This document describes 5 types of lasers: solid state lasers like ruby and neodymium-YAG lasers which have a solid lasing material, gas lasers like helium-neon which emit visible light, excimer lasers which use reactive gases to produce ultraviolet light, dye lasers which use organic dyes and are tunable, and semiconductor lasers also called diode lasers which are small electronic devices.

2. 1. Solid State Laser
2. Gas Laser
3. Excimer lasers
4. Dye lasers
5. Semiconductor lasers,

3. 1. Solid State Lasers: Solid state lasers have lasing material
distributed in a solid matrix, e.g., the ruby or neodymium-
YAG (yttrium aluminum garnet) lasers. The neodymium-
YAG laser emits infrared light at 1.064 micrometers.
2. Gas lasers: Gas lasers (helium and helium-neon, HeNe, are
the most common gas lasers) have a primary output of a
visible red light. CO2 lasers emit energy in the far-infrared,
10.6 micrometers, and are used for cutting hard materials.
3. Excimer lasers: 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 pseudomolecule or
dimer is produced and when lased, produces light in the
ultraviolet range.

4. 4. Dye lasers: 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 wave
lengths.
5. Semiconductor lasers: 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, e.g., the
writing source in some laser printers or compact disk
players.