Laser weapon

A laser weapon^[2] is a type of directed-energy weapon that uses lasers to inflict damage. Whether they will be deployed as practical, high-performance military weapons remains to be seen.^[3][4] One of the major issues with laser weapons is atmospheric thermal blooming, which is still largely unsolved. This issue is exacerbated when there is fog, smoke, dust, rain, snow, smog, foam, or purposely dispersed obscurant chemicals present. In essence, a laser generates a beam of light that requires clear air or a vacuum to operate.^[5]

Many types of laser have been identified as having the potential to be used as incapacitating non-lethal weapons. They can cause temporary or permanent vision loss when directed at the eyes. The extent, nature, and duration of visual impairment resulting from exposure to laser light depend on various factors, such as the laser's power, wavelength(s), collimation of the beam, orientation of the beam, and duration of exposure. Even lasers with a power output of less than one watt can cause immediate and permanent vision loss under certain conditions, making them potentially non-lethal but incapacitating weapons. However, the use of such lasers is morally controversial due to the extreme handicap that laser-induced blindness represents. The Protocol on Blinding Laser Weapons bans the use of weapons designed to cause permanent blindness. Weapons designed to cause temporary blindness, known as dazzlers, are used by military and sometimes law enforcement organizations. Incidents of pilots being exposed to lasers while flying have prompted aviation authorities to implement special procedures to deal with such hazards.^[6]

Laser weapons capable of directly damaging or destroying a target in combat are still in the experimental stage. The general idea of laser-beam weaponry is to hit a target with a train of brief pulses of light. The United States Navy has tested the very short-range (1 mile), 30-kW Laser Weapon System or LaWS to be used against targets like small UAVs, rocket-propelled grenades, and visible motorboat or helicopter engines.^[7][8] It has been described as "six welding lasers strapped together." A 60 kW system, HELIOS, is being developed for destroyer-class ships as of 2020^[update].^[9]

Laser-based directed-energy weapons have been under development for defense purposes, particularly for the destruction of incoming missiles. One such example is the Boeing Airborne Laser, constructed inside a Boeing 747 and designated as the YAL-1. This system was designed to eliminate short- and intermediate-range ballistic missiles during their boost phase.^[10] It was canceled in 2012.

Another laser-based defense system was researched for the Strategic Defense Initiative (SDI, nicknamed "Star Wars") and its successor programs. This project aimed to employ ground-based or space-based laser systems to destroy incoming intercontinental ballistic missiles (ICBMs). However, various practical challenges, such as directing a laser over a large distance through the atmosphere, complicated the implementation of these systems. Optical scattering and refraction would bend and distort the laser beam, making it difficult to aim and reducing its efficiency.

A related concept from the SDI project was the nuclear-pumped X-ray laser, an orbiting atomic bomb surrounded by laser media in the form of glass rods. When the bomb detonated, the rods would be exposed to highly-energetic gamma-ray photons, causing spontaneous and stimulated emission of X-ray photons within the rod atoms. This process would result in optical amplification of the X-ray photons, generating an X-ray laser beam that would be minimally affected by atmospheric distortion and capable of destroying ICBMs in flight. However, the X-ray laser would be a single-use device, as it would destroy itself upon activation. Some initial tests of this concept were conducted with underground nuclear testing, but the results were not promising. Research into this approach to missile defense was discontinued after the SDI program was canceled.

Iron Beam is a laser-based air defense system which was unveiled at the Singapore Airshow on February 11, 2014^[11] by Israeli defense contractor Rafael Advanced Defense Systems.^[12] The system is designed to destroy short-range rockets, artillery, and mortar bombs; it has a range of up to 7 km (4.3 mi), too close for the Iron Dome system to intercept projectiles effectively.^[12][13] In addition, the system could also intercept unmanned aerial vehicles (UAVs).^[14] Iron Beam will constitute the sixth element of Israel's integrated air defense system,^[12] in addition to Arrow 2, Arrow 3, David's Sling, Barak 8, and Iron Dome.^[15]

Iron Beam uses a fiber laser to destroy an airborne target. Whether acting as a stand-alone system or with external cueing as part of an air-defense system, a threat is detected by a surveillance system and tracked by vehicle platforms in order to engage.^[16]

Iron Beam is expected to be operational by the end of 2025.^[17][18]

In the 21st century, several countries have developed anti-drone laser systems to counter the increasing threat of small unmanned aerial vehicles (UAVs). These systems are designed to detect, track, and destroy drones using high-powered lasers, offering a cost-effective and flexible solution for airspace protection.

In the United States, Lockheed Martin demonstrated the capabilities of its ATHENA laser system in 2017, which uses a 30-kilowatt ALADIN laser to target and destroy UAVs.^[19] Another American company, Raytheon, developed the High-Energy Laser Weapon System (HELWS) in 2019, which is capable of detecting and destroying drones at a distance of up to three kilometers.^[19]

Turkey has also invested in the development of laser weapons, with companies like Roketsan producing the ALKA system, which combines laser and electromagnetic weapons to incapacitate and destroy single or group targets.^[19] Other Turkish companies, such as Aselsan and TUBITAK BILGEM, have also demonstrated laser systems capable of targeting small UAVs and explosive devices.^[19]

Germany is another leader in the development of combat laser systems, with defense company Rheinmetall working on stationary and mobile versions of its High Energy Laser (HEL) system since the 2000s.^[19] Rheinmetall's lasers are designed to protect against a variety of threats, including small and medium-sized UAVs, helicopters, missiles, mines, and artillery shells.^[19]

Israel has also been actively developing laser weapons, with companies like Rafael Advanced Defense Systems demonstrating the compact Drone Dome system in 2020, which is designed to destroy UAVs and their swarms.^[19] Another Israeli system, called Light Blade, was developed by OptiDefense to counter terrorist threats such as mini UAVs and explosive devices attached to balloons or kites.^[19]

The development and deployment of these anti-drone laser systems show the increasing importance of protecting airspace from emerging threats, while also providing a cost-effective and flexible solution for defense forces around the world.

An electrolaser first ionizes its target path, and then sends an electric current down the conducting track of ionized plasma, somewhat like lightning. It functions as a giant, high-energy, long-distance version of the Taser or stun gun.

Pulsed Energy Projectile or PEP systems emit an infrared laser pulse which creates rapidly expanding plasma at the target. The resulting sound, shock and electromagnetic waves stun the target and cause pain and temporary paralysis. The weapon is under development and is intended as a non-lethal weapon in crowd control though it can also be used as a lethal weapon.

A dazzler is a directed-energy weapon intended to temporarily blind or disorient its target with intense directed radiation. Targets can include sensors or human vision. Dazzlers emit infrared or invisible light against various electronic sensors, and visible light against humans, when they are intended to cause no long-term damage to eyes. The emitters are usually lasers, making what is termed a laser dazzler. Most of the contemporary systems are man-portable, and operate in either the red (a laser diode) or green (a diode-pumped solid-state laser, DPSS) areas of the electromagnetic spectrum.

Initially developed for military use, non-military products are becoming available for use in law enforcement and security.^[20][21]

The personnel halting and stimulation response rifle (PHASR) is a prototype non-lethal laser dazzler developed by the Air Force Research Laboratory's Directed Energy Directorate, U.S. Department of Defense.^[22] Its purpose is to temporarily disorient and blind a target. Blinding laser weapons have been tested in the past, but were banned under the 1995 United Nations Protocol on Blinding Laser Weapons, which the United States acceded to on 21 January 2009.^[23] The PHASR rifle, a low-intensity laser, is not prohibited under this regulation, as the blinding effect is intended to be temporary. It also uses a two-wavelength laser.^[24] The PHASR was tested at Kirtland Air Force Base, part of the Air Force Research Laboratory Directed Energy Directorate in New Mexico.

• ZM-87
• PY132A is a Chinese anti-drone dazzler.^[25]
• Soviet laser pistol was a prototype weapon designed for cosmonauts.
• Optical Dazzling Interdictor, Navy (AN/SEQ-4 ODIN) is a U.S. laser to be field tested in 2019 on an Arleigh Burke-class destroyer.^[26]

Leading Western companies in the development of laser weapons have been Boeing, Northrop Grumman, Lockheed Martin, Netherlands Organisation for Applied Scientific Research, Rheinmetall and MBDA.^{[27][28][29][30][31]}

Most of these projects have been canceled, discontinued, never went beyond the prototype or experimental stage, or are only used in niche applications like dazzling, blinding, mine clearance or close defense against small, unprotected targets. Effective, high performance laser weapons seem to be difficult to achieve using current or near-future technology.^[4][3][89]

Laser beams begin to cause plasma breakdown in the atmosphere at energy densities of around one megajoule per cubic centimeter. This effect, called "blooming," causes the laser to defocus and disperse energy into the surrounding air. Blooming can be more severe if there is fog, smoke, dust, rain, snow, smog, or foam in the air.

Techniques that may reduce these effects include:

• Spreading the beam across a large, curved mirror that focuses the power on the target, to keep energy density en route too low for blooming to happen. This requires a large, very precise, fragile mirror, mounted somewhat like a searchlight, requiring bulky machinery to slew the mirror to aim the laser.
• Using a phased array. For typical laser wavelengths, this method would require billions of micrometer-size antennae. There is currently no known way to implement these, though carbon nanotubes have been proposed. Phased arrays could theoretically also perform phase-conjugate amplification (see below). Phased arrays do not require mirrors or lenses, and can be made flat and thus do not require a turret-like system (as in "spread beam") to be aimed, though range will suffer if the target is at extreme angles to the surface of the phased array.^[90]
• Using a phase-conjugate laser system. This method employs a "finder" or "guide" laser illuminating the target. Any mirror-like ("specular") points on the target reflect light that is sensed by the weapon's primary amplifier. The weapon then amplifies inverted waves, in a positive feedback loop, destroying the target, with shockwaves as the specular regions evaporate. This avoids blooming because the waves from the target pass through the blooming, and therefore show the most conductive optical path; this automatically corrects for the distortions caused by blooming. Experimental systems using this method usually use special chemicals to form a "phase-conjugate mirror". In most systems, however, the mirror overheats dramatically at weapon-useful power levels.
• Using a very short pulse that finishes before blooming interferes, but this requires a very high power laser to concentrate large amounts of energy in that pulse which does not exist in a weaponized or easily weaponizable form.^[a]
• Focusing multiple lasers of relatively low power on a single target. This is increasingly bulky as the total power of the system increases.

Essentially, a laser generates a beam of light which will be delayed or stopped by any opaque medium and perturbed by any translucent or less than perfectly transparent medium just like any other type of light. A simple, dense smoke screen can and will often block a laser beam. Infrared or multi-spectrum^[91] smoke grenades or generators will also disturb or block infrared laser beams. Any opaque case, cowling, bodywork, fuselage, hull, wall, shield or armor will absorb at least the "first impact" of a laser weapon, so the beam must be sustained to achieve penetration.

The Chinese People's Liberation Army has invested in the development of specialized coatings that can deflect beams fired by U.S. military lasers. Laser light can be deflected, reflected, or absorbed by manipulating physical and chemical properties of materials. Artificial coatings can counter certain specific types of lasers, but a different type of laser may match the coating's absorption spectrum enough to transfer damaging amounts of energy. The coatings are made of several different substances, including low-cost metals, rare earths, carbon fiber, silver, and diamonds that have been processed to fine sheens and tailored against specific laser weapons. China is developing anti-laser defenses because protection against them is considered far cheaper than creating competing laser weapons.^[92]

Dielectric mirrors, inexpensive ablative coatings, thermal transport delay, and obscurants are also being studied as countermeasures.^[93] In not a few operational situations, even simple, passive countermeasures like rapid rotation (which spreads the heat and does not allow a fixed targeting point except in strictly frontal engagements), higher acceleration (which increases the distance and changes the angle quickly), or agile maneuvering during the terminal attack phase (which hampers the ability to target a vulnerable point, forces a constant re-aiming or tracking with close to zero lag, and allows for some cooling) can defeat or help to defeat non-highly pulsed, high-energy laser weapons.^[94]

Arthur C. Clarke envisaged particle beam weapons in his 1955 novel Earthlight, in which energy would be delivered by high-velocity beams of matter.^[95] After the invention of the laser in 1960, it briefly became the death ray of choice for science fiction writers.^[96] By the late 1960s and 1970s, as the laser's limits as a weapon became evident, the ray gun began to be replaced by similar weapons with names that better reflected the destructive capabilities of the device, such as the blaster in Star Wars or phasers in Star Trek, which were originally lasers.

• Directed-energy weapon
• Ivan's hammer
• Laser sight
• Space weapon
• Weapons in science fiction