RU2490788C1 - System for automatic adjustment of frequency of scattered lasers - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: system for automatic adjustment of frequency of scattered lasers with a continuous radiation mode includes multiple coupled automatic frequency adjustment circuits, each including series-connected photomixer, discriminator, integrator and direct current amplifier connected to a piezoelectric corrector of the radiation frequency of the corresponding continuous wave laser, wherein one automatic frequency adjustment system from two continuous wave lasers is mounted on an artificial earth satellite which is fixed relative the earth, and the other two are mounted on the earth's surface.

EFFECT: enabling measurement of blue shift of monochromatic radiation of a powerful continuous wave laser which is aimed at the earth's surface from an artificial earth satellite which is fixed over a given point on the earth's surface due to the effect of the earth's gravitational field.

2 dwg

Description

The invention relates to the field of radio engineering and automation in relation to systems for automatically adjusting the frequency of emission of continuous gas gas lasers with improved stabilization characteristics and can be used in space technology, in particular, to measure the "violet shift" of the frequency of laser radiation in the Earth's gravitational field.

Known automatic frequency control (AFC) systems for continuous gas coupled gas lasers, mutually coherent radiation of which is partially fed to a mixer, the output of which is an electric signal with a difference frequency, which, after amplification in the strip path, acts on a series-connected discriminator, integrator and constant amplifier current output connected to a piezoelectric corrector of the frequency of the radiation controlled by the frequency of the laser [1-7]. In this case, the radiation frequencies of two coupled lasers differ by the average discriminator tuning frequency. The indicated piezoelectric corrector is included in the composition of the laser cavity, changing its length, and therefore the frequency of the laser radiation also changes [8–9]. The action of such AFC systems with a low-power, highly stable laser, the oscillations of which are mixed with the vibrations of a powerful stabilized continuous-wave laser and are compared with the central frequency of the discriminator tuning, resulting in an error signal filtered by an integrator and amplified in a direct current amplifier, which controls the frequency of the high-power laser radiation, into the resonator of which a piezoelectric corrector connected to the resonator mirror is introduced, maintaining a constant time difference between the frequencies of both lasers s by a known value with high accuracy.

A disadvantage of the known AFC systems is the difficulty of automatically adjusting the frequency of one laser under another in the case of a significant dispersion of these lasers in space, for example, when one of them is installed on an artificial earth satellite (AES), motionless located relative to a given point on the earth's surface (as in the system’s repeater satellites Glanas), and another laser on the ground.

The specified disadvantage is eliminated in the claimed technical solution.

The aim of the invention is to provide the ability to measure the "violet displacement" of monochromatic radiation of a powerful continuous-wave laser directed to the earth's surface from an artificial earth satellite, motionlessly located above a given point on the earth's surface, due to the action of the Earth's gravitational field.

This goal is achieved in a system for automatically adjusting the frequency of scattered lasers with a continuous radiation mode, containing several mutually interconnected circuits of self-tuning the frequency, including each series-connected photo-mixer, discriminator, integrator and DC amplifier connected to a piezoelectric corrector of the radiation frequency of the corresponding continuous-wave laser, characterized in that one self-tuning system of two continuous-frequency lasers is highly unstable sensible and powerful, equipped with a transmitting telescope oriented to the earth’s surface, is located on an artificial earth satellite that is stationary relative to the earth, and the other two self-tuning systems are located on the earth’s surface, the first of them is connected through a receiving telescope to the radiation of a powerful laser of an artificial earth satellite, and its output through a low-noise strip amplifier is connected to a frequency-tunable discriminator, the additional output of which is connected to a frequency meter this discriminator, and the photo-mixer of the second terrestrial auto-frequency control system is optically coupled to a part of the laser radiation of the first terrestrial system and the second laser of the ground-based system, the radiation frequency of which is adjusted by the auto-frequency-controlled system, while the output of the DC amplifier is connected to the piezoelectric corrector of the second laser of the ground-based system, and transmitted digitally encoded over the air to an artificial earth satellite via an analog-to-digital terrestrial transmitter with a microwave antenna and digital-to-analog a receiver with a microwave antenna mounted on an artificial earth satellite and oriented to a terrestrial microwave antenna.

Achieving this goal is explained by an increase in the energy of photons in the earth’s gravitational field as they travel the space from an artificial earth satellite (AES) to the earth’s surface with a positive gradient of the gravitational field in the direction of propagation of photons of optical frequency and a negative gradient of the gravitational field for radio emission directed to the satellite, whose frequency five orders of magnitude lower than the frequency of laser radiation, which does not significantly affect the measurement error of the "violet shift" of the frequency due to the gravitational field Earth. Separation from the total frequency shift due to variations in the natural frequency of this laser due to its instability and the “violet shift” of the frequency in the earth’s gravitational field, the component of the “violet shift” of the frequency, is carried out by preliminary statistical methods for a sufficiently large period of time averaging the drift of the frequency of the laser radiation of a high-power laser installed on the satellite with the combined action of all three self-tuning systems on the ground, that is, in the absence of increment of photon energy under the action of the gradient of the gravitational field.

The invention is clear from the block diagram of the AFC system of laser systems dispersed in space shown in Fig. 1, which includes the following components.

On an artificial earth satellite:

1 - a powerful continuous laser,

2 - the first beam-splitting cube with a high reflection coefficient,

3 - transmitting telescope,

4 - highly stable low-power laser of continuous operation,

5 - reflector of a small part of the radiation of a powerful laser 1,

6 - second beam splitting cube,

7 - the first photo mixer,

8 - the first discriminator with a fixed setting,

9 - the first integrator,

10 is a first DC amplifier,

11 - receiving microwave antenna,

12 - digital-to-analog receiver (its output is connected to the piezoelectric corrector of laser 4).

On Earth:

13 - receiving telescope,

14 - laser of the first ground-based automatic frequency control system,

15 is a third beam splitting cube with a high transmittance,

16 - second photo mixer,

17 - low-noise strip amplifier

18 - second discriminator with the adjustment of the center frequency,

19 - second integrator,

20 is a second DC amplifier connected to the piezoelectric corrector of the laser 14,

21 - meter frequency settings of the second discriminator 18,

22 - fourth beam splitting cube,

23 - reflector of laser radiation 14,

24 - fifth beam splitting cube,

25 - the third mixer

26 - laser of the second ground-based frequency-tuning system,

27 - reflector of laser radiation 26,

28 - third discriminator with a fixed setting,

29 - the third integrator,

30 - the third DC amplifier connected to the piezoelectric corrector of the laser 26 and to the input of the analog-to-digital transmitter,

31 - analog-to-digital transmitter control signal laser 4 on the satellite,

32 - transmitting microwave antenna.

Figure 2 shows the structure of an analog-to-digital transmitter and a digital-to-analog receiver for controlling the frequency of a low-power highly stable continuous-wave laser 4, which is represented by the following blocks:

33 - analog-to-digital Converter,

34 - microwave modulator,

35 - master microwave generator,

36 - power amplifier,

37 - low noise input microwave device,

38 - microwave mixer,

39 - microwave oscillator

40 - intermediate frequency amplifier,

41 - amplitude detector with a limiter to a minimum,

42 - digital demodulator,

43 - digital-to-analog Converter,

44 - DC amplifier with adjustable initial level connected to the piezoelectric corrector of the laser 4.

Consider the action of the claimed system.

The whole system is set up on the ground. Let the radiation frequency of a high-power continuous-wave laser 1 be equal to ν _O1 , and the frequency of a highly stable low-power continuous-wave laser 4 is equal to ν _O2 and differ from the frequency ν _O1 by the difference Δf ₁ = ν _O2 -ν _O1 , to which the central frequency F _{O1 of the} first discriminator 8 is tuned with fixed setting, and the signal of frequency Δf at the output of ₁ is allocated first fotosmesitelya 7 by addition of oscillation lasers 1 and 4. If the inequality Δf ₁ ≠ F _O1 on output of the first discriminator 8 non-zero signal arises of either sign, depending on the detuning this discriminator relative frequency Δf _1, output signal of the discriminator 8 is integrated in the first integrator 9 with a time constant τ _I1 >> 1 / Δf _1, and after amplification in the first amplifier 10, the DC is supplied to pezokorrektor powerful laser 1 by aligning its frequency to obtain equality Δf ₁ = F _O1 , at which compliance is always maintained in the laser 1 frequency ν _O1 = ν _O2 -F _O1 in the steady state.

Photons of this frequency ν _O1 propagating from a satellite from a height H from the earth's surface receive additional energy due to their movement in the earth's gravitational field with a positive gradient. As it is easy to show, the addition of this energy in each of the photons perceived by the ground-based equipment is:

$$\Delta W=h\Delta {\nu }_F=\gamma M\left(h{\nu }_{O\mathrm{one}}/c^2\right)H/R\left(R+H\right)=g_O\left(h{\nu }_{O\mathrm{one}}/c^2\right)HR/\left(R+H\right),\left(\mathrm{one}\right)$$

where h = 6.62.10 ^-34 J.sec is the Planck constant, M is the mass of the Earth, c = 3.10 ⁸ m / s is the electrodynamic constant (the speed of light in the void), R is the radius of the Earth (m), g _O = 9, 81 m / s ² - acceleration of gravity on the surface of the Earth. If we take into account that the Earth’s radius is much greater than the satellite’s height, that is, R >> H, then Eq. (1) can be rewritten to the form hΔν _Ф ≈g _O (hν _O1 / c ² ) H, whence we get for the “violet shift” "The photon frequency under the influence of a gravitational field with a positive gradient:

$$\Delta {\nu }_F=g_O{\nu }_{O\mathrm{one}}HR/c^2\left(R+H\right)\approx g_O{\nu }_{O\mathrm{one}}H/c^2.\left(2\right)$$

Thus, optical vibrations coming to the earth’s surface will have a frequency

$${\nu }_O^{*}={\nu }_{O\mathrm{one}}+\Delta {\nu }_F={\nu }_{O2}-F_{O\mathrm{one}}+g_O{\nu }_{O\mathrm{one}}HR/c^2\left(R+H\right),\left(3\right)$$

на частоту второго дискриминатора 18 с перестраиваемой центральной частотой настройки F_O2 и при этом имеем соотношение:which is received by the receiving telescope 13, and the oscillations of this frequency are transmitted to the second mixer 16 together with the optical oscillations from the laser 14 of the first ground-based frequency-locked loop, the frequency of which ν _O3 differs from the frequency $${\nu }_O^{*}$$

on the frequency of the second discriminator 18 with a tunable central tuning frequency F _O2 and at the same time we have the ratio:

$${\nu }_{O3}={\nu }_O^{*}+F_{O2}={\nu }_{O2}-F_{O\mathrm{one}}+g_O{\nu }_{O\mathrm{one}}HR/c^2\left(R+H\right)-F_{O2},\left(\mathrm{four}\right)$$

where the frequency F _{O2 of the} second discriminator 18 can be tuned, which is indicated by the frequency meter 21.

Oscillations of the optical frequency ν _O3 are fed to the input of the third photo-mixer 25 and mixed in it with the optical oscillations of the laser 26 of the second ground-based frequency-locked loop, the frequency of which is ν _O4 = ν _O3 + F _O3 . When choosing F _O1 = F _O3 we get that the oscillation frequency V _O4 in the laser 26 will be maintained equal to:

$${\nu }_{O\mathrm{four}}={\nu }_{O2}+g_O{\nu }_{O\mathrm{one}}HR/c^2\left(R+H\right)-F_{O2},\left(5\right)$$

which follows from (4) by substituting the condition F _O1 = F _O3 , which is always easily satisfied.

Then, provided that the second discriminator 18 is tuned with the tunable central frequency so that the equality g _O ν _O1 HR / s ² (R + H) = F _{O2 is} satisfied, we finally have the equality of the form ν _O4 = ν _O2 , in other words, with the appropriate choice the initial level of the signal from the output of the first DC amplifier 10 in the satellite system, the frequency of its highly stable laser 4 will be exactly equal to the frequency of oscillations in the laser 14 of the first Earth's automatic frequency control system, which was required to be observed in a coupled system of lasers dispersed over nstv.

In this case, by setting the second discriminator 18, we provide the measurement of the desired value of the “violet bias” of the frequency, which is

$$\Delta {\nu }_F=F_{O2}=g_O{\nu }_{O\mathrm{one}}HR/c^2\left(R+H\right)\approx g_O{\nu }_{O\mathrm{one}}H/c^2.\left(6\right)$$

If we use Xe Cl lasers with a wavelength of 0.308 nm and, accordingly, a frequency of ν _O1 = 3.10 ⁸ /0.308.10 ^-6 = 0.974.10 ¹⁵ Hz, as for continuous lasers, then at H = 4.10 ⁵ m and R = 3.65.10 ⁶ m we obtain the frequency shift Δν _Ф = 9.81 _* 0.974.10 ¹⁵ _* 4.10 ⁵ _* 3.65.10 ^{6 /} 9.10 ¹⁶ _* 4.05.10 ⁶ = 3.827 10 ⁴ Hz = 38.27 kHz. The second discriminator 18 must be tuned to this frequency, and its tuning is fixed by the tuning frequency meter 21. Other discriminators - the first 8 and third 28 have fixed settings, for example, at the frequency F _O1 = F _O3 = 50 kHz.

It is important to note that transmitting the tuning signal of a highly stable low-power laser 4 over the radio channel on microwave oscillations, for example, at a frequency f _O = 10 GHz (wavelength λ _microwave = 3 cm), which propagates from the Earth to the satellite, that is, with a negative gradient of Earth's gravity , "red shift" in the radio frequency microwave receiving antenna 11 is so small in value, in particular equal Δν _microwave Δν = _f f _O / ν _O1 = 38,27 _* ¹⁰ October /0,974.10 ¹⁵ = ^-5 39,29.10 kGts≈ 0.4 Hz, which can be neglected by this error in changing the frequency of the “violet shift” of the frequency (38.27 kHz).

Thus, in addition to creating a stabilized system of coupled and substantially dispersed continuous-wave lasers, with the help of such a system, part of which is mounted on a satellite, it is possible to measure the effect of the “violet shift” of the frequency of optical oscillations in addition to the well-known “redshift”. We can therefore assume that when a light beam bends near strongly gravitating masses, for example, the Sun, associated with gravity, the resulting "red shift" is due precisely to the curvature of the beam, its deviation from the linear motion of the photons, and the energy received by the photon when approaching the gravitating object exactly equal to the energy given to them by this object when the photon is removed from it. An important physical conclusion is drawn from this that any forced curvature of the trajectory of a ray of light (generally an electromagnetic wave in a wide spectrum) is associated with the loss of energy by the photons for secondary radiation, and therefore a “red shift” occurs. This is a new physical phenomenon. Similarly to this effect, the author previously stated the pattern of conservation of the polarization of electromagnetic waves [10], in which any forced change in the polarization of the electromagnetic wave by the medium in which it propagates (for example, non-stationary anisotropic) leads to a “red shift” of the frequency, that is, energy loss and the appearance of secondary radiation [11-14].

Literature

1. Smaller O.F. Automatic frequency control device. Auth. testimonial. USSR No. 360125, publ. in the bull. No. 26 dated 09/09/1972.

2. Smaller O.F. AFC device, Aut. testimonial. USSR No. 322131, Particleboard, Prior, 03/02/1970.

3. Smaller O.F. AFC device, Aut. testimonial. USSR No. 329929, particleboard, prior, from 04.16.1970.

4. Smaller O.F. Device for frequency modulation of gas laser radiation, Auth. testimonial. USSR No. 1373188, particleboard, prior. from 12.16.1985.

5. Smaller O.F. A method for measuring the short-term stability of a gas laser radiation frequency, Auth. testimonial. USSR No. 1554719, Particleboard, prior. 11/06/1987.

6. Smaller O.F. A device for measuring short-term stabilization of the frequency of radiation of gas lasers, Auth. testimonial. USSR No. 1556291, Particleboard, prior. from 04/11/1988.

7. Smaller O.F. AFC device for laser Doppler locator, Auth. testimonial. USSR No. 1591675, Particleboard, prior. from 08.24.1988.

8. Semin V.E. and others. Monolithic quartz frequency discriminators, "Electronic Engineering", ser.5, Radio components and radio components, 1975, issue 5, p.119-121.

9. Vasiliev A.A. et al. Spatial Light Modulators, ed. Kompaneitsa I.N., M., Radio and Communications, 1987, p. 59-71.

10. Smaller O.F. The law of conservation of polarization of electromagnetic waves, Application for discovery, M., MAANO, Information No. BB-155 of 11/17/2003.

11. Smaller O.F. “Generation of microwaves in anisotropic media by the action of an optical shock wave,” report at the U-Union Seminar on Optoelectronics, Institute of Control Problems of the Academy of Sciences of the USSR, 04/22/1975, Moscow.

12. Smaller O.F. “A method of generating electrical oscillations and a device for its implementation”, Auth. testimonial. USSR No. 1380476 for pioneering invention, particleboard, Moscow.

13. Smaller O.F. “Device for detecting the resonance effect of the“ redshift ”of electromagnetic waves in anisotropic media”, RF Patent No. 2276394 bull No. 13 from 05/10/2006.

14. Smaller O.F. “Device for measuring the“ redshift ”of plane-polarized coherent radiation”, RF Patent No. 2276347, bull. No. 13 dated 05/10/2006.

Claims (1)

A system for automatically adjusting the frequency of scattered lasers with a continuous radiation regime, containing several mutually interconnected circuits of self-tuning the frequency, including each series-connected photo-mixer, discriminator, integrator and direct current amplifier connected to a piezoelectric corrector of the radiation frequency of the corresponding continuous-wave laser, characterized in that one automatic tuning system frequencies from two continuous-wave lasers - highly stable low-power and powerful, equipped with a transmitting telescope oriented to the earth’s surface is located on an artificial earth satellite immovable relative to the earth, and two other frequency-locking systems are located on the earth’s surface, the first of them is connected through a receiving telescope to the radiation of a powerful laser of an artificial earth satellite, and its output is through a low-noise bandpass the amplifier is connected with a frequency-tunable discriminator, the additional output of which is connected to a frequency meter for tuning this discriminator, and the mixer of the second terrestrial auto-frequency control system is optically coupled to a part of the laser radiation of the first terrestrial system and the second laser of the terrestrial system, the radiation frequency of which is tuned by the autotune system, while the output of the DC amplifier is connected to the piezoelectric corrector of the second laser of the terrestrial system, and is also transmitted in digitally encoded form over the air to an artificial earth satellite through an analog-to-digital terrestrial transmitter with a microwave antenna and a digital-to-analog receiver with a microwave antenna, set copulating artificial satellite and ground-oriented microwave antenna.

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