Semiconductor injection laser. Coursework semiconductor laser Calculation and design of a semiconductor laser

Semiconductor injection lasers, just like another type of solid-state radiators - leds, are the most important element of any optoelectronic system. The operation of both devices is based on the phenomenon electroluminescence. With regard to the above semiconductor emitters, the electroluminescence mechanism is realized by radiative recombination nonequilibrium charge carriers injected through p-n transition.

The first LEDs appeared at the turn of the 50s and 60s of the twentieth century, and already in 1961 N.G. Basov, O.N. Krokhin and Yu.M. Popov proposed to use injection in degenerate p-n junctions to obtain a laser effect. In 1962, American physicists R. Hall and collaborators managed to register the narrowing of the spectral line of the semiconductor LED, which was interpreted as a manifestation of the laser effect ("superradiance"). In 1970, Russian physicists - Zh.I. Alferov with collaborators were made the first heterostructure lasers. This made it possible to make the devices suitable for mass serial production, which was awarded the Nobel Prize in Physics in 2000. At present, semiconductor lasers are most widely used, mainly in devices for writing and reading information from computer, audio and video CDs. The main advantages of semiconductor lasers are:

1. profitability, ensured by high efficiency of pump energy conversion into coherent radiation energy;

2. small inertia, due to short characteristic times of establishment of the generation mode (~ 10 -10 s);

3. compactness, associated with the property of semiconductors to provide tremendous optical gain;

4. simple device, low-voltage power supply, compatibility with integrated circuits (“microchips”);

5. Opportunity smooth tuning of the wavelength in a wide range due to the dependence of the optical properties of semiconductors on temperature, pressure, etc.

Main Feature semiconductor lasers is the use in them optical transitions involving energy levels (energy states) main electronic energy zones crystal. This is the difference between semiconductor lasers and, for example, ruby ​​lasers, which use optical transitions between the impurity levels of the chromium ion Cr 3+ in Al 2 O 3 . Semiconductor compounds A III B V proved to be the most suitable for use in semiconductor lasers (see Introduction). It is on the basis of these compounds and their solid solutions most of the semiconductor lasers are manufactured by industry. In many semiconductor materials of this class, the recombination of excess current carriers is carried out by direct optical transitions between filled states near the bottom of the conduction band and free states near the top of the valence band (Fig. 1). High probability of optical transitions in direct-gap semiconductors and a high density of states in the bands make it possible to obtain high optical gain in a semiconductor.

Fig.1. Photon emission during radiative recombination in a direct-gap semiconductor with inverse population.

Let us consider the basic principles of operation of a semiconductor laser. If a semiconductor crystal is in a state thermodynamic equilibrium with the environment, then he is only capable of absorb radiation falling on it. Intensity of light that has traveled a distance in a crystal X, is given by the known relation Booger-Lambert

Here R- coefficient of reflection of light;

α - light absorption coefficient.

To light intensified passing through the crystal, and not weakened, it is required that the coefficient α was less than zero, which thermodynamically equilibrium environment is impossible. The operation of any laser (gas, liquid, solid state) requires that the working environment of the laser be in the state inverse population - such a state in which the number of electrons at high-lying energy levels would be greater than at lower levels (such a state is also called the "state with a negative temperature"). Let us obtain a relation describing the state with inverse population in semiconductors.

Let ε 1 And ε 2 – optically coupled between themselves energy levels, the first of which is in the valence, and the second - in the conduction band of the semiconductor (Fig. 2). The term "optically coupled" means that electron transitions between them are allowed by the selection rules. Absorbing a quantum of light with energy hv 12, the electron moves from the level ε 1 to the level ε 2. The speed of such a transition will be proportional to the probability of populating the first level f 1 , the probabilities that the second level is empty: (1- f 2), and photon flux density P(hν 12)

The reverse transition - from the upper level to the lower one, can occur in two ways - due to spontaneous And forced recombination. In the second case, the interaction of a light quantum with an electron located at the level ε 2 “forces” the electron to recombine with emission quantum of light identical the one that caused the process of forced recombination. That. in the system there is an amplification of light, which is the essence of the operation of the laser. The rates of spontaneous and forced recombination will be written as:

(3)

In a state of thermodynamic equilibrium

. (5)

Using condition 5, one can show that the coefficients AT 12, AT 21 And A 21(“Einstein coefficients”) are interconnected, namely:

, (6)

Where n- refractive index of the semiconductor; With is the speed of light.

In what follows, however, we will not take into account spontaneous recombination, since The spontaneous recombination rate does not depend on the photon flux density in the working laser medium, and the stimulated recombination rate will be at large values Р(hν 12) significantly exceed the rate of spontaneous recombination. In order for the light to be amplified, the rate of forced “top-down” transitions must exceed the rate of “bottom-up” transitions:

Having written down the probabilities of population of levels with energy by electrons ε 1 And ε 2 as

, (8)

we obtain the condition of inverse population in semiconductors

because minimum distance between levels ε 1 And ε 2 just equal to the band gap of the semiconductor ε g . This ratio is known as Bernard-Durafour ratio.

Formula 9 includes the values ​​of the so-called. quasi-Fermi levels- Fermi levels separately for the conduction band F C and valence band F V. Such a situation is possible only for a nonequilibrium, or rather, for quasi-equilibrium systems. For the formation of Fermi levels in both allowed bands (levels separating the electron-filled and empty states (see Introduction)), it is required that pulse relaxation time electrons and holes were several orders of magnitude less life time excess charge carriers:

As a result nonequilibrium in general, an electron-hole gas can be considered as a combination equilibrium electronic gas in the conduction band and equilibrium hole gas in the valence band (Fig. 2).

Fig.2. Energy diagram of a semiconductor with inverse level population. The states filled with electrons are shaded.

The procedure for creating an inverse population in the working medium of a laser (in our case, in a semiconductor crystal) is called pumping. Semiconductor lasers can be pumped from outside by light, a beam of fast electrons, a strong radio-frequency field, or impact ionization in the semiconductor itself. But the most simple, economical and, due to the fact that the most common method of pumping semiconductor lasers is injection charge carriers in a degenerate p-n junction(see the manual “Physics of semiconductor devices”; tunnel diode). The principle of such pumping is clear from Fig. 3, which shows energy diagram such a transition in a state of thermodynamic equilibrium and at large forward displacement. It can be seen that in the region d, directly adjacent to the p-n junction, an inverse population is realized - the energy distance between the quasi-Fermi levels is greater than the band gap.

Fig.3. A degenerate p-n junction in thermodynamic equilibrium (left) and with a large forward bias (right).

However, creating inverse population in a work environment is necessary, but also not a sufficient condition to generate laser radiation. In any laser, and in a semiconductor laser in particular, part of the pump power supplied to the device will be uselessly lost. And only when the pump power exceeds a certain value - generation threshold, the laser begins to work as a quantum light amplifier. When the generation threshold is exceeded:

· A) increases sharply intensity of radiation emitted by the device (Fig. 4a);

b) narrows spectral line radiation (Fig. 4b);

c) radiation becomes coherent and focused.

Fig.4. The increase in intensity (left) and the narrowing of the spectral line of radiation (right) of a semiconductor laser when the current exceeds the threshold value.

To achieve the threshold conditions for generation, the laser working medium is usually placed in optical resonator. This increases the length of the optical path light beam in the working environment, facilitates the achievement of the generation threshold, contributes to better focusing of the beam, etc. Of the variety of types of optical cavities in semiconductor lasers, the simplest Fabry-Perot resonator- two plane-parallel mirrors perpendicular to the p-n junction. Moreover, polished edges of the semiconductor crystal itself are used as mirrors.

Consider the passage of an electromagnetic wave through such a resonator. Let us take the transmittance and the reflection coefficient of the left mirror of the resonator as t1 And r1, right (through which the radiation goes out) - behind t2 And r2; resonator length - L. Let an electromagnetic wave fall on the left side of the crystal from the outside, the equation of which we write in the form:

. (11)

After passing through the left mirror, the crystal and the right mirror, part of the radiation will go through the right face of the crystal, and part will be reflected and again go to the left face (Fig. 5).

Fig.5. Electromagnetic wave in a Fabry-Perot resonator.

The further path of the beam in the resonator, the amplitudes of the outgoing and reflected beams are clear from the figure. Let us sum up the amplitudes of all electromagnetic waves emitted through the right side of the crystal:

= (12).

Let us require that the sum of the amplitudes of all waves emerging through the right face is not equal to zero even for a vanishingly small amplitude of the wave on the left face of the crystal. Obviously, this can only happen when the denominator of the fraction in (12) tends to zero. From here we get:

, (13)

and taking into account the fact that the light intensity , i.e. ; , Where R 1 , R 2 - reflection coefficients of mirrors - crystal faces "by intensity", and, moreover, , finally, we write the ratio for the generation threshold as:

. (14)

It follows from (11) that the factor 2r included in the exponent is related to the complex refractive index of the crystal:

On the right side of (15), the first term determines the phase of the light wave, and the second determines the amplitude. In an ordinary, thermodynamically equilibrium medium, light is attenuated (absorbed); in the active working medium of a laser, the same ratio should be written in the form , Where g - light gain, and the symbol a i marked all losses pump energy, not necessarily only of an optical nature. Then amplitude threshold condition rewritten as:

or . (16)

Thus, we have defined necessary(9) and sufficient(16) conditions for generation of a semiconductor laser. As soon as the value gain will exceed losses by the value determined by the first term in (16), light amplification will begin in the working medium with the inverse population of the levels. The value of the gain itself will depend on the pump power or, which is the same for injection lasers, on the value operating current. In the normal working area of ​​semiconductor lasers and linearly depends on the magnitude of the operating current

. (17)

From (16) and (17) for threshold current we get:

, (18)

where through I 0 is designated by the so-called. "Inversion threshold" - the value of the operating current at which the inverse population in the semiconductor is achieved. Because usually , the first term in (18) can be neglected.

Proportionality factor β for a laser using a conventional p-n junction and made, for example, from GaAs, can be calculated by the formula

, (19)

Where E and Δ E - position and half-width of the spectral line of the laser radiation.

Calculation according to formula 18 gives at room temperature T=300 K for such a laser very high values ​​of the threshold current density 5 . 10 4 A / cm 2, i.e. such lasers can be operated either with good cooling or with short pulses. Therefore, as noted above, only the creation in 1970 by the group of Zh.I. Alferov heterojunction lasers allowed reduce by 2 orders of magnitude threshold currents of semiconductor lasers, which eventually led to the mass application of these devices in electronics.

To understand how this was achieved, let's take a closer look. loss structure in semiconductor lasers. to non-specific common to any lasers, and in principle fatal losses losses should be attributed to spontaneous transitions and losses on thermalization.

Spontaneous transitions from the upper level to the lower will always be present, and since the light quanta emitted in this case will have a random distribution in phase and direction of propagation (there will not be coherent), then the expendi- ture of pump energy for the generation of spontaneously recombining electron-hole pairs should be attributed to losses.

With any method of pumping, electrons will be thrown into the conduction band of the semiconductor, with an energy greater than the energy of the quasi-Fermi level F C. These electrons, losing energy in collisions with lattice defects, quickly descend to the quasi-Fermi level - a process called thermalization. The energy lost by electrons during their scattering on lattice defects is the thermalization loss.

TO partially removable losses can be attributed to nonradiative recombination. In direct-gap semiconductors, deep impurity levels are usually responsible for nonradiative recombination (see "Photoelectric Effect in Homogeneous Semiconductors"). Thorough cleaning of the semiconductor crystal from impurities that form such levels reduces the probability of nonradiative recombination.

And finally, the losses non-resonant absorption and on leakage currents can be significantly reduced by using for the manufacture of lasers heterostructures.

Unlike conventional p-n junctions, where identical semiconductors are located to the right and left of the contact point, differing only in the composition of impurities and the type of conductivity, in heterostructures on both sides of the contact there are semiconductors of different chemical composition. These semiconductors have different band gaps, so at the point of contact there will be a “jump” in the potential energy of an electron (“hook” type or “wall” type (Fig. 6)).

Fig.6. An injection laser based on a two-sided heterostructure in a state of thermodynamic equilibrium (left) and in operating mode (right).

Depending on the type of semiconductor conductivity, heterostructures can be isotype(p-P; n-N heterostructures) and anisotype(p-N; n-P heterostructures). Capital letters in heterostructures usually denote a semiconductor with a larger bandgap. Far from any semiconductors are able to form high-quality heterostructures suitable for creating electronic devices on their basis. In order for the interface to contain as few defects as possible, the components of the heterostructure must have the same crystal structure and very close values lattice constant. Among semiconductors of group A III B V, only two pairs of compounds meet this requirement: GaAs-AlAs and GaSb-AlSb and their solid solutions(see Introduction), i.e. GaAs-Ga x Al 1- x As ; GaSb-Ga x Al 1- x Sb. Complicating the composition of semiconductors, it is possible to select other pairs suitable for creating heterostructures, for example, InP-In x Ga 1- x As y P 1- y ; InP- Al x Ga 1- x As y Sb 1- y . Injection lasers are also made from heterostructures based on A IV B VI semiconductor compounds, such as PbTe-Pb x Sn 1- x Te; PbSe-Pb x Sn 1- x Se - these lasers emit in the far infrared region of the spectrum.

Loss on leakage currents in heterolasers, it can be almost completely eliminated due to the difference in the band gaps of the semiconductors that form the heterostructure. Indeed (Fig. 3), the width of the region d near the usual p-n junction, where the condition of inverse population is satisfied, is only 1 μm, while the charge carriers injected through the junction recombine in a much larger region L n + L p with a width of 10 μm . Carrier recombination in this region does not contribute to coherent radiation. IN bilateral N-p-P heterostructure (Fig. 6) region with inverse population coincides with the layer thickness of the narrow-gap semiconductor at the center of the heterolaser. Almost all electrons and holes injected into this region from wide-gap semiconductors and recombine there. Potential barriers at the interface between wide-gap and narrow-gap semiconductors do not allow charge carriers to “spread”, which dramatically increases the efficiency of such a structure compared to a conventional (Fig. 3) p-n junction.

In a layer of a narrow-gap semiconductor, not only nonequilibrium electrons and holes will be concentrated, but also most of the radiation. The reason for this phenomenon is that the semiconductors that make up the heterostructure differ in the refractive index. As a rule, the refractive index is higher for a narrow-gap semiconductor. Therefore, all rays having an angle of incidence on the boundary of two semiconductors

, (20)

will undergo total internal reflection. Consequently, the radiation will be "locked" in the active layer (Fig. 7), which will significantly reduce the losses on non-resonant absorption(usually this is the so-called "absorption by free charge carriers").

Fig.7. Optical limitation in the propagation of light in a heterostructure. At an angle of incidence greater than θ, total internal reflection occurs from the interface between the semiconductors that make up the heterostructure.

All of the above makes it possible to obtain in heterolasers giant optical amplification with microscopic dimensions of the active region: active layer thickness , resonator length . Heterolasers operate at room temperature in continuous mode, and characteristic operating current density do not exceed 500 A/cm 2 . Radiation spectrum most commercially available lasers in which the working environment is gallium arsenide, represents a narrow line with a maximum in the near infrared region of the spectrum , although semiconductor lasers have been developed that emit visible radiation and lasers that emit in the far infrared region with .

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Introduction

One of the most remarkable achievements of physics in the second half of the twentieth century was the discovery of physical phenomena that served as the basis for the creation of an amazing device, the optical quantum generator, or laser.

The laser is a source of monochromatic coherent light with a highly directive light beam.

Quantum generators are a special class of electronic devices that incorporate the latest achievements in various fields of science and technology.

Gas lasers are lasers in which the active medium is a gas, a mixture of several gases, or a mixture of gases with metal vapor.

Gas lasers are the most widely used type of laser today. Among the various types of gas lasers, one can always find a laser that will satisfy almost any requirement for a laser, with the exception of very high power in the visible region of the spectrum in a pulsed mode.

High powers are needed for many experiments in studying the nonlinear optical properties of materials. At present, high powers in gas lasers have not been obtained because the density of atoms in them is not high enough. However, for almost all other uses, a particular type of gas laser can be found that will outperform both optically pumped solid-state lasers and semiconductor lasers.

A large group of gas lasers are gas-discharge lasers, in which the active medium is a rarefied gas (pressure 1–10 mm Hg), and pumping is carried out by an electric discharge, which can be glow or arc, and is created by direct current or high-frequency alternating current (10 –50 MHz).

There are several types of gas discharge lasers. In ion lasers, radiation is obtained due to the transitions of electrons between the energy levels of the ions. An example is the argon laser, which uses a DC arc discharge.

Lasers based on atomic transitions generate due to the transitions of electrons between the energy levels of atoms. These lasers produce radiation with a wavelength of 0.4–100 µm. An example is a helium-neon laser operating on a mixture of helium and neon at a pressure of about 1 mmHg. Art. For pumping, a glow discharge is used, created by a constant voltage of about 1000 V.

Molecular lasers also belong to gas-discharge lasers, in which radiation arises from electron transitions between the energy levels of molecules. These lasers have a wide frequency range, corresponding to wavelengths from 0.2 to 50 µm.

The most common of the molecular carbon dioxide laser (CO 2 laser). It can deliver power up to 10 kW and has a fairly high efficiency - about 40%. Nitrogen, helium and other gases are usually added to the main carbon dioxide. For pumping, a glow discharge of direct current or high-frequency is used. A carbon dioxide laser produces radiation with a wavelength of about 10 microns.

The design of quantum generators is very laborious due to the wide variety of processes that determine their performance, but despite this, carbon dioxide gas lasers are used in many areas.

On the basis of CO 2 lasers, laser guidance systems, location systems for monitoring the environment (lidars), technological installations for laser welding, cutting of metals and dielectric materials, installations for scribing glass surfaces, and surface hardening of steel products have been developed and successfully operated. Also, CO2 lasers are widely used in space communication systems.

The main objective of the discipline "optoelectronic quantum devices and devices" is to study the physical foundations, devices, principles of operation, characteristics and parameters of the most important devices and devices used in optical communication systems. These include quantum generators and amplifiers, optical modulators, photodetectors, nonlinear optical elements and devices, holographic and integrated optical components. This implies the relevance of the topic of this course project.

The purpose of this course project is to describe gas lasers and calculate the helium-neon laser.

In accordance with the goal, the following tasks are solved:

Studying the principle of operation of a quantum generator;

Study of the device and principle of operation of a CO 2 laser;

Study of safety documentation when working with lasers;

Calculation of CO 2 laser.

1 The principle of operation of a quantum generator

The principle of operation of quantum generators is based on the amplification of electromagnetic waves using the effect of stimulated (induced) radiation. Amplification is provided due to the release of internal energy during the transitions of atoms, molecules, and ions stimulated by external radiation from some excited upper energy level to a lower (located below). These forced transitions are caused by photons. The photon energy can be calculated by the formula:

hν \u003d E 2 - E 1,

where E2 and E1 are the energies of the upper and lower levels;

h = 6.626∙10-34 J∙s - Planck's constant;

ν = c/λ is the radiation frequency, c is the speed of light, λ is the wavelength.

Excitation, or, as it is commonly called, pumping, is carried out either directly from a source of electrical energy, or due to the flow of optical radiation, a chemical reaction, or a number of other energy sources.

Under conditions of thermodynamic equilibrium, the energy distribution of particles is uniquely determined by the temperature of the body and is described by the Boltzmann law, according to which the higher the energy level, the lower the concentration of particles in a given state, in other words, the lower its population.

Under the influence of pumping, which violates the thermodynamic equilibrium, the reverse situation can arise, when the population of the upper level exceeds the population of the lower one. A state occurs which is called population inversion. In this case, the number of forced transitions from the upper energy level to the lower one, in which induced radiation occurs, will exceed the number of reverse transitions, accompanied by absorption of the initial radiation. Since the direction of propagation, phase and polarization of the induced radiation coincide with the direction, phase and polarization of the acting radiation, the effect of its amplification arises.

A medium in which radiation amplification due to induced transitions is possible is called an active medium. The main parameter that characterizes its amplifying properties is the coefficient or amplification factor kν - the parameter that determines the change in the radiation flux at the frequency ν per unit length of the interaction space.

The amplifying properties of the active medium can be significantly improved by applying the principle of positive feedback known in radiophysics, when part of the amplified signal is returned back to the active medium and re-amplified. If, in this case, the gain exceeds all losses, including those that are used as a useful signal (useful losses), an auto-generation mode occurs.

Self-generation begins with the appearance of spontaneous transitions and develops to some stationary level, determined by the balance between gain and loss.

In quantum electronics, to create positive feedback at a given wavelength, mainly open resonators are used - a system of two mirrors, one of which (deaf) can be completely opaque, the second (output) is made translucent.

The region of laser generation corresponds to the optical range of electromagnetic waves; therefore, laser resonators are also called optical resonators.

A typical functional diagram of a laser with the above elements is shown in Figure 1.

An obligatory structural element of a gas laser should be a shell (discharge tube), in the volume of which there is a gas of a certain composition at a given pressure. On the end sides, the shell is closed with windows made of a material transparent to laser radiation. This functional part of the device is called the active element. Windows to reduce reflection losses from their surface are set at the Brewster angle. Laser radiation in such devices is always polarized.

The active element, together with the resonator mirrors installed outside the active element, is called the emitter. A variant is possible when the resonator mirrors are fixed directly on the ends of the shell of the active element, simultaneously performing the function of windows for sealing the gas volume (laser with internal mirrors).

The frequency dependence of the gain of the active medium (gain loop) is determined by the shape of the spectral line of the working quantum transition. Laser generation occurs only at such frequencies within this circuit, at which an integer number of half-waves fits in the space between the mirrors. In this case, as a result of the interference of direct and backward waves, so-called standing waves with energy nodes on the mirrors are formed in the resonator.

The structure of the electromagnetic field of standing waves in the resonator can be very diverse. Its specific configurations are called mods. Oscillations with different frequencies but the same field distribution in the transverse direction are called longitudinal (or axial) modes. They are associated with waves propagating strictly along the resonator axis. Oscillations that differ from each other in the distribution of the field in the transverse direction, respectively - transverse (or non-axial) modes. They are associated with waves propagating at various small angles to the axis and having, respectively, the transverse component of the wave vector. The following abbreviation is used to designate the various modes: TEMmn. In this notation, m and n are indices showing the periodicity of the field change on the mirrors along different coordinates in the transverse direction. If only the fundamental (lowest) mode is generated during laser operation, one speaks of single-mode operation. If there are several transverse modes, the mode is called multimode. When operating in a single-mode mode, generation is possible at several frequencies with a different number of longitudinal modes. If generation occurs only in one longitudinal mode, one speaks of a single-frequency mode.

Figure 1 - Scheme of a gas laser.

The following designations are used in the figure:

1. Mirrors of the optical resonator;
2. Optical resonator windows;
3. electrodes;
4. Discharge tube.

2 Design and principle of operation of a CO 2 laser

Schematically, the CO 2 laser device is shown in Figure 2.

Figure 2 - The principle of the CO2 laser device.

One of the most common types of CO 2 lasers are gas-dynamic lasers. In them, the population inversion necessary for laser radiation is achieved due to the fact that the gas preheated to 1500 K at a pressure of 20–30 atm. , enters the working chamber, where it expands, and its temperature and pressure are sharply reduced. Such lasers can produce continuous radiation with a power of up to 100 kW.

To create an active medium (as they say, “pumping”) of CO 2 lasers, a DC glow discharge is most often used. Recently, high-frequency discharge has been increasingly used. But this is a separate topic. The high-frequency discharge and the most important applications that it has found in our time (not only in laser technology) is the topic of a separate article. On the general principles of operation of electric-discharge CO 2 lasers, the problems that arise in this case, and some designs based on the use of a direct current discharge.

At the very beginning of the 1970s, in the course of the development of high-power CO 2 lasers, it became clear that the discharge was characterized by hitherto unknown features and instabilities that were detrimental to lasers. They pose almost insurmountable obstacles to attempts to fill a large volume with plasma at elevated pressure, which is exactly what is required to obtain high laser powers. Perhaps none of the problems of an applied nature has served the progress of the science of electric discharge in gases in recent decades as much as the task of creating high-power CW CO 2 lasers.

Consider the principle of operation of CO 2 laser.

The active medium of almost any laser is a substance, in certain molecules or atoms of which, in a certain pair of levels, an inverse population can be created. This means that the number of molecules in the upper quantum state corresponding to the radiative laser transition exceeds the number of molecules in the lower one. In contrast to the usual situation, a beam of light passing through such a medium is not absorbed, but amplified, which opens up the possibility of generating radiation.

Did you know, what is a thought experiment, gedanken experiment?
It is a non-existent practice, an otherworldly experience, the imagination of what is not really there. Thought experiments are like daydreams. They give birth to monsters. Unlike a physical experiment, which is an experimental test of hypotheses, a “thought experiment” magically replaces an experimental test with the desired, untested conclusions, manipulating logical constructions that actually violate logic itself by using unproved premises as proven ones, that is, by substitution. Thus, the main task of the applicants of "thought experiments" is to deceive the listener or reader by replacing a real physical experiment with his "doll" - fictitious reasoning on parole without physical verification itself.
Filling physics with imaginary, "thought experiments" has led to an absurd, surreal, confusing picture of the world. A real researcher must distinguish such "wrappers" from real values.

Relativists and positivists argue that the "thought experiment" is a very useful tool for testing theories (also arising in our minds) for consistency. In this they deceive people, since any verification can only be carried out by a source independent of the object of verification. The applicant of the hypothesis himself cannot be a test of his own statement, since the reason for this statement itself is the absence of contradictions visible to the applicant in the statement.

We see this in the example of SRT and GR, which have turned into a kind of religion that governs science and public opinion. No amount of facts that contradict them can overcome Einstein's formula: "If the fact does not correspond to the theory, change the fact" (In another version, "Does the fact not correspond to the theory? - So much the worse for the fact").

The maximum that a "thought experiment" can claim is only the internal consistency of the hypothesis within the framework of the applicant's own, often by no means true, logic. Compliance with practice does not check this. A real test can only take place in a real physical experiment.

An experiment is an experiment, because it is not a refinement of thought, but a test of thought. Thought that is consistent within itself cannot test itself. This has been proven by Kurt Gödel.