Simply stated, a laser is a device that amplifies light. The word laser is an acronym for Light Amplification by Stimulated Emission of Radiation.
Laser light is vastly different from ordinary light, such as from a light bulb or the sun. It is highly monochromatic (one color) and also coherent (all of the light waves are in step with each other.) It is for these reasons that laser light is used in holography, which requires a coherent light source.
These days, lasers are pretty much taken for granted. They are everywhere: in supermarket scanners, in CD and DVD players, in rifle scopes. We sometimes even play with our pets with a laser pointer, letting them chase the red dot around on the floor and walls.
But up until fairly recently, they were the stuff of science fiction. Even before there were any real lasers, the idea of “ray guns” captured the imagination of fiction authors.
Real lasers may not exactly be a ray gun, but some types come pretty close.
There are many different types of lasers. By far the most common today is the diode laser. If you have a CD or a DVD player of any kind, or a laser pointer or level, you have a diode laser. A diode is a tiny chip of crystalline material. When it is excited by an electrical current, it emits light. However, not every LED (Light Emitting Diode) is a laser diode. Many appliances have LEDs that are not lasers.
Until about twenty years ago, all diode lasers emitted only invisible light, usually in the infrared range. But recent breakthroughs in technology brought us the visible laser diode. When they first went on the market, visible diode lasers were quite expensive. Now, of course, they are everywhere and very cheap to buy. In addition to the common red diodes, you can also find green, blue, and sometimes other colors; although they cost more.
Another common type of laser, at least until the diode laser took over, is the gas laser. Gas lasers use a glass tube filled with various gasses, such as argon or helium and neon, to produce laser light. Depending on the type of gas used, you can get almost any color of the rainbow from these types of lasers. Some gas lasers, such as the carbon dioxide laser, emit invisible, yet highly powerful, beams. Carbon dioxide lasers are used in welding, and can burn through any earthly material!
Yet another type of laser is the solid-state laser. These are usually very powerful lasers capable of cutting and burning as well. They use a crystal rod of some type as a lasing material. The very first working laser, in fact, was a solid-state ruby laser. It used a ruby rod inside of a flash lamp.
All lasers, no matter what type they are, operate using the same basic principle. Whatever they use as lasing material, on one end will be a totally reflective surface, and on the other is a partially reflective surface. When electricity is applied, this excites the atoms within and they bounce back and forth between the two reflective ends. When enough momentum is gained, laser light bursts through the partially reflective end.
Lasers may be taken for granted now, but with all of their many uses and unlimited potential, they are no less fascinating than they have ever been.