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Laser as a physical device. Laser (optical quantum generator) (abbreviation of words English phrase: Light Amplification by Stimulated Emission of Radiation - amplification of light as a result of stimulated emission), a source of optical coherent radiation, characterized by high directivity and high energy density. There are gas lasers, liquid and solid-state (on dielectric crystals, glasses, semiconductors). The laser transforms various kinds energy into laser energy. There are continuous and pulsed lasers. Lasers are widely used in scientific research (in physics, chemistry, biology, etc.), in practical medicine (surgery, ophthalmology, etc.), and also in technology (laser technology). Lasers have made it possible to carry out optical communication and location; they are promising for the implementation of controlled thermonuclear fusion.
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Spontaneous and forced emission. 1917 A. Einstein: Mechanisms of light emission by matter Spontaneous (incoherent) Stimulated (coherent)
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Lasers A.M. Prokhorov N.G. Basov C. Towns In 1954 Generators were created for the first time electromagnetic radiation using the forced transition mechanism. T. Meiman In 1960 he created a laser in the optical range operating on ruby.
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Types of lasers Gas helium-neon argon krypton xenon nitrogen sec-hydrogen oxygen-iodine carbon dioxide (CO2) on carbon monoxide (CO) excimer Metal vapor -helium-cadmium -helium-mercury -helium-selenium - on steam copper - on gold vapor Solid-state - ruby - aluminum-yttrium - on yttrium-lithium fluoride - on yttrium vanadate - on neodymium glass - titanium-sapphire - alexandrite - fiber optic - on calcium fluoride Other types - semiconductor laser diode - on dyes - on free electrons - pseudo-nickel-samarium
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RUBY LASER The first quantum light generator was created in 1961 by Meiman (born 1927) using ruby. Ruby is a solid crystal, the basis of which is corundum, i.e. an aluminum oxide crystal (Al2O3), in which a small part of the aluminum atoms (about 0.05%) is replaced by Cr+++ chromium ions. To create an inverse population, optical pumping is used, i.e. illumination of a ruby crystal with a powerful flash of light. The ruby is given the shape of a cylindrical rod, the ends of which are carefully polished, silvered, and serve as mirrors for the laser. To illuminate the ruby rod, pulsed xenon gas-discharge flash lamps are used, through which batteries of high-voltage capacitors are discharged. The flash lamp has the shape of a spiral tube wrapped around a ruby rod. Under the action of a powerful light pulse, an inverse population is created in the ruby rod, and due to the presence of mirrors, laser generation is excited, the duration of which is slightly less than the duration of the flash of the pumping lamp.
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Helium-neon laser. A helium-neo new laser is a laser whose active medium is a mixture of helium and neon. Helium-neon lasers are often used in laboratory experiments and optics. It has an operating wavelength of 632.8 nm, located in the red part of the visible spectrum. Helium-neon laser. The glowing beam in the center is not actually a laser beam, but an electrical discharge that generates a glow, similar to how it happens in neon lamps. The beam is projected onto the screen on the right as a glowing red dot.
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All lasers consist of three main parts: - active (working) medium; - pumping systems (energy source); - optical resonator (may be absent if the laser operates in the amplifier mode). Each of them provides for the operation of the laser to perform its specific functions. The working medium of a helium-neon laser is a mixture of helium and neon in a ratio of 5:1, located in a glass flask under low pressure (usually about 300 Pa). The pump energy is supplied from two electrical dischargers with a voltage of about 1000 volts, located at the ends of the flask. The resonator of such a laser usually consists of two mirrors - completely opaque on one side of the bulb and the second, passing through itself about 1% of the incident radiation on the output side of the device. Helium-neon lasers are compact, the typical cavity size is from 15 cm to 0.5 m, their output power varies from 1 to 100 mW.
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Application of lasers Science Armament Medicine Industry and life Spectroscopy Distance measurement Photochemistry Magnetization Interferometry Holography Cooling Thermonuclear fusion Laser weapons star Wars» Target designators Laser sight Laser guidance Scalpel Spot welding tissue Surgery Diagnostics Removal of tumors Cutting, welding, marking, engraving CD, DVD players, printers, displays Photolithography, barcode reader Optical communication, navigation systems (l.gyroscope) Manipulation of micro-objects
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Laser accompaniment of musical performances (laser show) -Solid-state and liquid lasers.
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Semiconductor laser used in the imaging unit of a Hewlett-Packard printer
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At present, it is difficult to imagine progress in medicine without laser technologies, which have opened up new possibilities in solving numerous medical problems. The study of the mechanisms of the action of laser radiation of various wavelengths and energy levels on biological tissues makes it possible to create laser medical multifunctional devices, the range of application of which in clinical practice has become so wide that it is very difficult to answer the question: what diseases are lasers not used to treat? The development of laser medicine goes along three main branches: laser surgery, laser therapy and laser diagnostics. Our field of activity is lasers for applications in surgery and cosmetology, which have a sufficiently high power for cutting, vaporization, coagulation and other structural changes in biological tissue. The use of lasers in medicine.
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The word LASER is an acronym that stands for Amplification of Light by Stimulated Emission of Radiation ((L) light (A) amplification (S) stimulatedbythe (E) emissionof (R) radiation) and describes how light is generated. All lasers are optical amplifiers that work by pumping (exciting) an active medium placed between two mirrors, one of which transmits part of the radiation. The active medium is a set of specially selected atoms, molecules or ions, which can be in a gaseous, liquid or solid state and which, when excited by a pumping action, will generate laser radiation, i.e. emit radiation in the form of light waves (called photons). Pumping liquids and solids is achieved by irradiating them with the light of a flash lamp, and gases are pumped using an electric discharge. What is a laser?
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Properties of laser light The light beam is collimated, which means that it travels in one direction with very little divergence even over very long distances. Laser light is monochrome, consisting of a single color or a narrow range of colors. Ordinary light has a very wide range of wavelengths or colors Laser light is coherent, meaning that all light waves move in phase together in both time and space A laser is a device that creates and amplifies a narrow, intense beam of coherent light
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Today, lasers are widely used in medicine, manufacturing, the construction industry, geodesy, consumer electronics, scientific equipment and military systems. There are literally billions of lasers in use today. They are part of common devices such as barcode scanners used in supermarkets, scanners, laser printers and CD players. Application of lasers
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Since Maiman's invention of the ruby laser in 1960, many potential applications have been proposed. In the field of medicine, the possibilities of lasers began to develop rapidly after 1964, when the carbon dioxide laser was invented, which soon gave surgeons the ability to perform very complex operations using photons instead of a scalpel to perform operations. Laser light can penetrate the inside of the body, performing operations that were almost impossible to perform a few years ago, with minimal risk or discomfort to the patient. Shorter (green) lasers are used to "weld" the detached retina, and are used to stretch protein molecules to measure their strength, etc. The use of lasers in medicine
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In 1964, the possibility of using a ruby laser for the treatment of caries was suggested, which attracted the attention of the whole world. In 1967, when trying to remove caries and prepare the cavity with a ruby laser, he could not avoid damaging the dental pulp, despite the good results obtained on the extracted teeth. Later, similar basic studies with the CO2 laser also ran into this problem. To minimize heat buildup, pulsed lasers were used instead of continuous radiation. Further studies have shown that the laser can produce a small local anesthetic effect. Further developments have led to the creation of a laser that drills through enamel and dentin completely. At the same time, the laser saves more healthy tooth tissue. With today's lasers, there is virtually no unwanted heat, no noise and no vibration. When leaving the dental chair, most patients felt no pain, did not have to wait for the anesthetic and numbness to wear off, and experienced almost no postoperative discomfort. Lasers are accurate and virtually painless and can change your mind about going to the dentist. They can change everything. The use of lasers in dentistry
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Lasers are a significant breakthrough in dentistry, both for the gums and other soft tissues, and for the teeth themselves. Today, a significant number of laser technologies and treatments are widely used. Today, lasers are used in the following areas of dentistry: Prevention Periodontology Cosmetic dentistry Endodontics Surgery Implantodontics
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Currently, lasers are widely used in the woodworking industry, and in recent years, the area of their distribution has expanded significantly. The use of lasers facilitates the positioning of workpieces (video clip), the alignment of the external patterns of two workpieces, the minimization of waste, the installation of complex structural elements of buildings and structures. Lasers used in woodworking can produce a line, an intersection of lines (denoting a center), or a 2D or 3D image (projectors). Laser systems in woodworking
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as logical elements for input and reading from memory devices in computers laser printer optical transmission of information Lasers in computer science
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The laser can also be used for non-contact measurement of geometric dimensions (gap, length, width, thickness, height, depth, diameter). With the help of a laser, it is also possible to obtain complex measurements: deviation from verticality; surface flatness value; profile accuracy; It is possible to obtain derived quantities such as deflection and convexity. Laser measuring systems allow you to automatically control the parameters of products and immediately change the parameters of the production line if any deviation occurs. The product is exclusive in this area because it has the following properties: Highly accurate Allows you to control the quality and characteristics of geometrically complex parts Does not damage or destroy the surface of the product Works in any conditions on any surfaces Easily integrates into an existing production line Lasers in measurements
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Classification of lasers Class I lasers Do not pose a hazard under continuous observation or are designed to prevent human exposure to laser radiation (e.g. laser printers) Class 2 visible lasers (400 to 700 nm) Lasers emitting visible light, which due to natural human adverse reactions are not usually dangerous, but may be if you look directly at the laser light for an extended period of time. Class 3aLasers that do not normally cause harm with brief eye contact, but may be dangerous when viewed using a collecting optic (fiber optic magnifier or telescope) Class 3bLasers that pose a risk to the eyes and skin when exposed directly to laser light. Class 3b lasers do not generate hazardous diffuse reflections except at close range Class 4 lasers Lasers that pose a risk to the eye through direct, specular, and diffuse reflections. In addition, such lasers can be flammable and cause skin burns.
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EYE PROTECTION - Everyone in the operating room must wear protective goggles. The light emitted from the laser can seriously damage the cornea and retina of unprotected eyes. The goggles must have side protection and be worn over regular goggles. Laser protective goggles must be accessible and worn by all personnel within the Class 3b and Class 4 Laser Rated Hazardous Area where exposures in excess of the Maximum Allowable may occur. The absorption coefficient of the optical density of laser safety goggles for each laser wavelength is determined by the LaserSafetyOfficer (LSO). All laser safety goggles are clearly labeled with the optical density and wavelength that the goggles are intended to protect against. Laser safety goggles must be checked for damage before use. REFLECTION - Laser light is easily reflected and care must be taken not to direct the beam onto polished surfaces. ELECTRICAL HAZARD - The internal parts of the laser are high voltage and emit invisible laser beams without any shielding. Only specialists trained in electrical and laser safety are authorized to carry out internal maintenance. Security measures
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- a type of directed energy weapon based on the use of electromagnetic radiation from high-energy lasers. The striking effect of LO is determined mainly by the thermomechanical and shock-pulse effect of the laser beam on the target. Depending on the density of the laser radiation flux, these impacts can lead to temporary blinding of a person or to the destruction of the body of a rocket, aircraft, etc. In the latter case, as a result of the thermal effect of the laser beam, the shell of the target object is melted or evaporated. At a sufficiently high energy density in the pulsed mode, along with the thermal effect, a shock effect is carried out, due to the appearance of a plasma. Currently, work is underway in the United States to create aviation complex laser weapons. Initially, it is planned to work out a demonstration model for the Boeing-747 transport aircraft and, after completion of preliminary studies, move to 2004. to the full development stage. As of the middle of the 1990s, tactical laser weapons were considered the most developed, which ensured the destruction of optoelectronic means and human organs of vision. laser weapons
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The history of the creation of quantum generators; The principle of operation of lasers; Types of lasers; Application.
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Max Planck
1900 - M. Planck put forward the idea that matter emits and absorbs light in separate portions - quanta.
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Niels Bohr
1913 - N. Bohr showed that the energy of an atom is quantized, i.e. can take on a number of discrete values. When an atom moves from energy level to level, a photon is emitted
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Albert Einstein
1917 - A. Einstein predicted the possibility of induced (forced) emission of light by atoms.
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V. A. Fabrikant
1940 - V. A. Fabrikant pointed out the possibility of using the phenomenon of stimulated emission to amplify electromagnetic waves.
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A. M. Prokhorov, N. G. Basov, C. Townes
1954 - Soviet academicians N. G. Basov and A. M. Prokhorov and American physicist C. Towns developed a "maser" - a powerful emitter of radio waves. This outstanding scientific work was awarded the Nobel Prize in Physics in 1960. The first laser in the visible range of the spectrum was created in the United States. Currently, work is underway to create lasers in the X-ray and gamma ranges, which will make it possible to use lasers for controlled thermonuclear fusion.
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The principle of operation of lasers
Lasers produce coherent radiation of very high power. Necessary condition coherent radiation - creating an inversion of the populations of energy levels (there are more atoms at the level than at the level)
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ruby laser
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The pump lamp is a xenon discharge lamp with blue-green light, used to excite chromium ions.
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A ruby crystal (with an admixture of chromium - 0.05%) allows you to realize the state of inversion. The ends of the ruby rod are 2 mutually parallel mirrors, one is translucent, they act as an optical resonator. The direction of the ruby rod axis is the direction along which laser radiation will be generated.
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Types of lasers
Speaking about lasers, they usually mention the mode of operation (pulsed laser, continuous laser), the type of working substance (solid-state, liquid or gas laser), its material (helium-neon laser, ruby, laser on glass) or the color of its radiation (blue laser, red, infrared).
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Gas dynamic laser
In a powerful gas-dynamic laser, light is generated by a jet of hot gas at a pressure of tens of atmospheres.
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semiconductor laser
In a semiconductor laser, it emits a layer between two P- and n-type semiconductors. The entire laser, together with the electrical contacts, is slightly larger than a button.
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Dye lasers
The working substance of a dye laser is a liquid: a solution of organic dyes or salts of rare metals.
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Application of lasers
The laser is a truly great invention of the twentieth century, which has found application in many areas of human activity.
Student Abaluev Egor 11 "b"
Optical quantum generators whose radiation lies in the visible and infrared regions of the spectrum are called lasers.
A laser is a device in which energy, such as thermal, chemical, electrical energy, is converted into electromagnetic field energy - a laser beam.
An atom is in an excited state for about 10 -8 s, after which it spontaneously (spontaneously) passes into the ground state, while emitting a quantum of light.
Spontaneous emission occurs in the absence of external action on the atom and is explained by the instability of its excited state.
If the atom is subjected to external action, then its lifetime in the excited state is reduced, and the radiation will already be stimulated or induced. The concept of stimulated emission was introduced in 1916 by A. Einstein.
Stimulated emission is understood as the emission of excited atoms under the action of incident light Stimulated emission.
1940 V. A. Fabrikant (possibility of using the phenomenon of stimulated emission) 1954 N. G. Basov, A. M. Prokhorov and C. Towns (development of a microwave generator) 1963 N. G. Basov, A. M Prokhorov and C. Towns were awarded the Nobel Prize for the history of the invention of the laser.
Directivity Monochromaticity Coherence Intensity Properties of laser radiation.
When a laser is used, a system of three energy levels of an atom is often used, the second of which is metastable with an atom lifetime up to 10 -3 s.
Three-Level Optical Pump Scheme The "lifetimes" of the E2 and E3 levels are indicated. Level E2 is metastable. The transition between the levels E3 and E2 is nonradiative. The laser transition is carried out between levels E2 and E1.
The laser usually consists of three main elements: * Energy source (pumping mechanism) * Working fluid; * System of mirrors ("optical resonator").
The main part of a ruby laser is a ruby rod. Ruby is composed of Al and O atoms with an admixture of Cr atoms. It is the chromium atoms that give the ruby its color and have a metastable state.
Lasers are capable of producing beams of light with a very small divergence angle. All photons of laser radiation have the same frequency (monochromaticity) and the same direction (consistency). Lasers are powerful light sources (up to 10 9 W, i.e. more than the power of a large power plant).
Processing of materials (cutting, welding, drilling); In surgery instead of a scalpel; In ophthalmology; Holography; Communication using fiber optics; Laser location; The use of a laser beam as an information carrier.
What is a laser? LASER (optical quantum generator) is a device that converts pump energy (light, electrical, thermal, chemical, etc.) into the energy of a coherent, monochromatic, polarized and narrowly directed radiation flux. The word "laser" is an abbreviation of the words of the English phrase "Light Amplification by Stimulated Emission of Radiation" - amplification of light by stimulated emission.
Short story appearance of the laser 1916 - A. Einstein predicts the existence of the phenomenon of stimulated emission of the physical basis for the operation of any laser d. - theoretical substantiation of this phenomenon by P. Dirac d. - experimental confirmation of the phenomenon of stimulated emission by R. Ladenburg and G. Kopfermann d. - the first microwave generator (ammonia maser), the creators of Ch. Towns and independently of him A. Prokhorov and N. Basov, Mr. T. Meiman demonstrated the operation of the first optical quantum laser generator. In subsequent years, rapid development takes place, and more and more new types of lasers are invented (chemical, semiconductor, dye lasers, and others).
