Copper vapor lasers produce green and yellow light from a mixture of copper vapor with helium or neon. Dye Lasers . Dye lasers use liquid organic dyes. Dye lasers can produce a broad and almost continuous range of colors, most of them in the visible part of the spectrum. Energy to excite the dye is supplied by another light source, usually another laser-for example, copper vapor lasers.
Dye lasers are particularly well suited for applications in which a precise color is required.
Diode lasers, known as semiconductor lasers, are small and can be mass-produced relatively inexpensively. Their power output is limited by the ability to remove heat from the device. They are highly reliable and durable, with lifetimes described in geological terms. Most diode lasers produce infrared light. Their principal application is as the light source in optical fiber communications, compact disk players, and supermarket bar code readers, and they are also starting to be used for eye surgery.