L stands for Light.
The amazing thing about lasers is that they harness the power of light
and control it. Laser light has several special qualities:
- it comes in one color
- it comes in a thin beam
- it can be made very intense or not intense at all
- and it can be focused to a tiny spot.
These characteristics are very different from
light from a lightbulb. Lightbulb light:
- has many colors mixed together
- doesn't come in a narrow beam
- cannot be focused to as small a spot
- and cannot be as intense as a laser without expending tremendous amounts of energy.
So lasers are special because they allow us to control light in
new and important ways.
Light Amplification by the Stimulated Emission of Radiation