A chemical oxygen iodine laser (COIL) is a near–

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

chemical laser A chemical laser is a laser that obtains its energy from a chemical reaction. Chemical lasers can reach continuous wave output with power reaching to megawatt levels. They are used in industry for cutting and drilling. Common examples of chemical ...

. As the beam is infrared, it cannot be seen with the naked eye. It is capable of output power scaling up to megawatts in continuous mode. Its output

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

is 1315 nm, a transition wavelength of atomic

iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

Principles of operation

The laser is fed with gaseous

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

, molecular

, and an aqueous mixture of

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

and

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

. The aqueous peroxide solution undergoes

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

with chlorine, producing heat,

potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...

, and oxygen in excited state, singlet delta oxygen. Spontaneous transition of excited oxygen to the triplet sigma ground state is forbidden giving the excited oxygen a spontaneous lifetime of about 45 minutes. This allows the singlet oxygen to transfer its energy to the

atoms present in the gas stream;the atomic transition 2P3/2 to 2P1/2 in atomic iodine is nearly resonant with the singlet oxygen, so the energy transfer during the collision of the particles is rapid. The excited iodine atoms 2P1/2 then undergoes

stimulated emission Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level. The liberated energy transfers to th ...

and lases at 1.315 μm in the

optical resonator An optical cavity, resonating cavity or optical resonator is an arrangement of mirrors or other optical elements that forms a cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and provi ...

region of the laser. ( the upper and lower iodine atomic states are reversed with the 2P1/2 being the upper state) The laser operates at relatively low gas pressures, but the gas flow has to be nearing the speed of sound at the reaction time; even supersonic flow designs are described. The low pressure and fast flow make removal of heat from the lasing medium easy, in comparison with high-power solid-state lasers. The reaction products are potassium chloride, water, and oxygen. Traces of chlorine and iodine are removed from the exhaust gases by a halogen scrubber.

History and applications

COIL was developed by the

US Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...

in 1977, for military purposes. However, its properties make it useful for industrial processing as well; the beam is focusable and can be transferred by an

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

, as its wavelength is not absorbed much by

fused silica Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO2) in amorphous (non-crystalline) form. This differs from all other commercial glasses in which other ingredients are added which change ...

but is well absorbed by metals, making it suitable for laser cutting and drilling. Rapid cutting of

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

and

hastelloy Haynes International, Inc., headquartered in Kokomo, Indiana, is one of the largest producers of corrosion-resistant and high-temperature alloys. In addition to Kokomo, Haynes has manufacturing facilities in Arcadia, Louisiana, and Mountain Home, ...

with a fiber-coupled COIL has been demonstrated. In 1996, TRW Incorporated managed to get a continuous beam of hundreds of kilowatts of power that lasted for several seconds. RADICL, Research Assessment, Device Improvement Chemical Laser, is a 20 kW COIL laser tested by the United States Air Force in around 1998. COIL is a component of the United States' military

airborne laser An airborne laser (ABL) is a laser system operated from a flying platform, as in the: * Soviet/Russian Beriev A-60 (1981, active) * American Boeing YAL-1 (2002-2012, scrapped) * An American modified NKC-135A unit (1975-1984, in storage.) Developm ...

and

advanced tactical laser The Advanced Tactical Laser (ATL) program was a US military program to mount a high energy laser weapon on an aircraft, initially the AC-130 gunship, for use against ground targets in urban or other areas where minimizing collateral damage is impo ...

programs. On February 11, 2010, this weapon was successfully deployed to shoot down a

missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...

off the central

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

coast in a test conducted with a laser aboard a

Boeing 747 The Boeing 747 is a large, long-range wide-body airliner designed and manufactured by Boeing Commercial Airplanes in the United States between 1968 and 2022. After introducing the 707 in October 1958, Pan Am wanted a jet times its size, t ...

that took off from the Point Mugu Naval Air Warfare Center (for more details, see

Boeing YAL-1 The Boeing YAL-1 Airborne Laser Testbed (formerly Airborne Laser) weapons system was a megawatt-class chemical oxygen iodine laser (COIL) mounted inside a modified military Boeing 747-400F. It was primarily designed as a missile defense syste ...

Other iodine based lasers

All gas-phase iodine laser All gas-phase iodine laser (AGIL)Anil K. Maini. is a chemical laser using gaseous iodine as a lasing medium. Like the chemical oxygen iodine laser (COIL), it operates at the 1.315 µm wavelength (near-infrared). AGIL was developed in order to elim ...

(AGIL) is a similar construction using all-gas reagents, more suitable for aerospace applications. The

ElectricOIL The Electric Oxygen Iodine Laser, or ElectricOIL, or EOIL, is an infrared hybrid electrical / chemical laser. Its output wavelength is 1.315 μm, the wavelength of transition of atomic iodine. The lasing state I* is produced by near-resonant e ...

, or EOIL, offers the same iodine lasing species in an alternate gas-electric hybrid variant.

References

{{Chemical lasers

Principles of operation

History and applications

Other iodine based lasers

See also

References

External links