Excimer laser
Encyclopedia
An excimer laser is a form of ultraviolet laser which is commonly used in the production of microelectronic devices (semiconductor integrated circuits or “chips”), eye surgery
, and micromachining.
is short for 'excited dimer', while exciplex is short for 'excited complex
.' Most "excimer" lasers are of the noble gas halide type, for which the term excimer is strictly speaking a misnomer (since a dimer refers to a molecule of two identical or similar parts): The correct but less commonly used name for such is exciplex laser.
in Moscow
, using a xenon
dimer (Xe2) excited by an electron
beam to give stimulated emission
at 172 nm
wavelength. A later improvement, developed by many groups in 1975 was the use of noble gas
halides
(originally Xe
Br
). These groups include the Avco Everett Research Laboratory, Sandia Laboratories, the Northrop Research and Technology Center, and the United States Government's Naval Research Laboratory who also developed a XeCl Laser that was excited using a microwave discharge.
a combination of a noble gas
(argon
, krypton
, or xenon
) and a reactive
gas (fluorine
or chlorine
). Under the appropriate conditions of electrical stimulation and high pressure, a pseudo-molecule
called an excimer
(or in the case of noble gas halides, exciplex) is created, which can only exist in an energized state and can give rise to laser
light in the ultraviolet
range.
, but a repulsive (dissociative) ground state
. This is because noble gases such as xenon and krypton
are highly inert
and do not usually form chemical compound
s. However, when in an excited state (induced by an electrical discharge or high-energy electron beams, which produce high energy pulses), they can form temporarily-bound molecules with themselves (dimers) or with halogens (complexes
) such as fluorine
and chlorine
. The excited compound can give up its excess energy by undergoing spontaneous
or stimulated emission, resulting in a strongly repulsive ground state molecule which very quickly (on the order of a picosecond
) dissociates back into two unbound atoms. This forms a population inversion
.
of an excimer laser depends on the molecules used, and is usually in the ultraviolet:
Excimer lasers, such as XeF and KrF, can also be made slightly tunable using a variety of prism and grating intracavity arrangements.
and a pulse duration of ~10 ns
, although some operate at pulse repetition rates as high as 8 kHz and some have pulsewidths as large as 30 ns.
For electric discharge pump see: Nitrogen laser
.
s. Rather than burning or cutting material, the excimer laser adds enough energy to disrupt the molecular bonds of the surface tissue, which effectively disintegrates into the air in a tightly controlled manner through ablation
rather than burning. Thus excimer lasers have the useful property that they can remove exceptionally fine layers of surface material with almost no heating or change to the remainder of the material which is left intact. These properties make excimer lasers well suited to precision micromachining organic material (including certain polymer
s and plastics), or delicate surgeries
such as eye surgery
LASIK
.
Excimer lasers are widely used in high-resolution photolithography
machines, one of the critical technologies required for microelectronic chip manufacturing. Current state-of-the-art lithography tools use deep ultraviolet (DUV) light from the KrF and ArF excimer lasers with wavelengths of 248 and 193 nanometers (the dominant lithography technology today is thus also called “excimer laser lithography”), which has enabled transistor feature sizes to shrink below 45 nanometers. Excimer laser lithography has thus played a critical role in the continued advance of the so-called Moore’s law for the last 20 years.
The most widespread industrial application of excimer lasers has been in deep-ultraviolet photolithography
, a critical technology used in the manufacturing of microelectronic devices (i.e., semiconductor integrated circuits or “chips”). Historically, from the early 1960s through the mid-1980s, mercury-xenon lamps had been used in lithography for their spectral lines at 436, 405 and 365 nm wavelengths. However, with the semiconductor industry’s need for both higher resolution (to produce denser and faster chips) and higher throughput (for lower costs), the lamp-based lithography tools were no longer able to meet the industry’s requirements. This challenge was overcome when in a pioneering development in 1982, deep-UV excimer laser lithography was proposed and demonstrated at I.B.M. by K. Jain. With phenomenal advances made in equipment technology in the last two decades, and today microelectronic devices fabricated using excimer laser lithography totaling $400 billion in annual production, it is the semiconductor industry view that excimer laser lithography has been a crucial factor in the continued advance of Moore’s law, enabling minimum features sizes in chip manufacturing to shrink from 0.5 micrometer in 1990 to below 45 nanometers in 2010. This trend is expected to continue into this decade for even denser chips, with minimum features approaching 10 nanometers. From an even broader scientific and technological perspective, since the invention of the laser in 1960, the development of excimer laser lithography has been highlighted as one of the major milestones in the 50-year history of the laser.
The high-power ultraviolet output of excimer lasers also makes them useful for surgery (particularly eye surgery) and for dermatological treatment. Excimer laser light is typically absorbed within the first billionth of a meter (nanometer) of tissue. In 1980 - 1983, Samuel Blum was working with Rangaswamy Srinivasan
and James Wynne at IBM
’s T. J. Watson Research Center
when they observed the effect of the ultraviolet excimer laser on biological materials. Intrigued, they investigated further, finding that the laser made clean, precise cuts that would be ideal for delicate surgeries. This resulted in a fundamental patent and Blum, Srinivasan, and Wynne were elected to the National Inventors Hall of Fame
in 2002. Subsequent work introduced the excimer laser for use in angioplasty
. Kansas State University
pioneered the study of the excimer laser which made LASIK
surgery possible.http://www.mediarelations.k-state.edu/WEB/News/NewsReleases/priorasaccomplishments.html Xenon chloride (308 nm) excimer lasers can also treat a variety of dermatological conditions including psoriasis, vitiligo, atopic dermatitis, alopecia areata and leukoderma.
For applications in deep-UV photolithography for semiconductor chip manufacturing, excimer lasers have been highly industrialized, making them extremely reliable and easily serviceable. However, as light sources, excimer lasers are generally large in size, which is a disadvantage in their medical applications, although their sizes are rapidly decreasing with ongoing development.
Excimer lasers are also widely used in numerous fields of scientific research, both as primary sources and, particularly the XeCl laser, as pump sources for tunable dye lasers, mainly to excite laser dyes emitting in the blue-green region of the spectrum.
Eye surgery
Eye surgery, also known as orogolomistician surgery or ocular surgery, is surgery performed on the eye or its adnexa, typically by an ophthalmologist.-Preparation and precautions:...
, and micromachining.
Terminology
The term excimerExcimer
An excimer is a short-lived dimeric or heterodimeric molecule formed from two species, at least one of which is in an electronic excited state. Excimers are often diatomic and are composed of two atoms or molecules that would not bond if both were in the ground state. The lifetime of an excimer is...
is short for 'excited dimer', while exciplex is short for 'excited complex
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
.' Most "excimer" lasers are of the noble gas halide type, for which the term excimer is strictly speaking a misnomer (since a dimer refers to a molecule of two identical or similar parts): The correct but less commonly used name for such is exciplex laser.
History
The first excimer laser was invented in 1970 by Nikolai Basov, V. A. Danilychev and Yu. M. Popov, at the Lebedev Physical InstituteLebedev Physical Institute
The Lebedev Physics Institute of the Russian Academy of Sciences , situated in Moscow, is one of the leading Russian research institutes specializing in physics. It is also one of the oldest research institutions in Russia: its history dates back to a collection of physics equipment established by...
in Moscow
Moscow
Moscow is the capital, the most populous city, and the most populous federal subject of Russia. The city is a major political, economic, cultural, scientific, religious, financial, educational, and transportation centre of Russia and the continent...
, using a xenon
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
dimer (Xe2) excited by an electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
beam to give stimulated emission
Stimulated emission
In optics, stimulated emission is the process by which an atomic electron interacting with an electromagnetic wave of a certain frequency may drop to a lower energy level, transferring its energy to that field. A photon created in this manner has the same phase, frequency, polarization, and...
at 172 nm
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
wavelength. A later improvement, developed by many groups in 1975 was the use of noble gas
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
halides
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
(originally Xe
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
Br
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
). These groups include the Avco Everett Research Laboratory, Sandia Laboratories, the Northrop Research and Technology Center, and the United States Government's Naval Research Laboratory who also developed a XeCl Laser that was excited using a microwave discharge.
Construction
An excimer laser typically usesLaser construction
A laser is constructed from three principal parts:*An energy source ,*A gain medium or laser medium, and*Two or more mirrors that form an optical resonator.-Pump source:...
a combination of a noble gas
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
(argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
, krypton
Krypton
Krypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
, or xenon
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
) and a reactive
Reactive
Reactive may refer to:*Generally, capable of having a reaction*Reactance , the imaginary component of AC impedance*Reactive mind*Reactive programming...
gas (fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
or chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
). Under the appropriate conditions of electrical stimulation and high pressure, a pseudo-molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
called an excimer
Excimer
An excimer is a short-lived dimeric or heterodimeric molecule formed from two species, at least one of which is in an electronic excited state. Excimers are often diatomic and are composed of two atoms or molecules that would not bond if both were in the ground state. The lifetime of an excimer is...
(or in the case of noble gas halides, exciplex) is created, which can only exist in an energized state and can give rise to laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
light in the ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
range.
Operation
Laser action in an excimer molecule occurs because it has a bound (associative) excited stateExcited state
Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
, but a repulsive (dissociative) ground state
Ground state
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state...
. This is because noble gases such as xenon and krypton
Krypton
Krypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
are highly inert
Inert
-Chemistry:In chemistry, the term inert is used to describe a substance that is not chemically reactive.The noble gases were previously known as inert gases because of their perceived lack of participation in any chemical reactions...
and do not usually form chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s. However, when in an excited state (induced by an electrical discharge or high-energy electron beams, which produce high energy pulses), they can form temporarily-bound molecules with themselves (dimers) or with halogens (complexes
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
) such as fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
. The excited compound can give up its excess energy by undergoing spontaneous
Spontaneous emission
Spontaneous emission is the process by which a light source such as an atom, molecule, nanocrystal or nucleus in an excited state undergoes a transition to a state with a lower energy, e.g., the ground state and emits a photon...
or stimulated emission, resulting in a strongly repulsive ground state molecule which very quickly (on the order of a picosecond
Picosecond
A picosecond is 10−12 of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to 31,700 years....
) dissociates back into two unbound atoms. This forms a population inversion
Population inversion
In physics, specifically statistical mechanics, a population inversion occurs when a system exists in state with more members in an excited state than in lower energy states...
.
Wavelength determination
The wavelengthWavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of an excimer laser depends on the molecules used, and is usually in the ultraviolet:
| Excimer | Wavelength | Relative Power mW |
|---|---|---|
| Ar2* | 126 nm | |
| Kr2* | 146 nm | |
| Xe2* | 172 & 175 nm | |
| ArF | 193 nm | 60 |
| KrF | 248 nm | 100 |
| XeBr | 282 nm | |
| XeCl | 308 nm | 50 |
| XeF | 351 nm | 45 |
| KrCl | 222 nm | 25 |
Excimer lasers, such as XeF and KrF, can also be made slightly tunable using a variety of prism and grating intracavity arrangements.
Repetition rate
Excimer lasers are usually operated with a pulse repetition rate of around 100 HzHertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
and a pulse duration of ~10 ns
Nanosecond
A nanosecond is one billionth of a second . One nanosecond is to one second as one second is to 31.7 years.The word nanosecond is formed by the prefix nano and the unit second. Its symbol is ns....
, although some operate at pulse repetition rates as high as 8 kHz and some have pulsewidths as large as 30 ns.
For electric discharge pump see: Nitrogen laser
Nitrogen laser
A nitrogen laser is a gas laser operating in the ultraviolet range using molecular nitrogen as its gain medium, pumped by an electrical discharge....
.
Major applications
The UV light from an excimer laser is well absorbed by biological matter and organic compoundOrganic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s. Rather than burning or cutting material, the excimer laser adds enough energy to disrupt the molecular bonds of the surface tissue, which effectively disintegrates into the air in a tightly controlled manner through ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
rather than burning. Thus excimer lasers have the useful property that they can remove exceptionally fine layers of surface material with almost no heating or change to the remainder of the material which is left intact. These properties make excimer lasers well suited to precision micromachining organic material (including certain polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s and plastics), or delicate surgeries
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
such as eye surgery
Eye surgery
Eye surgery, also known as orogolomistician surgery or ocular surgery, is surgery performed on the eye or its adnexa, typically by an ophthalmologist.-Preparation and precautions:...
LASIK
LASIK
LASIK or Lasik , commonly referred to simply as laser eye surgery, is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism...
.
Excimer lasers are widely used in high-resolution photolithography
Photolithography
Photolithography is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate...
machines, one of the critical technologies required for microelectronic chip manufacturing. Current state-of-the-art lithography tools use deep ultraviolet (DUV) light from the KrF and ArF excimer lasers with wavelengths of 248 and 193 nanometers (the dominant lithography technology today is thus also called “excimer laser lithography”), which has enabled transistor feature sizes to shrink below 45 nanometers. Excimer laser lithography has thus played a critical role in the continued advance of the so-called Moore’s law for the last 20 years.
The most widespread industrial application of excimer lasers has been in deep-ultraviolet photolithography
Photolithography
Photolithography is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate...
, a critical technology used in the manufacturing of microelectronic devices (i.e., semiconductor integrated circuits or “chips”). Historically, from the early 1960s through the mid-1980s, mercury-xenon lamps had been used in lithography for their spectral lines at 436, 405 and 365 nm wavelengths. However, with the semiconductor industry’s need for both higher resolution (to produce denser and faster chips) and higher throughput (for lower costs), the lamp-based lithography tools were no longer able to meet the industry’s requirements. This challenge was overcome when in a pioneering development in 1982, deep-UV excimer laser lithography was proposed and demonstrated at I.B.M. by K. Jain. With phenomenal advances made in equipment technology in the last two decades, and today microelectronic devices fabricated using excimer laser lithography totaling $400 billion in annual production, it is the semiconductor industry view that excimer laser lithography has been a crucial factor in the continued advance of Moore’s law, enabling minimum features sizes in chip manufacturing to shrink from 0.5 micrometer in 1990 to below 45 nanometers in 2010. This trend is expected to continue into this decade for even denser chips, with minimum features approaching 10 nanometers. From an even broader scientific and technological perspective, since the invention of the laser in 1960, the development of excimer laser lithography has been highlighted as one of the major milestones in the 50-year history of the laser.
The high-power ultraviolet output of excimer lasers also makes them useful for surgery (particularly eye surgery) and for dermatological treatment. Excimer laser light is typically absorbed within the first billionth of a meter (nanometer) of tissue. In 1980 - 1983, Samuel Blum was working with Rangaswamy Srinivasan
Rangaswamy Srinivasan
Rangaswamy Srinivasan is an inventor at IBM Research. One of the famous inventions he has contributed to is LASIK.-Ablative Photodecomposition :...
and James Wynne at IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
’s T. J. Watson Research Center
Thomas J. Watson Research Center
The Thomas J. Watson Research Center is the headquarters for the IBM Research Division.The center is on three sites, with the main laboratory in Yorktown Heights, New York, 38 miles north of New York City, a building in Hawthorne, New York, and offices in Cambridge, Massachusetts.- Overview :The...
when they observed the effect of the ultraviolet excimer laser on biological materials. Intrigued, they investigated further, finding that the laser made clean, precise cuts that would be ideal for delicate surgeries. This resulted in a fundamental patent and Blum, Srinivasan, and Wynne were elected to the National Inventors Hall of Fame
National Inventors Hall of Fame
The National Inventors Hall of Fame is a not-for-profit organization dedicated to recognizing, honoring and encouraging invention and creativity through the administration of its programs. The Hall of Fame honors the men and women responsible for the great technological advances that make human,...
in 2002. Subsequent work introduced the excimer laser for use in angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
. Kansas State University
Kansas State University
Kansas State University, commonly shortened to K-State, is an institution of higher learning located in Manhattan, Kansas, in the United States...
pioneered the study of the excimer laser which made LASIK
LASIK
LASIK or Lasik , commonly referred to simply as laser eye surgery, is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism...
surgery possible.http://www.mediarelations.k-state.edu/WEB/News/NewsReleases/priorasaccomplishments.html Xenon chloride (308 nm) excimer lasers can also treat a variety of dermatological conditions including psoriasis, vitiligo, atopic dermatitis, alopecia areata and leukoderma.
For applications in deep-UV photolithography for semiconductor chip manufacturing, excimer lasers have been highly industrialized, making them extremely reliable and easily serviceable. However, as light sources, excimer lasers are generally large in size, which is a disadvantage in their medical applications, although their sizes are rapidly decreasing with ongoing development.
Excimer lasers are also widely used in numerous fields of scientific research, both as primary sources and, particularly the XeCl laser, as pump sources for tunable dye lasers, mainly to excite laser dyes emitting in the blue-green region of the spectrum.
See also
- Krypton fluoride laserKrypton fluoride laserA krypton fluoride laser is a particular type of excimer laser, which is sometimes called an exciplex laser. With its 248 nanometer wavelength, it is a deep ultraviolet laser which is commonly used in the production of semiconductor integrated circuits, industrial micromachining, and scientific...
- ExcimerExcimerAn excimer is a short-lived dimeric or heterodimeric molecule formed from two species, at least one of which is in an electronic excited state. Excimers are often diatomic and are composed of two atoms or molecules that would not bond if both were in the ground state. The lifetime of an excimer is...
- PhotolithographyPhotolithographyPhotolithography is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate...
- Moore's lawMoore's LawMoore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
- Beam homogenizerBeam homogenizerA beam homogenizer is a device that smooths out the irregularities in a laser beam profile and creates a more uniform one. Most beam homogenizers use a multifaceted mirror with square facets. The mirror reflects light at different angles to create a beam with uniform power across the whole beam...
- ElectrolaserElectrolaserAn electrolaser is a type of electroshock weapon which is also a directed-energy weapon. It uses lasers to form an electrically conductive laser-induced plasma channel...