Laser has many uses, including medical, industrial cutting, engraving, aerospace, etc.Today, we will introduce a common multipurpose laser - he-ne mixture laser. Helium-neon laser is the most important source of red light (632.8nm). It was the first gas laser successfully operated by human in 1961. So how exactly does he neon laser work? What does he-ne laser do?

Discovery of he-ne laser：

The he-ne gas laser was the first gas laser to be developed, and one of the most commonly used. It works at four levels. The laser produces neon atoms, and helium atoms only transfer the energy it absorbs to neon atoms by resonance, which plays a good role as a medium. When helium-neon atoms are in the discharge tube, helium atoms jump from the ground state to the metastable level through the excitation of electron collisions. When atoms at this level collide with neon atoms, energy is transferred to neon atoms and they transition to different energy states, thus producing lasers of different wavelengths such as 632.8nm, 1152nm and 3391nm. Helium gas ACTS as a laser medium and increases the output power of the laser. Neon gas ACTS as a laser generator. Helium-neon laser can generate multiple wavelength excitation spectral lines in the visible light and infrared region, among which the main ones are 0.6328 livemight red light, 1.15 livemight and 3.39 livemight infrared light.

The structure of he-ne laser：

He-ne laser is composed of three parts: laser discharge tube, harmonic cavity and excitation power supply. At the center of the laser tube is a capillary glass tube called a discharge tube (about 1mm in diameter). The coat is the gas storage part (about 45mm in diameter); A is the tungsten bar, which is the anode; K is a cylinder made of molybdenum or aluminum and used as the cathode. Two mirrors perpendicular to and parallel to the discharge tube are attached at both ends of the shell to form a plane-concave cavity. Both mirror plates are coated with a multilayer dielectric film, one is a total mirror, usually coated with 17 layers of film. Alternate vacuum evaporation of magnesium fluoride (MgF2 and zinc sulfide (ZnS). The other mirror ACTS as an output mirror, usually coated with either 7 or 9 layers (depending on the optimal transmittance). A mixture of He and Ne with a total pressure of about 2Torr (torr) is filled into the capillary tube, and the mixing pressure ratio is about 5:1-7:1. The inner tube is compact in structure and easy to use, so it is widely used. But sometimes for special needs also often choose the full outer cavity or half outer cavity. The discharge tube and the lens are completely separated and the semi-external tube is a combination of the above two forms.

The effect of he-ne laser：

He-ne laser is currently mainly used in the medical industry. In the medical field, helium-neon laser is mainly used for irradiation and has the functions of stimulation, anti-inflammatory, analgesia and vascular dilation. If internal medicine can be used for acupoint irradiation, body surface local irradiation; Dermatology is used to treat skin, mucous membrane ulcer. In addition, he-ne laser can also be used to treat amblyopia. Since the cone cells in the macular area of the fundus are very sensitive to red light at 632.8nm, helium-neon laser irradiation in the ophthalmology can directly stimulate the cone cells in the macular area and improve their excitability, thus achieving the therapeutic effect. It has the advantages of simple treatment, quick effect, safety and accuracy, and can be usedfor the treatment of various types of amblyopia.