Atomic Cooling: scientific laser systems (laboratory laser, laser equipment)

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Since 1976 scientists have been working on the idea of controlling (cooling, trapping) atoms with laser equipment. The atom trapped in the laboratory laser beam absorbs photons and becomes excited; photons can transmit their impulses to the atom. When atoms are de-excited, they reemit photons in random directions. As a result the atom experiences light pressure in the direction of the laser beam spread. Atoms get excited when the frequency drift is similar to the optical transition.

If an atomic gas is irradiated from each side with the laser frequency that is less than that of an atomic transition, the number of slow atoms grows leading to the temperature decrease.

The first atomic cooling experiment was conducted in the laser spectroscopy department of ISAN. Using the laboratory laser in dilatational cooling the transverse velocity is increased due to the growth of fluctuation atom impulses when laser light photons are absorbed and emitted. At some point of dilatational cooling its speed becomes comparable to that of the transverse one and for further dilatational cooling the transverse cooling of the beam has to be performed. First time it was done in the laboratory in 1984, and the record atom temperature of 0.003 K was reached. This temperature is close to the Doppler cooling.

All these experiments with scientific laser systems allowed decreasing the energy of neutral atoms to the levels when their space localization with electric, magnetic and laser fields became possible. This opened new opportunities for sharp decreasing the temperature of the atoms that were already cooled down.

ISAN was the first laboratory in the world to start experiments with controlling the atomic motion with laser equipment. Today there are dozens of laboratories around the world that work on this aspect using different scientific laser systems.

Different methods exist to cool neutral and excited particles (atoms, molecules and their ions), they are based on various dissipation processes. For example, electric cooling of excited particles is done through the collision of hot atoms and cold electron fluid. However, the most popular and effective way to cool neutral atoms (and localized ions as well) is the collision of those atoms and laser beam photons.

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