HOW THE LASER WORKS

Materials and Energy Sources

Different materials are used as the "medium" in differnt types of lasers:

• Glasses (often as long fibers) and crystals (often as rods)--light is commonly the energy source.
• Semiconductors--generally, these are the most compact and they are powered by electric current
• Gasses--powered by light, electric current, electron beams, or chemical reactions in the laser cavity.
• Liquids (usually inorganic dyes)--powered by light.
• Free electron--magnets provide energy to excite free electrons.

Some lasers and masers, especially ones designed solely for the amplification of weak signals, have an energy source that is separate from--and may use very different energy from--the signal that is the initial source of the stimulated emission.

Configurations

Besides simple single lasers, lasers may be used in tandem where one laser is used as the light source for a second one--and perhaps on and on. Because the quality of the light in a light powered laser is important, lasers become a valuable source of light to power other lasers.

Some lasers are microscopic in size (e.g., quantum-dot vertical-cavity surface-emitting solid state lasers) with thousands formed in a chip area no bigger than the head of a pin. Yet other kinds of lasers occupy large rooms. And lasers that use glass fibers can have considerable effective length yet arranged in a compact coil.