society of individuals and companies with an interest in optics and photonics. It publishes journals, organizes conferences and exhibitions, and ca ...

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 that 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 Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

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.

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 In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

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 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 oscillator Multiple-prism grating laser oscillators, F. J. Duarte, Narrow-linewidth pulsed dye laser oscillators, in ''Dye Laser Principles'' (Academic, New York, 1990) Chapter 4. or MPG laser oscillators, use multiple-prism beam expansion to illuminate a d ...

s. 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.

Awards

* James 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 The Otto Hahn Prize is awarded biennially jointly by the Society of German Chemists (), the German Physical Society () and the city of Frankfurt am Main for outstanding achievement in the field of chemistry, physics or applied engineering science. ...

(2005) * I. I. Rabi Award (2005) *

(2005) * Frederic Ives Medal (2005) *

Matteucci Medal The Matteucci Medal is an Italian award for physicists, named after Carlo Matteucci from Forlì. It was established to award physicists for their fundamental contributions. Under an Italian Royal Decree dated July 10, 1870, the Italian Society ...

(2001) *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 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 meda ...

(1995) *

King Faisal International Prize The King Faisal Prize (, formerly King Faisal International Prize), is an annual award sponsored by King Faisal Foundation presented to "dedicated men and women whose contributions make a positive difference". The foundation awards prizes in fiv ...

(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)

References

External links

*
Max-Planck-Institute of Quantum OpticsA video interview with Theodor HänschHänsch's homepage at LENS(Firenze)

taken at ''Lasers'' '95 including (right to left)

Marlan Scully Marlan Orvil Scully (born August 3, 1939) is an American physicist best known for his work in theoretical quantum optics. He is a professor at Texas A&M University and Princeton University. Additionally, in 2012 he developed a lab at the Baylor ...