A device that produces a concentrated coherent light beam by stimulated electronic or molecular transitions to lower energy levels. Laser is an acronym for light amplification by stimulated emission of radition.
The laser beam is a focused, high-power, coherent, monochromatic light beam. The laser was independently invented in 1960 by two scientists, one at Bell Laboratories and the other at Hughes Aircraft. Most of the early application development was conducted by Bell Laboratories. The original laser device consisted of a ruby rod surrounded by a xenon flash lamp that excited the chromium atoms in the ruby to higher energy states. Simultaneously stimulated and returning to the ground state, the atoms emit an intense amplified light beam. See Figure L-2 for a schematic diagram of a ruby laser The rapid flashing of the xenon lamp produced a seemingly steady state of emitted light. Only a focused, monochromatic light beam was permitted to leave the device. Initial application was limited to the low power of the ruby laser.
The three basic types of laser include solid state, gas discharge, and semi-conductor injection types. High power, pulsed outputs in the megawatt range are
provided by solid state lasers. Gas discharge lasers use helium, neon, krypton, or xenon to provide low power output frequencies that are continuous. Semi-conductor injection lasers have limited power output, are dependent on liquid nitrogen operating temperatures, and do not need a flashlamp for exciting the atoms since they convert electricity directly into light.
Early laser metal working applications were limited, but with the advent of higher-powered lasers, applications include welding, brazing, cutting, micro perforation, and metal removal. High-powered lasers can cut steel up to 25 mm (1 in.) thick.