Laser

: A powerful beam of light that can produce intense heat when focused at close range. Lasers are used in medicine in microsurgery, cauterization, for diagnostic purposes, etc. For example, lasers are employed in microsurgery to cut tissue and remove tissue. Technical Note: A laser concentrates high energies into an intense narrow beam of nondivergent monochromatic electromagnetic radiation; Lasers using various substances (ruby, argon, krypton, neodymium, helium-neon, carbon dioxide) are available. Laser is an acronym coined in 1960 from a forgettable term: Light Amplification by Stimulated Emission of Radiation.

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1. (noun) A device that concentrates high energies into an intense narrow beam of nondivergent monochromatic electromagnetic radiation; used in microsurgery, cauterization, and for a variety of diagnostic purposes. Lasers can be based on numerous chemical sources, gas, liquid, and solid, some of which are listed in chart. Lasers are widely used in printers of text or x-ray images. 2. (verb) To treat a structure with a l. beam. [acronym coined from light amplification by stimulated emission of radiation]

- argon l. l. used for ophthalmic procedures, including retinal photocoagulation and trabeculoplasty, consisting of photons in the blue (488 nm) or green (514 nm) spectrum.

- continuous wave l. a l. in which energy output is constant.

- excimer l. l. used particularly for refractive procedures, consisting of photons in the ultraviolet spectrum emitted by unstable dimers of argon and fluoride. [excited dimer]

- krypton l. l. used for ophthalmic procedures, particularly retinal photocoagulation in the presence of vitreous hemorrhage, consisting of photons in the red (647 nm) spectrum.

- KTP l. l. in the blue-green to green (532 nm) spectrum, used for hemostasis; produced by doubling the frequency of an Nd:YAG l. by passing the beam through a KTP crystal. [K (potassium) Titanyl Phosphate]

- Nd:YAG l. l. in the infrared spectrum (1064 nm), with a greater depth of penetration than other lasers. [Nd (neodymium) + Yttrium-A luminum-Garnet]

- pulsed l. a l. in which energy output is pulsed, allowing short bursts of high energy.

- pulsed dye l. extremely short bursts of focused yellow light absorbed by hemoglobin, used to treat hemangiomas without anesthesia in young children.

- pumped l. a l. whose energy level is increased by the application of separate sources of electrons or photons, which may themselves be primary lasers.

- Q-switched l. (quality-switched); a l. in which the quality, or energy storage capacity is altered between a very high and a low value.

- quasi-continuous wave l. a l. whose output can be controlled in milliseconds or similarly small increments by electronic control.

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light amplification by stimulated emission of radiation

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la·ser 'lā-zər n a device that utilizes the natural oscillations of atoms or molecules between energy levels for generating coherent electromagnetic radiation usu. in the ultraviolet, visible, or infrared regions of the spectrum

laser vt to subject to the action of a laser: treat with a laser <cutting a corneal flap to remove tissue and then \lasering the area under it (Jenny Manzer)>

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n.

a device that produces a very thin beam of light in which high energies are concentrated (the word derives from light amplification by stimulated emission of radiation). In surgery, lasers can be used to operate on small areas of abnormality without damaging delicate surrounding tissue. For example, lasers are used to unblock coronary arteries narrowed by atheroma and to remove certain types of birthmark (see naevus). Different types of laser are used in eye surgery for operations on the cornea, lens capsule, and retina (see argon laser, diode laser, excimer laser, YAG laser). Lasers are also used in the treatment of cervical intraepithelial neoplasia and in a specialized form (the Nd:YAG laser) for endometrial ablation.

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la·ser (laґzər) [light amplification by stimulated emission of radiation] a device that transforms light of various frequencies into an extremely intense, small, and nearly nondivergent beam of monochromatic radiation in the visible region with all the waves in phase. Capable of mobilizing immense heat and power when focused at close range, it is used as a tool in surgical procedures, in diagnosis, and in physiologic studies.

Relative positions of various types of lasers on the electromagnetic spectrum.