Advantages and disadvantages of CO2 lasers in lasers

Advantages and disadvantages of CO2 lasers in lasers

Laser selection: The mainstream laser types all support the laser cladding process, such as CO2 lasers, solid-state lasers, fiber lasers, semiconductor lasers, etc. At present, CO2 lasers and solid-state lasers are widely used. CO2 lasers are the most widely used and most types of lasers, and are widely used in the automotive industry, steel industry, shipbuilding industry, aviation and aerospace industry, electrical industry, machinery industry, metallurgical industry, metal processing and other fields. It accounts for about 40% of global industrial laser sales, and as high as 70% in North America.

Principle of CO2 Laser

Like other molecular lasers, the working principle of CO2 lasers is also rather messy. Molecules have three different motions, that is, the motion of electrons in the molecule, and its motion determines the electronic energy state of the molecule; the second is the atomic vibration in the molecule, that is, the atoms in the molecule coil around their equilibrium position and make periodic vibrations— And it is determined by the vibrational energy state of the molecule; the third is the tumbling of the molecule, that is, the molecule continuously rotates in space as a whole, and this motion of the molecule determines the tumbling energy state of the molecule. Molecular motion is extremely messy, so energy levels are also messy.

Advantages of CO2 Lasers

1. The output power range is large, and the 100KW laser welding machine has been used abroad for welding. Closed-tube CO2 lasers can have a continuous output power of tens of watts, which is far more than other gas lasers, and lateral-flow electro-excited CO2 lasers can have a continuous output of hundreds of thousands of watts. In addition, the transverse atmospheric pressure carbon dioxide laser has also reached a high level in terms of energy and power output from the pulse, which is comparable to that of solid-state lasers.

2. High energy conversion efficiency, the energy conversion efficiency of carbon dioxide laser can reach 30-40%, which also exceeds the general gas laser.

3. Using the transition between the vibrational and rotational energy levels of CO2 molecules, there are relatively abundant spectral lines, and there are dozens of spectral lines in the laser output near 10 microns. The high-pressure carbon dioxide laser discovered in recent years can even achieve continuously tunable output from 9 to 10 microns.

4. Its output band is exactly the atmospheric window, that is, the transmittance of the atmosphere to this wavelength is high. And the output beam has high optical quality, good coherence, narrow line width and stable operation.

5. It has good directivity, monochromaticity and good frequency stability. The density of the gas is small, and it is difficult to obtain a high concentration of excited particles. Therefore, the energy density of the CO2 gas laser output is usually smaller than that of the solid-state laser.

6. It can work in pulse mode or continuous mode, with a wide range of welding, which can be used for welding micro parts and thick workpieces.

7. The output wavelength is 10.6m, which is between the atmospheric windows of 8--14m, and has unique advantages in distance transmission.

8. The gas purity requirements are low, generally as long as the industrial purity carbon dioxide gas is sufficient.

9. The laser and power supply can be integrated in one system, with compact structure and simple design.

10. Long service life.

Disadvantages of CO2 Lasers

The conversion power of the CO2 laser is very high, but the maximum will not exceed 40%, that is to say, more than 60% of the energy will be converted into the heat energy of the gas, which will increase the temperature. The increase of the gas temperature will cause the de-excitation of the energy level on the laser and the thermal excitation of the energy level under the laser, which will reduce the inversion number of the particles. Moreover, the increase of the gas temperature will broaden the spectral line, resulting in a decrease in the gain coefficient. In particular, the increase in gas temperature will also cause the decomposition of CO2 molecules, reducing the concentration of CO2 molecules in the discharge tube. These factors will reduce the output power of the laser and even cause "temperature quenching".

The above content is the principle, structure, advantages and disadvantages of CO2 laser brought to you by Xiaobian today, I hope it will be useful to you. Generally speaking, the working substance of carbon dioxide laser is a mixture of carbon dioxide, helium and nitrogen. Nitrogen acts as a buffer gas and its molecules resonate to deliver stimulating energy to carbon dioxide molecules. Its output power and energy are large, and its high efficiency can reach 15%~25%. The continuous output power of its commercial devices can reach the order of 10,000 watts. It has been widely used in drilling, cutting, welding and heat treatment. It is an ideal laser in industrial applications.

Conventional solid-state lasers are usually pumped with high-power gas discharge lamps, which have a pumping efficiency of about 3% to 6%. The large amount of energy emitted by the pump lamp is converted into heat energy, which requires a bulky cooling system, and the unavoidable thermal lens effect deteriorates the beam quality. In addition, the life of the pump lamp is about 400 hours, and the operator needs to spend a lot of time changing the lamp frequently, interrupting the work of the system, which greatly reduces the efficiency of the automated production line. Compared with conventional lamp-pumped lasers, diode-pumped solid-state lasers have improved conversion efficiency, lifetime, and beam quality. The output wavelength of YAG laser is 1.06μm, which is one order of magnitude smaller than that of CO2 laser, so it is more suitable for laser cladding of such metals.