Class of methods for cooling atoms to very low temperatures
Simplified principle of Doppler laser cooling:
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A stationary atom sees the laser neither red- nor blue-shifted and does not absorb the photon.
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An atom moving away from the laser sees it red-shifted and does not absorb the photon.
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An atom moving towards the laser sees it blue-shifted and absorbs the photon, slowing the atom.
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The photon excites the atom, moving an electron to a higher quantum state.
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The atom re-emits a photon but in a random direction. The atom momentum vectors would add to the original if they were in the same direction but they are not so the atom has lost energy and, therefore, cooled.
Laser cooling includes several techniques where atoms, molecules, and small mechanical systems are cooled with laser light. The directed energy of lasers is often associated with heating materials, e.g. laser cutting, so it can be counterintuitive that laser cooling often results in sample temperatures approaching absolute zero. It is a routine step in many atomic physics experiments where the laser-cooled atoms are then subsequently manipulated and measured, or in technologies, such as atom-based quantum computing architectures. Laser cooling relies on the change in momentum when an object, such as an atom, absorbs and re-emits a photon (a particle of light). For example, if laser light illuminates a warm cloud of atoms from all directions and the laser's frequency is tuned below an atomic resonance, the atoms will be cooled. This common type of laser cooling relies on the Doppler effect where individual atoms will preferentially absorb laser light from the direction opposite to the atom's motion. The absorbed light is re-emitted by the atom in a random direction. After repeated emission and absorption of light the net effect on the cloud of atoms is that they will expand more slowly. The slower expansion reflects a decrease in the velocity distribution of the atoms, which corresponds to a lower temperature and therefore the atoms have been cooled. For an ensemble of particles, their thermodynamic temperature is proportional to the variance in their velocity, therefore the lower the distribution of velocities, the lower temperature of the particles.
The 1997 Nobel Prize in Physics was awarded to Claude Cohen-Tannoudji, Steven Chu, and William Daniel Phillips "for development of methods to cool and trap atoms with laser light".[1]
^"The Nobel Prize in Physics 1997". Nobel Foundation. Archived from the original on 7 October 2008. Retrieved 9 October 2008.
Lasercooling includes several techniques where atoms, molecules, and small mechanical systems are cooled with laser light. The directed energy of lasers...
sometimes used synonymously with laser cooling, though lasercooling includes other techniques. Doppler cooling was simultaneously proposed by two groups...
ultra-low-temperature physics, Sisyphus cooling, the Sisyphus effect, or polarization gradient cooling involves the use of specially selected laser light, hitting atoms...
Resolved sideband cooling is a lasercooling technique allowing cooling of tightly bound atoms and ions beyond the Doppler cooling limit, potentially to...
linear codes or stacked symbols. A technique that has recent success is lasercooling. This involves atom trapping, a method where a number of atoms are confined...
Optical molasses is a lasercooling technique that can cool neutral atoms to as low as a few microkelvin, depending on the atomic species. An optical...
level. Doppler cooling is the most common method of lasercooling. Sympathetic cooling is a process in which particles of one type cool particles of another...
has to be dissipated by the cooling system. In other words, the power efficiency is very low. A krypton laser is an ion laser using ions of the noble gas...
battery. It can be used either for heating or for cooling, although in practice the main application is cooling.[citation needed] It can also be used as a temperature...
portion of Mavalvala's work focused on the extension of laser-cooling techniques to optically cool and trap more and more massive objects, both for the LIGO...
specific direction and makes laser detuning a central tool of lasercooling and magneto-optical traps. Similar to the lasercooling of atoms, the sign of the...
respectively free space Raman cooling and Raman sideband cooling. Both techniques make use of Raman scattering of laser light by the atoms. The transition...
recoil limits, allowing lasercooling in narrow-line magneto-optical traps to the recoil limit without sub-Doppler cooling. Cooling beyond the recoil limit...
on the Sun.[citation needed] The Zeeman effect is utilized in many lasercooling applications such as a magneto-optical trap and the Zeeman slower.[citation...
pre-cooled via lasercooling in a magneto-optical trap. To reach the lowest possible temperature, further cooling is performed using evaporative cooling in...
with Claude Cohen-Tannoudji and Steven Chu for his contributions to lasercooling, a technique to slow the movement of gaseous atoms in order to better...
Laser hair removal is the process of hair removal by means of exposure to pulses of laser light that destroy the hair follicle. It had been performed...
amplifying motion, light can also damp the motion of objects. Lasercooling is a method of cooling materials very close to absolute zero by converting some...
One method that used to cool molecules to temperatures near absolute zero is lasercooling. In the Doppler cooling process, lasers are used to remove energy...
Sympathetic cooling is a process in which particles of one type cool particles of another type. Typically, atomic ions that can be directly lasercooled are used...
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