RU2382333C2 - Four-mode gyroscope on stabilised solid-state laser without dead band - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention is related to solid-state laser gyroscopes, intended for measurement of rotation speed or relative angular positions, and is used, in particular in the field of aeronavigation. Gyroscope comprises optical elements (8, 9) of polarisation separation, mutual (4) and nonmutual (5, 13) spinners of polarisation plane, as a result of which four linearly polarised optical modes are distributed in resonator (1), frequencies of which differ to a sufficient extent in order to avoid synchronisation of modes.

EFFECT: invention makes it possible to produce "fully optical" stable solid-state laser, which does not have movable parts and dead band.

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Description

The present invention relates to solid state laser gyroscopes for measuring rotational speed or angular positions. Equipment of this type is applicable, in particular, in the field of air navigation.

Laser gyroscopes were developed about 30 years ago and are widely used in our time. The principle of their operation is based on the Sagnac effect, which causes the appearance of a frequency difference Ω between two modes of optical radiation propagating in opposite directions, which is called counterpropagation, from a rotating bi-directional ring laser resonator. As a rule, the frequency difference Ω is equal to:

Ω = 4Aω / λL,

where L and A are the length and area of the resonator, respectively; λ is the average wavelength of laser radiation without taking into account the Sagnac effect; ω is the angular velocity of rotation of the laser gyro.

Using the value of Ω obtained by spectral analysis of the beat of two emitted beams, the value of ω is obtained with high accuracy.

Using an electronic counter due to the beating of interference strips moving during a change in the angular position, the relative value of the angular position is also obtained with high accuracy.

For the manufacture of a laser gyroscope, it is necessary to solve several technical problems. The first of these is related to the quality of the beating that occurs between the two beams, which determines the correct functioning of the laser. For the beat to be accurate, proper stability and relative similarity of the radiation intensity values in both directions are necessary. But in the case of solid-state lasers, the aforementioned stability and similarity are not guaranteed due to mode-mode competition, as a result of which one of the two opposite modes exclusively uses the available gain to the detriment of the other mode. The problem of the instability of bidirectional radiation from a solid-state ring laser can be solved by using an opposing reaction loop designed to correct the difference in the intensity values of two counter modes with the intensity brought to a predetermined value. Such a contour acts on the laser, linking to the direction of propagation of its loss, for example, using a reciprocal rotating element, a non-reciprocal rotating element and a polarizing element (patent application 03 03645), or tying its gain to the direction of propagation, for example, using a mutual rotating element , nonreciprocal rotating element and crystal with polarized radiation (patent application 03 14598). After such matching in intensity, the laser emits two oncoming beams with a stable intensity and can be used as a laser gyroscope.

The second technical difficulty is associated with low rotation speeds, since laser gyroscopes work precisely only outside a certain rotation speed. At a low rotation speed, the signal of the Sagnac beats disappears due to the interaction of two counterpropagating modes, also known as mode locking or mode coupling (synchronism), which is caused by backscattering of light by various optical elements located in the resonator. The range of rotation speeds in which this phenomenon is observed is usually called the dead band (dead zone), and it corresponds to a minimum beat frequency of the order of several tens of kilohertz. This problem is not only inherent in solid-state lasers, it is also characteristic of gyroscopes based on gas lasers. The most common solution with respect to laser gyroscopes of the indicated second type is to actuate the device mechanically by giving it a forced and known movement, which artificially removes the gyroscope as often as possible outside the dead zone.

The problem to which the invention is directed, is the layout of the optical devices necessary to control the instability of solid-state lasers using specific optical devices or devices that eliminate the deadband. Thus, the invention allows to obtain a "fully optical" stable solid-state laser that does not have moving parts and dead zones.

In particular, the invention relates to a laser gyroscope containing at least:

- ring optical resonator,

- solid state active medium,

- matching (tuning) device, comprising a first optical unit, consisting of a first nonreciprocal polarization plane rotator and an optical element, which is a mutual polarization plane rotator or birefringent element with the ability to control at least one of the effects or birefringence, and

- measuring device,

characterized in that the said resonator also contains

- a second optical unit, consisting of a first spatial filtering device and a first optical element of polarization separation,

- a third optical unit, consisting of a second spatial filtering device and a second optical element of polarization separation, the second and third optical units being located symmetrically to each other on both sides of the first optical unit,

- the fourth optical unit, consisting of sequentially located the first quarter-wave plate, the second nonreciprocal rotator of the plane of polarization and the second quarter-wave plate, the main axes of which are perpendicular to the main axes of the first quarter-wave plate,

as a result, the first linearly polarized mode propagating in the first direction and the second mode, linearly polarized perpendicular to the first, and the third mode propagating in the opposite direction, linearly polarized parallel to the first, and the fourth mode, linearly polarized parallel to the second, can be installed in the resonator moreover, the main axes of the first quarter-wave plate and the second quarter-wave plate are rotated relative to the directions of linear polarization of the four propagation modes radiation at an angle of 45 °, and the optical frequency of the four modes are different.

In a preferred embodiment, the measuring system comprises:

- optical devices that cause interference, on the one hand, the first and third modes of radiation propagation, and on the other hand, the second and fourth modes of radiation propagation,

- optoelectronic devices for determining, on the one hand, the first optical frequency difference between the first and third radiation propagation modes, and on the other hand, the second optical frequency difference between the second and fourth radiation propagation modes,

- electronic devices for obtaining a difference between the aforementioned first frequency difference and the second frequency difference.

The first frequency difference and the second frequency difference, as a rule, exceed a value of about 100 kHz. To obtain the angular position, the obtained frequency difference can be integrated over time by means of an electronic counter of interference fringes.

It is advisable to arrange a birefringent retardation plate in the resonator.

In a preferred embodiment of the invention, the first and second optical elements of polarization separation are birefringent retardant, or phase, plates with flat parallel sides, in which the birefringence axis is rotated by an angle of 45 ° relative to the plane of the sides.

It is advisable to include at least a fifth optical unit in the matching device, consisting of a third nonreciprocal polarization plane rotator and a second optical element, which is a birefringent element or mutual polarization plane rotator, the birefringence or mutual effect of which can be controlled, the first and third radiation propagation modes pass through the first nonreciprocal rotator of the plane of polarization and the first optical element, and the second and fourth modes radiation defamiliarisation - via the third non-reciprocal rotator and a second optical element. Birefringent elements are, in particular, birefringent retarding (phase) plates, such as quarter-wave plates.

For a better understanding of the essence of the invention and its other advantages, the following is a description of the invention illustrating the possibilities of its implementation, without limiting them, and accompanied by the accompanying drawings, where

figure 1 shows the General scheme proposed in the invention of a laser gyroscope,

figure 2 shows the principle of operation of the mutual rotator of the plane of polarization,

figure 3 shows the principle of operation of a nonreciprocal rotator of the plane of polarization,

on figa shows the principle of operation of the birefringent moderating plate for polarization separation,

on figb shows a similar diagram of such a retarding plate in the generalized Jones formalism,

figure 5 shows the action of the first, second and third optical units in the direction of direct propagation of radiation,

figure 6 shows the action of the first, second and third optical units in the direction of direct propagation of radiation in a modified embodiment of the invention,

7 shows the action of the fourth optical unit for the first and second modes of radiation propagation.

Proposed in the invention of the device must perform two specific functions:

- coordinate counter modes in intensity,

- eliminate the dead zone,

- do not introduce a systematic measurement error.

To perform the above functions, the devices generate four optical modes linearly polarized at different frequencies inside the resonator. The first and second modes propagate inside the resonator in the first direction, and the second radiation propagation mode acquires a linear polarization perpendicular to the polarization of the first mode, outside the fourth optical block, and circular polarization in the fourth optical block. The third and fourth modes propagate in the opposite direction, and the third and fourth modes of radiation propagation acquire linear polarization parallel to the polarization of the first and second modes, respectively, outside the fourth optical block, and circular polarization in the fourth optical block.

In accordance with the invention, these four modes are generated and controlled by the laser gyroscope shown in FIG. 1, where the optical element is a reciprocal rotator of the plane of polarization. This laser gyro has the following main components:

- ring optical resonator 1, containing at least one partially reflecting mirror 11 for processing counterpropagating modes of radiation propagation outside the resonator,

- solid-state active (reinforcing) medium 2,

- matching device 3, which controls the rotator (s) 5, 6 of the plane of polarization (control channels are shown in the diagram with dash-dot arrows),

- measuring device 6,

- an optical system including

i) a first optical unit consisting of a first nonreciprocal rotator 5 of the polarization plane and a reciprocal rotator 4 of the polarization plane,

ii) a second optical unit, consisting of a first spatial filtering device 7 and a first polarization separation optical element 8,

iii) a third optical unit, consisting of a second spatial filtering device 10 and a second polarization separation optical element 9, the second and third optical units being located symmetrically to each other on both sides of the first optical unit,

- the fourth optical unit, consisting of sequentially located the first quarter-wave plate 12, the second nonreciprocal rotator 13 of the plane of polarization and the second quarter-wave plate 14, the main axes of which are rotated 90 ° relative to the axes of the first quarter-wave plate.

The optical system includes a mutual rotator 4 of the plane of polarization and a nonreciprocal rotator 5 of the plane of polarization. The rotation of the plane of polarization of the wave (optical rotation) is said to be nonreciprocal, if the effects of rotation of the plane of polarization are summed up in the optical component with this characteristic after reflection of the wave (transmission and return). Such an optical component is called a nonreciprocal polarization plane rotator. For example, a material with the Faraday effect is a material in which, when exposed to a magnetic field, the plane of polarization of the rays passing through it rotates. This effect is not mutual. Consequently, the plane of polarization of the same beam passing in the opposite direction will rotate in the same direction. This principle is illustrated in figure 3. The direction (plane) of polarization of the linearly polarized beam 101 when this beam passes through the component 5 on the Faraday effect in the forward direction (the upper diagram in figure 3) is rotated by an angle β. If the same beam 103 is again passed through the component based on the Faraday effect, whose polarization direction (plane) was previously rotated through angle β and which propagates in the opposite direction, its polarization direction (plane) will again be rotated through angle β when passing through the component, while the total angle of rotation after reflection will be 2β (lower diagram in figure 3).

In a traditional reciprocal rotator 4, when the radiation propagates in the forward direction, the polarization direction is rotated by an angle + α, and when propagated in the opposite direction, the polarization direction is rotated by an angle -α, as a result of which the polarization direction returns to the original one, as illustrated in the diagrams shown in figure 2.

The optical system also has two optical elements of polarization separation. There are many geometric configurations that provide separation of polarized rays. As an example, FIG. 4a shows a birefringent retarding (phase) plate 8, which provides a linear separation of polarized beams. The retardation plate has two flat parallel sides and is cut from a uniaxial birefringent crystal, characterized by the refractive index of an ordinary wave and the refractive index of an unusual wave.

The change in the refractive index of an ordinary wave in the retardation plate is spherical, and the change in the refractive index of an extraordinary wave is ellipsoidal, as shown by the dashed line in Fig. 4a. Depending on the preferred direction (optical axis) shown in FIG. 4a by the double oblique arrow, the refractive indices of the ordinary wave and the extraordinary wave are equal. The retardation plate is cut along a plane passing at an angle of 45 ° to this direction. The drawing shows that when one light beam or a beam with linear polarization 102 falls normal to the input side of the birefringent retardation plate, it does not change direction when passing through the retardation plate. When, however, another light beam or beam 101 linearly polarized perpendicular to beam 102 is incident normally on the input side of the birefringent moderating plate, then when it passes through the moderating plate it is shifted in space. Thus, at the exit of the birefringent moderator plate, both beams 101 and 102 are parallel to each other and spaced apart by a distance d, as shown in FIG. 4a, the distance d depending on the optical characteristics and thickness of the moderator plate.

Figure 5 illustrates the operation of the optical system. The diagram shows the passage through the first optical block of the first radiation propagation mode 101 and the second radiation propagation mode 102 having linear polarization. Before the first spatial filtering device 7, the linear polarization vector of the first mode 101 lies in the sheet plane, and the linear polarization vector of the second mode 102 is perpendicular to the sheet plane. The indicated polarization directions are shown by straight arrows. It is obvious that during spatial filtering, such directions of polarization are preserved.

The first radiation propagation mode 101 with intensity I ₁ passes through the first optical element 8 of polarization separation and, as shown, at the exit from it passes parallel to its direction of incidence with an offset of a distance d. Then it passes through the mutual rotator 4 of the plane of polarization and then the nonreciprocal rotator 5 of the plane of polarization. Accordingly, when a beam passes through the first of the rotators, the direction of polarization of the beam rotates through an angle α, and after passing through a second rotator, through an angle α + β. At the output of the first rotator of the plane of polarization, the linear polarization of the first mode can be decomposed into two orthogonal components, the first of which is parallel to the original direction and has an intensity equal to the initial intensity I ₁ multiplied by the coefficient cos ² (α + β), and the second is perpendicular to the original direction and has an intensity equal to the initial intensity I ₁ times the coefficient sin ² (α + β). The first component passes through the second optical element 9 of polarization separation and is shifted by a distance of -d, and this second optical element (polarization separation) is located symmetrically to the first, after which the component passes through the second spatial filtering device 10 without attenuation, and the second filtering device is located on that same axis as the first filtering device. The second component passes through the second optical element 9 of polarization separation without bias (the dashed arrow in FIG. 5) and, therefore, cannot pass through the second filtering device.

At the end of the stroke, the attenuation coefficient of the first radiation propagation mode 101 is cos ² (α + β). Similarly, it is shown that the attenuation of the second radiation propagation mode 102 has the same coefficient. The third and fourth modes propagating in the opposite direction also have the same attenuation coefficient. It is easy to prove that this second coefficient is cos ² (α-β). It should be noted that the rays trapped in the radiation separation element can ultimately be directed to the photodetectors of the matching system to obtain data on the intensity of the rays.

It should also be noted that in a device of this type between two types of polarization, a mutual phase difference often occurs. Such a phase difference is advantageous because it corresponds to a bias capable of eliminating frequency capture (synchronism), but its value is not necessarily high enough. If necessary, using the birefringent element placed in the resonator, an additional phase difference is created.

Thus, the radiation modes have different attenuation depending on the direction of propagation, and the attenuation directly depends on the significance of the effects that influenced the polarization of both modes. Thus, the intensity of the counter modes can be controlled by adjusting at least one of the two values of α or β due to the effects or influences experienced by the polarization of these modes when passing through a matching device. Thus, the radiation intensities of different modes are coordinated by adjusting it to a certain constant value.

In this configuration, the attenuation of the first and second modes of radiation propagation, on the one hand, and the third and fourth modes of radiation propagation, on the other hand, is the same. Different attenuation values for modes propagating in one direction can be obtained using two independent loops with positive feedback, each of which affects its own polarization. This principle is illustrated in Fig.6. Between the second and third optical blocks, each of which consists of a spatial filtering device and an optical element of polarization separation, two optical blocks are placed, each of which consists of a non-reciprocal 5, 51 and mutual 4, 41 rotators of the plane of polarization; these two blocks are independently controlled by a matching device, not shown in FIG. Of course, the distance d between two polarized beams must be sufficient to accommodate different rotators of the plane of polarization. In this configuration, a solid-state active medium 2 may be located in the path of the divided beams, as shown in FIG. 6. Then the optical pumping occurs at two different points, and the diaphragm 10, which is a spatial filtering device, provides spatial superposition of the rays outside the beam separation device. An additional advantage of this embodiment of the invention is that all four modes are completely decoupled in terms of gain, thereby eliminating mode competition.

7 shows the action of the fourth optical unit. When the linearly polarized optical mode 101 (the right arrow in Fig. 7) passes through the first quarter-wave plate 12, then if the main axis of this slowing plate, indicated by a double arrow, is rotated by an angle of 45 ° relative to the direction of polarization, the output has a right circular polarization ( Fig. 7 is a solid semicircular arrow). When such a wave with circular polarization passes through the second optical nonreciprocal rotator 13 of the plane of polarization, it experiences a nonreciprocal phase shift, obtaining the phase difference γ. Then, the second quarter-wave plate 14, the main axis of which is perpendicular to the main axis of the first quarter-wave plate 12, again converts it into a wave with linear polarization. Thus, a non-reciprocal phase shift (non-reciprocal phase difference) is introduced into the mode passing through such a fourth optical unit, while maintaining the linear polarization of the wave. Naturally, if the wave is polarized linearly and perpendicular to the direction 101, it is converted into a wave with left circular polarization and receives a nonreciprocal phase difference γ.

Thus, using the above-described devices, it is possible to generate four modes inside the cavity in two in two opposite directions, to carry out their controlled attenuation to maintain their intensity at the same level, and also to introduce a mutual and nonreciprocal phase shift into such modes. To determine the eigen (normal) modes and their frequencies, the Jones matrix formalism is used. In the general case, this method consists in representing the influence of one component or another on the propagation mode of optical radiation by means of a 2 × 2 matrix assigned to a plane perpendicular to the propagation direction of the optical modes. In this case, a generalized Jones formalism is used, adapted to the case where there are two possible paths of ray propagation in the resonator, as was shown earlier. We call these paths “upper” and “lower”. In this case, the characteristic matrices are 4 × 4 matrices. In an orthonormal coordinate system (x, y), whose axes lie in a plane perpendicular to the direction of propagation of optical rays, the electric field of the optical mode is described by a vector with four components (T _x , T _y , B _x , B _y ), where the components (T _x , T _y ) represent the Jones vector of the electric field along the upper path, and the components (B _x , B _y ) represent the Jones vector of the electric field along the lower path, as shown in Fig. 4b, where the optical paths are shown passing through the uniaxial birefringent moderator plate, cut at an angle of 45 ° to its optical axis 8.

To obtain the resulting effect of all intracavity components, it is only necessary to determine the natural states of the product of various matrices representing these components. Since such a product is not necessarily commutative, the matrix may vary depending on the direction of propagation of the beam.

In this formalism, the first optical element of polarization separation, which consists of a birefringent crystal cut at an angle of 45 ° relative to its optical axis, is considered, when a beam passes through it in the proper direction, as a component with two inputs and two outputs, the "upper" and " bottom "which:

- sends the components B _x and T _x , which themselves propagate parallel to the axis of an ordinary ray by themselves, and

- “picks up” the components B _y and T _y , which propagate parallel to the axis of the extraordinary ray, sending them along T _y and 0, respectively. The component T _{y is} either stopped by the sides of the crystal, or does not coincide with the axes of propagation of rays in the resonator and is not capable of oscillations.

When the beam passes in the opposite direction, the crystal naturally “lowers” B _y and T _y , while B _x and T _x remain unchanged.

Taking into account the total birefringence of the cavity between the two polarization states, a phase difference ϕ / 2 arises. Therefore, in the direction of propagation of the radiation in which the optical rays rise, the Jones matrix for the first or second optical element of polarization separation is determined by the expression:

When a beam travels in the opposite direction, the first (or second) optical element of polarization separation understands optical rays. Therefore, the matrix has the form:

The matrix of spatial filtering devices has the following form:

An element that does not create a transverse effect and for which the 2 × 2 Jones matrix is denoted by m in the 4 × 4 matrix representation has the form:

Accordingly, the matrix of the remaining elements of the device can be written as follows.

For a mutual rotator of the plane of polarization, intersected by rays in the direction of rotation, called the straight line, the matrix R ₊ (α) has the form:

For a mutual rotator of the plane of polarization, intersected by rays in the direction of rotation, called the inverse, the matrix R _- (α) has the form:

The nonreciprocal rotator matrix does not depend on the direction of propagation and has the form:

The matrix of a quarter-wave plate rotated by 45 ° has the form:

The matrix of a quarter-wave plate rotated 135 ° has the form:

The matrices J ₊ and J _- , representing all the optical devices in the cavity for modes propagating in the forward and reverse directions, can be obtained by simple multiplication:

and

Knowledge of the J ₊ and J _- matrices helps to determine the natural states of optical modes that can propagate in the cavity. In each direction of propagation, there are two different natural states along the x and y axes, i.e. Only four of the following natural conditions:

(+, x): natural state for horizontal linear polarization of radiation propagating in the first direction,

(+, y): the natural state of the vertical linear polarization of the radiation propagating in the first direction,

(-, x): natural state of the horizontal linear polarization of radiation propagating in the opposite, i.e. opposite direction

(-, y): the natural state of the vertical linear polarization of radiation propagating in the opposite, i.e. opposite direction.

The natural state modulus (+, x) and (+, y) is cos (α + β), and the natural state modulus (-, x) and (-, y) is cos (α-β). Since the modulus varies with the direction of propagation by adjusting one of the two coefficients α or β, it is possible to match counter modes at a certain constant difference in intensity.

If the laser gyro does not rotate, the frequency ν of the optical mode in a ring laser resonator of length L is usually associated with the phase shift (phase difference) φ experienced by this mode after each round-trip of the resonator, by the following relation:

where n is an integer.

Thus, for a given n, the frequencies of various normal (eigen) are determined by the following expressions:

For fashion (+, x)

For fashion (+, y)

For fashion (-, x)

For fashion (-, y)

If the resonator rotates, then due to the Sagnac effect, the eigenfrequencies shift by a frequency of ± Ω / 2, the sign of which depends on the direction of propagation of the modes. In this case, the mode frequencies are determined by the following expressions:

For fashion (+, x)

For fashion (+, y)

For fashion (-, x)

For fashion (-, y)

Strictly speaking, if the frequencies of the optical modes must be determined with high accuracy, then the inconstancy of the cavity length due to birefringence and the Sagnac effect should be taken into account. It can be shown that these effects are negligible and do not affect the measurement accuracy.

In order to avoid interaction (coupling) of the modes and the appearance of a dead zone, it is necessary to ensure sufficient frequency diversity. Therefore, both terms (c / 2πL) γ and (c / 2πL) (φ-2γ) must exceed the specified minimum value determined by the required operating range of the laser gyroscope. To ensure that this condition is met, you can simply set the corresponding optical and geometric parameters of the reciprocal and nonreciprocal rotators of the plane of polarization.

The oscillation of the rays (+, x) and (-, x), on the one hand, and (+, y) and (-, y), on the other hand, creates two beat frequencies ν ₁ and ν ₂ :

The difference of these two frequencies Δν is equal to:

Δν = ν ₁ -ν ₂ = 2Ω

Thus, by measuring Δν, we obtain the beat frequency Ω to determine the angular velocity of rotation. This value does not depend on the values of the displacement of the resonator and any vibrations in it.

Various operations to determine the frequency difference Δν are performed by a measuring device, which includes:

- optical devices that cause interference, on the one hand, the first (+, x) and third (-, x) modes of radiation propagation, and on the other hand, the second (+, y) and fourth (-, y) modes of radiation propagation, moreover, it is possible to interfere with the mode (+, x) with the mode (-, y) on the one hand and the mode (+, y) with the mode (-, x) on the other,

- optoelectronic devices for determining, on the one hand, the first optical frequency difference ν ₁ between the first and third radiation propagation modes, and on the other hand, the second frequency difference ν ₂ between the second and fourth radiation propagation modes,

- electronic devices for obtaining a frequency difference Δν between the first frequency difference ν ₁ and the second frequency difference ν ₂ .

It may be appropriate to include the Fabry-Perot optical standard in the resonator. Naturally, it should not be excessively accurate in order to avoid too strong cohesion of the frequencies of various modes. It is advisable that the sides of the reference be inclined relative to the direction of propagation of the beam in order to avoid the spread of glassy reflections.

Of course, from several laser gyroscopes proposed in the invention, it is possible to assemble a system for measuring angular velocities or relative angular positions along three different axes, containing, for example, three laser gyroscopes mounted on a common mechanical structure.

Claims (8)

1. A laser gyroscope for measuring angular velocity or relative angular position relative to a given axis of rotation, comprising at least:
ring optical resonator (1),
solid state active medium (2),
matching device (3), comprising at least a first optical unit, consisting of a first nonreciprocal rotator (5) of the polarization plane and an optical element, which is a mutual rotator (4) of the polarization plane or birefringent element with the ability to control at least one of the effects or birefringence, and
measuring device (6),
characterized in that the said resonator (1) also contains
a second optical unit, consisting of a first spatial filtering device (7) and a first polarization separation optical element (8),
a third optical unit, consisting of a second spatial filtering device (10) and a second polarization separation optical element (9), the second and third optical units being located symmetrically to each other on both sides of the first optical unit,
the fourth optical unit, consisting of sequentially located the first quarter-wave plate (12), the second nonreciprocal rotator (13) of the plane of polarization and the second quarter-wave plate (14), the main axes of which are perpendicular to the main axes of the first quarter-wave plate,
as a result, the first linearly polarized mode and the second mode, linearly polarized perpendicular to the first, and the third mode, linearly polarized parallel to the first, and the fourth mode, linearly polarized parallel to the second, and the main axes of the first quarter-wave plate, can propagate in the resonator in the first direction and the second quarter-wave plate are rotated relative to the directions of linear polarization of the four modes of radiation propagation through an angle of 45 °, and the optical frequencies seh four different modes. 2. The laser gyroscope according to claim 1, characterized in that the resonator has a birefringent moderating plate, which helps to create or increase the frequency difference between the orthogonal polarization states. 3. Laser gyroscope according to claim 1, characterized in that the measuring device (6) contains
optical devices causing interference on the one hand of the first and third modes of radiation propagation, and on the other hand, the second and fourth modes of radiation propagation,
optoelectronic devices for determining, on the one hand, the first optical frequency difference between the first and third radiation propagation modes, and on the other hand, the second frequency difference between the second and fourth radiation propagation modes,
electronic devices for obtaining a frequency difference between the first frequency difference and the second frequency difference. 4. The laser gyroscope according to claim 3, characterized in that the first frequency difference and the second frequency difference exceed about 100 kHz. 5. The laser gyroscope according to claim 1, characterized in that the first (8) and second (9) optical elements of the polarization separation are uniaxial birefringent retardation plates with flat parallel sides, in which the optical axis is rotated about 45 ° relative to the plane of the sides. 6. The laser gyroscope according to claim 1, characterized in that the matching device (3) includes at least a fifth optical unit, consisting of a third nonreciprocal rotator (51) of the polarization plane and a second optical element, which is a reciprocal rotator (41) of the polarization plane or birefringent element with the ability to control at least one of the effects or birefringence independently of the first optical block, the first and third modes of radiation propagation passing through the first nonreciprocal a polarization plane rotator and a first optical element, and a third and fourth radiation propagation mode through a third nonreciprocal polarization plane rotator and a second optical element. 7. Laser gyroscope according to claim 1, characterized in that the resonator (1) contains a Fabry-Perot optical standard. 8. A system for measuring angular velocities or relative angular positions along three different axes, characterized in that it contains three laser gyroscopes in one of the preceding paragraphs, which are oriented in different directions and mounted on a common mechanical structure.

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