Lasers are sources of light with exceptional properties, as discussed in the article on laser light. For that reason, there is a great variety of laser applications, leading to a total of over 18 billion USD of global laser sales (as of 2021). The following sections give a brief overview of fields of applications. Many more specific topics are explained in more depth in further encyclopedia articles.
Lasers are widely used for laser material processing – mostly in manufacturing, e.g. for cutting, drilling, welding, cladding, soldering (brazing), hardening, surface modification, marking, engraving, micromachining, pulsed laser deposition, lithography, etc. In many cases, relatively high optical intensities are applied to a small spot, leading to intense heating, possibly evaporation and plasma generation. Essential aspects are the high spatial coherence of laser light, allowing for strong focusing, and often also the potential for generating intense pulses.
Laser processing methods have many advantages, compared with mechanical approaches. They allow the fabrication of very fine structures with high quality, avoiding mechanical stress such as caused by mechanical drills and blades. A laser beam with high beam quality can be used to drill very fine and deep holes, e.g. for injection nozzles. A high processing speed is often achieved, e.g. in the fabrication of filter sieves with many holes. Further, the lifetime limitation of mechanical tools is removed. It can also be advantageous for other reasons to process materials without touching them.
The requirements on optical power and beam quality apart from the wavelength depend very much on the application and the involved materials. For example, laser marking on plastics can be done with fairly low power levels, whereas cutting, welding or drilling on metals requires much more – often multiple kilowatts. Soldering applications may require a high power but only a moderate beam quality, whereas particularly remote welding (i.e., welding with a substantial distance between laser head and welded parts) depends on a high beam quality.
Laser-aided manufacturing often allows one to produce the essentially same parts with higher quality and/or lower cost. Also, it is often possible to realize entirely new part designs or the use of new materials. For example, automobile parts are increasingly made of light materials such as aluminum, which require tentatively more laser joining operations. Weight reductions are possible not only by the user of lighter materials, but also e.g. by producing them with shorter flanges due to higher precision than is feasible with conventional production methods.
Lasers are also widely used for alignment purposes. Alignment lasers may simply emit a Gaussian laser beam, forming a circular spot on a workpiece, a line, a cross, or some other pattern. They are important for many manufacturing processes.
There is a wide range of medical laser applications. Often these relate to the outer parts of the human body, which can easily be reached with light; examples are eye surgery and vision correction (LASIK), dentistry, dermatology (e.g. photodynamic therapy of cancer), and various kinds of cosmetic treatment such as tattoo removal and hair removal.
Lasers are also used for surgery (e.g. of the prostate), exploiting the possibility to cut tissues while causing minimal bleeding. Some operations can be done with endoscopic means; an endoscope may contain an optical fiber for delivering light to the operation scene and another fiber for imaging, apart from additional channels for mechanical instruments.
Very different types of lasers are required for medical applications, depending on the optical wavelength, output power, pulse format, etc. In many cases, the laser wavelength is chosen such that certain substances (e.g. pigments in tattoos or caries in teeth) absorb light more strongly than surrounding tissue so that they can be more precisely targeted.
Medical lasers are not always used for therapy. Some of them rather assist the diagnosis, e.g. via methods of ocular imaging (e.g. optical coherence tomography), laser microscopy or laser spectroscopy (see below).
For more details, see the article on medical lasers.
Laser scanners are scanning the direction of laser beams, which can read e.g. bar codes or other graphics over some distance. It is also possible to scan three-dimensional objects, e.g. in the context of crime scene investigation (CSI).
Lasers also allow for extremely precise time measurements and are therefore an essential component of optical clocks which are outperforming cesium atomic clocks.
Fiber-optic sensors, often probed with laser light, allow for the distributed measurement of temperature, stress, and other quantities e.g. in oil pipelines and wings of airplanes.
See the article on optical metrology for more details.
Optical data storage, e.g. in compact disks (CDs), DVDs, Blu-ray Discs and magneto-optical disks, nearly always relies on a laser source, which has a high spatial coherence and can thus be used to address very tiny spots in the recording medium, allowing a very high density data storage.
Another area is holography, where the temporal coherence can also be important. Holographic data storage can utilize three dimensions rather than only two on a surface, and therefore store substantially more data.
Optical fiber communication, extensively used particularly for long-distance optical data transmission, mostly relies on laser light in optical glass fibers. Free-space optical communications, e.g. for inter-satellite communications, is based on higher-power lasers, generating collimated laser beams which propagate over large distances with small beam divergence.
One may also transmit analog RF and microwave signals using radio and microwave over fiber technology.
Laser projection displays containing RGB sources can be used for cinemas, home videos, flight simulators, etc., and are often superior to other displays concerning possible screen dimensions, resolution and color saturation. However, further reductions in manufacturing costs will be essential for deep market penetration.
Laser spectroscopy is used in many different forms and in a wide range of applications. For example, atmospheric physics and pollution monitoring benefit from trace gas sensing with differential absorption LIDAR technology. Solid materials can be analyzed with laser-induced breakdown spectroscopy. Laser spectroscopy also plays a role in medicine (e.g. cancer detection), biology, and various types of fundamental research, partly related to metrology (see above).
There are various laser applications in the area of quantum photonics. For example, lasers can be used for initializing, manipulating and detecting quantum states of atoms or ions, or aid in trapping of atoms and ions. Methods of laser spectroscopy or quantum communications may also be involved.
For details, see the article on lasers for quantum photonics.
Laser microscopes and setups for optical coherence tomography (OCT) provide images of, e.g., biological samples with very high resolution, often in three dimensions. It is also possible to realize functional imaging.
Various Scientific Applications
Laser cooling makes it possible to bring clouds of atoms or ions to extremely low temperatures. This has applications in fundamental research and also for industrial purposes.
Particularly in biological and medical research, optical tweezers can be used for trapping and manipulating small particles, such as bacteria or parts of living cells.
Laser guide stars are used in astronomical observatories in combination with adaptive optics for atmospheric correction. They allow substantially increased image resolution even in cases where a sufficiently close-by natural guide star is not available.
There are experiments where lasers are used for laser lightning rods. Here, a highly intense laser beam is used to create a conducting channel in air such as to attract lightnings to some (not very high) metallic lightning rod. That way, it might become possible to protect a large area (e.g. an airport) without having a very high metallic lightning rod.
In the future, high-power laser systems might play a role in electricity generation. Laser-induced nuclear fusion is investigated as a alternative to other types of fusion reactors. High-power lasers can also be used for isotope separation.
There are a variety of military laser applications. In relatively few cases, lasers are used as weapons; the “laser sword” has become popular in movies, but not in practice. Some high-power lasers are currently developed for potential use as directed energy weapons on the battlefield, or for destroying missiles, projectiles and mines.
In other cases, lasers function as target designators or laser sights (essentially laser pointers emitting visible or invisible laser beams), or as irritating or blinding (normally not directly destroying) countermeasures e.g. against heat-seeking anti-aircraft missiles. It is also possible to blind soldiers temporarily or permanently with laser beams, although the latter is forbidden by the rules of war.
There are also many laser applications which are not specific for military use, e.g. in areas such as range finding, LIDAR, and optical communications.
Applications in Space
In space, lasers may be used for very different purposes. Some examples:
- Lasers can be used for free-space optical communications, e.g. between satellites. Compared with radio transmission, they can have vital advantages, such as reaching a higher bandwidth and requiring less space and volume.
- LIDAR can fulfill various functions, such as distant monitoring of surfaces and supporting docking and rendezvous operations.
- Some pulsed lasers are used for purposes like laser-induced breakdown spectroscopy, for example on planet missions.
- Various other kinds of scientific instrumentation can also be based on laser devices, e.g. for laser spectroscopy and for realizing optical tweezers in microgravity experiments.
See also the article on space-qualified lasers.
See also: lasers, laser material processing, lasers for material processing, lasers for quantum photonics, medical lasers, laser microscopy, laser spectroscopy, laser light, photonics, space-qualified lasers
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