CN116819183A - DC electric field intensity measuring device and method based on electromagnetic induction transparent spectrum - Google Patents

Abstract

The invention belongs to the technical field of electric field measurement, and discloses a direct current electric field intensity measuring device based on electromagnetic induction transparent spectrum, which comprises: the system comprises a detection laser, a pump laser, a first acousto-optic modulator, a second acousto-optic modulator, a first atomic gas chamber, a second atomic gas chamber, a first detector, a second detector and a computing unit; the first atomic gas chamber is positioned at the position to be measured, and the second atomic gas chamber is positioned at the electric field shielding position. According to the invention, two beams of detection light are respectively subjected to up-shift and down-shift by utilizing two acousto-optic modulators (AOMs) so as to be red-detuned and blue-detuned relative to an atomic transition line, then the red-detuned and blue-detuned detection light is overlapped and opposite-shot with one beam of pumping light in a high-resistance glass atomic bubble, a double-peak EIT splitting spectrum of the Lidberg atom is formed through the EIT energy level of the step-type three-energy-level Lidberg atom, and the electric field intensity is measured by taking the frequency difference between two resonance transmission peaks of the double-peak EIT spectrum obtained under the condition of no electric field as a reference standard, so that a complex frequency locking process can be avoided.

Description

DC electric field intensity measuring device and method based on electromagnetic induction transparent spectrum

Technical Field

The invention belongs to the technical field of optical measurement, and particularly relates to a direct current electric field strength measurement method and device based on electromagnetic induction transparent spectrum.

Background

Traditional measurement methods of direct current electric field strength include induced charge electric field measurement and optical electric field measurement based on electro-optic effect. The charge induction type electric field instrument designed based on the induction charge type electric principle is difficult to apply to live measurement on site, and is difficult to accurately measure a strong electric field, so that the detailed description of the space distribution of the electric field cannot be realized; an electric field tester based on an electro-optic effect reflects parameters of a tested electric field through the effect that laser generates double refraction when passing through a crystal placed in the electric field. Since the electro-optical crystal itself has temperature dependency, the electric field sensor based on the electro-optical effect generally has a temperature drift problem, and in addition, when a static or very low frequency electric field is induced by the electro-optical crystal, charge drift and change of electric field distribution will occur in the crystal, and an unstable condition of an output sensing signal will occur. Particularly, as the power grid is transformed into intellectualization and digitalization, the technical bottlenecks of the traditional power measurement equipment in measurement precision, reliability and adaptability are needed to be solved.

In recent years, the accurate measurement of an external electric field by using the Redberg atoms is attracting attention, and the theoretical basis for measuring the direct current field strength is the Stark effect of the Redberg atoms under the direct current field. The direct current electric field measurement based on the Redberg atoms does not depend on the ambient temperature, directly traces back to basic physical constants and atomic characteristic parameters, can be applied to field live measurement, and provides a new technology for realizing all-optical, high-sensitivity and calibration-free electric field measurement.

Electromagnetic Induction Transparency (EIT) spectroscopy is a common technical means for accurately measuring atomic energy levels. Electromagnetic induction transparency is a quantum interference effect, and an ultra-narrow transparent peak appears in the middle of the absorption peak of the detection light when the coupling light exists. The position of the transparent peak depends on the atomic energy level, and the frequency shift of the Redberg atomic energy level under the electric field when no electric field exists can be reversely deduced through the splitting of the EIT spectrum transmission peak under the direct-current electric field. 2007, british Du Lunda, c.s. adams study group [ Phys. Rev. Lett.,98,113003]The nondestructive detection of the Redberg atoms is realized in a room-temperature glass air chamber of the hot atoms by using EIT quantum coherence spectrum for the first time, and the electrons and ions generated by the atoms on the inner wall of the coupling photolysis adsorption glass bulb can shield the external direct current electric field of the glass bulb, so that the EIT spectrum of the Redberg atoms is influenced to measure the static direct current electric field. To overcome this shielding effect, university of amsterdam, netherlands, r.j.c. spreeuw research group [ phy.rev.a,87,042522 (2013)]And university of Eberhatscher, tuberbingham, germany J.Fort-gh research group [ New J.Phys.,17,053005 (2015))]Placing electrodes for generating DC electric field into glass bubbles, respectively using ⁸⁷ Rb atoms n=21 to 24 and n=35&The 70 Redberg state measures a DC electric field of 0-130V/cm and 0-500V/cm. The mode of placing the electrodes in the glass bubble can detect the field intensity of the direct current electric field, but is not suitable for external electric field measurement, and limits the application range of the electrode. In addition, the R.J.C.Spreeuw research group uses a radio frequency source loaded on the glass bubble inner polar plate as a frequency standard, so that the application of EIT spectrum in measuring a direct current electric field is more limited; the fort-gh research group uses an optical frequency comb to lock the frequencies of probe light and pump light, and uses the pump light to pass through an acousto-optic modulator (AOM) twice to realize frequency scanning. This approach requires frequency locking of the pump light, and even if such expensive optical comb systems are not used, frequency stabilization is performed using, for example, frequency modulation spectra, modulation transfer spectra, peak-Drever-Hall spectra, etc., additional complex experimental setup and frequency locking techniques are required.

Disclosure of Invention

The invention overcomes the defects existing in the prior art, and solves the technical problems that: the direct current electric field intensity measuring method and device based on the electromagnetic induction transparent spectrum are simple in structure and convenient to operate.

In order to solve the technical problems, the invention adopts the following technical scheme: a direct current electric field strength measurement device based on electromagnetic induction transparent spectrum, comprising: the system comprises a detection laser, a pump laser, a first acousto-optic modulator, a second acousto-optic modulator, a first atomic gas chamber, a second atomic gas chamber, a first detector, a second detector and a computing unit; the first atomic air chamber is positioned at the position to be detected, and the second atomic air chamber is positioned at the electric field shielding position;

the frequency of the detection laser is locked, the output detection light is divided into two beams, and after the two beams of detection light are subjected to frequency shift through the first acoustic optical modulator and the second acoustic optical modulator respectively, the two beams of detection light are respectively subjected to red detuning and blue detuning relative to the resonance frequency from an atomic ground state to an excited state; the method comprises the steps that after passing through a beam splitting assembly, the red-blue detuned detection light is split into two beams of red-blue detuned detection light which comprise red-blue detuned detection light and blue detuned detection light, wherein one beam of red-blue detuned detection light is incident into a first atomic gas chamber in a superposition manner, and the other beam of red-blue detuned detection light is incident into a second atomic gas chamber in a superposition manner; the red and blue detuned detection light passing through the first atomic gas chamber and the second atomic gas chamber is detected by the first detector and the second detector respectively;

the frequency of the pump laser scans at the transition of the energy levels of an atomic excitation state and a Redberg state, the output pump light is divided into two beams, and the two beams of pump light are respectively reversely overlapped with one beam of red and blue detuned detection light and are incident into the first atomic gas chamber and the second atomic gas chamber;

the computing unit is used for computing the energy level offset of the Redberg atoms in the electric field according to the scanning time interval of two peaks in the bimodal EIT spectrum obtained by the second detector and the scanning time interval in the bimodal EIT split spectrum obtained by the first detector, combining the frequency shift frequencies of the first acousto-optic modulator and the second acousto-optic modulator, and computing the electric field intensity according to the energy level offset.

The calculation formula of the electric field intensity is as follows:

wherein E represents the electric field intensity, alpha represents the polarizability, deltaW represents the energy level shift of the Redberg atoms in the electric field, and the calculation formula is as follows:

ΔW＝Δf*Δt/Δt ₀ ；

wherein Δf represents the frequency shift difference between the first acoustic optical modulator and the second acoustic optical modulator, Δt represents the scanning time interval corresponding to the energy level shift of the reed-burg atoms in the electric field, respectively ₀ Representing the scan time interval of two peaks in the bimodal EIT spectrum obtained by the second detector.

The first atomic gas chamber is a high-resistance glass atomic gas chamber.

The beam splitting assembly comprises a first beam splitting prism, a second beam splitting prism and a third beam splitting prism, wherein the first beam splitting prism and the second beam splitting prism are respectively positioned on a red-detuned and blue-detuned detection light path, the first beam splitting prism is used for splitting red-detuned detection light into two beams, the second beam splitting prism is used for splitting blue-detuned detection light into two beams, one beam of red-detuned detection light and blue-detuned detection light is transmitted by the first beam splitting prism to form one beam of red-blue-detuned detection light, and the other beam of red-detuned detection light and blue-detuned detection light is transmitted by the third beam splitting prism to form the other beam of red-blue-detuned detection light.

The direct current electric field strength measuring device based on the electromagnetic induction transparent spectrum further comprises a first radio frequency source and a second radio frequency source, wherein the first radio frequency source and the second radio frequency source are respectively used for driving the first acousto-optic modulator and the second acousto-optic modulator;

the atomic gas chamber detector further comprises a first light guide lens and a second light guide lens, wherein the first light guide lens is arranged between the first atomic gas chamber and the first detector, the second light guide lens is arranged between the second atomic gas chamber and the second detector, and the first light guide lens and the second light guide lens are respectively used for guiding red and blue detuned detection light passing through the first atomic gas chamber and the second atomic gas chamber to the first detector and the second detector.

The first and second light guides are dichroic mirrors.

The atoms in the first atom air chamber and the second atom air chamber are ⁸⁵ Rb atoms, the wavelength of the detection laser is 780nm, which is locked to by saturated absorption spectrum ⁸⁵ Rb atom|5S _1/2 ,F＝3>→|5P _3/2 ,F`＝3>And |5P <sub>3/2</sub> ,F`＝4>The pump laser has a wavelength of 515nm and a frequency of ⁸⁵ Rb atom|5P _3/2 ,F`＝4>→|10D _3/2 >Scanning near the transition;

or: the atoms in the first atomic gas chamber and the second atomic gas chamber are Cs atoms, the wavelength of the detection laser is 852nm, and the detection laser is locked to Cs atoms 6S through saturated absorption spectrum _1/2 ,F＝4>And |6P _3/2 ,F'＝5>The transition energy level of the pump laser is 510nm, and the frequency of the pump laser is Cs atom|5P _3/2 ,，F`＝4>→|10D _3/2 >Scanning near the transition.

The frequency of the detection laser is locked through saturated absorption spectrum, polarization spectrum frequency locking, DAVLL frequency locking, frequency modulation spectrum or modulation transfer spectrum.

In addition, the invention also provides a direct current electric field intensity measuring method based on the electromagnetic induction transparent spectrum, which is realized by adopting the direct current electric field intensity measuring device based on the electromagnetic induction transparent spectrum, and comprises the following steps:

s1, locking the frequency of a detection laser, simultaneously scanning the frequency of a pumping laser, and simultaneously determining the frequency shift frequency of a first acousto-optic modulator and a second acousto-optic modulator;

s2, acquiring a bimodal EIT splitting spectrum of a first channel and a bimodal EIT spectrum of a second channel through a first detector and a second detector;

s3, calculating the electric field intensity according to the scanning time interval corresponding to the peak value in the bimodal EIT splitting spectrum of the first channel and the bimodal EIT spectrum of the second channel and the frequency shift frequency of the first acoustic optical modulator and the second acoustic optical modulator.

The specific steps of the step S3 are as follows:

acquiring a scanning time interval delta t corresponding to a red detuned EIT spectrum peak and a blue detuned EIT spectrum peak in a bimodal EIT spectrum of a second channel ₀ ；

Acquiring a scanning time interval delta t of one spectrum peak value in a bimodal EIT split spectrum of a first channel relative to a corresponding peak value in the bimodal EIT spectrum;

the electric field intensity is calculated, and the calculation formula is as follows:

where E represents the electric field intensity, Δf represents the frequency shift difference between the first acoustic optical modulator and the second acoustic optical modulator, and α represents the polarization ratio.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a direct current electric field intensity measuring device and method based on electromagnetic induction transparent spectrum, which utilizes two acousto-optic modulators (AOMs) to respectively carry out up-shift and down-shift on two beams of detection light to enable the two beams of detection light to be red-detuned and blue-detuned relative to an atomic transition line, and then the red-detuned and blue-detuned detection light is overlapped and opposite to one beam of pumping light in a high-resistance glass atomic bubble to form a double peak EIT splitting spectrum of a Redburg atom. The other beam of red and blue detuned detection light and pumping light are oppositely incident into the reference atomic air chamber in the no-electric-field environment, the characteristic that the interval between two resonance transmission peaks is strictly equal to the frequency difference between two AOM radio frequencies is utilized, the bimodal EIT spectrum of the reference atomic air chamber is used as a frequency reference, and the field intensity of a direct current electric field where the high-resistance glass atomic bubble is positioned is calculated according to the theoretical formula of the atomic Redberg energy level splitting under the electric field.

Drawings

Fig. 1 is a schematic diagram of connection between an optical path (shown by a solid line) and a circuit (shown by a broken line) of a dc electric field strength measurement device based on electromagnetic induction transparent spectrum according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram of a bimodal EIT spectrum and a bimodal EIT split spectrum obtained in an embodiment of the present invention;

in the figure: 1 is a detection laser, 2 is a pump laser, 3 is a first acousto-optic modulator, 4 is a second acousto-optic modulator, 5 is a first atomic gas chamber, 6 is a second atomic gas chamber, 7 is a first detector, 8 is a second detector, 9 is a calculation unit, 10 is a first radio frequency source, 11 is a second radio frequency source, 13 is a first light guide mirror, 14 is a second light guide mirror, 15 is a first beam splitter prism, 16 is a second beam splitter prism, 17 is a third beam splitter prism, 18 is a wavelength meter, 19 is a detection beam splitter, and 20 is a pump beam splitter; 21 is an optical isolator, 22 is a frequency-locking beam splitter, 23 is a wavelength beam splitter, and 24 is a frequency-locking device.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

As shown in fig. 1, an embodiment of the present invention provides a dc electric field strength measurement device based on electromagnetic induction transparent spectrum, including: the device comprises a detection laser 1, a pump laser 2, a first acousto-optic modulator 3, a second acousto-optic modulator 4, a first atomic gas chamber 5, a second atomic gas chamber 6, a first detector 7, a second detector 8 and a calculation unit 9; the first atomic gas chamber 5 is positioned at the position to be detected, and the second atomic gas chamber 6 is positioned at the electric field shielding position; the frequency of the detection laser 1 is locked, the output detection light is divided into two beams by the detection beam splitter 19, and after the two beams of detection light are respectively subjected to frequency shift by the first acoustic optical modulator 3 and the second acoustic optical modulator 4, the two beams of detection light are respectively subjected to red detuning and blue detuning relative to the resonance frequency from an atomic ground state to an excited state; the red-blue detuned detection light and the blue-detuned detection light are divided into two beams by the beam splitting assembly 12, wherein the two beams comprise the red-blue detuned detection light and the blue-detuned detection light, one beam of red-blue detuned detection light is incident to the first atomic gas chamber 5 in a superposition manner, and the other beam of red-blue detuned detection light is incident to the second atomic gas chamber 6 in a superposition manner; the red and blue detuned detection light passing through the first atomic gas chamber 5 and the second atomic gas chamber 6 is detected by the first detector 7 and the second detector 8 respectively; the frequency of the pump laser 2 scans at the transition of the energy levels of the atomic excitation state and the Redberg state, the output pump light is divided into two beams by the pump beam splitter 20, and the two beams of pump light are respectively reversely overlapped with one beam of red-blue detuned detection light and are incident to the first atomic gas chamber 5 and the second atomic gas chamber 6; the calculating unit 9 is configured to calculate electric field intensity according to a scanning time interval of two peaks in the bimodal EIT split spectrum obtained by the second detector 8 and a scanning time interval in the bimodal EIT split spectrum obtained by the first detector 7, and by combining the frequency shift frequencies of the first acoustic optical modulator 3 and the second acoustic optical modulator 4.

Specifically, in this embodiment, the first atomic gas chamber 5 is a high-resistance glass atomic gas chamber. The high-resistance glass is adopted as the atomic air chamber, so that the electric field shielding effect can be avoided, and the static direct current electric field intensity outside the atomic air chamber is measured.

Specifically, in this embodiment, the beam splitting assembly 12 includes a first beam splitting prism 15, a second beam splitting prism 16, and a third beam splitting prism 17, where the first beam splitting prism 15 and the second beam splitting prism 16 are respectively located on the red detuned and blue detuned detection light paths, the first beam splitting prism 15 is used to split the red detuned detection light into two beams, the second beam splitting prism 16 is used to split the blue detuned detection light into two beams, one beam of red detuned detection light and the blue detuned detection light forms a combined beam of red and blue detuned detection light after passing through the first beam splitting prism 15, and the other beam of red detuned detection light and the blue detuned detection light forms another beam of red and blue detuned detection light after passing through the third beam splitting prism 16.

Further, in this embodiment, the first beam splitter prism 15, the second beam splitter prism 16, and the third beam splitter prism 17 are polarization beam splitter prisms, and a half-wave plate is disposed between the first beam splitter prism 15 and the second beam splitter prism 16, and between the second beam splitter prism 16 and the third beam splitter prism 17, the intensity of the red detuned detection light or the blue detuned detection light in the two red and blue detuned detection light can be adjusted through the half-wave plate. In addition, the light inlet sides of the first acoustic optical modulator 3 and the second acoustic optical modulator 4 are also provided with half-wave plates, so that the polarization state of the light beam can be adjusted.

Specifically, the direct current electric field strength measurement device based on the electromagnetic induction transparent spectrum of the present embodiment further includes a first radio frequency source 10 and a second radio frequency source 11, where the first radio frequency source 10 and the second radio frequency source 11 are respectively used to drive the first acousto-optic modulator 3 and the second acousto-optic modulator 4. The frequency shift frequencies of the first acoustic optical modulator 3 and the second acoustic optical modulator 4 are-10 MHz and 10MHz respectively, and in addition, the frequency shift frequencies can be other values within-20 to-5 MHz and 5 to 20MHz, and the sizes can be unequal.

Specifically, the direct current electric field strength measurement device based on electromagnetic induction transparent spectrum of the present embodiment further includes a first light guide lens 13 and a second light guide lens 14, where the first light guide lens 13 is disposed between the first atomic gas chamber 5 and the first detector 7, and the second light guide lens 14 is disposed between the second atomic gas chamber 6 and the second detector 8, and is used for guiding red and blue detuned detection light passing through the first atomic gas chamber 5 and the second atomic gas chamber 6 to the first detector 7 and the second detector 8, respectively. Further, the first light guide 13 and the second light guide 14 are dichroic mirrors, which are highly reflective to the probe light and highly transmissive to the pump light. In addition, the dichroic mirror can also be highly reflective to the pump light, and the probe light is highly transparent, and at this time, the positions of the probe light and the optical path of the pump light can be interchanged, so that those skilled in the art can fully know how to arrange the optical paths under the teaching of the present specification, and the description is omitted here.

Specifically, in the present embodiment, the atoms in the first and second atomic gas chambers 5, 6 are ⁸⁵ Rb atoms, the wavelength of the detection laser 1 is 780nm, which is locked to by saturated absorption spectrum ⁸⁵ Rb atom|5S _1/2 ,F＝3>→|5P _3/2 ,F`＝3>And |5P <sub>3/2</sub> ,F`＝4>The pump laser 2 has a wavelength of 515nm and a frequency of 515nm ⁸⁵ Rb atom|5P _3/2 ,F`＝4>→|10D _3/2 >Scanning near the transition. In addition, EITOther reed-burg states can also be selected for spectrally corresponding reed-burg states, e.g., nS _1/2 ，nD _3/2 Or nD _5/2 A reed burg state.

In addition, in the present embodiment, the atoms in the first and second atomic gas chambers 5, 6 may be Cs atoms, and the wavelength of the detection laser 1 is 852nm, which is locked to Cs atom|6s by saturated absorption spectrum _1/2 ,F＝4>And |6P _3/2 ,F'＝5>The transition energy level of the pump laser 2 is 510nm, and the frequency of the pump laser is Cs atom|5P _3/2 ,，F`＝4>→|10D _3/2 >Scanning near the transition.

Below to ⁸⁵ Rb atoms are examples, which illustrate the measurement principle of the present invention.

The detection laser 1 emits 780nm laser light and is locked to the detection laser by saturated absorption spectrum ⁸⁵ Rb atom|5S _1/2 ,F＝3>→|5P _3/2 ,F`＝3>And |5P <sub>3/2</sub> ,F`＝4>Is a cross transition line of (c). The laser beam is separated into two beams of light by a detection beam splitter 19 consisting of a half wave plate and a polarization beam splitting prism, and the two beams of light respectively pass through a first acousto-optic modulator 3 and a second acousto-optic modulator 4, wherein the first acousto-optic modulator 3 tunes the laser frequency of the beam 1 to ⁸⁵ Rb atom|5S _1/2 ,F＝3>→|5P _3/2 ,F`＝4>The transition red detunes by 10MHz (i.e. -10 MHz), and the second acoustic optical modulator 4 tunes the laser frequency of the beam 2 to <sup>85</sup> Rb atom|5S <sub>1/2</sub> ,F＝3>→|5P <sub>3/2</sub> ,F`＝4>The blue of the transition is detuned by 10MHz (namely +10MHz), and the frequency difference (20 MHz) between the blue and the blue is the frequency scale. After passing through the beam splitting component 12, the two beams of detection light are respectively split into two beams of red and blue detuned detection light which respectively comprise red detuned detection light and blue detuned detection light, and then respectively pass through a first atomic air chamber 5 formed by high-resistance glass and a second atomic air chamber 6 formed by common glass, and are reflected by a first light guide mirror 13 and a second light guide mirror 14 and then are input into the first detector 7 and the second detector 8, and an electric signal converted from light intensity is monitored by an oscilloscope in the computing unit 9.

The pump laser 2 emits 515nm laser light, and the two beams of laser light are separated by the same pump beam splitter 20 and respectively pass through the first light guide mirror 13 and the second light guide mirrorThe second light guide 14 is reversely overlapped with the detection light after being transmitted. The laser frequency can be adjusted to be |5P by monitoring the pump frequency with the wavemeter 18, adjusting the laser voltage, current, temperature, etc _3/2 ,F`＝4>→|10D <sub>3/2</sub> >Scanning near the transition can form two sets of EIT spectra, i.e., bimodal EIT spectra, as shown in the channel 1 reference spectrum of fig. 2. When the pump frequency is lower than |5P <sub>3/2</sub> ,F`＝4>→|10D _3/2 >At a transition frequency of 10MHz, a non-resonant EIT structure is formed with blue detuned probe light, absorption of the blue detuned probe light is suppressed, and probe light intensity is increased to form a transmission peak, which is called blue detuned EIT spectrum. When the pump light frequency is higher than |5P _3/2 ,F`＝4>→|10D _3/2 >At a transition frequency of 10MHz, a non-resonant EIT structure is formed with the red detuned probe light, the absorption of the red detuned probe light is suppressed, the light intensity of the detector is increased, and another transmission peak is formed, which is called red detuned EIT spectrum. Thus by sweeping the frequency of the coupled laser, the frequency separation between the two formants of the bimodal EIT spectrum measured by the photodetector is exactly equal to the frequency difference between the drive frequencies of the two acousto-optic modulators (AOMs) (in this embodiment the frequency difference is 20 MHz).

According to quantum mechanics theory, a Redberg atom with a total angular momentum J has m _J Magnetic sub-level of, -J, m under electric field _J >The energy shift that occurs for the magnetic sub-level compared to the energy in the absence of the electric field can be expressed by the following equation:

wherein DeltaW represents an energy level shift of one of the sub-energy levels of the Redberg atoms, E is the field strength, alpha is the polarizability, and it and the total angular momentum quantum number J and the component m of J along the direction of the electric field _J Related to the following. Specifically, α comprises two terms, one is scalar polarizability α describing the average energy shift ₀ Another term is tensor polarizability α representing stark energy level splitting ₂ The method is specifically expressed as follows:

in the above formula, E (n, s, l, J), E (n ', s ', l ', J) represent atomic energy eigenstates (n represents a main quantum number, s represents an electron spin quantum number, l is an orbit quantum number) in the absence of an electric field, < n, s, l, j||n ', s ', l ', J ' > are corresponding transition dipole matrix elements, and { } is a Wigner 3-J symbol in quantum mechanics. The polarizability is calculated by considering the overall effect of quantum states near |n, s, l, J > and generally considering the number of main quanta adjacent to n+ -5, and the number of orbital quanta l+ -10 is accurate enough. From equation (2), it can be seen that the polarizability depends on the total angular momentum quantum number J and its component m _J Is the absolute value of (c).

The calculation of the Redberg atomic polarizability according to formula (2) requires the application of complex quantum mechanics theory knowledge, but the Atom Calculator program (https:// Atom calc. Org /) issued by the Adams teaching group in UK Du Lunda can obtain the polarizability coefficient of the Redberg atomic state by inputting the parameters of the Redberg atoms (including the absolute value of atomic species, the number of main quanta, the number of orbital quanta, the total number of quanta, the number of quanta of magnon levels and the electric field range). With Rb atom|10D referred to in this patent _3/2 >The Redberg states are illustrated with a total angular momentum J=3/2, m _J The range of values can be (3/2, 1/2, -1/2, -3/2), for a total of 4 magnetic sub-levels. Wherein the magnetic energy level |j=3/2, m _J ＝3/2>And |j=3/2, m _J ＝-3/2>M in (2) _J The absolute values of (a) are the same, and the energy is the same according to the formula (2) (called energy level degeneracy); also the magnetic sub-level |j=3/2, m _J ＝1/2>And |j=3/2, m _J ＝-1/2>Similarly, the energy levels are the same, so the Redberg energy under the electric fieldStage |10D _3/2 >Splitting into 2 sub-energy levels, as shown by the measured spectrum of channel 2 of fig. 2, which is a bimodal EIT split spectrum; these 2 sub-energy levels of the split are labeled as |10D _3/2 ，3/2>And |10D _3/2，1/2 >(only two spectral line diagrams of blue detuned EIT spectral splitting are shown in the figure for simplicity). The Rb atom|10D can be obtained by inputting "Rb 10D_ {3/2}3/2 0-600V/cm" and "Rb 10D_ {3/2}1/2 0-600V/cm" into the program provided by Atom Calculator, respectively _3/2,3/2 >And |10D _3/2,1/2 >The polarizability of (B) was 943Hz cm ² /V ² And 1470Hz cm ² /V ² . If the energy level shift between the two sub-energy levels and the no electric field can be measured, the electric field strength can be obtained by substituting the above-mentioned polarization value according to formula (1).

Redberg state |10D _3/2 >Two sub-energy levels |10D under electric field _3/2,3/2 >And |10D _3/2,1/2 >Is determined according to the schematic diagram shown in fig. 2. The frequency difference Deltaf between the blue detuned EIT spectrum and the red detuned EIT spectrum without electric field is equal to the radio frequency difference of the two AOMs, thereby obtaining the sweep frequency rate k=Deltaf/Deltat of the laser ₀ Further, it is possible to obtain |10D _3/2,3/2 >And |10D _3/2,1/2 >The frequency offsets of the frequency ranges are respectively delta f delta t _3/2 /Δt ₀ And Δf.DELTAt _1/2 /Δt ₀ Substitution into equation (1) yields the use of the Redberg state |10D _3/2 >Is |10d _3/2,3/2 >And |10D _3/2,1/2 >The measured electric field strength. The two measured values should be equal in theory, and in actual operation, the electric field intensity measurement average value can be finally obtained through multiple measurement due to errors.

Therefore, in the present embodiment, the calculation formula of Δw is:

ΔW＝Δf*Δt _3/2 /Δt ₀ the method comprises the steps of carrying out a first treatment on the surface of the Or Δw=Δf×Δt _1/2 /Δt ₀ ；(5)

Wherein Δf represents the difference in frequency shift between the first acoustic optical modulator 3 and the second acoustic optical modulator 4, Δt _3/2 And Deltat _1/2 Respectively represent |10D _3/2,3/2 >And |10D _3/2,1/2 >Relative to the correspondingScanning time interval of EIT spectrum peak without electric field, delta t ₀ Representing the scan time interval of the bimodal EIT spectrum obtained by the second detector 8.

In addition, the scan time difference Δt '(Δt' =Δt) corresponding to the two sub-energy levels may also be directly measured _3/2 +Δt _1/2 ) The electric field strength is calculated as:

wherein alpha is ^3/2 And alpha ^1/2 Respectively representing the polarizability of the two sub-energy levels corresponding to the bimodal EIT split spectrum.

Specifically, in this embodiment, the frequency of the detection laser 1 is locked by a saturated absorption spectrum, a polarization spectrum frequency locking, a DAVLL frequency locking, a frequency modulation spectrum or a modulation transfer spectrum.

As shown in fig. 1, in this embodiment, the output ends of the detection laser 1 and the pump laser 2 are further provided with an optical isolator 21 for isolating the influence of stray light on the laser source, and in addition, the output end of the detection laser 1 is further provided with a frequency locking beam splitter 22 that splits a part of the output light of the detection laser 1 into a frequency locking device 24 for locking the frequency of the detection laser 1. The output of the pump laser 2 is further provided with a wavelength splitter 23 which splits a part of the output light of the pump laser 2 to the wavemeter 18 for observing the wavelength of the pump laser 2.

Specifically, in this embodiment, the detecting beam splitter 19, the pumping beam splitter 20, the frequency-locking beam splitter 22, and the wavelength beam splitter 23 may be a combination of a half-wave plate and a polarizing beam splitter prism, and this beam splitting manner may be convenient for adjusting the beam splitting intensity.

Example two

The second embodiment of the invention provides a direct current electric field strength measurement method based on electromagnetic induction transparent spectrum, which is realized by adopting the direct current electric field strength measurement device based on electromagnetic induction transparent spectrum, and comprises the following steps:

s1, locking the frequency of the detection laser 1, simultaneously scanning the frequency of the pump laser 2, and simultaneously determining the frequency shift frequency of the first acoustic optical modulator 3 and the second acoustic optical modulator 4;

s2, acquiring a bimodal EIT splitting spectrum of a first channel and a bimodal EIT spectrum of a second channel through a first detector 7 and a second detector 8;

s3, calculating the electric field intensity according to the scanning time interval corresponding to the peak value in the bimodal EIT splitting spectrum of the first channel and the bimodal EIT spectrum of the second channel and the frequency shift frequency of the first acoustic optical modulator 3 and the second acoustic optical modulator 4.

The specific steps of the step S3 are as follows:

s301, acquiring a scanning time interval delta t corresponding to a red detuned EIT spectrum peak and a blue detuned EIT spectrum peak in a bimodal EIT spectrum of a second channel ₀ ；

S302, acquiring a scanning time interval delta t of a spectrum peak value in a bimodal EIT split spectrum of a first channel relative to a corresponding peak value in the bimodal EIT spectrum;

s303, calculating the electric field intensity, wherein the calculation formula is as follows:

wherein E represents the electric field strength, W ₁ The frequency shift difference between the first acoustic optical modulator 3 and the second acoustic optical modulator 4 is shown, and α represents the polarization ratio.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (10)

1. The utility model provides a direct current electric field intensity measuring device based on electromagnetic induction transparent spectrum which characterized in that includes: the device comprises a detection laser (1), a pump laser (2), a first acousto-optic modulator (3), a second acousto-optic modulator (4), a first atomic gas chamber (5), a second atomic gas chamber (6), a first detector (7), a second detector (8) and a calculating unit (9); the first atomic air chamber (5) is positioned at a position to be detected, and the second atomic air chamber (6) is positioned at an electric field shielding position;

the frequency of the detection laser (1) is locked, the output detection light is divided into two beams, and after the two beams of detection light are subjected to frequency shift through the first acoustic optical modulator (3) and the second acoustic optical modulator (4), the two beams of detection light are respectively subjected to red detuning and blue detuning relative to the resonance frequency from an atomic ground state to an excited state; the red-blue detuned detection light and the blue-detuned detection light are divided into two beams by the beam splitting assembly (12), wherein the two beams comprise the red-blue detuned detection light and the blue-detuned detection light, one beam of the red-blue detuned detection light is coincided and incident to the first atomic gas chamber (5), and the other beam of the red-blue detuned detection light is coincided and incident to the second atomic gas chamber (6); the red and blue detuned detection light passing through the first atomic gas chamber (5) and the second atomic gas chamber (6) is detected by the first detector (7) and the second detector (8) respectively;

the frequency of the pump laser (2) scans at the transition of the energy levels of an atomic excitation state and a Redberg state, the output pump light is divided into two beams, and the two beams of pump light are respectively reversely overlapped with one beam of red-blue detuned detection light and are incident into the first atomic gas chamber (5) and the second atomic gas chamber (6);

the computing unit (9) is used for computing the energy level offset of the Redberg atoms in the electric field according to the scanning time interval of two peaks in the bimodal EIT spectrum obtained by the second detector (8) and the scanning time interval in the bimodal EIT split spectrum obtained by the first detector (7) and combining the frequency shift frequencies of the first acousto-optic modulator (3) and the second acousto-optic modulator (4), and computing the electric field intensity according to the energy level offset.

2. The device for measuring the field strength of a direct current electric field based on electromagnetic induction transparent spectrum according to claim 1, wherein the calculation formula of the electric field strength is:

wherein E represents the electric field intensity, alpha represents the polarizability, deltaW represents the energy level shift of the Redberg atoms in the electric field, and the calculation formula is as follows:

ΔW＝Δf*Δt/Δt ₀ ；

wherein Δf represents the frequency shift difference of the first acoustic optical modulator (3) and the second acoustic optical modulator (4), and Δt represents the scanning time interval corresponding to the energy level shift of the Redburg atoms in the electric field, respectively ₀ Representing the scan time interval of two peaks in the bimodal EIT spectrum obtained by the second detector (8).

3. The direct current electric field strength measurement device based on electromagnetic induction transparent spectrum according to claim 1, wherein the first atomic gas chamber (5) is a high-resistance glass atomic gas chamber.

4. The direct current electric field strength measurement device based on electromagnetic induction transparent spectrums according to claim 1, wherein the beam splitting assembly (12) comprises a first beam splitting prism (15), a second beam splitting prism (16) and a third beam splitting prism (17), the first beam splitting prism (15) and the second beam splitting prism (16) are respectively positioned on detection light paths of red detuning and blue detuning, the first beam splitting prism (15) is used for splitting red detuning detection light into two beams, the second beam splitting prism (16) is used for splitting blue detuning detection light into two beams, one beam of red detuning detection light and one beam of blue detuning detection light form one beam of red blue detuning detection light after being transmitted by the first beam splitting prism (15), and the other beam of red detuning detection light and the other beam of blue detuning detection light form the other beam of red blue detuning detection light after being transmitted by the third beam splitting prism (17).

5. The direct current electric field strength measurement device based on electromagnetic induction transparent spectrum according to claim 1, further comprising a first radio frequency source (10) and a second radio frequency source (11), wherein the first radio frequency source (10) and the second radio frequency source (11) are respectively used for driving the first acoustic optical modulator (3) and the second acoustic optical modulator (4);

the atomic gas chamber detector further comprises a first light guide lens (13) and a second light guide lens (14), wherein the first light guide lens (13) is arranged between the first atomic gas chamber (5) and the first detector (7), and the second light guide lens (14) is arranged between the second atomic gas chamber (6) and the second detector (8) and is used for guiding red and blue detuned detection light passing through the first atomic gas chamber (5) and the second atomic gas chamber (6) to the first detector (7) and the second detector (8).

6. A direct current electric field strength measuring device based on electromagnetic induction transparent spectrum according to claim 5, characterized in that the first (13) and second (14) light guide lenses are dichroic mirrors.

7. The electromagnetic induction transparent spectrum-based direct current electric field strength measurement device according to claim 1, wherein atoms in the first atomic gas chamber (5) and the second atomic gas chamber (6) are ⁸⁵ Rb atoms, the wavelength of the detection laser (1) is 780nm, which is locked to by saturated absorption spectrum ⁸⁵ Rb atom|5S _1/2 ,F＝3>→|5P _3/2 ,F`＝3>And |5P <sub>3/2</sub> ,F`＝4>The wavelength of the pump laser (2) is 515nm, and the frequency is that of ⁸⁵ Rb atom|5P _3/2 ,F`＝4>→|10D _3/2 >Scanning near the transition;

or: the atoms in the first atomic gas chamber (5) and the second atomic gas chamber (6) are Cs atoms, the wavelength of the detection laser (1) is 852nm, and the detection laser is locked to Cs atoms|6S through saturated absorption spectrum _1/2 ,F＝4>And |6P _3/2 ,F'＝5>The transition energy level of the pump laser (2) is 510nm, and the frequency of the pump laser is Cs atom|5P _3/2 ,，F`＝4>→|10D _3/2 >Scanning near the transition.

8. The direct current electric field strength measurement device based on electromagnetic induction transparent spectrum according to claim 1, wherein the frequency of the detection laser (1) is locked by saturated absorption spectrum, polarization spectrum frequency locking, DAVLL frequency locking, frequency modulation spectrum or modulation transfer spectrum.

9. A direct current electric field intensity measuring method based on electromagnetic induction transparent spectrum, which is realized by adopting the direct current electric field intensity measuring device based on electromagnetic induction transparent spectrum as claimed in claim 1, and is characterized by comprising the following steps:

s1, locking the frequency of a detection laser (1), simultaneously scanning the frequency of a pump laser (2), and simultaneously determining the frequency shift frequency of a first acousto-optic modulator (3) and a second acousto-optic modulator (4);

s2, acquiring a bimodal EIT splitting spectrum of a first channel and a bimodal EIT spectrum of a second channel through a first detector (7) and a second detector (8);

s3, calculating the electric field intensity according to the scanning time interval corresponding to the peak value in the bimodal EIT splitting spectrum of the first channel and the bimodal EIT spectrum of the second channel and the frequency shift frequency of the first acoustic optical modulator (3) and the second acoustic optical modulator (4).

10. The method for measuring the field strength of a direct current electric field based on electromagnetic induction transparent spectrum according to claim 9, wherein the specific steps of the step S3 are as follows:

acquiring a scanning time interval delta t corresponding to a red detuned EIT spectrum peak and a blue detuned EIT spectrum peak in a bimodal EIT spectrum of a second channel ₀ ；

Acquiring a scanning time interval delta t of one spectrum peak value in a bimodal EIT split spectrum of a first channel relative to a corresponding peak value in the bimodal EIT spectrum;

the electric field intensity is calculated, and the calculation formula is as follows:

wherein E represents the electric field intensity, Δf represents the frequency shift difference between the first acoustic optical modulator (3) and the second acoustic optical modulator (4), and α represents the polarization ratio.