The brief analysis of the laser cooling principle of optical fiber laser marking machine
Doppler cooling technology, it is very important in the laser cooling technology with a cooling technology. The principle of doppler cooling technology is through the laser photons to block the thermal motion of the atom, which hinder the process is realized by reducing the atomic momentum. Quantum mechanics is put forward, the atoms can only absorb specific frequency of photons, so as to change its momentum. Doppler effect is pointed out that the wave frequency high when waves move to the observer, and in the lower frequency waves away from the observer. When the observer moves can also get the same conclusion. For it was the same as atom, when the movement direction of the atom and photon motion instead, is the frequency of the photon will increase, and when the atoms at the same time, the direction of movement direction on the photon is the photon frequency will decrease. Then, another physics is light although there is no static quality, but its momentum. So comprehensive above a few physics characteristic, we can build a simple model of laser cooling. Laser frequency is adjustable within a certain range, and to adjust to the laser frequency is slightly lower than an atom absorbs frequency, will have unexpected results. When using such a beam of light of a particular molecule, this situation occurs. If the atom is towards the laser beam movement, caused by the doppler effect, the frequency of the photon to increase, and the frequency of the original laser photons is just slightly smaller than the atomic absorption frequency, is at this time due to the doppler effect is just by atomic absorption. Laser frequency is adjustable within a certain range, and to adjust to the laser frequency is slightly lower than an atom absorbs frequency, will have unexpected results. When using such a beam of light of a particular molecule, this situation occurs. If the atom is towards the laser beam movement, caused by the doppler effect, the frequency of the photon to increase, and the frequency of the original laser photons is just slightly smaller than the atomic absorption frequency, is at this time due to the doppler effect is just by atomic absorption. And the absorption of momentum change. Because the movement direction of the photon and the atomic movement in the opposite direction, after the photon collisions with atoms, atomic transition to the excited state, and the momentum is reduced, so the kinetic energy is reduced. Direction of motion with other atoms, then its corresponding to the frequency of the photon doesn't increase, so can't absorb the photons in a laser beam, so there will be no momentum increase the occurrence of this phenomenon, relative to the kinetic energy is the same. When we use more laser beams to illuminate the atoms, from different angles in the different direction of the atoms of the momentum will be reduced, and thus a decrease in kinetic energy. Decreases due to the laser only the momentum of the atom, so in the process for a period of time, most of the atomic momentum will reach a low level, so as to achieve the purpose of refrigeration. But the range of this technology application is mostly used to cool atoms, and for molecules, the method, its hard to be cooled to cryogenic. But ultracold molecules is greater than the meaning of ultracold atoms, because of its properties is more complicated. At present, the method of cooling the molecular is the super cold alkali atoms together, produce double alkali molecules. Not long ago, Yale has fluoride strontium ( SrF) Cooling to hundreds of slightly open. Laser cooling, also known as anti stokes fluorescent cooling, is developing the new concept of the cooling method of its basic principle is anti stokes effect, the scattering and the photon energy difference of refrigeration. Anti stokes effect is a special kind of scattering effect, the scattering fluorescence photon wavelengths shorter than incident photon wavelengths. Therefore, fluorescent scattering photon energy is higher than the incident photon energy, the process can be simple to understand as: with low energy laser photons luminous medium, light scattering medium of high-energy photons, will shine medium energy out of the original medium and refrigeration. Compared with the traditional cooling methods, laser have played an important role in providing cooling power, and scattering of anti stokes fluorescent is heat carrier.