RU2101745C1 - Method for converting electromagnetic radiation energy of optical or lower-frequency range into wave excitation energy of nonlinear media - Google Patents

Abstract

FIELD: plasma electronics; generation and amplification of electromagnetic microwave oscillations or waves for heating nonlinear media including plasma. SUBSTANCE: method involves the following procedures: electromagnetic radiation is passed through nonlinear medium; electromagnetic radiation with arbitrary spectrum width is subjected to pulse-position modulation by constant-frequency oscillations so that set of frequencies equally spaced apart through modulation frequency corresponded to each carrier frequency of source nonmodulated radiation in frequency spectrum of modulated radiation; nonlinear medium and modulation frequency are chosen so that inherent frequency of wave excitations of nonlinear medium were equal to or a multiple of modulation frequency; synchronism condition is provided for harmonics of modulated source radiation and induced wave excitations interacting in nonlinear medium. In addition, energy of wave excitations occurring in nonlinear medium is stored by passing modulated electromagnetic radiation over closed loop many times through same section of nonlinear medium using one or more resonators. EFFECT: improved conversion efficiency. 15 cl, 4 dwg

Description

 The invention relates to methods for converting the energy of optical or lower-frequency electromagnetic radiation into various types of energy depending on the types of wave excitations of a nonlinear medium: molecular, acoustic, electric, temperature, plasma wave excitations, etc., and can be used in plasma electronics to generate and amplification of electromagnetic microwave oscillations or waves for heating a non-linear medium, including plasma.

A known method of converting the energy of intense optical monochromatic, for example laser, radiation into the energy of wave excitations of a nonlinear medium, which consists in transmitting intense coherent laser radiation through a nonlinear medium. The basis of this method is the phenomenon of stimulated light scattering [1]
In this case, for efficient energy conversion, the condition of synchronism should be fulfilled for the incident laser wave, scattered laser wave, and wave excitations induced in the medium interacting in a nonlinear medium.

 The considered method allows the conversion of the energy of the initial intense optical (laser) radiation into the energy of various wave excitations of a nonlinear medium, depending on the type of stimulated scattering. In particular, in stimulated Raman scattering (SRS), a nonlinear medium is converted into energy of molecular wave excitations, in stimulated Mandelstamm-Brillouin scattering (SBS), acoustic wave excitations are converted into energy, etc.

 However, this method has a low efficiency of converting the energy of intense optical (laser) radiation into the energy of wave excitations of a nonlinear medium (as a rule, the conversion efficiency is less than hundredths of a percent) and, in addition, for optical radiation with a wide spectrum, energy conversion is not possible by the above method.

), подобранными таким образом, чтобы разность частот W₁-W₂ совпадала с частотой Ω_i одного из собственных резонансов среды, т.е. с одной из собственных частот волновых возбуждений, в рассматриваемом случае, с ленгмюровской (плазменной) частотой волновых возбуждений в плазме (ленгмюровские волновые возбуждения или волновые возбуждения плотности пространственного заряда или плазменные возбуждения).A known method of converting the energy of optical radiation into the energy of wave excitations of a nonlinear medium, adopted as a prototype, including transmitting optical radiation through a nonlinear medium [2]
In this method, the initial optical radiation propagating in a nonlinear medium is a superposition of two plane monochromatic waves with frequencies W ₁ and W ₂ (and wave vectors

), selected so that the frequency difference W ₁ -W ₂ coincides with the frequency Ω _{i of} one of the natural resonances of the medium, i.e. with one of the natural frequencies of wave excitations, in the case under consideration, with the Langmuir (plasma) frequency of wave excitations in a plasma (Langmuir wave excitations or wave excitations of space charge density or plasma excitations).

In this case, the conversion of a part of the energy of the initial optical radiation, which is a two-frequency laser radiation with frequencies W ₁ and W _2, into the wave excitation energy of a plasma with a Langmuir frequency is used to accelerate charged particles.

This method of energy conversion is valid for the initial two-frequency electromagnetic radiation with frequencies W ₁ and W _{2 in the} lower frequency range, for example, the microwave range, provided that W ₁ -W ₂ = Ω _i
Although the implementation of this method is also possible with two-frequency laser radiation of low power, in general, this method has the same disadvantages as the previous one. The maximum efficiency of this method, as well as the previous one, cannot exceed the value of Ω _i / W ₁ which, as a rule, is less than hundredths of a percent, and for optical radiation with a wide spectrum, energy conversion by the above method is impossible.

 The proposed invention solves the problem of increasing the efficiency of converting the energy of electromagnetic radiation with an arbitrary spectral width (both monochromatic or quasimonochromatic, and radiation with a wide spectrum) into the energy of wave excitations of a nonlinear medium.

 This goal is achieved by the fact that in the known method of converting the energy of electromagnetic radiation of the optical or lower frequency range into the energy of wave excitations of a nonlinear medium, including the transmission of optical or lower frequency electromagnetic radiation through a nonlinear medium, it is new that the original electromagnetic radiation with an arbitrary spectrum width is modulated in time by oscillations of a constant frequency so that in the frequency spectrum of the modulated electromagnetic radiation, each carrier frequency of the initial unmodulated electromagnetic radiation (i.e., each frequency of the initial radiation before modulation) corresponded to many frequencies equally spaced from each other by the modulation frequency, the nonlinear medium and the modulation frequency are selected so that the natural frequency of these wave excitations of the nonlinear medium is equal to or a multiple of the modulation frequency, while the condition of synchronism for interacting in a nonlinear medium harmonics (spectral components) of the modulated initial radiation and data of wave excitations induced in the medium.

 A higher efficiency of converting the energy of electromagnetic radiation of the optical or lower frequency range into the energy of wave excitations of a nonlinear medium is achieved due to the interaction between the many harmonics of modulated radiation (spectral components of modulated radiation) and wave excitations in a nonlinear medium. This interaction occurs due to the propagation in this medium of many harmonics of modulated radiation with frequencies that differ from each other by the modulation frequency, provided that the modulation frequency and the nonlinear medium are selected in the above way, and this interaction will be most effective if the synchronism condition is fulfilled.

 In this case, the condition of synchronism is the condition of effective energy exchange during the interaction in the nonlinear medium of harmonics (spectral components) of the modulated initial radiation and wave excitations induced in this medium, which consists in maintaining certain phase relations between harmonics and wave excitations throughout the interaction region. In particular, the phase incursion over the entire interaction region for harmonics of modulated radiation and wave excitations interacting in a given medium should not exceed π, which implies that the synchronism condition can be satisfied when the phase velocities in the medium of interacting harmonics and wave excitations are equal.

In the most general case of the present invention there is always a certain amount of nonlinear medium along the propagation direction of the radiation modulated by L _o ≤L _COH (wherein L _coh coherent interaction length or coherence length), in which all the phase velocities of the interacting media in the harmonic wave and the excitation can be considered the same, i.e. there always exists the size of a nonlinear medium on which the condition of synchronism is satisfied automatically without special measures. This is true both in the case of wave excitations without dispersion and in the case of wave excitations in a nonlinear medium with dispersion.

To fulfill the condition of synchronism with the dimensions of a nonlinear medium (along the direction of propagation of modulated radiation) L _o > L _coh , special measures must be taken. In particular, in the case of the original electromagnetic radiation of the microwave range in the present invention, it is possible to use moderators in the form of spirals to match the phase velocities of the harmonics of the modulated microwave radiation and wave excitations in a nonlinear medium.

 The converted electromagnetic radiation in the present invention can be both optical and lower frequency, for example, radio emission, in particular microwave radiation, both continuous and pulsed, and have an arbitrary spectrum width.

 Monochromatic or quasi-monochromatic radiation, radiation with a wide spectrum (for example, laser radiation or light from incandescent lamps, mercury lamps, solar radiation, etc.) can be used as converted electromagnetic radiation.

 As nonlinear media, various nonlinear media can be used, in particular dielectric media with an inversion center: centrosymmetric crystals, gases, liquids, as well as plasma, etc.

 The geometry of the shape of these media can be different, along with lengthy extended nonlinear media, nonlinear media with fiber or waveguide geometry can be used, i.e. media with transverse dimensions commensurate with the wavelength of the source electromagnetic radiation.

 To implement the modulation of the source of electromagnetic radiation in the present invention, the following types of modulation can be used: modulation of the source radiation in phase or frequency by oscillations of a constant frequency, including harmonic oscillations; amplitude modulation by periodic non-harmonic oscillations of constant frequency, including pulse modulation.

 With these types of modulation, the basic condition for modulating the radiation in this invention is fulfilled, namely: in the frequency spectrum of the modulated electromagnetic radiation of the optical or lower frequency range, each carrier frequency of the initial unmodulated radiation (i.e., each frequency of the initial radiation before modulation) must correspond many frequencies equally spaced from each other by the modulation frequency.

 To further increase the efficiency of this transformation, one can additionally accumulate the energy of wave excitations arising in a nonlinear medium.

 An additional accumulation of energy of wave excitations of a nonlinear medium can be achieved by repeatedly passing the modulated initial electromagnetic radiation through a closed circuit through the same section of the nonlinear medium. In this case, multiple passage of modulated radiation along a closed loop through the same section of a nonlinear medium can be achieved using elements such as mirrors, prisms, etc.

 For additional energy storage of wave excitations of a nonlinear medium, resonators can be used that can accumulate the energy of these wave excitations with a resonant frequency that coincides with the frequency of these wave excitations, while the nonlinear medium can be placed both inside and outside the resonator. Such energy storage is possible only for types of wave excitations for which there are corresponding resonators. Only acoustic resonators are able to accumulate the energy of acoustic wave excitations of a nonlinear medium, only electromagnetic resonators can accumulate the energy of electromagnetic wave excitations of a nonlinear medium, etc. The higher the quality factor of resonators capable of storing the energy of these wave excitations of the medium, the more efficient the accumulation process. When a nonlinear medium is placed outside the resonator, the transformed energy of wave excitations of a nonlinear medium (for example, electromagnetic wave excitations) can be removed from the medium, brought to the resonator, and stored in it. A nonlinear medium can be placed inside the resonator (for example, inside a volumetric microwave resonator in the case of high-frequency (microwave) electromagnetic wave excitations of a nonlinear medium), while the process of accumulating the converted wave excitation energy will be carried out directly in the medium placed in this resonator. You can also use several such resonators that can accumulate the energy of these wave excitations with the same resonant frequency, which coincides with the frequency of these wave excitations. For this, the converted wave air energy accumulated in the first resonator (resonator of the first stage) is fed to the second resonator (resonator of the second stage), where the accumulation process continues. Then, the energy stored in the second resonator is supplied for subsequent storage to the third resonator (resonator of the third stage), etc.

частота модуляции.The most effective for this conversion is laser radiation, due to the possibility of achieving high power and low angular divergence. In the case of pulsed laser radiation, it is necessary that the pulse duration time T _i substantially exceeds the period of modulating oscillations of a constant frequency T _mod (T _i >> T _mod ), where

modulation frequency.

 In the case of using solar radiation as the initial radiation, this invention allows to convert the energy of solar radiation into the energy of high-frequency electromagnetic wave excitations of a nonlinear medium, for example, plasma, i.e. convert the energy of solar radiation into electromagnetic energy of the microwave range.

 Of all the modulations used in this invention, the simplest and most effective is the modulation in phase or frequency by harmonic oscillations of a constant frequency.

 The use of nonlinear media with fiber or waveguide geometry in this invention allows one to control dispersion, as well as to achieve high electromagnetic field strengths in the medium at sufficiently low levels of the initial radiation power, which leads to an increase in the energy conversion efficiency, all other things being equal.

 Of particular note, plasma can be used as a non-linear medium in this invention.

In a plasma, which is a partially or fully ionized gas, in which the densities of positive and negative charges are almost the same, the following wave excitations can occur: longitudinal with Langmuir frequency (Langmuir or plasma or space charge density excitations), longitudinal ion-sound, transverse electromagnetic frequency W> Ω _e , where Ω _e is the Langmuir frequency.

 The magnetic field significantly changes the wave properties of the plasma. When a plasma is placed in a magnetic field, the number of possible wave excitations in the plasma, into the energy of which the energy of the initial electromagnetic radiation of the optical or lower frequency range can be converted, increases.

 The properties of a set of mobile charged particles in solid conductors (conduction electrons in metals or electrons and holes in semiconductors) can be close to the properties of a gas-discharge plasma. A similar set of mobile charged particles in a solid is called a solid state plasma. The solid state plasma can also be used in this invention as a nonlinear medium for converting various kinds of wave excitations into energy that can arise in a solid state plasma.

 The proposed method of energy conversion allows heating of a nonlinear medium, in particular plasma. To heat a nonlinear medium, a medium is chosen in which wave excitations could dissipate into heat. Next, it is necessary to convert these wave excitations into energy by the proposed method, while the converted energy of these wave excitations of a nonlinear medium will dissipate into heat, heating this medium.

 The present invention allows amplification, multiplication of frequencies and the generation of high-frequency electromagnetic waves or water, in particular electromagnetic waves or microwave waves.

 To amplify using the proposed method a high-frequency electromagnetic signal, which is high-frequency electromagnetic oscillations generated from an independent high-frequency generator, it is necessary to modulate the initial electromagnetic radiation of the optical or lower frequency range with these oscillations, select a nonlinear medium so that this medium is capable of occurring in it high-frequency electromagnetic wave excitations with a frequency that matches the mode frequency ulation (i.e., with the frequency of amplified oscillations). When the converted electromagnetic energy of these high-frequency wave excitations is removed from the medium, high-frequency oscillations are obtained with the same frequency as the amplified oscillations, which modulate electromagnetic radiation, but are more powerful, i.e. amplification of modulating oscillations occurs.

 In this case, the amplification of high-frequency oscillations, which modulate the initial electromagnetic radiation, occurs due to the conversion of the energy of the original electromagnetic radiation of the optical or lower frequency range into the energy of high-frequency electromagnetic wave excitations of a nonlinear medium.

 To generate high-frequency electromagnetic oscillations, it is necessary in the above case of amplification of electromagnetic oscillations to carry out positive feedback using a feedback circuit between amplified high-frequency oscillations output from the medium (output of the amplification circuit) and amplified modulating oscillations (input of the modulator or input of the amplification circuit).

 To multiply frequencies, i.e., to increase an integer number of times the frequency of electromagnetic high-frequency oscillations in the above case of amplification of electromagnetic oscillations, a nonlinear medium is selected so that the natural frequency of high-frequency electromagnetic wave excitations of the nonlinear medium is a multiple of the modulation frequency (i.e., the frequency of electromagnetic oscillations that modulate the initial electromagnetic radiation of the optical or lower frequency range). In this case, using the proposed method, the medium is converted into energy of electromagnetic wave excitations with a frequency that is a multiple of the modulation frequency, and when the electromagnetic energy of these excitations is removed from the medium, high-frequency oscillations are obtained with a frequency an integer number of times higher than the frequency of the initial modulating oscillations.

 In FIG. 1-4 are examples of energy conversion of the initial electromagnetic radiation of the optical or lower frequency range into the energy of wave excitations of a nonlinear medium by the proposed method.

 In FIG. 1 shows a diagram of the conversion of the energy of the initial laser radiation into the energy of Langmuir plasma wave excitations; in FIG. 2 is a diagram of amplification of high-frequency electromagnetic waves using the proposed method of energy conversion; in FIG. 3 is a diagram of generating high frequency electromagnetic waves based on the present invention; in FIG. 4 is a plasma heating circuit using the present invention.

 List of positions: 1 collimated laser beam; 2 - modulator; 3 modulated laser radiation; 4 electron-ion plasma formed by a direct current discharge; 5 transparent glass flask; 6, 7 cathode and anode of an arc discharge; 8 modulating high-frequency electromagnetic signal (modulating oscillations); 9 - electromagnetic resonator; 10 feedback circuit; 11 beam splitting mirror; 12, 13, 14 mirrors.

 Example 1. The implementation of the conversion of the energy of the original laser radiation into the energy of the Langmuir wave excitations of the plasma.

 In FIG. 1, a high-frequency signal 8, which is harmonic electromagnetic waves and generated from an independent high-frequency generator, is fed to a modulator 2, with which modulate the initial continuous-wave laser radiation 1 in phase (or frequency) by harmonic modulating oscillations of a constant frequency.

 As modulators performing phase modulation of the initial radiation 1 by high-frequency oscillations in FIG. 1-4, electro-optical Pokkels modulators can be used.

 A modulator can also be a mirror oscillating with a frequency Ω. For this purpose, the mirror is either directly attached to the end of the piezoelectric transducer, or the reflective coating is sprayed onto the end of the piezoelectric transducer. When an electromagnetic signal with a constant frequency W is applied to a piezoelectric transducer, it begins to vibrate with a frequency W together with a mirror or with a mirror coating due to the inverse piezoelectric effect. The initial radiation 1, reflected from such a mirror oscillating with a given frequency W, is modulated by the above method.

The frequency of the modulating signal (i.e., the modulation frequency) W must be equal to or close to the Langmuir frequency W _{e of a} given plasma 4, i.e. Ω = Ω _e
The laser radiation 3 modulated by a high-frequency modulating signal is passed through a plasma 4 placed in a transparent glass flask 5. An electron-ion plasma is created using a direct current discharge, for which a cathode 6 and an anode 7 of an arc discharge are used.

The synchronism condition is fulfilled for the harmonics of modulated laser radiation interacting in the plasma and Langmuir wave excitations. For this plasma dimension along the direction of propagation of the modulated laser beam is selected to be L _o ≤L _COH (wherein L _coh coherent interaction length or coherence length) that leads to the automatic implementation of synchronism condition. In the case under consideration, the size L _coh is determined as follows (see expression 4).

где C скорость света в вакууме;

коэффициент преломления плазмы на частоте омега₀ исходного лазерного излучения

коэффициент преломления плазмы на частотах, приближающихся к ленгмюровской частоте.

where C is the speed of light in vacuum;

plasma refractive index at omega ₀ frequency of the initial laser radiation

plasma refractive index at frequencies approaching the Langmuir frequency.

It follows that when the plasma Langmuir frequency is of the order of hundreds of megahertz (Ω _e ≈10 ⁸ Hz), the size of L _coh is calculated in meters.

 In this case, when the laser radiation modulated in phase (or frequency) is transmitted through the plasma, the energy of this laser radiation will be converted into the energy of plasma wave excitations with a Langmuir frequency (Langmuir plasma wave excitations).

 Example 2. The implementation of the amplification of high-frequency electromagnetic waves by converting the energy of the original laser radiation into the energy of the Langmuir wave excitations of the plasma, followed by the withdrawal of the converted energy from the plasma.

The same as in example 1, only for the implementation of amplification of high-frequency electromagnetic waves 8, in the circuit of FIG. 2, these amplified vibrations using modulator 2 modulate the laser radiation 1 in the above manner. Plasma 4 is selected so that the Langmuir plasma frequency Ω _e coincides with the frequency Ω of the amplified oscillations 8 (i.e., with the modulation frequency). The converted energy is removed from plasma 4 and, with the aim of increasing the efficiency of this conversion, is supplied using a coaxial cable or waveguide to an electromagnetic resonator 9 with a resonant frequency (or with one of the resonant frequencies, if there are several), coinciding with the Langmuir frequency. In the resonator 9 there is an additional accumulation of converted energy output from the plasma.

 As a result, a high-frequency signal with the same frequency as the amplified, but more powerful, i.e. the signal is amplified due to the energy of laser radiation, which is converted into the energy of the Langmuir wave excitations of the plasma by the proposed method.

 The higher the quality factor of the resonator 9, the more efficiently the energy conversion process proceeds and the higher the gain.

 Calculations show that when using resonators with a very high Q factor, for example, cryoelectronic superconducting resonators, the efficiency of this energy conversion can reach 90% even at relatively low powers (of the order of one watt) of the initial laser radiation.

With a change in the concentration of charges in the plasma, it is possible to change the Langmuir frequency of the plasma and thereby vary the frequency at which amplification is possible. For achievable concentrations of charges of the order of 10 ⁹ -10 ¹⁴ cm ^{-3, the} Langmuir frequency can lie in the range of decimeter, centimeter, and even millimeter waves.

 Example 3. The same as in example 2, only to prevent the loss of converted energy when outputting from plasma 4 and supplying to the resonator 9, as the resonator 9 in the circuit of FIG. 1, microwave resonators with a capacitive gap can be used, and a glass flask with plasma can be placed in the capacitive gap of this resonator.

 Example 4. The same as in example 2, only for additional accumulation of converted energy using several resonators combined in cascades. To do this, the converted energy stored in the resonator 9 using a coaxial cable or waveguide can be fed to the next resonator with the same resonant frequency (resonator of the second stage), in which the process of accumulation of the converted energy will continue, etc. To prevent the influence of each subsequent resonator on the previous one, you can use valves located between the resonators and transmitting the converted energy in only one direction from the previous resonator to the next, for example, ferrite valves.

Example 5. The same as in example 2, only the energy of the initial laser radiation 1 is converted into the energy of the transverse transverse electromagnetic wave excitations of the microwave range with a frequency greater than Langmuir (w> W _e ), including the energy of microwave wave excitations plasma placed in a magnetic field. In this case, the frequency of the amplified modulating signal (i.e., the modulation frequency) should coincide with the frequency of the data of the transverse electromagnetic wave excitations of the microwave range in the plasma and with the resonant frequency of the microwave resonator 9, in which the converted energy is accumulated. In this case, the plasma through which the modulated laser radiation is passed can also be located inside the volumetric microwave resonator with the above resonant frequency. The energy conversion efficiency values in the example under consideration are the same as in example 2.

Example 6. The same as in example 2, only as the initial radiation using solar radiation. In this case, the amplification of the high-frequency modulating signal occurs due to the conversion of the energy of solar radiation into the energy of the Langmuir wave excitations of the plasma with subsequent removal from the plasma and the accumulation of the converted microwave energy in the cavity. The efficiency values of the considered energy conversion can reach 70%
Example 7. The same as in example 6, only additionally using a rectifier device, such as a microwave rectifier, further energy is converted from the amplified high-frequency signal into direct or alternating current energy by rectifying this signal.

 Example 8. The same as in example 2, only instead of a glass flask 5 filled with plasma 4, a thin glass tube filled with plasma is used with transverse tube dimensions comparable with the wavelength of the original laser radiation, i.e. use a plasma waveguide.

 The waveguide or fiber geometric shape of the plasma in this case allows one to achieve high electromagnetic field strengths in the plasma at sufficiently low power levels of the initial laser radiation. As a result, either the requirements for the power of the original laser radiation are reduced when the same energy conversion efficiency is achieved as in Example 2, or the requirements for the Q factor of the resonators are reduced, compared with Example 2, to achieve similar efficiency.

 Example 9. The same as in example 8, only as a plasma waveguide used a narrow plasma cylinder with the above transverse dimensions, held by magnetic pressure when placing the plasma in a magnetic field (plasma waveguide with a free boundary).

 Example 10. The same as in example 8, only as a plasma waveguide using solid state plasma.

 Example 11. The implementation of the frequency multiplication of the high-frequency electromagnetic signal.

The circuit of FIG. 2 can operate in a frequency multiplication mode, i.e. increase by an integer number of times the frequency of the electromagnetic signal received at the input, in this case the high-frequency modulating signal 8. For this, the plasma is selected so that the Langmuir frequency Ω _{e of} this plasma 4 is a multiple of the modulation frequency ((i.e., the frequency Ω of the amplified signal) W _e = nΩ where n = 2, 3. In this case, at the output of the resonator 9, due to the conversion of the laser radiation energy into Langmuir plasma wave excitations, followed by the output of the converted energy from the plasma and its accumulation in the resonator, high-frequency signal with a frequency coinciding with the Legnmuir and multiple frequencies of the modulating signal, i.e. multiplying the frequency of the input modulating signal by an integer number of times.

 Example 12. The implementation of the generation of high-frequency electromagnetic waves.

 The same as in Example 2, only for converting the high-frequency electromagnetic signal amplification circuit shown in FIG. 2, in the circuit for generating these signals (i.e., for self-excitation of the circuit in FIG. 2), positive feedback is carried out using the feedback circuit.

 In FIG. 3 shows a circuit for generating a high frequency electromagnetic signal. The circuit of FIG. 3 differs from the circuit in FIG. 2 by the presence of feedback circuit 10 between the amplified high-frequency signal (output of the amplification circuit) and the amplified modulating signal (input of the amplification circuit).

 Example 13. The implementation of plasma heating by converting the energy of laser radiation into the energy of the Langmuir wave excitations of the plasma, which can dissipate into heat (see Fig. 4).

 In the previous examples, the conversion of the Langmuir wave excitations of the plasma into energy with the subsequent removal of the converted energy from the plasma was used.

 However, the situation changes if the converted energy of the Langmuir wave excitations is not removed from the plasma. In this case, the converted energy of the wave excitations of the plasma with the Langmuir frequency will dissipate into heat, heating the plasma.

 In FIG. 4 shows a plasma heating circuit based on this energy conversion.

Continuous laser radiation 1 is modulated with a modulator 2 in phase (or frequency) by harmonic oscillations of constant purity Ω. Moreover, the modulation frequency W is equal to (or close to) the Langmuir frequency W _{e of} this plasma 4, i.e. Ω = Ω _e Then, the modulated laser radiation 3 is passed through a plasma 4 located in a glass flask 5 and created using a direct current discharge, for which electrodes 6 and 7 are used.

In order to increase the efficiency of this energy conversion, the synchronism condition is fulfilled for the harmonics of modulated laser radiation interacting in the plasma and Langmuir wave excitations. For this purpose, the size of the plasma along the direction of propagation of the modulated laser beam is selected to be L _o ≤L _coh, where L _coh size was determined as in Example 1.

 When the laser radiation modulated in phase (or frequency) is transmitted through the plasma, the energy of this laser radiation is converted into the energy of wave excitations of the plasma with the Langmuir frequency, followed by the dissipation of the converted energy into heat if the converted energy is not removed from the plasma.

To further increase the efficiency of energy conversion is further carried out the accumulation of plasma at the plasma wave excitation portion size L _o ≤L _coh by repeatedly passing the modulated laser radiation as aforesaid in a closed circuit through one and the same plasma portion size L _o ≤L _coh. For this, in the circuit of FIG. 3 use a beam splitting mirror 11 and mirrors 12, 13, 14.

Each time passage of the modulated laser light through the plasma size L _o ≤L _kog synchronism condition will be carried out and transformation into energy Langmuir plasma wave excitation will occur with subsequent dissipation into heat.

Repeated passes of the modulated laser light through the same portion of the plasma size L _o ≤L _kog energy conversion efficiency of the laser radiation energy in Langmuir wave excitation is increased as compared with the single pass through the accumulation of wave excitation energy at each pass. As a result, the efficiency of the plasma heating process is also increased.

 If you do not take into account losses due to reflection from mirrors, the efficiency of this energy conversion, and hence the heating efficiency, can approach theoretical (see expression 3). Calculations show that in practice, when used in the circuit of FIG. 3 mirrors 11, 12, 13, 14 of high quality, conversion efficiency can reach several tens of percent.

 Example 14. The same as in example 13 only for the multiple passage of modulated laser radiation in a closed circuit through the same plasma section using a Fabry-Perot resonator, between the mirrors of which are placed a glass flask 5 with plasma 4.

Example 15. The same as in example 13, only laser radiation of pulsed action 1 is used, provided that the pulse duration time T _i substantially exceeds the period of modulating oscillations T _m (T _i > T _m .

Example 16. The same as in example 12, only the frequency of the Langmuir wave excitations of the plasma Ω _{e is a} multiple of the modulation frequency Ω i.e. W _e = nΩ where n = 2,3.

 Example 17. The same as in example 13, they only modulate the initial laser radiation in amplitude by oscillations of a constant frequency of a rectangular shape (that is, with rectangular pulses) with a frequency that matches (or close) the Langmuir frequency.

 Example 18. The same as in example 13, only as the initial radiation 1 use microwave radiation. In this case, the plasma is heated by converting the energy of electromagnetic radiation from the microwave range into the energy of Langmuir excitations of the plasma, followed by the dissipation of the converted energy into heat if the converted energy is not removed from the plasma.

 Consider the theory of this method of converting the energy of electromagnetic radiation of the optical or lower frequency range into the energy of wave excitations of a nonlinear medium.

As the initial electromagnetic radiation, we study a plane laser wave with a cyclic frequency ω _o After modulating the laser radiation in phase (or frequency) by harmonic oscillations with a frequency Ω (coinciding with the frequency of these wave excitations of a nonlinear medium), the spectrum of the modulated laser radiation turns out to be discrete, symmetrical with respect to w _o and containing a set of frequencies of the form ω _m = ω _o + mΩ where 0, ± 1, ± 2, (or ω _n = ω _o ± nΩ where n 0, 1, 2,) with amplitudes distributed over the Bessel functions.

где m 0, ±1, ±2,)
На входе в нелинейную среду z=0 электрическое поле модулированного по фазе лазерного излучения имеет вид:

где Ω- циклическая частота фазовой модуляции, A_Σ(O)- амплитуда плоской лазерной волны до модуляции J_m(δ)- функция Бесселя первого рода порядка m, δ <<1 индекс модуляции, величина l >> 1 определяется шириной частотного диапазона прозрачности нелинейной среды.Thus, in the frequency spectrum of the modulated laser radiation, the carrier frequency ω _{o of the} original unmodulated laser radiation (i.e., the frequency of the initial laser radiation before modulation) corresponds to a plurality of frequencies equally spaced from each other by the modulation frequency (frequency

where m 0, ± 1, ± 2,)
At the entrance to the nonlinear medium z = 0, the electric field of the phase-modulated laser radiation has the form:

where Ω is the cyclic frequency of the phase modulation, A _Σ (O) is the amplitude of the plane laser wave before modulation J _m (δ) is the first-order Bessel function of order m, δ << 1 is the modulation index, l >> 1 is determined by the width of the frequency range of transparency nonlinear medium.

 For simplicity of consideration, we assume that the synchronism condition is fulfilled for electromagnetic waves interacting in a nonlinear medium (harmonics or spectral components of modulated laser radiation) and wave excitations.

Последнее равенство по существу выражает собой закон сохранения энергии для процесса модуляции.According to the well-known property of Bessel functions of the first kind:

The last equality essentially expresses the law of conservation of energy for the modulation process.

Отсюда следует, что при δ <1/7 (значение индекса модуляции d <<1 характерно для всех оптических модуляторов по фазе или частоте) на основную гармонику с несмещенной частотой w_o приходится более 99% всей мощности исходного излучения, а на все остальные гармоники с частотами ω_o±nΩ менее 1% где n=1,2,3,
Поэтому распространение модулированного по фазе (или частоте) лазерного излучения в нелинейной среде при соблюдении условия синхронизма для распространяющихся и взаимодействующих в этой среде волн и волновых возбуждений можно рассматривать как распространение в нелинейной среде совокупности гармоник модулированного излучения (гармонических волн) с частотами ω_o (на эту гармонику приходится более 99% мощности исходного излучения) и ω_o± nΩ где n=1,2,3, в результате которого возникают синфазные взаимодействия между гармониками, распространяющимися в данной среде, и волновыми возбуждениями.For small values of δ << 1:

It follows that for δ <1/7 (the modulation index d << 1 is characteristic of all optical modulators in phase or frequency), the main harmonic with an unbiased frequency w _o accounts for more than 99% of the total power of the initial radiation, and all other harmonics with frequencies ω _o ± nΩ less than 1% where n = 1,2,3,
Therefore, the propagation of phase-modulated (or frequency) laser radiation in a nonlinear medium, subject to the condition of synchronism for the waves propagating and interacting in this medium, and wave excitations can be considered as the propagation in a nonlinear medium of a combination of harmonics of modulated radiation (harmonic waves) with frequencies ω _o (at this harmonic accounts for more than 99% of the power of the radiation source) and ω _o ± nΩ where n = 1,2,3, which arise as a result of interaction between the common mode harmonics propagate yuschimisya in this environment, and wave excitations.

In the field of a powerful harmonic with a frequency ω _{o, the} energy of weak waves with frequencies ω _o + nΩ will not increase and the energy of these harmonics during propagation in this nonlinear medium can be neglected.

где Δε - изменение диэлектрической проницаемости среды, κ⁽³⁾- кубическая нелинейная восприимчивость среды, E₁ комплексная амплитуда плоской волны с частотой ω₁= ω_o E₂ комплексная амплитуда плоской волны с частотой ω₂= ω_o-Ω
Поскольку разность частот ω₁-ω₂ совпадает с частотой Ω_i одного из собственных резонансов среды, глубина модуляции волны изменений диэлектрической проницаемости среды испытывает резонансное возрастание, вследствие наличия резонанса у нелинейной восприимчивости κ⁽³⁾ и распространение волны De есть распространение оптически наведенных волновых возбуждений в среде с частотой W_i(Ω_i=Ω)
Фактически в результате такого параметрического взаимодействия часть энергии основной гармоники модулированного излучения с частотой ω_o преобразуется в энергию волновых возбуждений среды с частотой Ω_i= Ω и в энергию гармоники модулированного излучения с частотой ω_o-Ω
С квантовой точки зрения из одного фотона основной гармоники с энергией hω_o образуются фотон с энергией h (ω_o-Ω) и квазичастица с энергией hΩ_i/ соответствующая данному волновому возбуждению:
hω_o_→ h(ω_o-Ω_i)+hΩ_i (Ω=Ω_i)
где h постоянная Планка.Therefore, the consideration of energy conversion by the proposed method is reduced to the consideration of in-phase interactions arising from the propagation of many harmonics of modulated radiation with frequencies ω _o and ω _o -nΩ where n = 1,2,3,
First, we consider the in-phase interactions arising in a nonlinear medium with an inversion center during the propagation of two harmonics of modulated radiation with frequencies ω _o and ω _o -Ω under the condition that the frequency Ω (modulation frequency) coincides with the natural frequency of excitation of the medium W _i ( Ω = Ω _i )
Due to the beat of harmonics with frequencies ω _o and ω _o -Ω in the medium, a wave of changes in the dielectric constant of the medium with a difference frequency will be induced:

where Δε is the change in the dielectric constant of the medium, κ ⁽³⁾ is the cubic nonlinear susceptibility of the medium, E _{1 is the} complex amplitude of a plane wave with frequency ω ₁ = ω _o E _{2 is the} complex amplitude of a plane wave with frequency ω ₂ = ω _o -Ω
Since the frequency difference ω ₁ -ω ₂ coincides with the frequency Ω _{i of} one of the natural resonances of the medium, the modulation depth of the wave of changes in the dielectric constant of the medium undergoes a resonant increase, due to the presence of resonance in the nonlinear susceptibility κ ⁽³⁾ and the propagation of the wave De is the propagation of optically induced wave excitations in a medium with a frequency W _i (Ω _i = Ω)
In fact, as a result of this parametric interaction, part of the energy of the fundamental harmonic of the modulated radiation with frequency ω _{o is} converted into the energy of wave excitations of the medium with a frequency Ω _i = Ω and into harmonic energy of modulated radiation with a frequency ω _o -Ω
From the viewpoint of the quantum of one photon with the fundamental harmonic energy generated hω _o photon of energy h (ω _o -Ω) and quasiparticle energy with hΩ _{i /} wave corresponding to a given excitation:
ω _o _ → h (ω _o -Ω _i ) + hΩ _i (Ω = Ω _i )
where h is Planck's constant.

Реальная нелинейная среда обладает конечным оптическим диапазоном прозрачности. Обозначим нижнюю границу частотного диапазона прозрачности через ω_грн
Из (2) следует, что распад фотонов прекращается, когда ω_o-nΩ = ω_грн
Поэтому количество квазичастиц с энергией hΩ_i(Ω=Ω_i) соответствующих волновым возбуждениям среды и образующихся вследствие распада одного фотона основной гармоники с частотой ω_o по схеме (2), равно:

Максимально допустимый КПД (η) данного преобразования энергии в этом случае можно определить:

Такой высокий теоретический КПД преобразования энергии исходного лазерного излучения в энергию волновых возбуждений среды достигается в данном способе за счет многоволнового взаимодействия, возникающего вследствие распространения в нелинейной среде множества гармоник модулированного излучения при соблюдении условия синхронизма. Подобное взаимодействие между гармониками модулированного излучения и волновыми возбуждениями описывается многоступенчатой схемой распада фотонов (2), что и приводит, по сравнению с одноступенчатой схемой распада фотонов, лежащей в основе известных способов, к повышению КПД(η) преобразования энергии.Simultaneously with the interaction under consideration, in-phase interaction will occur due to the propagation in the medium of harmonics of modulated radiation with frequencies ω _o -Ω and ω _o -2Ω
As a result of this interaction, the harmonic energy with a frequency ω _o -Ω is converted into the energy of wave excitations of the medium with a frequency Ω _i = Ω and into harmonic energy with a frequency ω _o -2Ω
h (ω _o - Ω) _ → h (ω _o -2Ω) + hΩ
Also, at the same time, interaction will occur due to the propagation of harmonics with frequencies in a non-linear medium:
ω _o −2Ω and ω _o −3Ω, ω _o −3Ω and ω _o −4Ω, ... etc.
As a result, the multi-wave interaction arising as a result of propagation in a nonlinear medium under the condition of synchronism of the set of harmonics of modulated radiation with frequencies ω _o , ω _o -Ω, ω _o -2Ω, ... etc. etc. is described by the following photon decay scheme

A real nonlinear medium has a finite optical transparency range. Denote the lower boundary of the frequency range of transparency by ω _UAH
From (2) it follows that the decay of photons ceases when ω _o -nΩ = ω _UAH
Therefore, the number of quasiparticles with an energy hΩ _i (Ω = Ω _i ) corresponding to wave excitations of the medium and generated as a result of the decay of one fundamental photon with a frequency ω _o according to scheme (2) is equal to:

The maximum allowable efficiency (η) of a given energy conversion in this case can be determined:

Such a high theoretical efficiency of converting the energy of the initial laser radiation into the energy of wave excitations of the medium is achieved in this method due to the multi-wave interaction arising from the propagation of many harmonics of modulated radiation in a nonlinear medium under the condition of synchronism. Such an interaction between the harmonics of modulated radiation and wave excitations is described by a multi-stage photon decay scheme (2), which leads, in comparison with the single-stage photon decay scheme, which underlies the known methods, to an increase in the energy conversion efficiency (η).

 As already noted, efficient energy conversion in the proposed method is possible if the synchronism condition is fulfilled for harmonics of modulated radiation and wave excitations interacting in a nonlinear medium.

Beats caused by two harmonics of modulated radiation with frequencies w _o and ω _o -Ω induce wave excitations in the medium (see expression 1).

Similar expressions describe wave excitations induced in the medium by beats of harmonics of modulated radiation with frequencies ω _o -Ω and ω _o -2Ω, ω _o -2Ω and ω _o -3Ω, ... etc. etc.

In this case, the condition of synchronism is that the wave excitations induced by the beats of all the corresponding harmonics of the modulated radiation are coherent with each other, i.e. the phase difference between all wave excitations should not exceed π (Δφ ≤ π)
There is always a certain amount of nonlinear medium along the propagation direction of the radiation modulated by L _o ≤L _COH (wherein L _coh coherent interaction length or coherence length) at which the synchronism condition is automatically satisfied. This is true both in the case of wave excitations without dispersion, and in the case of wave excitations of a medium with dispersion.

где C скорость исходного лазерного излучения,

коэффициент преломления среды на частоте ω_o - исходного лазерного излучения,

коэффициент преломления среды на частоте ω_грн-
Остановимся на требованиях к стабильности частоты модуляции в данном способе преобразования энергии.For example, in the case of a real nonlinear medium with a specific frequency range of transparency, the lower boundary of which is ω _UAH , and with a natural frequency of dispersionless wave excitation Ω _i = Ω, it can be shown that:

where C is the speed of the initial laser radiation,

the refractive index of the medium at a frequency ω _o - the original laser radiation,

the refractive index of the medium at a frequency ω _UAH -
Let us dwell on the requirements for the stability of the modulation frequency in this method of energy conversion.

 Obviously, the length of the train of modulating oscillations should exceed the size of the nonlinear medium on which the considered transformation takes place (see Fig. 1 or 4), or that the same coherence time of modulating oscillations should exceed the time during which the converted energy of wave excitations is accumulated in resonators (see figure 2 and 3).

Для случая преобразования энергии, показанном на фиг. 3, имеем:

где Q добротность резонатора.As a result, for the converted energy case shown in FIG. 1, you can get

For the case of energy conversion shown in FIG. 3, we have:

where Q is the resonator Q factor.

 Unlike the known methods of energy conversion, functioning only under the condition of a narrow spectral composition of the initial optical or lower frequency electromagnetic radiation, the proposed method of energy conversion functions in the case of the initial optical or lower frequency electromagnetic radiation with an arbitrary spectral width.

Let optical radiation with a wide spectral composition be used as the initial radiation, for example, radiation with a frequency of the spectrum width ω _in ÷ ω _n
In this case, the initial optical radiation with a wide spectrum can be considered as a set of independent monochromatic spectral components with frequencies ω _i ∈ [ω _in , ω _n ]
Therefore, after preliminary modulation of the initial radiation with a wide spectrum in phase (or frequency) by harmonic oscillations of a constant frequency Ω, each independent spectral component of the initial radiation with a frequency w _i will be modulated in phase (or frequency) by harmonic oscillations with a frequency Ω
The energy conversion mechanism in this invention for a single monochromatic spectral component, modulated by phase (or frequency) by oscillations with a frequency W, was essentially considered above using the example of the initial laser radiation.

Это означает, что вся энергия исходного излучения с широким спектром, складывающаяся из энергий отдельных спектральных составляющих, может преобразована в энергию волновых возбуждений нелинейной среды описанным выше образом.Therefore, the energy of each independent spectral component modulated in phase (or frequency) will be converted into the energy of wave excitations of a nonlinear medium in the manner described above with the maximum allowable conversion efficiency:

This means that all the energy of the initial radiation with a wide spectrum, consisting of the energies of the individual spectral components, can be converted into the energy of wave excitations of a nonlinear medium in the manner described above.

Note that this method of energy conversion also functions when the natural frequency of these medium excitations Ω _{i is a} multiple of the modulation frequency Ω, i.e., when Ω _i = nΩ, where n = 2,3,4, ...
Suppose, for example, that laser radiation with a frequency ω _o is used as the initial radiation and that Ω _i = 2Ω
In this case, after the laser radiation is modulated in the manner described above and the modulated laser radiation is transmitted through a nonlinear medium, these wave excitations will arise due to beats between the harmonics of the modulated radiation with frequencies ω _o and ω _o −2Ω, ω _o −2Ω and ω _o −4Ω, and etc.
Under the condition of synchronism for electromagnetic waves interacting in a nonlinear medium (harmonics of modulated laser radiation) and these wave excitations, the energy conversion efficiency increases.

Claims (15)

 1. A method of converting the energy of electromagnetic radiation of the optical or lower frequency range into the energy of wave excitations of a non-linear medium, comprising transmitting electromagnetic radiation through a non-linear medium, characterized in that the electromagnetic radiation with an arbitrary spectrum width is modulated in time by oscillations of a constant frequency so that in the frequency spectrum modulated radiation, each carrier frequency of the original unmodulated radiation corresponded to many frequencies equal to ootstoyaschih from each other to the modulation frequency, the modulation frequency is selected so that the natural frequency wave excitations nonlinear medium is equal to or multiple of the frequency modulation is thus carried out synchronism condition for interacting in a nonlinear medium harmonics of the modulated source of radiation and the data wave excitations induced in the medium.  2. The method according to claim 1, characterized in that in order to increase the efficiency of this conversion, the energy of wave excitations arising in a nonlinear medium is additionally stored.  3. The method according to claims 1 and 2, characterized in that the energy storage of wave excitations of the medium is carried out by repeatedly passing the modulated electromagnetic radiation in a closed circuit through the same section of the nonlinear medium.  4. The method according to claims 1 and 2, characterized in that for the accumulation of energy of wave excitations of the medium, one or more resonators are used that can accumulate the energy of these wave excitations, with a resonant frequency coinciding with the frequency of wave excitations, while the nonlinear medium is placed both inside one of the resonators, and outside of these resonators.  5. The method according to p. 1, characterized in that as the electromagnetic radiation using radiation from continuous lasers.  6. The method according to p. 1, characterized in that the radiation of pulsed lasers is used as electromagnetic radiation, provided that the pulse duration time significantly exceeds the period of modulating oscillations.  7. The method according to p. 1, characterized in that the use of solar radiation as electromagnetic radiation.  8. The method according to claim 1, characterized in that the modulation is carried out in phase or frequency by harmonic oscillations.  9. The method according to claim 1, characterized in that as a nonlinear medium, a nonlinear medium with waveguide geometry is used.  10. The method according to p. 1, characterized in that the plasma is used as a non-linear medium.  11. The method according to claims 1 and 10, characterized in that the plasma is placed in a magnetic field.  12. The method according to p. 1, characterized in that the plasma of solids is used as a non-linear medium.  13. The method according to claim 1, characterized in that for converting the wave excitations dissipating into heat into energy, a medium is selected that is capable of generating these excitations in it, and the initial energy is converted into the energy of these excitations.  14. The method according to claim 1, characterized in that the initial radiation is modulated by electromagnetic waves, and the medium is selected so that it is capable of generating high-frequency electromagnetic wave excitations in it, and the initial energy is converted into the energy of these excitations, and the converted energy removed from the environment.  15. The method according to PP.1 and 14, characterized in that they provide positive feedback using the feedback circuit between the converted oscillations output from the medium and modulating electromagnetic oscillations.

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