Technical College national university
"Lviv Polytechnic"
Abstract
On the topic: "The importance of opening a laser and its capabilities"
Completed: student 31KI
Kobrinovich R. V.
Accepted:
Fedina N. D.
Lviv 2019
Content
History of the invention of the laser
Application in medicine
Application of laser beam in industry
Application of lasers in computer engineering
References
A laser is a device for generating or amplifying monochromatic light, generating a narrow beam of light capable of propagating over long distances without scattering, and creating an extremely large radiation power density when focusing.
Lasers have come into human life and life in a relatively short time. The creation of the laser was preceded by a long history. The invention of this useful device humanity owes to radiophysicists, namely Alexander Prokhorov and Nikolai Basov. Through the research of these scientists, a new page in the history of technical science was opened. Of course, over time, studies of Soviet scientists, in turn, were replenished with new ideas of American physicists who have increasingly refined this device. The first ruby laser created by American scientist Maiman made a huge impression on others. In addition to ruby, many other compounds can be used as active substances in lasers.
Java's invention of a gas laser is interesting. However, the most important thing in the end was the invention in 1962 by Soviet physicists of a semiconductor laser.
In 1964 Prokhorov, Bass and Towns were awarded the Nobel Prize in Physics "for fundamental work in quantum electronics that led to the creation of oscillators and amplifiers based on the laser-maser principle." At first, after the invention, it was believed that the maser was a purely human creation, but later astronomers discovered that some of the distant galaxies function as giant masers. The huge gas clouds, the size of billions of kilometers, create the conditions for generation, and the source of pumping is cosmic radiation. Masers are used in engineering, in physical research, as well as standard frequency quantum generators.
Interestingly, the first microwave generator, an ammonia maser, was created in 1954. The role of feedback was played by a three-dimensional resonator, the dimensions of which were about 12.6 mm (the wavelength emitted during the transition of ammonia from the excited oscillatory level to the main one). To amplify the electromagnetic radiation of the optical range, it was necessary to create a three-dimensional resonator whose dimensions would be in the order of microns. Due to the technological difficulties involved, many scientists at the time believed that it was impossible to create a visible radiation generator.
The work of the first optical quantum generator (laser) was demonstrated on May 16, 1960. The artificial ruby crystal was used as the active medium, and the Fabry-Feather resonator formed by silver mirror coatings deposited at the end of the crystal served as a volumetric resonator. This laser operated in pulsed mode at a wavelength of 694.3 nm. In December of the same year, a helium-neon laser was created, which emits in a continuous mode. Initially, the laser operated in the infrared range, then was modified to emit visible red light with a wavelength of 632.8 nm.
The physics of lasers is still intensively developing. Since the invention of the laser, almost every year its new types, adapted for different purposes. In 1961, a neodymium glass laser was created, and over the next five years, laser diodes, dye lasers, carbon dioxide lasers, and chemical lasers were developed. In 1963, J. Alferov and G. Kremer (Nobel Prize in Physics 2000) developed the theory of semiconductor hetero structures, on the basis of which many lasers were created.
The unique properties of laser radiation have made it possible to use them in various fields of science and technology, for example, in optical communication systems.
Lasers are widely used in medicine, especially in ophthalmology, surgery and oncology, capable of creating a small spot, due to their high monochromaticity and focus. In ophthalmology, laser radiation with an energy of 0.2 - 0.3 j allows for a number of complex operations without breaking the integrity of the eye itself. One such operation is the welding and strengthening of the detached retina by coagulation adhesions. In addition, the laser beam is used to burn malignant and benign tumors. In surgery, the continuous beam of a continuous laser (up to 100 watts) is an extremely sharp and sterile scalpel that performs bloodless operations even on the liver and spleen. The use of continuous and pulsed lasers to burn wounds and stop bleeding in patients with reduced blood clotting has considerable potential.
The use of a laser scalpel for surgery determines the following properties:
- it produces a relatively bloodless incision because, at the same time as the tissue section, it coagulates the wound edges by "brewing" not very large blood vessels;
- the laser scalpel differs in the constancy of cutting properties. Contact with a solid object (such as a bone) does not disrupt the scalpel. For a mechanical scalpel, this situation would be fatal;
- the laser beam due to its transparency allows the surgeon to see the operated area. The blade of an ordinary scalpel, as well as the blade of an electric knife, always to some extent obstructs the working field from the surgeon;
- the laser beam cuts the fabric at a distance without having any mechanical effect on the fabric;
- the laser scalpel provides absolute sterility, because only radiation interacts with the tissue;
- the laser beam acts strictly locally, the evaporation of the tissue occurs only at the point of focus.
Adjacent tissue areas are damaged much less than using a mechanical scalpel;
- as clinical practice has shown, the wound from the laser scalpel almost does not hurt and heals
faster.
The practical application of lasers in surgery began in the USSR in 1966 at the AV Vishnevsky Institute. The laser scalpel has been used in operations on the internal organs of the thoracic and abdominal cavities. Currently, the laser beam is made by skin and plastic operations, operations of the esophagus, stomach, intestines, kidneys, liver, spleen and other organs. It is very tempting to perform laser surgery on organs containing a large number of blood vessels, such as the heart, liver.
Optical quantum generators and their radiation have found application in many industries. For example, in the industry there is a use of lasers for welding, processing and cutting metal and dielectric materials and parts in instrumentation, mechanical engineering and in the textile industry.
Beginning in 1964, low-productivity mechanical hole drilling was replaced by laser drilling. The term laser drilling should not be taken literally. The laser beam does not drill the hole: it pierces it through intense evaporation of the material at the point of impact.
Laser processing of metals. The possibility of receiving high-power light beams of up to 1012 -1016 W / cm2 by laser focusing with spot radiation up to 10-100 microns in diameter makes the laser a powerful means of processing optically opaque materials that are not available for conventional methods (gas and arc welding). This allows for new technological operations, such as drilling very narrow channels in refractory materials, different operations in the manufacture of film circuits, as well as increasing the speed of processing parts. When drilling holes in diamond circles, it reduces the machining time of one circle from 2-3 days to 2 minutes. The most widely used laser in microelectronics, where it is better to weld the joints rather than soldering. Main advantages: absence of mechanical contact, possibility of processing of inaccessible parts, possibility of creation of narrow channels directed at an angle to the work surface.
The laser is also used in the manufacture of fine wires of copper, bronze, tungsten and other metals. In the manufacture of wires, the technology of drawing (drawing) wire through holes of very small diameter is used. These holes (or drawing channels) are drilled in materials that have a particularly high hardness, for example, in superhard alloys. The hardest is known to be a diamond. Therefore, it is best to draw a thin wire through the holes in the diamond. Only they allow to get a wire with a diameter of only 10 microns. However, the mechanical drilling of one hole in the diamond takes 10 hours. But it is quite easy to punch this hole with a series of several powerful laser pulses. As in the case of punching holes in clock-type cameos, solid-state pulsed lasers are used to drill the diamond.
Laser drilling is widely used to obtain openings in materials that are highly brittle. As an example, the substrates of circuits made of alumina ceramics. Due to the high brittleness of ceramics, mechanical drilling is performed on "raw" material. Burn ceramics after drilling. There is some deformation of the product, the relative position of the drilled holes is distorted. When using "laser drills", you can safely work with ceramic substrates, have already passed firing.
Interesting use of the laser and as a universal soldering iron. Suppose an accident occurred inside the cathode-ray tube - any wire broke or broke, contact broke. The tube failed. It would seem that the breakage is irreparable, because the CRT is a device, all the internal components of which are in a vacuum, inside a glass cylinder, and no soldering iron there to penetrate. However, the laser beam can solve such problems as well. By directing the beam to the correct point and focusing it properly, welding work can be performed.
The main example of semiconductor lasers is the magnetic-optical drive.
MO drive is based on a combination of magnetic and optical storage principle. Information is recorded by laser beam and magnetic field, and read by a laser alone.
In the process of writing to the MO disk, the laser beam heats certain points on the disk, and under the influence of temperature, the polarity resistance, for the heated point, drops sharply, which allows the magnetic field to change the polarity of the point. After heating, the resistance increases again but the polarity of the heated point remains in accordance with the magnetic field applied to it at the time of heating. There are currently two cycles, the erasure cycle and the write cycle, in the existing MO storage devices. In the process of erasing, the magnetic field has the same polarity corresponding to binary zeros. The laser beam heats the entire area erased and thus writes a sequence of zeros to the disk. In the recording cycle, the polarity of the magnetic field changes to the opposite, corresponding to the binary unit. In this cycle, the laser beam is switched on only in the areas which should contain binary units and leaving the areas with binary zeros unchanged.
In the process of reading from the MO disk uses the Kerr effect, which is to change the polarization plane of the reflected laser beam, depending on the direction of the magnetic field of the reflecting element. The reflective element in this case is a magnetized point recording on the surface of the disk corresponding to one bit of information. When reading, a laser beam of low intensity is used, which does not lead to the heating of the reading area, thus, when reading stored information is not destroyed.
This method, unlike that used in optical disks, deforms the surface of the disk and allows re-recording without additional equipment. This method also has the advantage over traditional magnetic recording in terms of reliability. Since the magnetization of the disk regions is possible only under the action of high temperature, the probability of accidental magnetization is very low, unlike traditional magnetic recording, which can be caused by accidental magnetic fields.
The scope of MO drives is determined by its high reliability, volume, and variability characteristics. MO disk is required for tasks requiring large disk volume, such tasks as CAD, image processing. However, the slow speed of access to the data makes it impossible to use MO disks for tasks with critical reactivity of systems. Therefore, the use of MO disks in such tasks is to store temporary or backup information on them. For MO disks, it is a very good use to back up your hard drives or databases. Unlike traditionally used streamers for this purpose, storing backup information on the MO disks significantly increases the speed of data recovery after failure. This is because the MO drives are random access devices, allowing only the data to be recovered in the event of a failure. In addition, with this recovery method, there is no need to completely shut down the system until the data is completely restored. These advantages, combined with the high reliability of information storage, make the use of MO disks in backup a cost-effective, albeit more expensive, solution than streamer.