ABSTRACT
This chapter deals with the tools of light. The technology by which light is created and controlled may be the dominating theme of the twenty-first century. Laser is a device that uses quantum mechanical principles and stimulated emission to produce a coherent and highly collimated beam of light that is primarily characterized by one wavelength. A light-emitting diode is a solid-state electronic device that emits incoherent, narrow-spectrum light when electrically biased in the forward direction. The color of the light emitted depends on the chemical composition of the semiconducting materials of which the diode is made. An optical fiber is a transparent, thin fiber, most often made of glass, which is a highly effective light guide for transmitting light over long distances. The combination of the optical fiber with the laser has enabled a virtual revolution in the technology of long-distance communication.
