Light Amplification by Stimulated Emission of Radiation is a mechanism for emitting electromagnetic radiation, often visible light, via the process of stimulated emission. The emitted laser light is (usually) a spatially coherent, narrow low-divergence beam, that can be manipulated with lenses. In laser technology, "coherent light" denotes a light source that produces (emits) light of in-step waves of identical frequency, phase, and polarization. The laser's beam of coherent light differentiates it from light sources that emit incoherent light beams, of random phase varying with time and position. Laser light is generally a narrow-wavelength electromagnetic spectrum monochromatic light; yet, there are lasers that emit a broad spectrum of light, or emit different wavelengths of light simultaneously.

In 1917, Albert Einstein established the theoretic foundations for the LASER and the MASER in the paper Zur Quantentheorie der Strahlung; via a re-derivation of Max Planck’s law of radiation, conceptually based upon probability coefficients for the absorption, spontaneous emission, and stimulated emission of electromagnetic radiation; in 1928, Rudolf W. Ladenburg confirmed the existences of the phenomena of stimulated emission and negative absorption; in 1939, Valentin A.Fabrikant predicted the use of stimulated emission to amplify “short” waves; in 1947, Willis E. Lamb and R.C.Rutherford found apparent stimulated emission in hydrogen spectra and effected the first demonstration of stimulated emission in 1950, Alfred Kastler proposed the method of optical pumping, experimentally confirmed, two years later, by Brossel, Kastler, and Winter. On 16 May 1960, Theodore Maiman demonstrated the first functional laser at the Hughes Research Laboratories,capable of producing short pulses.

1. Gain medium 2. Laser pumping energy 3. High reflector 4. Output coupler 5. Laser beam A laser consists of a gain medium inside a highly reflective optical cavity, as well as a means to supply energy to the gain medium. The gain medium is a material with properties that allow it to amplify light by stimulated emission. In its simplest form, a cavity consists of two mirrors arranged such that light bounces back and forth, each time passing through the gain medium. Typically one of the two mirrors, the output coupler, is partially transparent. The output laser beam is emitted through this mirror.

Medicine: Bloodless surgery, laser healing, surgical treatment, kidney stone treatment, eye treatment, dentistry Industry: Cutting, welding, material heat treatment, marking parts, non-contact measurement of parts Law enforcement: used for latent fingerprint detection in the forensic identification field Cosmetic skin treatments: acne treatment, cellulite and striae reduction, and hair removal. Product development/commercial: laser printers, optical discs (e.g. CDs and the like), barcode scanners, thermometers, laser pointers, holograms, bubblegrams. Laser lighting displays: Laser light shows

TThe first working laser was actually demonstrated by Theodore Maiman at the Hughes Research Laboratories back in SSome lasers are gas, chemical, solid state, dye and stimulated electron lasers. TThe most powerful laser recorded was at 1.25 petawatts in a laboratory in California in LLasers actually are grouped into classes for levels of danger. Class 1-5. If you reach 5 it can mean permanent blindness and burning skin! SScientists are working on a laser to draw lightning strikes away from airports and power plants

LLasers we come across today operate at a low level of power. LLasers in CD-ROMs drives will be around 5mW, DVD players around 5-10mW, recordable CD drives-100mW. LLasers could not be seen in space either because they have no matter. The matter causes the scattering effect which would give the appearance of a light beam SScientists are working on a laser to draw lightning strikes away from airports and power plants TThere is a laser technology called Clear Scan that can rid you of spider veins, vascular lesions and skin discolorations. TThe world’s most powerful laser can have the power of a hydrogen bomb! TThey are used in eye surgeries and tattoo removals.

 a. einsten Photo effect explanation :light is a beam of particles  1917-a.einsten Postulated the stimulated emission  1939 –v.fabrikant Investigated the stimulated emission as a possibility for the light amplification  basov, theoretical foundations for the light amplicification through active medium  1960-t.maiman First laser(ruby)