1. A device that generates an intense, narrow beam of light created by bombarding an active medium with energy in the form of high-voltage electricity, high-intensity light, or radio frequency waves. By passing through a mirrored tube, the photons are released as a nondivergent ("collimated"), monochromatic (all one wavelength), coherent (all in phase) beam. Lasers are used in microsurgery, for cauterization, excision, and for a variety of diagnostic purposes. The wavelength delivered depends on the active medium excited; targetted tissues ("chromophores") are determined by the laser wavelength that they absorb. Laser dosage, or fluence, delivered is derived by dividing the energy delivered by the cross-sectional area of the beam (Joules/CM2). Lasers can be based on numerous chemical sources, gas, liquid, and solid. Lasers are widely used in printers of text or X-ray images. 2. To treat a structure with a laser beam.