List of laser applications

Many scientific, military, medical and commercial laser applications have been developed since the invention of the laser in 1958. The coherency, high monochromaticity, and ability to reach extremely high powers are all properties which allow for these specialized applications.

Scientific

In science, lasers are used in many ways, including:

• A wide variety of interferometric techniques
• Raman spectroscopy
• Laser induced breakdown spectroscopy
• Atmospheric remote sensing
• Investigating nonlinear optics phenomena
• Holographic techniques employing lasers also contribute to a number of measurement techniques.
• Laser based LIght Detection And Ranging (LIDAR) technology has application in geology, seismology, remote sensing and atmospheric physics.
• Lasers have been used aboard spacecraft such as in the Cassini-Huygens mission.
• In astronomy, lasers have been used to create artificial laser guide stars, used as reference objects for adaptive optics telescopes.

Lasers may also be indirectly used in spectroscopy as a micro-sampling system, a technique termed Laser ablation (LA), which is typically applied to ICP-MS apparatus resulting in the powerful LA-ICP-MS.

The principles of laser spectroscopy are discussed by Demtröder and the use of tunable lasers in spectroscopy are described in Tunable Laser Applications. ).

Spectroscopy

Most types of laser are an inherently pure source of light; they emit near-monochromatic light with a very well defined range of wavelengths. By careful design of the laser components, the purity of the laser light (measured as the "linewidth") can be improved more than the purity of any other light source. This makes the laser a very useful source for spectroscopy. The high intensity of light that can be achieved in a small, well collimated beam can also be used to induce a nonlinear optical effect in a sample, which makes techniques such as Raman spectroscopy possible. Other spectroscopic techniques based on lasers can be used to make extremely sensitive detectors of various molecules, able to measure molecular concentrations in the parts-per-10¹² (ppt) level. Due to the high power densities achievable by lasers, beam-induced atomic emission is possible: this technique is termed Laser induced breakdown spectroscopy (LIBS).

Lunar laser ranging

Main article: Lunar laser ranging experiment

When the Apollo astronauts visited the moon, they planted retroreflector arrays to make possible the Lunar Laser Ranging Experiment. Laser beams are focused through large telescopes on Earth aimed toward the arrays, and the time taken for the beam to be reflected back to Earth measured to determine the distance between the Earth and Moon with high accuracy.

Photochemistry

Some laser systems, through the process of modelocking, can produce extremely brief pulses of light - as short as picoseconds or femtoseconds (10⁻¹² - 10⁻¹⁵ seconds). Such pulses can be used to initiate and analyse chemical reactions, a technique known as photochemistry. The short pulses can be used to probe the process of the reaction at a very high temporal resolution, allowing the detection of short-lived intermediate molecules. This method is particularly useful in biochemistry, where it is used to analyse details of protein folding and function.

Laser cooling

A technique that has recent success is laser cooling. This involves atom trapping, a method where a number of atoms are confined in a specially shaped arrangement of electric and magnetic fields. Shining particular wavelengths of laser light at the ions or atoms slows them down, thus cooling them. As this process is continued, they all are slowed and have the same energy level, forming an unusual arrangement of matter known as a Bose-Einstein condensate.

Nuclear fusion

Some of the world's most powerful and complex arrangements of multiple lasers and optical amplifiers are used to produce extremely high intensity pulses of light of extremely short duration. These pulses are arranged such that they impact pellets of tritium-deuterium simultaneously from all directions, hoping that the squeezing effect of the impacts will induce atomic fusion in the pellets. This technique, known as "inertial confinement fusion", so far has not been able to achieve "breakeven", that is, so far the fusion reaction generates less power than is used to power the lasers, but research continues.

Microscopy

Confocal laser scanning microscopy and Two-photon excitation microscopy make use of lasers to obtain blur-free images of thick specimens at various depths. Laser capture microdissection use lasers to procure specific cell populations from a tissue section under microscopic visualization.

Additional laser microscopy techniques include harmonic microscopy, four-wave mixing microscopy and interferometric microscopy.

Military

Military uses of lasers include applications such as target designation and ranging, defensive countermeasures, communications and directed energy weapons.

Directly as an energy weapon

Directed energy weapons are being developed, such as Boeing’s Airborne Laser which was constructed inside a Boeing 747. Designated the YAL-1, it is intended to kill short- and intermediate-range ballistic missiles in their boost phase.

• Made by Northrop Grumman:
  • On March 18, 2009 Northrop Grumman announced that its engineers in Redondo Beach had successfully built and tested an electric laser capable of producing a 100-kilowatt ray of light, powerful enough to destroy cruise missiles, artillery, rockets and mortar rounds. An electric laser is theoretically capable, according to Brian Strickland, manager for the United States Army's Joint High Power Solid State Laser program, of being mounted in an aircraft, ship, or vehicle because it requires much less space for its supporting equipment than a chemical laser.
  • On April 6, 2011, the U.S. Navy successfully tested a laser gun, manufactured by Northrop Grumman, that was mounted on the former USS Paul Foster, which is currently used as the navy's test ship. When engaged during the test that occurred off the coast of Central California in the Pacific Ocean test range, the laser gun was documented as having "a destructive effect on a high-speed cruising target," said Chief of Naval Research Admiral Nevin Carr.
  • Northrop Grumman has announced the availability of a high-energy solid-state laser weapon system that they call FIRESTRIKE, introduced on 13 November 2008. The system is modular, using 15 kW modules that can be combined to provide various levels of power.

• On 19 July 2010 an anti-aircraft laser described as the Laser Close-In Weapon System was unveiled at the Farnborough Airshow.

• The Zeus laser weapon is the first laser and the first energy weapon of any type to be used on a battlefield. It is used for neutralizing mines and unexploded ordnance.
• Laser Area Defense System.
• Lockheed Martin’s Area Defense Anti-Munitions
• The Mid-Infrared Advanced Chemical Laser (MIRACL) is an experimental U.S. Navy deuterium fluoride laser and was tested against an Air Force satellite in 1997.
• In 2011, the U.S. Navy began to test the Maritime Laser Demonstrator (MLD), a laser for use aboard its warships. By 2013, the Navy was announcing active deployment in 2014.
• Personnel Halting and Stimulation Response, or PHaSR, is a non-lethal hand-held weapon developed by the United States Air Force Its purpose is to "dazzle" or stun a target. It was developed by Air Force's Directed Energy Directorate.
• Tactical High Energy Laser (THEL) is a weaponized deuterium fluoride laser developed in a joint research project by Israel and the U.S. It is designed to shoot down aircraft and missiles. See also National missile defense.
• The Boeing Laser Avenger
• The U.S. Air Force's Airborne Laser, or Advanced Tactical Laser, is a plan to mount a CO2 gas laser or COIL chemical laser on a modified Boeing 747 to shoot down missiles.
• Portable Efficient Laser Testbed (PELT)
• Laser AirCraft CounterMeasures (ACCM)
• In April 2013, the U.S. Navy created the Laser Weapon System (LAWS), which is intended to hold off approaching unmanned aerial vehicles and speedboats. The system, which can burn through steel, reportedly costed $40 million and took six years to develop.
• See also Electrolaser#Examples of electrolasers.

Defensive countermeasures

Defensive countermeasure applications can range from compact, low power infrared countermeasures to high power, airborne laser systems. IR countermeasure systems use lasers to confuse the seeker heads on heat-seeking anti-aircraft missiles. High power boost-phase intercept laser systems use a complex system of lasers to find, track and destroy intercontinental ballistic missiles (ICBM). In this type of system a chemical laser, one in which the laser operation is powered by an energetic chemical reaction, is used as the main weapon beam (see Airborne Laser). The Mobile Tactical High-Energy Laser (MTHEL) is another defensive laser system under development; this is envisioned as a field-deployable weapon system able to track incoming artillery projectiles and cruise missiles by radar and destroy them with a powerful deuterium fluoride laser.

Another example of direct use of a laser as a defensive weapon was researched for the Strategic Defense Initiative (SDI, nicknamed "Star Wars"), and its successor programs. This project would use ground-based or space-based laser systems to destroy incoming intercontinental ballistic missiles (ICBMs). The practical problems of using and aiming these systems were many; particularly the problem of destroying ICBMs at the most opportune moment, the boost phase just after launch. This would involve directing a laser through a large distance in the atmosphere, which, due to optical scattering and refraction, would bend and distort the laser beam, complicating the aiming of the laser and reducing its efficiency.

Another idea from the SDI project was the nuclear-pumped X-ray laser. This was essentially an orbiting atomic bomb, surrounded by laser media in the form of glass rods; when the bomb exploded, the rods would be bombarded with highly-energetic gamma-ray photons, causing spontaneous and stimulated emission of X-ray photons in the atoms making up the rods. This would lead to optical amplification of the X-ray photons, producing an X-ray laser beam that would be minimally affected by atmospheric distortion and capable of destroying ICBMs in flight. The X-ray laser would be a strictly one-shot device, destroying itself on activation. Some initial tests of this concept were performed with underground nuclear testing; however, the results were not encouraging. Research into this approach to missile defense was discontinued after the SDI program was cancelled.

Disorientation

Some weapons simply use a laser to disorient a person. One such weapon is the Thales Green Laser Optical Warner.

Targeting

Target designator

Main article: Laser designator

A target designator

Another military use of lasers is as a laser target designator. This is a low-power laser pointer used to indicate a target for a precision-guided munition, typically launched from an aircraft. The guided munition adjusts its flight-path to home in to the laser light reflected by the target, enabling a great precision in aiming. The beam of the laser target designator is set to a pulse rate that matches that set on the guided munition to ensure munitions strike their designated targets and do not follow other laser beams which may be in use in the area. The laser designator can be shone onto the target by an aircraft or nearby infantry. Lasers used for this purpose are usually infrared lasers, so the enemy cannot easily detect the guiding laser light.

Firearms

Laser sight

Laser sight used by the Israel Defense Forces during commando training

Smith & Wesson revolver equipped with a laser sight mounted on the trigger guard.

The laser has in most firearms applications been used as a tool to enhance the targeting of other weapon systems. For example, a laser sight is a small, usually visible-light laser placed on a handgun or a rifle and aligned to emit a beam parallel to the barrel. Since a laser beam has low divergence, the laser light appears as a small spot even at long distances; the user places the spot on the desired target and the barrel of the gun is aligned (but not necessarily allowing for bullet drop, windage, distance between the direction of the beam and the axis of the barrel, and the target mobility while the bullet travels).

Most laser sights use a red laser diode. Others use an infrared diode to produce a dot invisible to the naked human eye but detectable with night vision devices. The firearms adaptive target acquisition module LLM01 laser light module combines visible and infrared laser diodes. In the late 1990s, green diode pumped solid state laser (DPSS) laser sights (532 nm) became available. Modern laser sights are small and light enough for attachment to the firearms.

In 2007, LaserMax, a company specializing in manufacturing lasers for military and police firearms, introduced the first mass-production green laser available for small arms. This laser mounts to the underside of a handgun or long arm on the accessory rail. The green laser is supposed to be more visible than the red laser in bright lighting conditions because, for the same wattage, green light appears brighter than red light.

Eye-targeted lasers

A non-lethal laser weapon was developed by the U.S. Air Force to temporarily impair an adversary’s ability to fire a weapon or to otherwise threaten enemy forces. This unit illuminates an opponent with harmless low-power laser light and can have the effect of dazzling or disorienting the subject or causing him to flee. Several types of dazzlers are now available, and some have been used in combat.

There remains the possibility of using lasers to blind, since this requires much lower power levels, and is easily achievable in a man-portable unit. However, most nations regard the deliberate permanent blinding of the enemy as forbidden by the rules of war (see Protocol on Blinding Laser Weapons). Although several nations have developed blinding laser weapons, such as China's ZM-87, none of these are believed to have made it past the prototype stage.

In addition to the applications that crossover with military applications, a widely known law enforcement use of lasers is for lidar to measure the speed of vehicles.

Medical

See also: Laser medicine

• Cosmetic surgery (removing tattoos, scars, stretch marks, sunspots, wrinkles, birthmarks, and hairs): see laser hair removal. Laser types used in dermatology include ruby (694 nm), alexandrite (755 nm), pulsed diode array (810 nm), Nd:YAG (1064 nm), Ho:YAG (2090 nm), and Er:YAG (2940 nm).
• Eye surgery and refractive surgery
• Soft tissue surgery: CO₂, Er:YAG laser
• Laser scalpel (General surgery, gynecological, urology, laparoscopic)
• Photobiomodulation (i.e. laser therapy)
• "No-Touch" removal of tumors, especially of the brain and spinal cord.
• In dentistry for caries removal, endodontic/periodontic procedures, tooth whitening, and oral surgery

Industrial and commercial

Lasers used for visual effects during a musical performance. (A laser light show.)

Levelling of ceramic tiles floor with a laser device

Industrial laser applications can be divided into two categories depending on the power of the laser: material processing and micro-material processing.

In material processing, lasers with average optical power above 1 kilowatt are used mainly for industrial materials processing applications. Beyond this power threshold there are thermal issues related to the optics that separate these lasers from their lower-power counterparts. Laser systems in the 50-300W range are used primarily for pumping, plastic welding and soldering applications. Lasers above 300W are used in brazing, thin metal welding, and sheet metal cutting applications. The required brightness (as measured in by the beam parameter product) is higher for cutting applications than for brazing and thin metal welding. High power applications, such as hardening, cladding, and deep penetrating welding, require multiple kW of optical power, and are used in a broad range of industrial processes.

Micro material processing is a category that includes all laser material processing applications under 1 kilowatt. The use of lasers in Micro Materials Processing has found broad application in the development and manufacturing of screens for smartphones, tablet computers, and LED TVs.

A detailed list of industrial and commercial laser applications includes:

• Laser cutting
• Laser welding
• Laser drilling
• Laser marking
• Laser cladding, a surface engineering process applied to mechanical components for reconditioning, repair work or hardfacing
• Photolithography
• Optical communications over optical fiber or in free space
• Laser peening
• Guidance systems (e.g., ring laser gyroscopes)
• Rangefinder / surveying,
• LIDAR / pollution monitoring,
• Digital minilabs
• Barcode readers
• Laser engraving of printing plate
• Laser bonding of additive marking materials for decoration and identification,
• Laser pointers
• Laser accelerometers
• OLED display manufacturing
• Holography
• Bubblegrams
• Optical tweezers
• Writing subtitles onto motion picture films.
• Power beaming, which is a possible solution to transfer energy to the climber of a Space elevator
• 3D laser scanners for accurate 3D measurement
• Laser line levels are used in surveying and construction. Lasers are also used for guidance for aircraft.
• Extensively in both consumer and industrial imaging equipment.
• In laser printers: gas and diode lasers play a key role in manufacturing high resolution printing plates and in image scanning equipment.
• Diode lasers are used as a lightswitch in industry, with a laser beam and a receiver which will switch on or off when the beam is interrupted, and because a laser can keep the light intensity over larger distances than a normal light, and is more precise than a normal light it can be used for product detection in automated production.
• Laser alignment
• Additive manufacturing
• plastic welding

In consumer electronics, telecommunications, and data communications, lasers are used as the transmitters in optical communications over optical fiber and free space.

• To store and retrieve data in optical discs
• Laser lighting displays (pictured) accompany many music concerts.

Images

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  RGB Lasers

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  Q-line Laser

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  Lasers were used in the 2005 Classical Spectacular concert

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  A laser harp

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  The surface of a test target is instantly vaporized and bursts into flame upon irradiation by a high power continuous wave carbon dioxide laser emitting tens of kilowatts of far infrared light. Note the operator is standing behind sheets of plexiglas, which is opaque in the far infrared.

See also

• List of laser articles
• Non-lethal weapon

External links

• The International Scientific Laboratory for Optical Diagnostics
• How to make a Burning Laser Gun
• Coherent.com article on Applications for lasers