Laser ::
A laser (from the acronym Light Amplification by Stimulated Emission of Radiation) is an optical source that emits photons in a coherent beam. The verb to lase means "to produce coherent light" or possibly "to apply laser light to", and is a back-formation of the term laser.
Laser light is typically near-monochromatic, i.e. consisting of a single wavelength or color, and emitted in a narrow beam. This is in contrast to common light sources, such as the incandescent light bulb, which emit incoherent photons in almost all directions, usually over a wide spectrum of wavelengths.
Laser action is explained by the theories of quantum mechanics and thermodynamics. Many materials have been found to have the required characteristics to form the laser gain medium needed to power a laser, and these have led to the invention of many types of lasers with different characteristics suitable for different applications.
The laser was proposed as a variation of the maser principle in the late 1950s, and the first laser was demonstrated in 1960. Since that time, laser manufacturing has become a multi-billion dollar industry, and the laser has found applications in fields including science, industry, medicine, and consumer electronics.
LED ::
light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction. This effect is a form of electroluminescence. The color of the emitted light depends on the chemical composition of the semiconducting material used, and can be near-ultraviolet, visible or infrared.[1] Rubin Braunstein (born 1922) of the Radio Corporation of America first reported on infrared emission from GaAs and other semiconductor alloys in 1955.[2] Experimenters at Texas Instruments, Bob Biard and Gary Pittman, found in 1961 that gallium arsenide gave off infrared (invisible) light when electric current was applied. Biard and Pittman were able to establish the priority of their work and received the patent for the infrared light-emitting diode. Nick Holonyak Jr. (born 1928) of the General Electric Company developed the first practical visible-spectrum LED in 1962.[3]