Welding and metal processing

Laser gas required for carbon dioxide laser metal cutting

The metal-cut carbon dioxide laser generating gas is generally high purity pure carbon dioxide with a purity of 99.999%, high purity helium gas with a purity of 99.999%, and high purity nitrogen gas with a purity of 99.999%, which are mixed according to a specific ratio given by the laser manufacturer. Laser mixed gas, some laser cutting machines themselves have laser gas premixing equipment, laser manufacturers only need to purchase high purity carbon dioxide, high purity helium and high purity nitrogen, premixed by the laser cutting machine with premixed equipment . The laser cutting machine has high requirements on the laser gas. When the laser gas contains more impurities, it will affect the laser beam and affect the laser cutting quality.

  When cutting metal with a carbon dioxide laser cutting machine, a laser mixed gas composed of carbon dioxide, helium and nitrogen generates laser light, which is generally divided into laser oxygen combustion-assisted cutting and laser melting cutting. Oxygen combustion-assisted cutting is generally used for cutting carbon steel steel sheets, and melting and cutting are generally used. Used to cut stainless steel plates and aluminum alloy plates. Oxygen-assisted laser cutting uses a carbon dioxide laser as a laser source, using oxygen as a cutting gas, and the oxygen ejected reacts with the cut metal to release a large amount of heat, and blows out the molten metal oxide to complete the laser of the carbon steel plate. Cutting. Laser melt cutting refers to laser cutting a metal that is not easily oxidized by a laser mixed gas. The laser is heated by a laser mixed gas to melt the metal, and then the molten metal is blown away by high pressure nitrogen to complete the stainless steel and the aluminum alloy. Cutting, as the cutting speed increases, the cutting quality is worse.

When laser cutting carbon steel materials, liquid oxygen low temperature dewar tanks are generally used.

Supply should be high pressure oxygen, the general process is:

 Cryogenic liquid oxygen dewar tank --> Vaporizer --> Liquid oxygen regulator --> Laser cutting equipment

When laser cutting metal materials such as stainless steel and aluminum alloy that are not easily oxidized, liquid nitrogen low temperature dewar tanks are generally used to supply high pressure nitrogen. The general liquid nitrogen supply process is:

Low temperature liquid nitrogen dewar tank --> liquid nitrogen vaporizer --> liquid nitrogen regulator --> laser cutting equipment

Helium laser

Helium-neon lasers, commonly referred to as HeNe lasers, are small gas lasers for a variety of industrial and scientific applications. These lasers are mainly used in the red light band of 632.8 nm in the visible spectrum. Thorlabs' Red Opium Gas Laser product line's stable output power ranges from 0.5 mW to 35 mW and the output light is a basic Gaussian beam. Depending on the model selected, the output light will be linearly polarized or randomly polarized (unpolarized).

The gain medium of the HeNe laser is a mixture of helium and neon in a sealed low-pressure glass tube with a ratio of 5:1 to 20:1. The excitation source for these lasers is a high voltage discharge through the anode and cathode across the glass tube. The optical cavity of the laser consists of a high mirror and an output coupling mirror. The high mirror at one end of the laser tube is a high reflectivity plane mirror, and the output coupling mirror at the other end of the laser tube has a transmittance of about 1 %. HeNe lasers tend to be relatively small, with a cavity length between about 15 cm and 0.5 m and a light output power between 1 mW and 100 mW. Thorlabs offers up to 50 milliwatts of output power.

 Thorlabs' stable HeNe lasers provide frequency stability or strength stability. In frequency stabilization mode, it will keep the laser frequency or wavelength constant. In the intensity stable mode, it will keep the output power constant. Stable HeNe lasers are required for many spectroscopy, interferometer and wavelength meter applications.

Excimer laser cesium fluoride 308nm treatment of vitiligo

Since the excimer laser was developed in the 1980s, the excimer laser has been transformed from civilian technology to civilian use so far, and has been widely used in various fields. The cesium chloride (XeCI) excimer laser is a laser generated by a mixture of Xe, HCl, H2, and Ne gas in a certain ratio, and the 308 nm laser is generated. Chlorine Cl is a halogen element, and 氙Xe is an inert gas. Under normal conditions, chlorine and ruthenium do not react, and there are no chlorine and ruthenium compounds in nature, but pre-ionization pumping at high pressure and strong electric field. Under the action, chlorine can accept an electron of ruthenium to form a ruthenium chloride molecule. The ruthenium chloride is unstable for a short period of time and will soon dissociate into chlorine and ruthenium. This unstable molecule is called excimer. The laser generated by the excitation of the unstable ruthenium chloride excimer is an ultraviolet laser having a wavelength of 308 nm.

   The cesium chloride XeCl 308nm excimer laser was originally developed by the US military for the military field, because it has been found to treat skin diseases. The US FDA has been used in the field of dermatological treatment since 2000!

Application of excimer laser in silicon substrate processing and silicon wafer etching

Silicon substrate processing based on excimer laser

Using advanced excimer laser processing, amorphous silicon with low electron mobility can be converted into a higher performance polysilicon film, which can not only provide the required driving for the emerging active matrix organic light emitting diode technology (AM-OLED). Current, and can provide faster voltage switching for high resolution active matrix LCDs (AM-LCDs). By selectively annealing and recrystallizing the amorphous silicon layer by excimer laser, a highly ordered microstructure can be obtained, thereby realizing the transition of the amorphous silicon layer to the polysilicon layer. Due to the short wavelength and small penetration depth of the 308 nm excimer laser, the glass substrate under the silicon will not be affected by the high power excimer laser beam.

In addition, considering the output power of the excimer laser several hundred watts, rapid large-area processing is also feasible. The final result is a significant increase in electron mobility above 100 cm2/V-sec, which is two orders of magnitude higher than conventional amorphous silicon layers. The polycrystalline silicon layer shown in Figure 9 has a highly ordered lattice structure that allows electrons to move more easily.

Therefore, excimer laser processing can drive such high-resolution active-matrix liquid crystal (AM-LCD) and active-matrix organic light-emitting diode (AM-OLED), which rely on high electron mobility, to enter the market faster. These display products have the advantage of being faster, brighter, thinner and lighter. In short, due to its low-temperature annealing characteristics, excimer laser surface conversion technology has become the basic process of alternative display technologies based on flexible polymer substrates (not glass substrates) such as bendable e-books and newspapers.