Overview of How Lasers Work

There are many different types of lasers. The laser medium can be a solid, gas, liquid or semiconductor. Lasers are commonly designated by the type of lasing material employed:

Solid-state lasers have lasing material distributed in a solid matrix (such as the ruby or neodymium-yttrium aluminum garnet (YAG) lasers). The neodymium-YAG laser emits infrared light at 1,064 nanometers (nm). A nanometer is 1 x 10-9 meters.

Gas lasers (helium and helium-neon, HeNe, are the most common gas lasers) have a primary output of visible red light. CO2 lasers emit energy in the far-infrared, and are used for cutting hard materials.

Excimer lasers (the name is derived from the terms excited and dimers) use reactive gases such as chlorine and fluorine mixed with inert gases such as argon, krypton or xenon. When electrically stimulated, a pseudo molecule or dimer is produced and when lased, produces light in the ultraviolet range.

Dye lasers use complex organic dyes like rhodamine 6G in liquid solution or suspension as lasing media. They are tunable over a broad range of wavelengths. Semiconductor lasers, sometimes called diode lasers, are not solid-state lasers. These electronic devices are generally very small and use low power. They may be built into larger arrays, such as the writing source in some laser printers or compact disc players.

The first type of laser was called a ruby laser. A ruby laser is a solid-state laser and emits at a wavelength of 694 nm. Other lasing mediums can be selected based on the desired emission wavelength (see table below), power needed, and pulse duration. Some lasers are very powerful, such as the CO2 laser, which can cut through steel. The reason that the CO2 laser is so dangerous is because it emits laser light in the infrared and microwave region of the spectrum. Infrared radiation is heat, and this laser basically melts through whatever it is focused upon.

Other lasers, such as diode lasers, are very weak and are used in today’s red pocket lasers that are used to point at things. These lasers typically emit a red beam of light that has a wavelength between 630 nm and 680 nm. Lasers are used in industry and research to do many things, including using the intense laser light to excite other molecules to observe what happens to them.