Basic Science of Material Processing Lasers

CO2 Lasers

CO2 lasers are a type of gas laser that use carbon dioxide gas as the lasing medium. They work by exciting the gas molecules in a sealed tube with an electrical discharge, which causes the molecules to emit photons of light. These photons bounce back and forth between two mirrors at either end of the tube, gaining energy with each pass, until they form a highly concentrated beam of light that can be used for cutting, welding, engraving, and other industrial applications.

The key to the operation of CO2 lasers is the fact that carbon dioxide gas has a unique molecular structure that allows it to absorb and emit light at a specific wavelength of 10.6 microns. This wavelength is in the far infrared part of the electromagnetic spectrum, which makes it ideal for cutting and engraving materials that are difficult to work with using other types of lasers.

CO2 lasers are highly efficient and can produce a continuous beam of light with a power output ranging from a few watts to several kilowatts. They are widely used in manufacturing, medicine, and scientific research, and have played a key role in many technological advancements over the past few decades.

Fiber Lasers

A fiber laser is a type of laser that uses an optical fiber as the laser medium, instead of a gas or a solid-state crystal. The fiber is doped with rare-earth elements, such as ytterbium or erbium, which are capable of absorbing and emitting light at specific wavelengths. When a light source, such as a semiconductor diode, pumps energy into the fiber, it excites the rare-earth atoms and causes them to emit photons at a particular wavelength.

The photons produced in the fiber are then amplified as they travel through the fiber, bouncing back and forth between two mirrors at the ends of the fiber, until they reach a high enough intensity to escape as a laser beam. The laser beam produced by a fiber laser is very high-quality and can be focused to a very small spot, making it useful for a wide range of applications, including materials processing, communication, and medical treatment.

One of the key advantages of fiber lasers is their efficiency. Because the fiber is so small and can be coiled into a compact package, the laser can be designed to have a very high power-to-volume ratio, meaning that it can produce a lot of power in a small space. Additionally, the rare-earth dopants used in the fiber have a high quantum efficiency, meaning that they can convert a large fraction of the energy input into light output. These factors make fiber lasers very energy-efficient and cost-effective for many applications.

Overall, the science behind fiber lasers involves the excitation and amplification of photons in a doped optical fiber, and the resulting laser beam can be used for a wide range of applications in science, industry, and medicine.