A CO2 laser is a type of gas laser that uses carbon dioxide (CO2) as the active laser medium. It works by exciting the CO2 gas molecules, which then emit light, creating a laser beam. CO2 lasers are commonly used for cutting, engraving, and welding applications, as well as in medical and industrial settings. Here's a step-by-step explanation of how a CO2 laser works:
Gas mixture: The CO2 laser consists of a sealed tube filled with a mixture of gases, including carbon dioxide (CO2), nitrogen (N2), and helium (He). A small percentage of other gases, like hydrogen (H2) or xenon (Xe), might also be added to enhance performance.
Electrical excitation: An electric current is applied to the gas mixture using electrodes or radio frequency (RF) energy. The electric discharge excites the nitrogen molecules, causing them to enter a higher energy state.
Energy transfer: The excited nitrogen molecules collide with CO2 molecules, transferring their energy to them. This process is called vibrational excitation, and it raises the energy state of the CO2 molecules.
Population inversion: As more and more CO2 molecules become excited, a condition known as population inversion is achieved. This means that there are more CO2 molecules in an excited state than in their normal, lower-energy state.
Stimulated emission: When an excited CO2 molecule returns to a lower energy state, it emits a photon (a particle of light). If this photon encounters another excited CO2 molecule, it can stimulate that molecule to emit another photon with the same wavelength and phase as the original photon. This process is called stimulated emission.
Light amplification: The laser tube contains mirrors at both ends, one of which is partially transparent. The photons generated by stimulated emission bounce back and forth between these mirrors, causing more and more CO2 molecules to undergo stimulated emission. This process amplifies the light, creating a coherent and highly focused beam of infrared light.
Laser beam output: The partially transparent mirror allows a small percentage of the amplified light to escape the laser tube. This forms the laser beam, which can be focused and directed onto a workpiece for cutting, engraving, or welding.
The wavelength of the light emitted by a CO2 laser is typically around 10.6 micrometers, which is in the infrared region of the electromagnetic spectrum. This wavelength is particularly effective at being absorbed by many materials, allowing the CO2 laser to be used for a wide range of applications.