الفهرس 
History of laserOnly 14 pages are availabe for public view
 |  | from | 122 |  |  |
| | | from | 122 | | |
Abstract
Laser is a narrow beam of light with high concentration of energy that can be focused to a very narrow spot. The word laser is abbreviation of the words : Light AmplifIcation by Stimulated Emission of Radiation. It was first described by Albert Einstien in 1917. In 1960 laser was generated and emitted by Maiman at. a wave length of 0.69 microris in short pulses lasting one millisecond or less. For laser production there must be an active medium. an optical resonator and an exciting system. Most lasers are named according to their active media which are either solid as Nd-YAG (Neodymium - Yetrium aluminium garent), glass and ruby. liquid as organic and inorganic dyes or gas like CO and Argon lasers. The optjcal resonator is a 2- tube closed at both ends by concave mirrors and contains the active medium. The exciting system is usually a light source and a reflector. Absorption of laser beam by tissues depends upon the wave length. colour and water content of the impacted materials. Laser has the superiority over ordinary methods due to its excellent properties which are: 1- It is associated with minimal bleeding during operations because it seals blood vessels be l ow Imm in diameter.