Lasers and laser systems are becoming quite common in today's high technology society. Lasers are used for a variety of applications. Directional Lasers emit light that is highly directional, that is, laser light is emitted as a relatively narrow beam in a specific direction. Ordinary light, such as from a lightbulb, is emitted in many directions away from the source. The light from a laser is said to be coherent, which means that the wavelengths of the laser light are in phase in space and time.
Ordinary light can be a mixture of many wavelengths.
The lasing medium of a laser is a substance that emits light in all directions and can be a gas, liquid, solid, or semiconducting material. The excitation mechanism of a laser is the source of energy used to excite the lasing medium. Excitation mechanisms typically used are electricity from a power supply, a flashtube, lamp, or the energy from another laser. A laser's feedback mechanism is used to reflect light from the lasing medium back into itself and typically consists of two mirrors at each end of the lasing medium. As the light is bounced between the mirrors, it increases in strength, resulting in amplification of the energy from the excitation mechanism in the form of light.