Which of the following serves as the active medium in a CO2 laser?

In a CO2 laser, the active medium is a gas, specifically a mixture of carbon dioxide, nitrogen, and helium. This gas mixture is essential for the laser's operation, as it facilitates the process of stimulated emission, which is the fundamental principle behind laser technology. In a CO2 laser, when electrical energy is applied, it excites the gas molecules, allowing them to emit photons in a coherent beam of light.

The choice of a gaseous medium is crucial because carbon dioxide can produce a specific wavelength of infrared light, which is particularly effective in various applications, including medical and industrial uses. Additionally, gas lasers like the CO2 laser are known for their ability to produce high power outputs, which is beneficial for cutting and engraving materials.

In contrast, solid and liquid mediums refer to other types of lasers, such as solid-state lasers (which use a solid crystalline material) or dye lasers (which use liquid dye solutions). Fiber mediums pertain to fiber lasers, which utilize optical fibers as the gain medium. Each active medium has unique properties that determine the functionality and applicability of the laser, but for CO2 lasers, the gas medium is what defines its operation and effectiveness.