List of laser types
Gas lasers
Table:
Laser gain medium and type

Operation wavelength(s)

Pump source

Applications and notes

Helium–neon laser

632.8 nm (543.5 nm, 593.9 nm, 611.8 nm, 1.1523 μm, 1.52 μm, 3.3913 μm)

Electrical discharge

Interferometry, holography, spectroscopy, barcode scanning, alignment, optical demonstrations.

Argon laser

454.6 nm, 488.0 nm, 514.5 nm (351 nm, 363.8, 457.9 nm, 465.8 nm, 476.5 nm, 472.7 nm, 528.7 nm, also frequency doubled to provide 244 nm, 257 nm)

Electrical discharge

Retinal phototherapy (for diabetes), lithography, confocal microscopy, spectroscopy pumping other lasers.

Krypton laser

416 nm, 530.9 nm, 568.2 nm, 647.1 nm, 676.4 nm, 752.5 nm, 799.3 nm

Electrical discharge

Scientific research, mixed with argon to create "white-light" lasers, light shows.

Xenon ion laser

Many lines throughout visible spectrum extending into the UV and IR.

Electrical discharge

Scientific research.

Nitrogen laser

337.1 nm

Electrical discharge

Pumping of dye lasers, measuring air pollution, scientific research. Nitrogen lasers can operate superradiantly (without a resonator cavity). Amateur laser construction. See TEA laser

Carbon dioxide laser

10.6 μm, (9.4 μm)

Transverse (high-power) or longitudinal (low-power) electrical discharge

Material processing (laser cutting, laser beam welding, etc.), surgery, dental laser, military lasers.

Carbon monoxide laser

2.6 to 4 μm, 4.8 to 8.3 μm

Electrical discharge

Material processing (engraving, welding, etc.), photoacoustic spectroscopy.

Excimer laser

193 nm (ArF), 248 nm (KrF), 308 nm (XeCl), 353 nm (XeF)

Excimer recombination via electrical discharge

Ultraviolet lithography for semiconductor manufacturing, laser surgery, LASIK.

Looking at the given table and the context paragraphs listed.

Solve the question: Which laser is commonly used for a fabrication or sculptural process that joins materials , usually metals or thermoplastics , by using high heat to melt the parts together and allowing them to cool causing fusion ? Respond with the correct answer (omit explanations) in JSON format as {"answer": "YOUR ANSWER"}. Base your answer solely on the given information.

A helium-neon laser or HeNe laser , is a type of gas laser whose gain medium consists of a mixture of 90% helium and 10% neon at a total pressure of about 1 torr inside of a small electrical discharge . The best-known and most widely used HeNe laser operates at a wavelength of 632.8 nm , in the red part of the visible spectrum .
The nanometre ( international spelling as used by the International Bureau of Weights and Measures ; SI symbol : nm ) or nanometer ( American spelling ) is a unit of length in the metric system , equal to one billionth ( short scale ) of a metre ( 0.000000001 m ) . The name combines the SI prefix nano- ( from the Ancient Greek νάνος , nanos , dwarf ) with the parent unit name metre ( from Greek μέτρον , metrοn , unit of measurement ) . It can be written in scientific notation as 1×10−9 m , in engineering notation as 1 E−9 m , and as simply 1/1000000000 metres . When used as a prefix for something other than a unit of measure ( as in nanoscience ) , nano refers to nanotechnology , or phenomena typically occurring on a scale of nanometres ( see nanoscopic scale ) . The nanometre is often used to express dimensions on an atomic scale : the diameter of a helium atom , for example , is about 0.06 nm , and that of a ribosome is about 20 nm . The nanometre is also commonly used to specify the wavelength of electromagnetic radiation near the visible part of the spectrum : visible light ranges from around 400 to 700 nm . The ångström , which is equal to 0.1 nm , was formerly used for these purposes , but is still used in other fields . Since the late 1980s , in usages such as the 32 nm and the 22 nm semiconductor node , it has also been used to describe typical feature sizes in successive generations of the ITRS Roadmap for miniaturization in the semiconductor industry .
The micrometre ( international spelling as used by the International Bureau of Weights and Measures ; SI symbol : μm ) or micrometer ( American spelling ) , also commonly known by the previous name micron , is an SI derived unit of length equalling 1×10−6 metre ( SI standard prefix micro- = 10−6 ) ; that is , one millionth of a metre ( or one thousandth of a millimetre , 0.001 mm , or about 0.000039 inch ) . The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria , and for grading wool by the diameter of the fibres . The width of a single human hair ranges from approximately 20 to 200 μm . The longest human chromosome is approximately 10 μm in length .
Interferometry is a family of techniques in which waves , usually electromagnetic waves , are superimposed , causing the phenomenon of interference , which is used to extract information . Interferometry is an important investigative technique in the fields of astronomy , fiber optics , engineering metrology , optical metrology , oceanography , seismology , spectroscopy ( and its applications to chemistry ) , quantum mechanics , nuclear and particle physics , plasma physics , remote sensing , biomolecular interactions , surface profiling , microfluidics , mechanical stress/strain measurement , velocimetry , optometry , and making holograms . :1-2 Interferometers are widely used in science and industry for the measurement of small displacements , refractive index changes and surface irregularities . In most interferometers , light from a single source is split into two beams that travel in different optical paths , which are then combined again to produce interference ; however , under some circumstances , two incoherent sources can also be made to interfere . The resulting interference fringes give information about the difference in optical path lengths . In analytical science , interferometers are used to measure lengths and the shape of optical components with nanometer precision ; they are the highest precision length measuring instruments existing . In Fourier transform spectroscopy they are used to analyze light containing features of absorption or emission associated with a substance or mixture . An astronomical interferometer consists of two or more separate telescopes that combine their signals , offering a resolution equivalent to that of a telescope of diameter equal to the largest separation between its individual elements .
A hologram is a physical recording of an interference pattern which uses diffraction to reproduce a three-dimensional light field , resulting in an image which retains the depth , parallax , and other properties of the original scene . Holography is the science and practice of making holograms . A hologram is a photographic recording of a light field , rather than an image formed by a lens . The holographic medium , i.e. , the object produced by a holographic process ( which itself may be referred to as a hologram ) is usually unintelligible when viewed under diffuse ambient light . It is an encoding of the light field as an interference pattern of variations in the opacity , density , or surface profile of the photographic medium . When suitably lit , the interference pattern diffracts the light into an accurate reproduction of the original light field , and the objects that were in it exhibit visual depth cues such as parallax and perspective that change realistically with the relative position of the observer . That is , the view of the image from different angles represents the subject viewed from similar angles.In this sense , holograms do not simply produce the illusion of depth but are truly three-dimensional images . In its pure form , holography requires the use of laser light for illuminating the subject and for viewing the finished hologram . A microscopic level of detail throughout the recorded scene can be reproduced . In common practice , however , major image quality compromises are made to eliminate the need for laser illumination to view the hologram , and in some cases , to make it . Holographic portraiture often resorts to a non-holographic intermediate imaging procedure , to avoid the hazardous high-powered pulsed lasers otherwise needed to optically freeze moving subjects as perfectly as the extremely motion-intolerant holographic recording process requires . Holograms can now also be entirely computer-generated to show objects or scenes that never existed .
Spectroscopy /spɛkˈtrɒskəpi/ is the study of the interaction between matter and electromagnetic radiation ( via electron spectroscopy , atomic spectroscopy , etc ) . Historically , spectroscopy originated through the study of visible light dispersed according to its wavelength , by a prism . Later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency , predominantly in the electromagnetic spectrum , though matter waves and acoustic waves can also be considered forms of radiative energy ; recently , with tremendous difficulty , even gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory ( LIGO ) and laser interferometry . Spectroscopic data are often represented by an emission spectrum , a plot of the response of interest , as a function of wavelength or frequency . Spectroscopy , primarily in the electromagnetic spectrum , is a fundamental exploratory tool in the fields of physics , chemistry , and astronomy , allowing the composition , physical structure and electronic structure of matter to be investigated at atomic scale , molecular scale , macro scale , and over astronomical distances . Important applications arise from biomedical spectroscopy in the areas of tissue analysis and medical imaging .
A barcode or bar code is a method of representing data in a visual , machine-readable form . Initially , barcodes represented data by varying the widths and spacings of parallel lines . These barcodes , now commonly referred to as linear or one-dimensional ( 1D ) , can be scanned by special optical scanners , called barcode readers . Later , two-dimensional ( 2D ) variants were developed , using rectangles , dots , hexagons and other geometric patterns , called matrix codes or 2D barcodes , although they do not use bars as such . 2D barcodes can be read or deconstructed using application software on mobile devices with inbuilt cameras , such as smartphones . The barcode was invented by Norman Joseph Woodland and Bernard Silver and patented in the US in 1951 . The invention was based on Morse code that was extended to thin and thick bars . However , it took over twenty years before this invention became commercially successful . An early use of one type of barcode in an industrial context was sponsored by the Association of American Railroads in the late 1960s . Developed by General Telephone and Electronics ( GTE ) and called KarTrak ACI ( Automatic Car Identification ) , this scheme involved placing colored stripes in various combinations on steel plates which were affixed to the sides of railroad rolling stock . Two plates were used per car , one on each side , with the arrangement of the colored stripes encoding information such as ownership , type of equipment , and identification number . The plates were read by a trackside scanner , located for instance , at the entrance to a classification yard , while the car was moving past .
An ion laser is a gas laser that uses an ionized gas as its lasing medium . Like other gas lasers , ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry-Pérot resonator . Unlike helium-neon lasers , the energy level transitions that contribute to laser action come from ions . Because of the large amount of energy required to excite the ionic transitions used in ion lasers , the required current is much greater , and as a result all but the smallest ion lasers are water-cooled . A small air-cooled ion laser might produce , for example , 130 milliwatts of output light with a tube current of about 10 amperes and a voltage of 105 volts . Since one ampere times one volt is one watt , this is an electrical power input of about one kilowatt . Subtracting the ( desirable ) light output of 130 mW from power input , this leaves the large amount of waste heat of nearly one kW . This has to be dissipated by the cooling system . In other words , the power efficiency is very low .
Second-harmonic generation ( SHG , also called frequency doubling ) is a nonlinear optical process in which two photons with the same frequency interact with a nonlinear material , are combined , and generate a new photon with twice the energy of the initial photons ( equivalently , twice the frequency and half the wavelength ) , that conserves the coherence of the excitation . It is a special case of sum-frequency generation ( 2 photons ) , and more generally of harmonic generation . The second-order nonlinear susceptibility of a medium characterizes its tendency to cause SHG . Second-harmonic generation , like other even-order nonlinear optical phenomena , is not allowed in media with inversion symmetry . However , effects such as the Bloch-Siegert shift ( oscillation ) , found when two-level systems are driven at Rabi frequencies comparable to their transition frequencies , will give rise to second harmonic generation in centro-symmetric systems . In some cases , almost 100% of the light energy can be converted to the second harmonic frequency . These cases typically involve intense pulsed laser beams passing through large crystals , and careful alignment to obtain phase matching . In other cases , like second-harmonic imaging microscopy , only a tiny fraction of the light energy is converted to the second harmonic - but this light can nevertheless be detected with the help of optical filters . Generating the second harmonic , often called frequency doubling , is also a process in radio communication ; it was developed early in the 20th century , and has been used with frequencies in the megahertz range . It is a special case of frequency multiplication .
The retina is the innermost , light-sensitive layer of tissue of the eye of most vertebrates and some molluscs . The optics of the eye create a focused two-dimensional image of the visual world on the retina , which translates that image into electrical neural impulses to the brain to create visual perception , the retina serving a function analogous to that of the film or image sensor in a camera . The neural retina consists of several layers of neurons interconnected by synapses , and is supported by an outer layer of pigmented epithelial cells . The primary light-sensing cells in the retina are the photoreceptor cells , which are of two types : rods and cones . Rods function mainly in dim light and provide black-and-white vision . Cones function in well-lit conditions and are responsible for the perception of colour , as well as high-acuity vision used for tasks such as reading . A third type of light-sensing cell , the photosensitive ganglion cell , is important for entrainment of circadian rhythms and reflexive responses such as the pupillary light reflex . Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses that are sent to various visual centres of the brain through the fibres of the optic nerve . Neural signals from the rods and cones undergo processing by other neurons , whose output takes the form of action potentials in retinal ganglion cells whose axons form the optic nerve . Several important features of visual perception can be traced to the retinal encoding and processing of light . In vertebrate embryonic development , the retina and the optic nerve originate as outgrowths of the developing brain , specifically the embryonic diencephalon ; thus , the retina is considered part of the central nervous system ( CNS ) and is actually brain tissue . It is the only part of the CNS that can be visualized non-invasively .
Light therapy - or phototherapy , classically referred to as heliotherapy - consists of exposure to daylight or to specific wavelengths of light using polychromatic polarised light , lasers , light-emitting diodes , fluorescent lamps , dichroic lamps or very bright , full-spectrum light . The light is administered for a prescribed amount of time and , in some cases , at a specific time of day . One common use of the term is associated with the treatment of skin disorders , chiefly psoriasis , acne vulgaris , eczema and neonatal jaundice . Light therapy which strikes the retina of the eyes is used to treat diabetic retinopathy and also circadian rhythm disorders such as delayed sleep phase disorder and can also be used to treat seasonal affective disorder , with some support for its use also with non-seasonal psychiatric disorders . [ medical citation needed ]
Diabetes mellitus ( DM ) , commonly known as diabetes , is a group of metabolic disorders characterized by a high blood sugar level over a prolonged period of time . Symptoms often include frequent urination , increased thirst , and increased hunger . If left untreated , diabetes can cause many complications . Acute complications can include diabetic ketoacidosis , hyperosmolar hyperglycemic state , or death . Serious long-term complications include cardiovascular disease , stroke , chronic kidney disease , foot ulcers , damage to the nerves , and damage to the eyes . Diabetes is due to either the pancreas not producing enough insulin , or the cells of the body not responding properly to the insulin produced . There are three main types of diabetes mellitus :
Lithography ( from Ancient Greek λίθος , lithos , meaning 'stone ' , and γράφειν , graphein , meaning 'to write ' ) is a method of printing originally based on the immiscibility of oil and water . The printing is from a stone ( lithographic limestone ) or a metal plate with a smooth surface . It was invented in 1796 by German author and actor Alois Senefelder as a cheap method of publishing theatrical works . Lithography can be used to print text or artwork onto paper or other suitable material . Lithography originally used an image drawn with oil , fat , or wax onto the surface of a smooth , level lithographic limestone plate . The stone was treated with a mixture of acid and gum arabic , etching the portions of the stone that were not protected by the grease-based image . When the stone was subsequently moistened , these etched areas retained water ; an oil-based ink could then be applied and would be repelled by the water , sticking only to the original drawing . The ink would finally be transferred to a blank paper sheet , producing a printed page . This traditional technique is still used in some fine art printmaking applications . In modern lithography , the image is made of a polymer coating applied to a flexible plastic or metal plate . The image can be printed directly from the plate ( the orientation of the image is reversed ) , or it can be offset , by transferring the image onto a flexible sheet ( rubber ) for printing and publication . As a printing technology , lithography is different from intaglio printing ( gravure ) , wherein a plate is either engraved , etched , or stippled to score cavities to contain the printing ink ; and woodblock printing or letterpress printing , wherein ink is applied to the raised surfaces of letters or images .
Confocal microscopy , most frequently confocal laser scanning microscopy ( CLSM ) or laser confocal scanning microscopy ( LCSM ) , is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a spatial pinhole to block out-of-focus light in image formation . Capturing multiple two-dimensional images at different depths in a sample enables the reconstruction of three-dimensional structures ( a process known as optical sectioning ) within an object . This technique is used extensively in the scientific and industrial communities and typical applications are in life sciences , semiconductor inspection and materials science . Light travels through the sample under a conventional microscope as far into the specimen as it can penetrate , while a confocal microscope only focuses a smaller beam of light at one narrow depth level at a time . The CLSM achieves a controlled and highly limited depth of focus .
An ion laser is a gas laser that uses an ionized gas as its lasing medium . Like other gas lasers , ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry-Pérot resonator . Unlike helium-neon lasers , the energy level transitions that contribute to laser action come from ions . Because of the large amount of energy required to excite the ionic transitions used in ion lasers , the required current is much greater , and as a result all but the smallest ion lasers are water-cooled . A small air-cooled ion laser might produce , for example , 130 milliwatts of output light with a tube current of about 10 amperes and a voltage of 105 volts . Since one ampere times one volt is one watt , this is an electrical power input of about one kilowatt . Subtracting the ( desirable ) light output of 130 mW from power input , this leaves the large amount of waste heat of nearly one kW . This has to be dissipated by the cooling system . In other words , the power efficiency is very low .
Argon is a chemical element with the symbol Ar and atomic number 18 . It is in group 18 of the periodic table and is a noble gas . Argon is the third-most abundant gas in the Earth 's atmosphere , at 0.934% ( 9340 ppmv ) . It is more than twice as abundant as water vapor ( which averages about 4000 ppmv , but varies greatly ) , 23 times as abundant as carbon dioxide ( 400 ppmv ) , and more than 500 times as abundant as neon ( 18 ppmv ) . Argon is the most abundant noble gas in Earth 's crust , comprising 0.00015% of the crust . Nearly all of the argon in the Earth 's atmosphere is radiogenic argon-40 , derived from the decay of potassium-40 in the Earth 's crust . In the universe , argon-36 is by far the most common argon isotope , as it is the most easily produced by stellar nucleosynthesis in supernovas . The name argon is derived from the Greek word ἀργόν , neuter singular form of ἀργός meaning lazy or inactive , as a reference to the fact that the element undergoes almost no chemical reactions . The complete octet ( eight electrons ) in the outer atomic shell makes argon stable and resistant to bonding with other elements . Its triple point temperature of 83.8058 K is a defining fixed point in the International Temperature Scale of 1990 . Argon is produced industrially by the fractional distillation of liquid air . Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive ; for example , an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning .
An ion laser is a gas laser that uses an ionized gas as its lasing medium . Like other gas lasers , ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry-Pérot resonator . Unlike helium-neon lasers , the energy level transitions that contribute to laser action come from ions . Because of the large amount of energy required to excite the ionic transitions used in ion lasers , the required current is much greater , and as a result all but the smallest ion lasers are water-cooled . A small air-cooled ion laser might produce , for example , 130 milliwatts of output light with a tube current of about 10 amperes and a voltage of 105 volts . Since one ampere times one volt is one watt , this is an electrical power input of about one kilowatt . Subtracting the ( desirable ) light output of 130 mW from power input , this leaves the large amount of waste heat of nearly one kW . This has to be dissipated by the cooling system . In other words , the power efficiency is very low .
Ultraviolet ( UV ) is electromagnetic radiation with wavelength from 10 nm ( with a corresponding frequency of approximately 30 PHz ) to 400 nm ( 750 THz ) , shorter than that of visible light but longer than X-rays . UV radiation is present in sunlight , and constitutes about 10% of the total electromagnetic radiation output from the Sun . It is also produced by electric arcs and specialized lights , such as mercury-vapor lamps , tanning lamps , and black lights . Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms , it can cause chemical reactions and causes many substances to glow or fluoresce . Consequently , the chemical and biological effects of UV are greater than simple heating effects , and many practical applications of UV radiation derive from its interactions with organic molecules . Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact . For humans , suntan and sunburn are familiar effects of exposure of the skin to UV light , along with an increased risks of skin cancer . The amount of UV light produced by the Sun means that the Earth would not be able to sustain life on dry land if most of that light were not filtered out by the atmosphere . More energetic , shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground . However , ultraviolet light is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates , including humans ( specifically , UVB ) . The UV spectrum thus has effects both beneficial and harmful to life . The lower wavelength limit of human vision is conventionally taken as 400 nm , so ultraviolet rays are invisible to humans , although some people can perceive light at slightly shorter wavelengths than this .
Infrared radiation ( IR ) , sometimes called infrared light , is electromagnetic radiation ( EMR ) with wavelengths longer than those of visible light . It is therefore generally invisible to the human eye , although IR at wavelengths up to 1050 nanometers ( nm ) s from specially pulsed lasers can be seen by humans under certain conditions . IR wavelengths extend from the nominal red edge of the visible spectrum at 700 nanometers ( frequency 430 THz ) , to 1 millimeter ( 300 GHz ) . Most of the thermal radiation emitted by objects near room temperature is infrared . As with all EMR , IR carries radiant energy and behaves both like a wave and like its quantum particle , the photon . Infrared radiation was discovered in 1800 by astronomer Sir William Herschel , who discovered a type of invisible radiation in the spectrum lower in energy than red light , by means of its effect on a thermometer . Slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared . The balance between absorbed and emitted infrared radiation has a critical effect on Earth 's climate . Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements . It excites vibrational modes in a molecule through a change in the dipole moment , making it a useful frequency range for study of these energy states for molecules of the proper symmetry . Infrared spectroscopy examines absorption and transmission of photons in the infrared range . Infrared radiation is used in industrial , scientific , military , law enforcement , and medical applications .
A nitrogen laser is a gas laser operating in the ultraviolet range ( typically 337.1 nm ) using molecular nitrogen as its gain medium , pumped by an electrical discharge . The wall-plug efficiency of the nitrogen laser is low , typically 0.1% or less , though nitrogen lasers with efficiency of up to 3% have been reported in the literature . The wall-plug efficiency is the product of the following three efficiencies :
A superradiant laser is a laser that does not rely on a large population of photons within the laser cavity to maintain coherence . Rather than relying on photons to store phase coherence , it relies on collective effects in an atomic medium to store coherence . Such a laser uses repumped Dicke superradiance ( or superfluorescence ) to sustain emission of light that can have a substantially narrower linewidth than a conventional laser .
A TEA laser is a gas laser energized by a high voltage electrical discharge in a gas mixture generally at or above atmospheric pressure . The most common types are carbon dioxide lasers and excimer lasers , both used extensively in industry and research ; less common are nitrogen lasers . The acronym TEA stands for Transversely Excited Atmospheric .
The carbon dioxide laser ( CO2 laser ) was one of the earliest gas lasers to be developed . It was invented by Kumar Patel of Bell Labs in 1964 , and is still one of the most useful . Carbon dioxide lasers are the highest-power continuous wave lasers that are currently available . They are also quite efficient : the ratio of output power to pump power can be as large as 20% . The CO2 laser produces a beam of infrared light with the principal wavelength bands centering on 9.4 and 10.6 micrometers ( μm ) .
Laser cutting is a technology that uses a laser to slice materials . While typically used for industrial manufacturing applications , it is also starting to be used by schools , small businesses , and hobbyists . Laser cutting works by directing the output of a high-power laser most commonly through optics . The laser optics and CNC ( computer numerical control ) are used to direct the material or the laser beam generated . A commercial laser for cutting materials involved a motion control system to follow a CNC or G-code of the pattern to be cut onto the material . The focused laser beam is directed at the material , which then either melts , burns , vaporizes away , or is blown away by a jet of gas , leaving an edge with a high-quality surface finish . Industrial laser cutters are used to cut flat-sheet material as well as structural and piping materials .
Laser beam welding ( LBW ) is a welding technique used to join pieces of metal or thermoplastics through the use of a laser . The beam provides a concentrated heat source , allowing for narrow , deep welds and high welding rates . The process is frequently used in high volume applications using automation , as in the automotive industry . It is based on keyhole or penetration mode welding .
Surgery [ a ] is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pathological condition such as a disease or injury , to help improve bodily function or appearance or to repair unwanted ruptured areas . The act of performing surgery may be called a surgical procedure , operation , or simply surgery . In this context , the verb operate means to perform surgery . The adjective surgical means pertaining to surgery ; e.g . surgical instruments or surgical nurse . The person or subject on which the surgery is performed can be a person or an animal . A surgeon is a person who practices surgery and a surgeon 's assistant is a person who practices surgical assistance . A surgical team is made up of surgeon , surgeon 's assistant , anaesthetist , circulating nurse and surgical technologist . Surgery usually spans minutes to hours , but it is typically not an ongoing or periodic type of treatment . The term surgery can also refer to the place where surgery is performed , or , in British English , simply the office of a physician , dentist , or veterinarian .
A dental laser is a type of laser designed specifically for use in oral surgery or dentistry . In the United States , the use of lasers on the gums was first approved by the Food and Drug Administration in the early 1990s , and use on hard tissue like teeth or the bone of the mandible gained approval in 1996 . Several variants of dental lasers are in use with different wavelengths and these mean they are better suited for different 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 .
Carbon monoxide ( CO ) is a colorless , odorless , and tasteless flammable gas that is slightly less dense than air . It is toxic to animals that use hemoglobin as an oxygen carrier ( both Invertebrate and vertebrate ) when encountered in concentrations above about 35 ppm , although it is also produced in normal animal metabolism in low quantities , and is thought to have some normal biological functions . In the atmosphere , it is spatially variable and short lived , having a role in the formation of ground-level ozone . Carbon monoxide consists of one carbon atom and one oxygen atom , connected by a triple bond that consists of two covalent bonds as well as one dative covalent bond . It is the simplest oxocarbon and is isoelectronic with other triply-bonded diatomic molecules having ten valence electrons , including the cyanide anion , the nitrosonium cation and molecular nitrogen . In coordination complexes the carbon monoxide ligand is called carbonyl .
Engraving is the practice of incising a design onto a hard , usually flat surface by cutting grooves into it with a burin . The result may be a decorated object in itself , as when silver , gold , steel , or glass are engraved , or may provide an intaglio printing plate , of copper or another metal , for printing images on paper as prints or illustrations ; these images are also called engravings . Engraving is one of the oldest and most important techniques in printmaking . Wood engraving is a form of relief printing and is not covered in this article . Engraving was a historically important method of producing images on paper in artistic printmaking , in mapmaking , and also for commercial reproductions and illustrations for books and magazines . It has long been replaced by various photographic processes in its commercial applications and , partly because of the difficulty of learning the technique , is much less common in printmaking , where it has been largely replaced by etching and other techniques . Engraving is also loosely but incorrectly used for any old black and white print ; it requires a degree of expertise to distinguish engravings from prints using other techniques such as etching in particular , but also mezzotint and other techniques . Many old master prints also combine techniques on the same plate , further confusing matters . Line engraving and steel engraving cover use for reproductive prints , illustrations in books and magazines , and similar uses , mostly in the 19th century , and often not actually using engraving . Traditional engraving , by burin or with the use of machines , continues to be practised by goldsmiths , glass engravers , gunsmiths and others , while modern industrial techniques such as photoengraving and laser engraving have many important applications . Engraved gems were an important art in the ancient world , revived at the Renaissance , although the term traditionally covers relief as well as intaglio carvings , and is essentially a branch of sculpture rather than engraving , as drills were the usual tools .
Welding is a fabrication or sculptural process that joins materials , usually metals or thermoplastics , by using high heat to melt the parts together and allowing them to cool causing fusion . Welding is distinct from lower temperature metal-joining techniques such as brazing and soldering , which do not melt the base metal . In addition to melting the base metal , a filler material is typically added to the joint to form a pool of molten material ( the weld pool ) that cools to form a joint that , based on weld configuration ( butt , full penetration , fillet , etc . ) , can be stronger than the base material ( parent metal ) . Pressure may also be used in conjunction with heat , or by itself , to produce a weld . Welding also requires a form of shield to protect the filler metals or melted metals from being contaminated or oxidized . Many different energy sources can be used for welding , including a gas flame ( chemical ) , an electric arc ( electrical ) , a laser , an electron beam , friction , and ultrasound . While often an industrial process , welding may be performed in many different environments , including in open air , under water , and in outer space . Welding is a hazardous undertaking and precautions are required to avoid burns , electric shock , vision damage , inhalation of poisonous gases and fumes , and exposure to intense ultraviolet radiation . Until the end of the 19th century , the only welding process was forge welding , which blacksmiths had used for millennia to join iron and steel by heating and hammering . Arc welding and oxy-fuel welding were among the first processes to develop late in the century , and electric resistance welding followed soon after . Welding technology advanced quickly during the early 20th century as the world wars drove the demand for reliable and inexpensive joining methods .
Photoacoustic spectroscopy is the measurement of the effect of absorbed electromagnetic energy ( particularly of light ) on matter by means of acoustic detection . The discovery of the photoacoustic effect dates to 1880 when Alexander Graham Bell showed that thin discs emitted sound when exposed to a beam of sunlight that was rapidly interrupted with a rotating slotted disk . The absorbed energy from the light causes local heating , generating a thermal expansion which creates a pressure wave or sound . Later Bell showed that materials exposed to the non-visible portions of the solar spectrum ( i.e. , the infrared and the ultraviolet ) can also produce sounds . A photoacoustic spectrum of a sample can be recorded by measuring the sound at different wavelengths of the light . This spectrum can be used to identify the absorbing components of the sample . The photoacoustic effect can be used to study solids , liquids and gases .
An excimer laser , sometimes more correctly called an exciplex laser , is a form of ultraviolet laser which is commonly used in the production of microelectronic devices , semiconductor based integrated circuits or chips , eye surgery , and micromachining .
An excimer ( originally short for excited dimer ) is a short-lived dimeric or heterodimeric molecule formed from two species , at least one of which has completely filled valence shell by electrons ( for example , noble gases ) . In this case , formation of molecules is possible only if such atom is in an electronic excited state . Heteronuclear molecules and molecules that have more than two species are also called exciplex molecules ( originally short for excited complex ) . 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 very short , on the order of nanoseconds . Binding of a larger number of excited atoms forms Rydberg matter clusters , the lifetime of which can exceed many seconds .
Ultraviolet ( UV ) is electromagnetic radiation with wavelength from 10 nm ( with a corresponding frequency of approximately 30 PHz ) to 400 nm ( 750 THz ) , shorter than that of visible light but longer than X-rays . UV radiation is present in sunlight , and constitutes about 10% of the total electromagnetic radiation output from the Sun . It is also produced by electric arcs and specialized lights , such as mercury-vapor lamps , tanning lamps , and black lights . Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms , it can cause chemical reactions and causes many substances to glow or fluoresce . Consequently , the chemical and biological effects of UV are greater than simple heating effects , and many practical applications of UV radiation derive from its interactions with organic molecules . Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact . For humans , suntan and sunburn are familiar effects of exposure of the skin to UV light , along with an increased risks of skin cancer . The amount of UV light produced by the Sun means that the Earth would not be able to sustain life on dry land if most of that light were not filtered out by the atmosphere . More energetic , shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground . However , ultraviolet light is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates , including humans ( specifically , UVB ) . The UV spectrum thus has effects both beneficial and harmful to life . The lower wavelength limit of human vision is conventionally taken as 400 nm , so ultraviolet rays are invisible to humans , although some people can perceive light at slightly shorter wavelengths than this .
A semiconductor material has an electrical conductivity value falling between that of a conductor , such as metallic copper , and an insulator , such as glass . Its resistance falls as its temperature rises ; metals are the opposite . Its conducting properties may be altered in useful ways by introducing impurities ( doping ) into the crystal structure . Where two differently-doped regions exist in the same crystal , a semiconductor junction is created . The behavior of charge carriers which include electrons , ions and electron holes at these junctions is the basis of diodes , transistors and all modern electronics . Some examples of semiconductors are silicon , germanium , gallium arsenide , and elements near the so-called metalloid staircase on the periodic table . After silicon , gallium arsenide is the second most common semiconductor [ citation needed ] and is used in laser diodes , solar cells , microwave-frequency integrated circuits and others . Silicon is a critical element for fabricating most electronic circuits . Semiconductor devices can display a range of useful properties such as passing current more easily in one direction than the other , showing variable resistance , and sensitivity to light or heat . Because the electrical properties of a semiconductor material can be modified by doping , or by the application of electrical fields or light , devices made from semiconductors can be used for amplification , switching , and energy conversion . The conductivity of silicon is increased by adding a small amount ( of the order of 1 in 108 ) of pentavalent ( antimony , phosphorus , or arsenic ) or trivalent ( boron , gallium , indium ) atoms . This process is known as doping and resulting semiconductors are known as doped or extrinsic semiconductors .
LASIK or Lasik ( laser-assisted in situ keratomileusis ) , commonly referred to as laser eye surgery or laser vision correction , is a type of refractive surgery for the correction of myopia , hyperopia , and astigmatism . LASIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye 's cornea in order to improve visual acuity . For most people , LASIK provides a long-lasting alternative to eyeglasses or contact lenses . LASIK is most similar to another surgical corrective procedure , photorefractive keratectomy ( PRK ) , and LASEK . All represent advances over radial keratotomy in the surgical treatment of refractive errors of vision . For patients with moderate to high myopia or thin corneas which can not be treated with LASIK and PRK , the phakic intraocular lens is an alternative . As of 2018 , roughly 8 million Americans have had LASIK and , as of 2016 , more than 40 million procedures have been performed since 1991 . However , the procedure seems to be a declining option for many in the United States , dropping more than 50 percent , from about 1.5 million surgeries in 2007 to 604,000 in 2015 , according to the eye-care data source Market Scope . A study in the journal Cornea determined the frequency with which LASIK was searched on Google from 2007 to 2011 . Within this time frame , LASIK searches declined by 40% in the United States . Countries such as the U.K. and India also showed a decline , 22% and 24% respectively . Canada , however , showed an increase in LASIK searches by 8% .