A laser (from the acronym Light Amplification by Stimulated Emission of Radiation) is a device which produces a narrow, intense beam of electromagnetic radiation. A laser transfers energy to anything it strikes, and a sufficiently intense laser beam can burn through material.
Laser light has useful characteristics:
- A laser beam is "monochromatic", meaning that every photon of light in the beam has the same frequency. Consistent frequency is achieved by exciting atoms of a single element, stimulating them to release photons of light at a frequency specific to that element.
- A laser beam is "coherent", meaning that light waves in the beam are synchronized.
- A laser beam is "directional", meaning that all light rays in the beam are travelling in exactly the same direction.
Theodore H. Maiman invented the first laser in 1960 . Practical modern applications for lasers include reading and writing digital information, security systems, targeting devices on weapons, and precision cutting of certain materials. Several military organizations are researching laser weapons systems, but these are still in the R&D stage.
Laser have many practical applications, the most simple of which is the laser pointer used by many instructors. Because of their tight beams and monochromatic characteristics, lasers are ideal for guiding weapons to their targets. These laser-guided weapons are extremely effective and can often do more damage than 3 - 5 times the same volume of unguided weapons.
Lasers are also very effective at measuring distances to targets very precisely. Laser range-finders, using invisible light frequencies, can be used covertly, allowing quick and accurate gunfire on intended targets. Laser ranging can also be used by aircraft and satellites to create extremely detailed maps of areas with extremely high precision. Apollo astronauts and the Soviet Union (using two unmanned rovers) placed retroreflectors on the surface of the Moon, allowing for accurate measurement of the distance between the Earth and the Moon.
In the 1980s, the United States attempted to develop a satellite-based laser system for defence against intercontinental ballistic missiles. While this system was never completed, prototype lasers were built that could shoot down small missiles, and the technology is currently being investigated for point defense applications.
In the field of medicine, lasers can be used to perform surgery, and because of the nature of how the laser cuts, they cause less blood loss than the same procedures using conventional cutting methods.
Lasers in Science Fiction
Weaponized lasers are common in science fiction, ranging from small arms to spacecraft-scale weapons. Sci-fi laser weapons do not always share the characteristics of real-life lasers, however. In many science fiction franchises, the term "laser" seems to have taken on a far more generic definition, encompassing any beam-style directed-energy weapon.
Often, one or more of the following attributes can be found in sci-fi lasers that are incompatible with real-life laser behavior:
- Visible in a vacuum
- Light is only visible when it reflects to a detector (an eye or camera, for example). Because the photons in a laser beam are all going in the same direction, the beam can only be made "visible" if the photons were to reflect off of something (such as dust).
- Slower-than-light propagation
- Because a laser beam is a type of light beam, a laser would naturally propagate at lightspeed.
- Theodore H. Maiman article at the IEEE Virtual Museum
- Lasers on How Stuff Works