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, t ...

is 1315 nm, a transition wavelength of atomic iodine. Airbornelaserturret

Principles of operation

The laser is fed with gaseous

chlorine Chlorine is a chemical element with the 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 between them. Chlorine i ...

, molecular iodine, 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, 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 iodine 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 and lases at 1.315 μm in the optical resonator 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 Sig ...

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 mea ...

, 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 ch ...

but is well absorbed by metals, making it suitable for laser cutting and drilling. Rapid cutting of stainless steel 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 and advanced tactical laser 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 rocke ...

off the central

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

coast in a test conducted with a laser aboard a Boeing 747 that took off from the Point Mugu Naval Air Warfare Center (for more details, see Boeing YAL-1).

Other iodine based lasers

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