Research On Laser Cooling Characteristics Based On Four-Wave Mixing Effect

The potential of traditional refrigeration technology has been fully explored after hundreds of years of development.In some high-tech fields,traditional refrigeration equipment is no longer applicable due to problems such as high energy consumption and heavy equipment.Finding new refrigeration methods has become the top priority of scientific research and laser cooling technology has emerged as the times require.Because of its excellent characteristics such as long life,light weight,and environmental protection,laser cooling has a very bright prospect.So,in recent decades,laser cooling has been a very popular research direction.This paper mainly explores the theories of laser cooling,and studies the methods of using four-wave mixing effect to cool atoms and the application of optical pumping effect in laser cooling of solid materials.What we want do is improving the cooling efficiency by using laser.In the process of four-wave mixing,because of the interaction between the light field and the atoms,there will produce an anti-Stokes effect.So,the four-wave mixing effect can be used to cool atoms.During the research process,we compared the cooling efficiency under different conditions and different parameters,and found that the Rabi frequency,longitudinal and transverse relaxation time,pump wave,and probe wave all have different effects on the cooling result.Through simulation,the curves or surfaces under different conditions is obtained.The impulse of light field and the two-level atomic system forms a semi-upper surface with the Rabi frequency and the detuning of the probe wave.Finally,it is found that while Rabi frequency satisfies?T₂=1.414,the ratio of transverse and longitudinal relaxation time is T₂/T₁=2,and the pump wave detuning satisfies that(?₁-?_ba)T₂=-3,the best cooling effect can be achieved.When using optical pumping to perform laser cooling on materials doped with rare-earth metal elements,the most important thing what we need to do is to realize the population reversal of the material and emit anti-Stokes fluorescence.Our studies have shown that the laser cooling of solid materials is very sensitive to the background absorption coefficient.In order to improve the cooling efficiency and obtain better cooling effect,we should try to lower the background absorption coefficient.What's more,we also found that larger quantum efficiency result to better laser cooling effect,and the power of optical pumping needs to be selected appropriately.If the power is too small,the cooling effect is bad and if the power is too large,it will inhibit the absorption of photons by the material and destroy the quality of the material.At the same time,it is important to use the principle of total reflection or mirror to lengthen the optical path of the laser in the material to improvement of the cooling power.