Theodor W. Hänsch
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Theodor Wolfgang Hänsch (b. 30 October 1941 in Heidelberg, Germany) is a German physicist. He shared one half of the 2005 Nobel Prize in Physics with John L. Hall, for "contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique". The other half was awarded to 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.
After gaining his doctorate in Heidelberg, Hänsch was a professor at Stanford University, California from 1975 to 1986. In 1986 Hänsch returned to Germany to head the Max-Planck-Institut für Quantenoptik. In 1989, he received the Gottfried Wilhelm Leibniz Award 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.
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 1990's, 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-recepient of the Nobel Prize in Physics for 2005.
