HELLO DIMONOVS !!!
PRICE-50-300R
PRICE-50R
[
PRICE-50R
10- tube of super glue
12- laser printer
chip LM2621
R2 150kΩ
R3 150kΩ
R4 500 Ohm
C2 100uF 6.3V any
So, everything is there ??? GETTING STARTED 
HERE IS A SCHEME for assembly 
(I can send the drawing by PM) 
100% LOSS OF VISION! 
Best regards, T3012, aka KV.
DimonVideo DimonVideo
HELLO DIMONOVS !!!
Today, I will tell YOU how to make a powerful laser pointer at home.
To do this, we need 17 things:
1- faulty (dead) DVD drive, speed 16-22X (the higher the speed, the more powerful the laser is in it)
PRICE-50-300R
2- cheap Chinese flashlight (3 batteries)
PRICE-50R
3- cheap "double barrel" laser pointer (laser pointer + LED flashlight)
[
PRICE-50R
4- soldering iron, power 40W (W), voltage 220V (V) with a thin tip.
5- low-melting solder (POS60-POS61 type), pine rosin.
6- a piece of one-sided fiberglass with dimensions 35X10mm
7- ferric chloride (sold in radio stores) price-80-100R
8- tool (tweezers, magnifying glass, small screwdrivers, pliers, long-nose pliers, etc.)
9- these are the terminal lobes
(sold in any electric store) cost from 10-35R
10- tube of super glue
11- alcohol (can be found in the pharmacy)
12- laser printer
13- page of any glossy magazine (always glossy, smooth, you can use photo paper as well)
14- electric iron (we take at home. From mom, sister, grandmother, wife, until they see)
15- radio parts (you can add some from the dead drive itself, in particular the Schottky diode, resistors, capacitors)
list of parts and their denomination (ALL PARTS SMD, i.e. for surface mounting (space saving))
chip LM2621
R1 needs to be selected .. the current on the Laser diode depends on it. I have 78kOhm current 250-300mA NO MORE !!! otherwise it will burn !!!
R2 150kΩ
R3 150kΩ
R4 500 Ohm
C1 0.1μF ceramics, for example k10-17
C2 100uF 6.3V any
C3 33μF 6.3V, preferably tantalum.
C4 33pF ceramics, for example k10-17
C5 0.1μF ceramics, for example k10-17
VD1 any 3 ampere. eg
1N5821, 30BQ060, 31DQ10, MBRS340T3, SB360, SK34A, SR360
L1 on the photo you can see how it looks .. and so, 15 turns on a suitable ring or ferrite frame. you can disassemble either a computer power supply unit or an energy-saving light bulb, or a charger for a mobile phone, including a car charger for a mobile phone.
All this is not so important, the microcircuit will expose everything as it should.
16- multimeter type DT890G, allowing to measure capacitance, resistance, voltage and so on.
17- well, of course, straight HANDS and "friendship with a soldering iron" or a friend who is friends with a soldering iron
So, everything is there ??? GETTING STARTED
We take the keychain-pointer, and disassemble it (CAREFULLY, DO NOT DAMAGE THE INTERIOR, we will need them)
we take out the batteries, and with pliers, gently shaking to the sides, we take out the front plastic head (where the flashlight and laser are)
Then, through the side where this (cork) was, we take out the insides, pushing them with a pencil from the side of the battery compartment
Then, very carefully, with a small piece with a flat sting, we unscrew the plastic nut in the collimator (the brass tube where the lens and the frameless laser itself are located). We take out the contents (the plastic nut itself, the lens, the spring)
warming up the EMPTY collimator with a soldering iron, disconnect it from the board with the button.
We disassemble the drive and take out the carriage of the laser device
EXTREMELY carefully take out the LASER, having previously wrapped the legs of the Laser with a wire, from static.
this is itself, the Laser Diode.
We take a Chinese flashlight and disassemble it. Roughly analogous to a flashlight pointer.
Now, we will put all the little things in a reliable box, and we will make a heat sink for the Laser.
We take previously purchased terminals
and saw off from them in part, so that we get a type of washer, equal in length to the length of the collimator, and so that they (the washers fit tightly into each other, including the collimator itself) If they do not go into each other, we drill with drills with a diameter of 5, 5-12mm for different washers, or we can grind.
It should look something like this:
We push the collimator a little further, about 5mm, this is important for fixing the Laser Diode.
Yes, we fix the washers themselves with super glue.
So, now we mount the Laser Diode, after inserting a 5mm drill to the collimator and pressing the collimator with pliers, from the side of the slots where the board was.
We solder 2 wires to the LD legs. ATTENTION L.D. we call the device with a multimeter of the DT890G type (it rings like a regular diode.)
Next, we need to assemble the driver circuit.
HERE IS A SCHEME for assembly
HERE is an approximate drawing of the conductors on the board
(I can send the drawing by PM)
We transfer the board drawing to glossy paper with a laser printer (laser-ironing method, read on the Internet)
we make a board, and we solder parts on it. It should look like this:
Assembly method, your imagination. I assembled the driver in the battery compartment, in place of the third battery.
used VARTA 800mA / H batteries
I used the lens from a flashlight pointer, but you can also use my own lens from the drive
only it has a smaller focal length, you will have to put another spring in order to support the lens closer to the Laser Diode.
Attention! LASER RADIATION IS EXTREMELY DANGEROUS FOR THE EYES!
NEVER SEND PEOPLE OR ANIMALS FROM THE SIDE!
100% LOSS OF VISION!
i got such a device:
DO NOT turn on L.D itself without a radiator, it gets very hot and burns out. Set the current consumption by the Laser Diode to 250-300mA using the resistor R1 (it is advisable to temporarily put a resistor of 100k, and instead of the Laser Diode (so as not to burn the LD), a chain of 4 diodes KD105 connected in series)
Best regards, T3012, aka KV. "\u003e
Who in childhood did not dream of laser? Some men still dream. Conventional laser pointers with low power are no longer relevant for a long time, as their power leaves much to be desired. There are only 2 ways left: buy an expensive laser or make it at home using improvised means.
There are the following methods of making a laser with your own hands:
- From an old or broken DVD drive
- From a computer mouse and flashlight
- From a kit of parts purchased from an electronics store
How to make a laser at home from an old oneDVD drive
How to make a laser from a computer mouse
The power of a laser made from a computer mouse will be much less than the power of a laser made from the previous method. The manufacturing procedure is not very different.
- The first step is to find an old or unwanted mouse with a visible laser of any color. Mice with an invisible glow will not work for obvious reasons.
- Then carefully disassemble it. Inside, you will notice a laser that will have to be soldered with a soldering iron
- Now repeat steps 3-5 from the above instructions. The difference between such lasers, we repeat, is only in power.
It is the most advanced, but also expensive technology. But with its help, you can achieve results that are beyond the power of other metal processing methods. The ability of laser beams to shape any material you want is truly endless.
The unique capabilities of a laser are based on characteristics:
- Sharp directionality - due to the ideal directionality of the laser beam, energy is focused at the point of impact with a minimum of losses,
- Monochromaticity - the wavelength of the laser beam is fixed, and the frequency is constant. This allows you to focus it with conventional lenses,
- Coherence - laser beams have a high level of coherence, therefore, their resonant vibrations increase the energy by several orders of magnitude,
- Power - The above properties of laser beams provide the highest density energy focusing on the smallest material area. This allows you to destroy or burn any material in a microscopically small area.
Device and principles of operation
Any laser device consists of the following components:
- energy source;
- working body that produces energy;
- an optoamplifier, a fiber-optic laser, a system of mirrors that amplify the radiation of the working body.
The laser beam creates a point heating and melting of the material, and after prolonged exposure - its evaporation. As a result, the seam comes out with an uneven edge, the evaporating material is deposited on the optics, which shortens its service life.
To obtain even thin seams and remove vapors, the technique of blowing out melt products from the zone of laser action with inert gases or compressed air is used.
Factory model lasers equipped with high grade materials can provide a good indentation rate. But for domestic use, they have too high a price.
Models made at home are capable of cutting into metal to a depth of 1-3 cm. This is enough to make, for example, details for decorating gates or fences.
Depending on the technology used, there are 3 types of cutters:
- Solid state. Compact and easy to use. The active element is a semiconductor crystal. The low-power models have an affordable price.
- Fiber. Fiberglass is used as a radiation and pumping element. The advantages of fiber laser cutters are high efficiency (up to 40%), long service life and compactness. As little heat is generated during operation, there is no need to install a cooling system. Modular designs can be produced to combine the power of multiple heads. The radiation is transmitted over flexible optical fiber. The performance of such models is higher than solid-state ones, but their cost is more expensive.
- ... These are inexpensive but powerful emitters based on the use of the chemical properties of a gas (nitrogen, carbon dioxide, helium). They can be used to cook and cut glass, rubber, polymers and metals with a very high level of thermal conductivity.
Homemade household laser
To carry out repair work and the manufacture of metal products in everyday life, laser cutting of metal with your own hands is often required. Therefore, home craftsmen have mastered the manufacture and successfully use hand-held laser devices.
At the cost of manufacturing for household needs, a solid-state laser is more suitable.
The power of a home-made device, of course, cannot even be compared with production devices, but it is quite suitable for domestic use.
How to assemble a laser using inexpensive parts and unnecessary items.
To make the simplest device you will need:
- laser pointer;
- rechargeable flashlight;
- cD / DVD-RW writer (old and faulty one will do);
- soldering iron, screwdrivers.
How to make a handheld laser engraver
Laser cutter manufacturing process
- From the computer drive, you need to remove the red diode, which burns the disc during recording. Please note that the drive must be a writing drive.
After dismantling the upper fasteners, remove the carriage with the laser. To do this, carefully remove the connectors and screws.
To remove the diode, it is necessary to unsolder the fasteners of the diode and remove it. This must be done very carefully. The diode is very sensitive and can be easily damaged by dropping it or shaking it violently.
- The diode contained in it is removed from the laser pointer, and a red diode is inserted from the drive instead. The pointer body is disassembled into two halves. The old diode is shaken out by tipping it with the edge of a knife. Instead, a red diode is placed and secured with glue.
- It is easier and more convenient to use a flashlight as a laser cutter body. The upper fragment of the pointer with a new diode is inserted into it. The glass of the flashlight, which is an obstacle to the directional laser beam, and parts of the pointer must be removed.
When connecting the diode to battery power, it is important to clearly observe the polarity.
- At the last stage, they check how securely all the elements of the laser are fixed, the wires are correctly connected, the polarity is observed and the laser is installed evenly.
The laser cutter is ready. Due to its low power, it cannot be used in work with metal. But if you need a device that cuts paper, plastic, polyethylene and other similar materials, then this cutter is fine.
How to increase the power of a laser for cutting metal
You can make a more powerful laser for cutting metal with your own hands by equipping it with a driver assembled from several parts. The board provides the cutter with the required power.
You will need the following parts and devices:
- cD / DVD-RW writer (old or faulty one will do), with a write speed of more than 16x;
- 3.6 volt batteries - 3 pcs.;
- 100 pF and 100 mF capacitors;
- resistance 2-5 Ohm;
- collimator (instead of a laser pointer);
- steel LED lantern;
- soldering iron and wires.
Do not connect the current source directly to the diode, otherwise it will burn out. The diode takes power from the current, not from the voltage.
Beams are focused into a thin beam using a collimator. It is used instead of a laser pointer.
Sold in an electrical store. This part has a socket where the laser diode is mounted.
The assembly of the laser cutter is the same as the above model.
To remove static from the diode, they are wound around it. Antistatic bracelets can be used for the same purpose.
To check the operation of the driver, measure the current supplied to the diode with a multimeter. To do this, a non-working (or second) diode is connected to the device. For most home-made devices, a current of 300-350 mA is sufficient.
If a more powerful laser is needed, the indicator can be increased, but not more than 500 mA.
It is better to use an LED flashlight as a housing for homemade products. It is compact and easy to use. To prevent the lenses from getting dirty, the device is stored in a special case.
Important! The laser cutter is a kind of weapon, so you cannot point it at people, animals or give it to children. It is not recommended to carry it in your pocket.
It should be noted that laser cutting of thick workpieces with your own hands is impossible, but he will cope with everyday tasks.
Many radio amateurs at least once in their lives wanted to make a laser with their own hands. It was once believed that it was possible to collect it only in scientific laboratories. Yes, this is so when it comes to huge laser installations. However, a simpler laser can be assembled, which will also be quite powerful. The idea seems very complicated, but in reality it is not difficult at all. In our video article, we'll show you how you can build your own laser at home.
Do-it-yourself powerful laser
Diy laser scheme
It is very important to follow basic safety rules. Firstly, when checking the operation of the device or when it is already completely assembled, in no case should it be directed into the eyes, at other people or animals. Your laser will be so powerful that it can light a match or even a sheet of paper. Secondly, follow our scheme and then your device will work for a long time and efficiently. Thirdly, do not let children play with it. Finally, store the assembled device in a safe place.
To assemble a laser at home, you will not need too much time and components. So, first you need a DVD-RW drive. He can be both working and non-working. It doesn't matter. But it is very important that this is exactly a recording device, and not a regular drive for playing discs. The write speed of the drive must be 16x. It is possible and higher. Next, you need to find a module with a lens, thanks to which the laser can focus at one point. An old Chinese pointer may well work for this. It is best to use an unnecessary steel lantern as the body of the future laser. The "filling" for it will be wires, batteries, resistors and capacitors. Also, do not forget to prepare a soldering iron - without it, assembly will be impossible. Now let's see how the laser should be assembled from the components described above.
Diy laser scheme
The first thing to do is to disassemble the DVD drive. Remove the optical part from the drive by disconnecting the ribbon cable. Then you will see a laser diode - it must be carefully removed from the case. Remember that a laser diode is extremely sensitive to temperature fluctuations, especially cold. Until you install the diode in the future laser, it is best to rewind the diode leads with a thin wire.
Most often, laser diodes have three leads. The one in the middle gives a minus. And one of the extreme is a plus. You should take two finger-type batteries and connect to the diode removed from the case with a 5 ohm resistor. For the laser to light up, you need to connect the minus of the battery to the middle terminal of the diode, and the plus to one of the extreme. Now you can assemble the laser emitter circuit. By the way, the laser can be powered not only from batteries, but also from a rechargeable battery. This is everyone's business.
You can use an old Chinese pointer so that your device is going to a point when turned on, replacing the laser from the pointer with the one you have assembled. The whole structure can be neatly packed into the case. So it will look more beautiful and last longer. An unnecessary steel lantern can serve as a housing. But it can also be almost any capacity. We choose a flashlight not only because it is more durable, but also because it will make your laser look much more presentable.
Thus, you yourself have seen that assembling a sufficiently powerful laser at home does not require deep knowledge of science or prohibitively expensive equipment. Now you can assemble the laser yourself and use it as intended.
THE MOST POWERFUL LASER ON YUTUBE 10000 mW! SWORD OF THE JEDI!
HOW TO MAKE A CUTTING LASER FROM DVD DRIVE
Today we will talk about how to make a powerful green or blue laser yourself at home from improvised materials with your own hands. We will also consider the drawings, diagrams and the device of homemade laser pointers with an incendiary beam and a range of up to 20 km
The basis of the laser device is an optical quantum generator, which, using electrical, thermal, chemical or other energy, produces a laser beam.
The operation of a laser is based on the phenomenon of stimulated (induced) radiation. Laser radiation can be continuous, with constant power, or pulsed, reaching extremely high peak powers. The essence of the phenomenon is that an excited atom is able to emit a photon under the action of another photon without absorbing it, if the energy of the latter is equal to the difference between the energies of the levels of the atom before and after radiation. In this case, the emitted photon is coherent to the photon that caused the radiation, that is, it is its exact copy. Thus, the light is amplified. This differs from spontaneous emission, in which the emitted photons have random directions of propagation, polarization and phase
The probability that a random photon will cause the induced emission of an excited atom is exactly equal to the probability that this photon will be absorbed by an atom in an unexcited state. Therefore, to amplify light, it is necessary that there are more excited atoms in the medium than unexcited ones. In a state of equilibrium, this condition is not fulfilled; therefore, various systems for pumping the laser active medium (optical, electrical, chemical, etc.) are used. In some schemes, the working element of the laser is used as an optical amplifier for radiation from another source.
There is no external photon flux in a quantum generator; an inverse population is created inside it using various pump sources. There are different pumping methods depending on the sources:
optical - powerful flash lamp;
gas discharge in the working substance (active medium);
injection (transfer) of current carriers in a semiconductor in the
p — n transitions;
electronic excitation (irradiation in a vacuum of a pure semiconductor with an electron flow);
thermal (heating the gas with its subsequent sharp cooling;
chemical (use of the energy of chemical reactions) and some others.
The primary source of generation is the process of spontaneous emission, therefore, to ensure the continuity of photon generations, the existence of a positive feedback is necessary, due to which the emitted photons cause subsequent acts of induced emission. For this, the active medium of the laser is placed in an optical cavity. In the simplest case, it consists of two mirrors, one of which is semitransparent - through it the laser beam partially leaves the resonator.
Reflecting from the mirrors, the radiation beam repeatedly passes through the cavity, causing induced transitions in it. The radiation can be either continuous or pulsed. At the same time, using various devices to quickly turn off and on the feedback and thereby reduce the pulse period, it is possible to create conditions for generating very high power radiation - these are the so-called giant pulses. This mode of laser operation is called Q-switched mode.
The laser beam is a coherent, monochrome, polarized narrowly directed light flux. In short, this is a beam of light emitted not only by synchronous sources, but also in a very narrow range, and directed. A sort of extremely concentrated light flux.
The radiation generated by the laser is monochromatic, the probability of emission of a photon of a certain wavelength is greater than that of a closely located one, associated with broadening of the spectral line, and the probability of induced transitions at this frequency also has a maximum. Therefore, gradually in the process of generation, photons of a given wavelength will dominate over all other photons. In addition, due to the special arrangement of the mirrors, only those photons are retained in the laser beam that propagate in a direction parallel to the optical axis of the resonator at a short distance from it, the rest of the photons quickly leave the cavity volume. Thus, the laser beam has a very small divergence angle. Finally, the laser beam has a strictly defined polarization. For this, various polarizers are introduced into the resonator, for example, they can be flat glass plates installed at a Brewster angle to the direction of propagation of the laser beam.
The working wavelength of the laser, as well as other properties, depend on what working fluid is used in the laser. The working fluid is "pumped" with energy to obtain the effect of inversion of electron populations, which causes stimulated emission of photons and the effect of optical amplification. The simplest form of an optical resonator is two parallel mirrors (there can also be four or more), located around the working body of the laser. The stimulated radiation of the working medium is reflected back by the mirrors and is amplified again. Until the moment it comes out, the wave can be reflected many times.
So, let us briefly formulate the conditions necessary to create a source of coherent light:
you need a working substance with an inverse population. Only then can the amplification of light be obtained due to forced transitions;
the working substance should be placed between the mirrors that provide feedback;
the gain given by the working substance, which means that the number of excited atoms or molecules in the working substance must be greater than the threshold value, which depends on the reflection coefficient of the output mirror.
The following types of working bodies can be used in the design of lasers:
Liquid. It is used as a working medium, for example, in dye lasers. The composition contains an organic solvent (methanol, ethanol or ethylene glycol), in which chemical dyes (coumarin or rhodamine) are dissolved. The operating wavelength of liquid lasers is determined by the configuration of the dye molecules used.
Gases. In particular, carbon dioxide, argon, krypton or gas mixtures such as in helium-neon lasers. These lasers are usually "pumped" with energy by means of electrical discharges.
Solids (crystals and glasses). The solid material of such working bodies is activated (doped) by adding a small amount of chromium, neodymium, erbium or titanium ions. The crystals commonly used are: yttrium aluminum garnet, yttrium lithium fluoride, sapphire (alumina) and silicate glass. Solid state lasers are usually "pumped" by a flash lamp or other laser.
Semiconductors. A material in which the transition of electrons between energy levels can be accompanied by radiation. Semiconductor lasers are very compact, "pumped" with an electric current, which allows them to be used in home appliances such as CD players.
To turn an amplifier into an oscillator, it is necessary to provide feedback. In lasers, it is achieved by placing an active substance between reflective surfaces (mirrors), forming a so-called "open resonator" due to the fact that part of the energy emitted by the active substance is reflected from the mirrors and returns to the active substance
The Laser uses various types of optical resonators - with flat mirrors, spherical, combinations of flat and spherical, etc. In optical resonators that provide feedback in the Laser, only certain types of electromagnetic field oscillations can be excited, which are called natural oscillations or resonator modes.
The modes are characterized by frequency and shape, that is, the spatial distribution of vibrations. In a resonator with flat mirrors, types of oscillations are predominantly excited, corresponding to plane waves propagating along the resonator axis. A system of two parallel mirrors resonates only at certain frequencies - and also plays the role in a laser that an oscillatory circuit plays in conventional low-frequency generators.
The use of an open resonator (and not a closed - closed metal cavity - characteristic of the microwave range) is fundamental, since in the optical range a resonator with dimensions L \u003d? (L is the characteristic size of the resonator,? Is the wavelength) simply cannot be manufactured, and for L \u003e\u003e? a closed resonator loses its resonant properties, since the number of possible modes of oscillation becomes so large that they overlap.
The absence of side walls significantly reduces the number of possible types of oscillations (modes) due to the fact that waves propagating at an angle to the axis of the resonator quickly leave its limits, and allows maintaining the resonance properties of the resonator at L \u003e\u003e?. However, the resonator in the laser not only provides feedback due to the return of the radiation reflected from the mirrors to the active substance, but also determines the spectrum of the laser radiation, its energy characteristics, and the directivity of the radiation.
In the simplest plane-wave approximation, the resonance condition in a resonator with flat mirrors is that an integer number of half-waves fits into the resonator length: L \u003d q (λ / 2) (q is an integer), which leads to an expression for the frequency of the oscillation type with the index q:? q \u003d q (C / 2L). As a result, the radiation spectrum of lasers, as a rule, is a set of narrow spectral lines, the intervals between which are the same and equal to c / 2L. The number of lines (components) at a given length L depends on the properties of the active medium, i.e., on the spectrum of spontaneous emission at the used quantum transition and can reach several tens and hundreds. Under certain conditions, it turns out to be possible to isolate one spectral component, i.e., to implement a single-mode generation regime. The spectral width of each of the components is determined by the energy loss in the cavity and, first of all, by the transmission and absorption of light by the mirrors.
Frequency profile of the gain in the working medium (it is determined by the width and shape of the working medium line) and the set of natural frequencies of the open resonator. For open resonators with a high Q factor used in lasers, the resonator passband Δp, which determines the width of the resonance curves of individual modes, and even the distance between adjacent modes ΔΔh turn out to be less than the gain line width ΔΔh, and even in gas lasers, the broadening of the lines is the smallest. Therefore, several types of resonator oscillations fall into the amplification circuit.
Thus, the laser does not necessarily generate at the same frequency; more often, on the contrary, generation occurs simultaneously on several types of oscillations, for which the gain? more losses in the resonator. In order for the laser to operate at one frequency (in single-frequency mode), it is usually necessary to take special measures (for example, to increase losses, as shown in Fig. 3) or to change the distance between the mirrors so that only one fashion. Since in optics, as noted above, ?h\u003e p and the lasing frequency in a laser is determined mainly by the resonator frequency, in order to keep a stable lasing frequency, it is necessary to stabilize the resonator. So, if the gain in the working substance overlaps the losses in the resonator for certain types of oscillations, generation occurs on them. The seed for its occurrence is, as in any generator, noise, which is spontaneous emission in lasers.
In order for the active medium to emit coherent monochromatic light, it is necessary to introduce feedback, that is, to direct part of the light flux emitted by this medium back into the medium for stimulated emission. Positive feedback is carried out using optical resonators, which in an elementary version are two coaxially (parallel and along the same axis) mirrors, one of which is semitransparent, and the other is "dull", that is, fully reflects the light flux. The working substance (active medium), in which the inverse population is created, is placed between the mirrors. The stimulated radiation passes through the active medium, amplifies, reflects from the mirror, passes through the medium again, and becomes even more amplified. Through a semitransparent mirror, part of the radiation is emitted into the external medium, and part is reflected back into the medium and amplified again. Under certain conditions, the flux of photons inside the working substance will begin to grow like an avalanche, and the generation of monochromatic coherent light will begin.
The principle of operation of an optical resonator, the predominant number of particles of the working substance, represented by open circles, are in the ground state, that is, at the lower energy level. Only a small number of particles, represented by dark circles, are in an electronically excited state. When the working substance is exposed to a pumping source, the main number of particles passes into an excited state (the number of dark circles has increased), and an inverted population is created. Further (Fig. 2c) there is a spontaneous emission of some particles in an electronically excited state. Radiation directed at an angle to the resonator axis will leave the working substance and the resonator. Radiation, which is directed along the axis of the resonator, will approach the mirror surface.
In a semitransparent mirror, part of the radiation will pass through it into the environment, and some will be reflected and again directed into the working substance, involving particles in an excited state in the process of forced radiation.
At the "dull" mirror, the entire ray flux will be reflected and again pass through the working substance, inducing radiation of all the remaining excited particles, where the situation is reflected when all excited particles have given up their stored energy, and at the exit of the resonator, on the side of the semitransparent mirror, a powerful flux of induced radiation is formed.
The main structural elements of lasers include a working substance with certain energy levels of their constituent atoms and molecules, a pump source that creates an inverse population in the working substance, and an optical resonator. There are a large number of different lasers, but they all have the same and, moreover, a simple schematic diagram of the device, which is shown in Fig. 3.
The exception is semiconductor lasers due to their specificity, since they have everything special: the physics of the processes, and the pumping methods, and the design. Semiconductors are crystalline formations. In an individual atom, the energy of an electron takes on strictly defined discrete values, and therefore the energy states of an electron in an atom are described in terms of levels. In a semiconductor crystal, energy levels form energy bands. In a pure semiconductor that does not contain any impurities, there are two bands: the so-called valence band and the conduction band located above it (on the energy scale).
Between them there is a gap of forbidden energy values, which is called a forbidden zone. At a semiconductor temperature equal to absolute zero, the valence band must be completely filled with electrons, and the conduction band must be empty. In real conditions, the temperature is always above absolute zero. But an increase in temperature leads to thermal excitation of electrons, some of them jump from the valence band to the conduction band.
As a result of this process, a certain (relatively small) number of electrons appears in the conduction band, and the corresponding number of electrons will not be enough in the valence band until it is completely filled. An electron vacancy in the valence band appears to be a positively charged particle called a hole. The quantum transition of an electron through the band gap from bottom to top is considered as the process of generating an electron-hole pair, with electrons concentrated at the lower edge of the conduction band, and holes - at the upper edge of the valence band. Crossings through the forbidden zone are possible not only from bottom to top, but also from top to bottom. This process is called electron-hole recombination.
When a pure semiconductor is irradiated with light, the photon energy of which slightly exceeds the band gap, three types of interaction of light with matter can occur in a semiconductor crystal: absorption, spontaneous emission, and forced emission of light. The first type of interaction is possible when a photon is absorbed by an electron located near the upper edge of the valence band. In this case, the energy power of the electron will become sufficient to overcome the forbidden zone, and it will make a quantum transition to the conduction band. Spontaneous emission of light is possible with the spontaneous return of an electron from the conduction band to the valence band with the emission of an energy quantum - a photon. External radiation can initiate a transition to the valence band of an electron located near the lower edge of the conduction band. The result of this, the third type of interaction of light with the substance of the semiconductor, will be the creation of a secondary photon, identical in its parameters and direction of motion to the photon that initiated the transition.
To generate laser radiation, it is necessary to create an inverted population of "working levels" in a semiconductor - to create a sufficiently high concentration of electrons at the lower edge of the conduction band and, accordingly, a high concentration of holes at the edge of the valence band. For these purposes, pure semiconductor lasers are usually pumped by an electron flow.
The mirrors of the resonator are polished semiconductor crystal faces. The disadvantage of such lasers is that many semiconductor materials generate laser radiation only at very low temperatures, and the bombardment of semiconductor crystals with a stream of electrons causes it to be strongly heated. This requires additional cooling devices, which complicates the design of the apparatus and increases its dimensions.
The properties of semiconductors with impurities differ significantly from the properties of pure, pure semiconductors. This is due to the fact that atoms of some impurities easily donate one of their electrons to the conduction band. These impurities are called donor impurities, and a semiconductor with such impurities is called an n-semiconductor. Atoms of other impurities, on the contrary, capture one electron from the valence band, and such impurities are acceptor, and a semiconductor with such impurities is a p-semiconductor. The energy level of impurity atoms is located inside the forbidden band: for n-semiconductors - near the lower edge of the conduction band, for y-semiconductors - near the upper edge of the valence band.
If an electric voltage is created in this region so that there is a positive pole on the side of the p-semiconductor and negative on the side of the n-semiconductor, then under the action of the electric field, electrons from the n-semiconductor and holes from the p-semiconductor will move (injected) into area of \u200b\u200bpn - transition.
When electrons and holes recombine, photons will be emitted, and in the presence of an optical cavity, laser radiation can be generated.
The mirrors of the optical resonator are polished semiconductor crystal faces oriented perpendicular to the pn junction plane. Such lasers are diminutive, since the dimensions of a semiconductor active element can be about 1 mm.
Depending on the feature under consideration, all lasers are subdivided as follows).
First sign. It is customary to distinguish between laser amplifiers and generators. In amplifiers, weak laser radiation is supplied at the input, and at the output it is correspondingly amplified. There is no external radiation in the generators; it arises in the working substance due to its excitation with the help of various pump sources. All medical laser machines are generators.
The second sign is the physical state of the working substance. In accordance with this, lasers are divided into solid-state (ruby, sapphire, etc.), gas (helium-neon, helium-cadmium, argon, carbon dioxide, etc.), liquid (liquid dielectric with impurity working atoms of rare-earth metals) and semiconductor (arsenide -gallium, arsenide-phosphide-gallium, selenide-lead, etc.).
The method of exciting the working substance is the third distinguishing feature of lasers. Depending on the excitation source, lasers are distinguished with optical pumping, pumped by a gas discharge, electronic excitation, injection of charge carriers, with thermal, chemical pumping, and some others.
The laser emission spectrum is the next classification feature. If the radiation is concentrated in a narrow range of wavelengths, then the laser is considered to be monochromatic and its technical data indicates a specific wavelength; if in a wide range, then the laser should be considered broadband and the wavelength range is indicated.
Pulse lasers and continuous-wave lasers are distinguished by the nature of the emitted energy. You should not confuse the concepts of a pulsed laser and a laser with frequency modulation of continuous radiation, since in the second case we receive, in fact, intermittent radiation of different frequencies. Pulsed lasers have a high power in a single pulse, reaching 10 W, while their average pulse power, determined by the corresponding formulas, is relatively low. For cw lasers with frequency modulation, the power in the so-called pulse is lower than the cw power.
According to the average output radiation power (the next feature of the classification), lasers are divided into:
· High-energy (generated flux density, radiation power on the surface of an object or biological object - over 10 W / cm2);
· Medium-energy (generated flux density, radiation power - from 0.4 to 10 W / cm2);
· Low-energy (generated flux density, radiation power - less than 0.4 W / cm2).
· Soft (generated energy irradiance - E or power flux density on the irradiated surface - up to 4 mW / cm2);
Average (E - from 4 to 30 mW / cm2);
· Hard (E - more than 30 mW / cm2).
In accordance with the "Sanitary Norms and Rules for the Construction and Operation of Lasers No. 5804-91", lasers are divided into four classes according to the degree of hazard of generated radiation for service personnel.
Lasers of the first class include such technical devices, the output collimated (enclosed in a limited solid angle) radiation of which does not pose a danger when irradiating the eyes and skin of a person.
Class II lasers are devices whose output radiation is hazardous if the eyes are exposed to direct and specularly reflected radiation.
Lasers of the third class are devices whose output radiation is dangerous when the eyes are irradiated with direct and specularly reflected, as well as diffusely reflected radiation at a distance of 10 cm from a diffusely reflecting surface, and (or) when the skin is irradiated with direct and specularly reflected radiation.
Lasers of the fourth class are devices whose output radiation is dangerous when the skin is irradiated by diffusely reflected radiation at a distance of 10 cm from the diffusely reflecting surface.