What’s type the beam of green laser pointer is

What’s type the beam of green laser pointer is?
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Laser cooling (laser cooling) the interaction of atoms with laser and slow atomic motion in order to obtain high-tech ultra-low temperature atomic. Teachers now can turn pages of the screen at anywhere they stand by operating the green laser pointer.The main purpose of the early important technology is to accurately measure the various atomic parameters for high-resolution ultra-high-precision laser spectroscopy and quantum frequency standards (atomic clocks), but later became achieve atomic Bose - Einstein condensation of the key experimental methods. Although the early 20th century, people have noticed the light on the role of atoms with radiation pressure, but after the invention of the laser, before developing the use of light pressure to change the speed of atomic technology.The first generation of green laser pointer has become the mainstream of daily application. It was found that when the atoms in the atomic transition frequency is slightly lower than the energy gap and a pair of opposite laser beam propagation in the movement, due to the Doppler effect, atomic absorption and atomic motion tends to the opposite direction of the photon, while the direction of the road with the same less likely to absorb photons; absorption of photons to be isotropic spontaneous emission. What’s the safe class of a green laser pointer?It seems equally, the net effect of two laser beams is to produce an atomic motion in the opposite direction of the damping force, so that the slow movement of atoms (ie, cool). In 1985 the U.S. National Institute of Standards and Technology Phillips (willam D. Phillips) and Stanford University, Zhu Meng Wen (Steven Chu) first achieved atomic laser cooling experiments, and has been very low temperature (24μK) of sodium atoms the gas. They further with the formation of three-dimensional magneto-optical laser beam about the atomic imprisoned in a small area of space to be cooled, to obtain a lower temperature of the "optical adhesive." , Many new methods of laser cooling are emerging, in which there were famous "speed selection coherent population imprisoned" and "Raman cooling", the former by the Ecole Normale Superieure in Paris, France Cohen - Da Nuoji (Claud Cohen-Tannodji ) suggested that the latter proposed by Zhu Wen model, they are using this technique were obtained below the photon recoil limit of very low temperature. Since then, it has also developed a combination of magnetic field and a series of laser cooling techniques, including polarization gradient cooling, magnetic cooling and so on. Zhu Wen model, Cohen - Da Nuoji and hence the three Phillips won the 1997 Nobel Prize in Physics. What’s the circuit control of a normal green laser pointer?Laser cooling has many applications, such as: atom optics, atom etching, atomic clocks, optical lattice, optical tweezers, Bose - Einstein condensation, atom lasers, high-resolution spectra and the interaction between light and matter such as basic research and so on.