Feature | Laser Cooling Technology

First of all, temperature is a physical quantity that expresses the degree of hot and cold of an object. Microscopically, it is the intensity of thermal motion of molecules/atoms of an object. The faster the movement, the higher the reflected temperature; the slower the movement, the lower the reflected temperature. So, as long as we can slow down the molecular/atomic thermal motion, cooling can be achieved. Laser cooling technology uses the Doppler effect to selectively reverse the impact of photons on moving atoms, reducing their kinetic energy, thereby achieving the cooling effect.

Application of Laser Cooling in Cryogenic Physics

Frequency determines the energy of light, and atoms can only absorb a fixed amount of energy. In other words, atoms can only absorb photons of a certain frequency, which is the natural frequency of atoms. When we want to cool an atom, we emit a beam of photons with a frequency slightly lower than the atom's natural frequency. At this time, for the oncoming atom, the frequency of this beam of photons will increase, just as high as The atom's natural frequency is then absorbed and then slowed down. As for atoms that move in the same direction, the frequency of this beam of light will decrease, so it cannot be absorbed.

Requirements for lasers

1. Higher power: in order to obtain enough cold atoms.

2. High power stability, high wavelength (frequency stability).

2. Narrow linewidth (Single Frequency Laser): The linewidth is smaller than the natural linewidth of the corresponding cooling transition energy level.

3. Low noise: The noise at low frequency is close to the frequency of atomic motion. If the noise is too large, the atom will be heated.