Lasers :: essays research papers

The laser is a device that produces a beam of light. The beam is produced by a process known as stimulated emission, and the word “laser'; is an acronym for the phrase “light amplification by stimulated emission of radiation.'; Lasers amplify light and produce coherent light beams. A light beam is coherent when its waves or photons are in step with one another. Laser light can be made extremely intense, highly directional, and very pure in color. BASIC PRINCIPLES   Ã‚  Ã‚  Ã‚  Ã‚  Light can be characterized both by its frequency, or number of wave crests passing a given point per second, and by its wavelength. Different wavelengths of light are seen as different colors. Like radio waves, light can also carry information. The information in the beam varies in the frequency or shape of the light wave. Because light waves are of much higher frequencies than radio waves, the have a higher information carrying capacity. In beams of light,individual photon waves are not moving along together because they are not being emitted at the same instant but instead in random short bursts. Such beams are called incoherent.   Ã‚  Ã‚  Ã‚  Ã‚  The process for laser action, was first proposed by Albert Einstein in 1917. The working principles of lasers were outlined by the American physicists Arthur Leonard Schawlow and Charles Hard Townes in their 1958 patent application. The patent was granted but was later challenged by the American physicist and engineer Gordon Gould. In 1960 the American physicist Theodore Maiman observed the first laser action in solid ruby. HOW A LASER WORKS   Ã‚  Ã‚  Ã‚  Ã‚  A laser is made up of several basic components. One is called active medium, which consists of atoms of a gas, molecules in a liquid, ions in a crystal, or any of several other possibilities. Another component consists of some method of introducing energy into the active medium, such as a flash lamp. The third basic component is a pair of mirrors placed on either side of the active meduim, one of which transmits part of the radiation that strikes it. Atoms initially in a lower state are raised to the upper state by energy from a flash lamp or some other pumping source. Some of these atoms emit light in random directions. Light traveling vertical to the mirrors stays within the active medium long enough to stimulate emission from other atoms. Light traveling in other directions are soon lost. Some light reaching the output mirror is transmitted to form the laser beam, some is reflected back through the medium to continue the stimulated-emission process.