- Person
- Arthur Schawlow
- Lived
- 1921–1999
- Field
- Physics, lasers
- From
- American
The story
Arthur Schawlow, whose father was a Jewish immigrant from Riga, co-authored the 1958 paper that set out the principles of the laser. From 1961 he was a professor at Stanford University, where, often with his colleague Theodor Hänsch, he pioneered laser spectroscopy, using the sharp, intense light of lasers to measure the energy levels of atoms and molecules with unprecedented precision.
In January 1975 Hänsch and Schawlow published a short paper in the journal Optics Communications titled “Cooling of gases by laser radiation.” The idea was simple and startling. An atom absorbs light only at particular frequencies. If laser light is tuned slightly below that frequency, an atom moving toward the laser sees the light shifted up toward its natural frequency by the Doppler effect and absorbs it, receiving a small kick that slows it down, while atoms moving away are hardly affected. With beams coming from several directions, the atoms in a gas can be slowed in every direction, which is the same as cooling them. The same year David Wineland and Hans Dehmelt independently proposed a related scheme for single trapped ions.
Laser cooling became one of the most important techniques in modern physics. Cold atoms barely move, so the Doppler shifts that blur measurements almost disappear. That makes possible the most precise atomic clocks, including optical clocks, which measure time more precisely than ever before. Laser-cooled atoms, further cooled by evaporation, were used to create the first Bose–Einstein condensates in 1995, a new state of matter. Laser cooling is also essential for quantum computers built from trapped ions or neutral atoms, where cooling keeps the fragile quantum states from being disturbed, and it has been used to cool molecules and even antihydrogen.
Schawlow shared the 1981 Nobel Prize in Physics for his contribution to laser spectroscopy, but laser cooling may prove the most far-reaching of his ideas: a short proposal from 1975 that grew into a whole branch of physics.
Why it matters
Laser cooling, which Schawlow and Hänsch proposed, underpins the most accurate atomic clocks, new states of matter and trapped-atom quantum computers.
About Arthur Schawlow
Co-inventor, with Charles Townes, of the laser concept behind fibre optics, barcode scanners and eye surgery; pioneer of laser spectroscopy; and early proponent of cooling atoms with light.
More about Arthur Schawlow
Sources
- Laser cooling Wikipedia
- Arthur L. Schawlow, Biographical NobelPrize.org
- Arthur Leonard Schawlow Wikipedia
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