Lasers have become an important tool in contemporary society. They have numerous applications in various fields, including communications, business, home entertainment, medicine, military weaponry, and scientific research. Lasers work on the principle of "coherent light." By contrast, normal light sources such as the sun or a light bulb are considered to be "incoherent." This is because these light sources release photons by means of spontaneous emission. As a result of this phenomenon, such sources "emit light in all directions with a great range of wavelengths" (2:47). A laser, on the other hand, "puts out a narrow beam of light of a single color at a time" and "all its waves rise and fall together" (2:47). The projection of light from a laser is controlled by an outside energy source. As a result, laser light is caused by stimulated emission, and its waves are not random.
Lasers work by creating light energy, amplifying it, and then directing it out in a single, powerful beam. Various types of media can be used for the creation of light energy. Therefore, there are various types of lasers which exist today. Some lasers use solid materials, such as crystals for producing light. Others use gases, chemicals, or dyes as a basis for light. Semiconductors, materials which transmit electricity "better than nonconductors such as rubber, but not as well as copper," are also often used as a medium for light production (3:70). Inside the laser, the chosen material is placed between two mirrors which are facing one another. One of the mirrors is more transparent than the other, thereby allowing the light to be directed out in the form of a beam. In order to cause the material inside the laser to produce light, energy is pumped in from an outside source (3:65). In a semiconductor type of laser, an electrical device can be used to stimulate the material. In most other types of lasers, the material is excited by aiming a fla...