Laser physics

Laser technology is one of the most rapidly developing areas in modern technology. When the laser was invented, in 1960, it was classified as a solution in search of a problem, and today laser technology is applied in many different areas such as: medicine, communication, daily use, military, and industry. To explain how the laser can be applied in such diverse areas, we need to understand the basic physical principles of the operation of a laser. Laser is a powerful source of light having extraordinary properties which are not found in the normal light sources like tungsten lamps, mercury lamps, etc. The unique property of laser is that its light waves travel very long distances with e very little divergence.
Lasers are devices that produce intense beams of light which are monochromatic, coherent, and highly collimated. The wavelength (color) of laser light is extremely pure (monochromatic) when compared to other sources of light, and all of the photons (energy) that make up the laser beam have a fixed phase relationship (coherence) with respect to one another. Light from a laser typically has very low divergence. It can travel over great distances or can be focused to a very small spot with a brightness which exceeds that of the sun. Because of these properties, lasers are used in a wide variety of applications in all walks of life.
The basic operating principles of the laser were put forth by Charles Townes and Arthur Schalow from the Bell Telephone Laboratories in 1958, and the first actual laser, based on a pink ruby crystal, was demonstrated in 1960 by Theodor Maiman at Hughes Research Laboratories. Since that time, literally thousands of lasers have been invented (including the edible “Jello” laser), but only a much smaller number have found practical applications in scientific, industrial, commercial, and military applications.