laser

Device for producing a narrow beam of light, capable of travelling over vast distances without dispersion, and of being focused to give enormous power densities (10⁸ watts per cm² for high-energy lasers). The laser operates on a principle similar to that of the maser (a high-frequency microwave amplifier or oscillator). The uses of lasers include communications (a laser beam can carry much more information than can radio waves), cutting, drilling, welding, satellite tracking, medical and biological research, and surgery. Sound wave vibrations from the window glass of a room can be picked up by a reflected laser beam. Lasers are also used as entertainment in theatres, concerts, and light shows.

Laser material
Any substance in which the majority of atoms or molecules can be put into an excited energy state can be used as laser material. Many solid, liquid, and gaseous substances have been used, including synthetic ruby crystal (used for the first extraction of laser light in 1960, and giving a high-power pulsed output) and a helium–neon gas mixture, capable of continuous operation, but at a lower power. A silicon-based laser was created in 2004, using the natural atomic vibrations of silicon nanocrystals to generate the light.

Applications
Carbon dioxide gas lasers (CO₂ lasers) can produce a beam of 100 watts or more power in the infrared (wavelength 10.6 μm) and this has led to an important commercial application, the cutting of material for suits and dresses in hundreds of thicknesses at a time. Dye lasers, in which complex organic dyes in solution are the lasing material, can be tuned to produce light of any chosen wavelength over a range of a sizeable fraction of the visible spectrum.