A polarization-entangled photon voltage sensor

Abstract

The present invention relates to a polarization-entangled photon voltage sensor, comprising a type II self-parametric down-conversion polarization-entangled photon source, a high-potential sensing optical path, and a ground-potential measurement optical path. The sensing optical path comprises a BZN ceramic, an electro-optical crystal, a quarter-wave plate, and a white screen. The measurement optical path comprises a collimating beam expander and a radial polarization grating. The type II self-parametric down-conversion polarization-entangled photon source outputs two polarization-entangled photons. One photon enters the high-potential sensing optical path and sequentially passes through the BZN ceramic, the electro-optical crystal, and the quarter-wave plate before annihilating on the white screen. The other photon enters the ground-potential measurement optical path, passes through the collimating beam expander to form spatial light, and then passes through a radial polarization grating for polarization analysis. The electro-optical phase delay is converted into a synchronous translation of a fixed light spot. By using an image sensor to position the light spot, direct linear measurement of the electro-optical phase delay can be achieved, thereby obtaining a voltage to be measured. The present invention overcomes the problems of optical power dependence, nonlinear measurement, and the inherent half-wave voltage of the crystal that limits the measurement range and sensitivity of Pockels effect optical voltage sensors.

Description

Technical Field

[0001] The present invention belongs to the field of high voltage measurement, and in particular relates to a polarization entangled photon voltage sensor. Background Art

[0002] Voltage transformers are one of the four key devices at the interface between the primary and secondary systems of a power grid. They are fundamental to power system protection, control, and metering, and their role is crucial. However, existing voltage measurement technologies suffer from several fundamental flaws and no longer meet the requirements of smart grid development. For example, electromagnetic voltage transformers face challenges such as high insulation costs, environmental pollution, and high maintenance requirements. Capacitive voltage transformers are subject to issues such as leakage of insulating oil and gas, and capacitance drift. Optical voltage sensors also suffer from nonlinear measurement, dependence on optical power, and temperature drift.

[0003] Currently, applications of quantum sensing technology often involve measuring electric fields in space. For example, microwave electric field measurements based on Rydberg atoms have the advantages of high sensitivity and resolution, and have been a research hotspot in recent years. Applying quantum sensing technology to high-voltage measurement in power systems is a novel approach. Summary of the Invention

[0004] In view of this, an object of the present invention is to provide a polarization entangled photon voltage sensor to solve the above problems.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A polarization-entangled photon voltage sensor comprises a type II self-parametric down-conversion polarization-entangled photon source, a high-potential sensing optical path, and a ground-potential measurement optical path; the sensing optical path comprises BZN ceramics, an electro-optical crystal, a quarter-wave plate, and a white screen; the measurement optical path comprises a collimating beam expander and a radial polarization grating; the type II self-parametric down-conversion polarization-entangled photon source outputs two polarization-entangled photons, one of which enters the high-potential sensing optical path, passes through the BZN ceramics, the electro-optical crystal, and the quarter-wave plate in sequence, and is annihilated on the white screen; the other photon enters the ground-potential measurement optical path, passes through the collimating beam expander to form spatial light, and then passes through the radial polarization grating for polarization analysis, converting the electro-optical phase delay into a synchronous translation of a fixed light spot. By positioning the light spot using an image sensor, direct linear measurement of the electro-optical phase delay can be achieved, thereby obtaining the voltage to be measured.

[0007] Furthermore, under the action of the electric field to be measured, the polarization plane of the photon rotates when passing through the electro-optical crystal, and the rotation angle is proportional to the voltage to be measured.

[0008] Furthermore, the rotation angle of the polarization plane of the photons in the measuring light path is the same as that of the photons in the sensing light path.

[0009] Furthermore, the use of an image sensor to locate the light spot can achieve direct linear measurement of the electro-optical phase delay, specifically:

[0010] The two-photon polarization entangled state generated by the type II self-parametric down-conversion polarization entangled photon source is:

[0011]

[0012] Where H and V represent horizontal polarization and vertical polarization respectively, and α represents the phase difference between horizontal polarization and vertical polarization;

[0013] Let one of the photons enter the sensing optical path and pass through the electro-optical crystal. Under the action of the electric field, the photon polarization entangled state acquires a new phase difference δ, that is:

[0014]

[0015] in is the phase delay produced by the electro-optical crystal. When the sensing photon passes through the λ / 4 wave plate, its entangled state changes to:

[0016] δ=θ+α (3)

[0017] Where θ is the polarization rotation angle of the sensing photon after passing through the quarter-wave plate, which is related to satisfy:

[0018]

[0019] At this time, the two-photon polarization entangled state becomes:

[0020]

[0021] Another photon enters the measurement optical path. When it passes through the radial polarization grating, the polarization state of the photon is detected. That is, there is a 50% probability of it being in the |H> state and a 50% probability of it being in the |V> state, that is:

[0022]

[0023] When the measurement optical path detects the |V> state, the phase δ at this time can be directly measured by the radial polarization grating, that is:

[0024]

[0025] Combining formula (3) and formula (4), we can get

[0026] The Jones matrix of incident light passing through the radial polarization grating is expressed as:

[0027] G(x,y)=T[β(x,y)]G[κ(x,y)]T -1 [β(x,y)] (10)

[0028] Where T[β(x,y)] is the rotation matrix, β is the direction of the metal grid; G[κ(x,y)] is represented by a diagonal matrix:

[0029]

[0030] where t TM , t TE are the diffraction efficiencies of the transmitted components of the TM and TE waves, respectively; ξ is the phase difference between the two light waves;

[0031] Each metal grid unit of the radial polarization grating is described as a linear polarizer with the transmission axis perpendicular to β, and equation (12) is rewritten as:

[0032]

[0033] Assuming that the angle between the direction of the incident light polarization plane and the x-axis of the system is δ and the amplitude is 1, the Jones matrix of the incident light vector is:

[0034]

[0035] After the incident light passes through the radial polarization grating, the Jones matrix of the outgoing light vector is:

[0036]

[0037] The expression of the outgoing light intensity is:

[0038]

[0039] Order I out Taking the minimum value, we get:

[0040] β=δ (16)

[0041] Therefore, when equation (16) is satisfied, the light intensity transmitted from the corresponding grating unit is the minimum value, and its location is the center of the dark fringe. Assuming that the length of the grating is l, the range of the dark fringe translation is 0 to l. Assuming that when δ = 0°, the center of the dark fringe is located on the 0° grating unit, then the relationship between the spot displacement Δx and δ satisfies:

[0042]

[0043] According to the above formula, we can get:

[0044]

[0045] Based on Matlab, the outgoing light intensity distribution after the radial polarization grating is obtained. The light spot moves synchronously with the change of δ. By measuring the displacement of the light spot, the direct linear measurement of δ can be achieved. Combining equations (6) and (7), we can get

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention realizes linear measurement of electro-optical phase delay, and this mode is independent of the incident light intensity and the output light intensity; the size of the electro-optical phase delay is no longer limited by approximate linearity and is therefore independent of the half-wave voltage; therefore, in principle, it overcomes the problems of optical power dependence of Pockels effect optical voltage sensors, nonlinear measurement, and the limitations of the crystal's inherent half-wave voltage on measurement range and measurement sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic structural diagram of the present invention;

[0049] Figure 2 is a schematic structural diagram of a radial polarization grating in one embodiment of the present invention;

[0050] Figure 3 The invention is based on the outgoing light intensity distribution after the radial polarization grating is polarized.

[0051] Among them, 1-Type II self-parametric down-conversion polarization entangled photon source, 2-BZN ceramics, 3-electro-optical crystal, 4-quarter wave plate, 5-white screen, 6-collimating beam expander, 7-radial polarization grating, 8-outgoing light spot of radial polarization grating analyzer. DETAILED DESCRIPTION

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] Please refer to Figure 1 The present invention provides a polarization entangled photon voltage sensor, comprising a type II self-parametric down-conversion polarization entangled photon source, a high-potential sensing optical path and a ground-potential measuring optical path; the sensing optical path comprises BZN ceramics, an electro-optical crystal, a quarter-wave plate and a white screen; the measuring optical path comprises a collimating beam expander and a radial polarization grating; the type II self-parametric down-conversion polarization entangled photon source outputs two polarization entangled photons, one of which enters the high-potential sensing optical path, and passes through the BZN ceramics, the electro-optical crystal and the quarter-wave plate in sequence, and is annihilated on the white screen; the other photon enters the ground-potential measuring optical path, forms spatial light through the collimating beam expander, and then passes through the radial polarization grating for polarization analysis, converting the electro-optical phase delay into a synchronous translation of a fixed light spot. The light spot can be positioned by using an image sensor to achieve direct linear measurement of the electro-optical phase delay, thereby obtaining the voltage to be measured.

[0054] In this embodiment, under the action of the measured electric field, the polarization plane of the photon rotates when passing through the electro-optical crystal, and the rotation angle is proportional to the measured voltage. The rotation angle of the polarization plane of the photon in the measuring optical path is the same as that of the photon in the sensing optical path.

[0055] In this embodiment, direct linear measurement of electro-optical phase delay can be achieved by positioning the light spot using an image sensor, specifically:

[0056] The two-photon polarization entangled state generated by the type II self-parametric down-conversion polarization entangled photon source is:

[0057]

[0058] Where H and V represent horizontal polarization and vertical polarization respectively, and α represents the phase difference between horizontal polarization and vertical polarization.

[0059] Let one of the photons enter the sensing optical path and pass through the electro-optical crystal. Under the action of the electric field, the photon polarization entangled state acquires a new phase difference δ, that is:

[0060]

[0061] in is the phase delay produced by the electro-optical crystal. When the sensing photon passes through the λ / 4 wave plate, its entangled state changes to:

[0062] δ=θ+α(3)

[0063] Where θ is the polarization rotation angle of the sensing photon after passing through the quarter-wave plate, which is related to satisfy:

[0064]

[0065] At this time, the two-photon polarization entangled state becomes:

[0066]

[0067] Another photon enters the measurement optical path. When it passes through the radial polarization grating, the polarization state of the photon is detected. That is, there is a 50% probability of it being in the |H> state and a 50% probability of it being in the |V> state, that is:

[0068]

[0069] When the measurement optical path detects the |V> state, the phase δ at this time can be directly measured by the radial polarization grating, that is:

[0070]

[0071] Combining formula (3) and formula (4), we can get

[0072] The structure of the radial polarization grating is shown in the attached figure. Figure 2 As shown in the figure, the polarization analysis principle is as follows. The Jones matrix of the incident light passing through the radial polarization grating is expressed as:

[0073] G(x,y)=T[β(x,y)]G[κ(x,y)]T -1 [β(x,y)](10)

[0074] Where T[β(x,y)] is the rotation matrix, β is the direction of the metal grid (which changes regularly between -50° and 50°). G[κ(x,y)] can be represented by a diagonal matrix:

[0075]

[0076] where t TM , t TE are the diffraction efficiencies (i.e., transmittances) of the TM and TE wave transmission components, respectively; ξ is the phase difference between the two light waves. Since the grating has a very high extinction ratio (t TE < <t TM ), t TE Therefore, each metal grid unit of the radial polarization grating is described as a linear polarizer with the transmission axis perpendicular to β, and Equation (12) is rewritten as:

[0077]

[0078] Assuming that the angle between the direction of the incident light polarization plane and the x-axis of the system is δ and the amplitude is 1, the Jones matrix of the incident light vector is:

[0079]

[0080] After the incident light passes through the radial polarization grating, the Jones matrix of the outgoing light vector is:

[0081]

[0082] The expression of the outgoing light intensity is:

[0083] I out =E o * ut ·E out =t TM exp(2jξ)sin 2 (β-δ)(15)

[0084] Order I out Taking the minimum value, we get:

[0085] β=δ(16)

[0086] Therefore, when equation (16) is satisfied, the light intensity transmitted from the corresponding grating unit is the minimum value, and its position can be approximated as the center of the dark stripe. When δ changes, the dark stripe position linearly translates along the grating unit. The grating direction of the radial polarization grating is β = -50° ~ 50°, then the range of δ is 0° ~ 100°; assuming the length of the grating is l, the range of dark stripe translation is 0 ~ l. Assuming that when δ = 0°, the center of the dark stripe is on the 0° grating unit, then the relationship between the spot displacement Δx and δ satisfies:

[0087]

[0088] According to the above formula, we can get:

[0089]

[0090] It can be seen that the radial polarization grating can realize the linear measurement of the polarization plane angle δ. Based on Matlab, the output light intensity distribution after the radial polarization grating is analyzed is shown in the attached figure. Figure 3 As shown in the figure, the light spot moves synchronously with the change of δ, and the direct linear measurement of δ can be achieved by measuring the displacement of the light spot. Combining equations (6) and (7), we can get

[0091] In this embodiment, a temperature drift self-compensation method is used to address the temperature drift problem of the electro-optical crystal. The electric field intensity temperature coefficient of the voltage divider medium and the electro-optic effect temperature coefficient of the electro-optical crystal are used to offset each other, thereby eliminating the influence of temperature on the electro-optic effect of the crystal. In short, this method is based on the coordination of an insulating voltage divider medium with a certain dielectric constant and the optical transmission length of the electro-optical crystal. Applicable voltage divider media include BZN ceramics. Depending on the material composition, the dielectric constant temperature coefficient can be positive or negative, but all are within the applicable range. For example, the dielectric constant of the selected BZN ceramic is 95, and the dielectric constant temperature coefficient is -0.36×10 -4 The electro-optical crystal uses BGO crystal, which has a dielectric constant of 16.3 and a dielectric constant temperature coefficient of 1.84×10 -4 When the ratio of the light transmission length of BGO crystal to BZN ceramic is 1:14.6, the influence of temperature on the electro-optical effect of BGO crystal can be eliminated.

[0092] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A polarization entangled photon voltage sensor, characterized in that: It includes a type II self-parametric down-conversion polarization-entangled photon source, a high-potential sensing optical path, and a ground-potential measurement optical path; the sensing optical path includes BZN ceramics, an electro-optical crystal, a quarter-wave plate, and a white screen; the measurement optical path includes a collimating beam expander and a radial polarization grating; the type II self-parametric down-conversion polarization-entangled photon source outputs two polarization-entangled photons, one of which enters the high-potential sensing optical path, passes through the BZN ceramics, the electro-optical crystal, and the quarter-wave plate in sequence, and is annihilated on the white screen; the other photon enters the ground-potential measurement optical path, forms spatial light through the collimating beam expander, and then passes through the radial polarization grating for polarization analysis, converting the electro-optical phase delay into a synchronous translation of a fixed light spot. The light spot is positioned by an image sensor to achieve direct linear measurement of the electro-optical phase delay, thereby obtaining the voltage to be measured; Under the action of the electric field to be measured, the polarization plane of the photon rotates when passing through the electro-optical crystal, and the rotation angle is proportional to the voltage to be measured; The rotation angle of the polarization plane of the photons in the measuring light path is the same as that of the photons in the sensing light path.

2. The polarization entangled photon voltage sensor according to claim 1, characterized in that: The direct linear measurement of electro-optical phase delay can be achieved by positioning the light spot using an image sensor, specifically: The two-photon polarization entangled state generated by the type II self-parametric down-conversion polarization entangled photon source is: Where H and V represent horizontal polarization and vertical polarization respectively, and α represents the phase difference between horizontal polarization and vertical polarization; Let one of the photons enter the sensing optical path and pass through the electro-optical crystal; under the action of the electric field, the photon polarization entangled state acquires a new phase difference δ, that is: in is the phase delay produced by the electro-optical crystal; the sensing photon then passes through the λ / 4 wave plate, and its entangled state changes to: δ=θ+α (3) Where θ is the polarization rotation angle of the sensing photon after passing through the quarter-wave plate, which is related to satisfy: At this time, the two-photon polarization entangled state becomes: Another photon enters the measurement optical path. When it passes through the radial polarization grating, the polarization state of the photon is detected. That is, there is a 50% probability of it being in the |H> state and a 50% probability of it being in the |V> state, that is: When the measurement optical path detects the |V> state, the phase δ at this time can be directly measured by the radial polarization grating, that is: Combining formula (3) and formula (4), we can get The Jones matrix of incident light passing through the radial polarization grating is expressed as: G(x,y)=T[β(x,y)]G[κ(x,y)]T -1 [β(x,y)] (10) Where T[β(x,y)] is the rotation matrix, β is the direction of the metal grid; G[κ(x,y)] is represented by a diagonal matrix: where t TM , t TE are the diffraction efficiencies of the transmitted components of the TM and TE waves, respectively; ξ is the phase difference between the two light waves; Each metal grid unit of the radial polarization grating is described as a linear polarizer with the transmission axis perpendicular to β, and equation (12) is rewritten as: Assuming that the angle between the direction of the incident light polarization plane and the x-axis of the system is δ and the amplitude is 1, the Jones matrix of the incident light vector is: After the incident light passes through the radial polarization grating, the Jones matrix of the outgoing light vector is: The expression of the outgoing light intensity is: Order I out Taking the minimum value, we get: β=δ (16) Therefore, when equation (16) is satisfied, the light intensity transmitted from the corresponding grating unit is the minimum value, and its location is the center of the dark fringe. Assuming that the length of the grating is l, the range of the dark fringe translation is 0 to l. Assuming that when δ = 0°, the center of the dark fringe is located on the 0° grating unit, then the relationship between the spot displacement Δx and δ satisfies: According to the above formula, we can get: Based on Matlab, the outgoing light intensity distribution after the radial polarization grating is obtained. The light spot moves synchronously with the change of δ. By measuring the displacement of the light spot, the direct linear measurement of δ can be achieved. Combining equations (6) and (7), we can get

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