A method, storage medium and system for measuring microwave polarization direction

Abstract

The present invention relates to a method for measuring microwave polarization direction, comprising the steps of: constructing a Rydberg atom microwave electric field sensor; radiating signal microwaves and localized microwaves into a rubidium atomic vapor pool to achieve interference, and measuring the resulting beat frequency signal using the Rydberg atom microwave electric field sensor; and adjusting the polarization direction of the signal microwave electric field to convert the microwave polarization measurement into a beat frequency amplitude measurement. The present invention also provides a storage medium and a system for measuring microwave polarization direction. The method, storage medium, and system for measuring microwave polarization direction described herein greatly simplify the theoretical analysis and experimental system for measuring microwave polarization using Rydberg atoms.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave measurement, and in particular relates to a method, a storage medium and a system for measuring the polarization direction of microwaves. Background Art

[0002] Precisely measuring various microwave parameters has important applications in radar, communications, remote sensing, and nondestructive detection. In recent years, atom-based quantum sensors have developed rapidly, leveraging the quantum properties of atoms to achieve higher precision and sensitivity than traditional measurements. Rydberg atom-based microwave electric field sensors, among others, offer unique advantages over traditional electronic measurement methods, including full-bandwidth, traceability to fundamental physical constants, self-calibration, and all-optical readout without the interference of electronic dark current noise. These sensors have garnered widespread attention and research.

[0003] Microwave electric field sensors based on Rydberg atoms have achieved significant breakthroughs and progress in areas such as microwave electric field intensity measurement, microwave phase measurement, and microwave frequency measurement. However, these applications all assume that the polarization direction of the microwave electric field to be measured is known. Typically, the microwave electric field is linearly polarized, parallel to the polarization of the probe light.

[0004] However, since atoms have different Zeeman sub-levels, when the microwave polarization changes, different Zeeman sub-levels will participate in the interaction with the microwave. Since the dipole moments of different Zeeman sub-level transitions are different, the EIT-AT splitting spacing caused by the same microwave electric field intensity is different. In practical applications, it is necessary to first measure the microwave polarization and polarization. Only after the microwave polarization direction is clear can the Rydberg atom electromagnetic induced transparency be used to make absolute and precise measurements of the microwave electric field, phase, and frequency. Summary of the Invention

[0005] In response to the defects existing in the prior art, the purpose of the present invention is to provide a method, storage medium and system for measuring the polarization direction of microwaves so as to realize that the amplitude of the output beat signal is only related to the projection of the signal microwave polarization on the polarization of the local microwave electric field, and is immune to the polarization of the light field that forms Rydberg electromagnetic induction transparency, thereby greatly simplifying the theoretical analysis and experimental system of measuring microwave polarization using Rydberg atoms.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for measuring the polarization direction of microwaves, comprising the steps of: constructing a Rydberg atomic microwave electric field sensor; radiating signal microwaves and localized microwaves into a rubidium atomic vapor pool to achieve interference, and measuring the beat frequency signal formed by the interference through the Rydberg atomic microwave electric field sensor; adjusting the polarization direction of the signal microwave electric field to convert the measurement of microwave polarization into the measurement of the beat frequency amplitude.

[0007] Furthermore, the signal microwave and the local microwave are radiated into the rubidium atomic vapor pool through two microwave antennas respectively, wherein the polarization direction of the local microwave is constant.

[0008] Furthermore, the microwave antenna is a rectangular horn antenna.

[0009] Furthermore, the rectangular horn antenna of the signal microwave electric field is fixed on an electric rotating platform, so that the polarization direction of the signal microwave can be adjusted by rotating the electric rotating platform.

[0010] Furthermore, the electric rotating platform can rotate continuously within a range of 360 degrees, and the step accuracy is less than 0.05 degrees.

[0011] Furthermore, the beat frequency signal is measured by the Rydberg atom microwave electric field sensor to obtain a periodic sinusoidal change of the detection light intensity over time. The relationship between the detection light intensity and the signal microwave electric field amplitude is:

[0012] T p ∝E LO +E SIG sin(Δ MW t)

[0013] Among them, T p is the detection light intensity; E LO is the amplitude of the local microwave electric field; E SIG is the amplitude of the signal microwave electric field; Δ MW is the beat frequency.

[0014] Furthermore, the change in the polarization direction of the signal microwave electric field is used as a projection on the polarization direction of the local microwave electric field, and the relationship between the amplitude of the detection light intensity and the angle between the amplitude and polarization direction of the signal microwave electric field is obtained as follows:

[0015] A p ∝|E LO +E SIG cosθ|

[0016] Among them, A p is the amplitude of the detected light intensity; E LO is the amplitude of the local microwave electric field; E SIG is the amplitude of the signal microwave electric field; θ is the polarization angle.

[0017] Furthermore, the frequency of the beat frequency is 1 kHz, the amplitude of the local microwave electric field is 6.43 mV / cm, and the amplitude of the signal microwave electric field is 1.73 mV / cm.

[0018] The present invention also provides a storage medium, in which a computer program is stored, wherein the computer program is configured to execute the method for measuring the polarization direction of microwaves when running.

[0019] The present invention provides a system for measuring microwave polarization direction, comprising: a Rydberg atomic microwave electric field sensor construction module, used for constructing a Rydberg atomic microwave electric field sensor to measure a beat frequency signal; a microwave adjustment module, used for generating local microwaves with a constant polarization direction and signal microwaves with an adjustable polarization direction, and radiating the local microwaves and the signal microwaves into a rubidium atomic vapor pool to achieve interference; and a conversion module, used for converting the measurement of microwave polarization into the measurement of beat frequency amplitude.

[0020] The present invention achieves the following advantages: by changing the polarization direction of the signal microwave electric field and measuring the resulting change in the beat signal, a relationship is established between the amplitude of the beat signal and the polarization direction of the signal microwave electric field. This allows the polarization of the signal microwave electric field to be measured directly using the amplitude of the beat signal. This ensures that the amplitude of the output beat signal is solely related to the projection of the signal microwave polarization onto the local microwave polarization, making it immune to the polarization of the light field that forms Rydberg electromagnetic induction transparency. This significantly simplifies the theoretical analysis and experimental system for measuring microwave polarization using Rydberg atoms. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the steps of a method for measuring the polarization direction of microwaves according to the present invention;

[0022] Figure 2 This is a schematic diagram of the energy levels of the Rydberg atomic microwave electric field sensor experiment;

[0023] Figure 3 Schematic diagram of the experimental setup for the method of measuring microwave polarization direction;

[0024] Figure 4 Schematic diagram of the relationship between the amplitude of the beat signal and the polarization of the signal microwave electric field;

[0025] Figure 5 Schematic diagram of experimental results of polarization resolution accuracy and linearity;

[0026] Figure 6 Schematic diagram of the relationship between the amplitude and polarization of the microwave electric field to be measured when the detection light is circularly polarized and the coupled light is linearly polarized;

[0027] Figure 7 Schematic diagram of the relationship between the amplitude and polarization of the microwave electric field to be measured when both the detection light and the coupling light are circularly polarized. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1-3 As shown, the present invention provides a method for measuring the polarization direction of microwaves, which includes the steps of:

[0030] S1, construction of Rydberg atomic microwave electric field sensor;

[0031] Specifically, use 87 Rb atom, the Rydberg atom involved consists of four energy levels, namely 5S 1 / 2 (F=2), 5P 3 / 2 (F=3), 61D 5 / 2 (F=4), 62P 3 / 2 (F=3), but not limited to these specific atomic energy levels. The 780nm laser (probe light) acts on 5S 1 / 2 (F=2)→5P 3 / 2 (F=3) transition, 480nm laser (coupled light) acts on 5P 3 / 2 (F=3)→61D 5 / 2 (F=4) transition, 9.2GHz microwave acts on 61D 5 / 2 (F=4)→62P 3 / 2 (F=3) transition. A 780nm laser (probe light) and a 480nm laser (coupling light) propagate toward each other in a rubidium atomic vapor cell, creating electromagnetically induced transparency (EIT) of the Rydberg atoms. Applying a microwave electric field causes Autler-Townes splitting of the EIT. Changes in the microwave electric field intensity can be measured by observing changes in the transmittance of the probe light at the EIT resonance position.

[0032] In a specific embodiment, the parameters of the laser include: a detection light power of 60 microwatts, a diameter of about 800 micrometers in the rubidium atomic vapor, a coupling light power of 50 milliwatts, and a diameter of about 900 micrometers in the rubidium atomic vapor.

[0033] It should be noted that in this embodiment, the intensity of the coupled light is modulated with a 30kHz sinusoidal period using an acousto-optic modulator, and the 30kHz modulated signal is simultaneously sent to a lock-in amplifier as a reference signal, which is then used to improve the signal-to-noise ratio of the detection light. During the experiment, the frequency of the detection light was locked at 5S 1 / 2 (F=2)→5P 3 / 2 (F=3) transition, the frequency of the coupled light is locked at 5P 3 / 2 (F=3)→61D 5 / 2 When microwaves are applied to the rubidium atomic vapor cell, the intensity of the probe light changes, and the intensity of the microwave electric field is obtained by measuring the change in the transmittance (or intensity) of the probe light.

[0034] S2, radiating the signal microwave and the local microwave into the rubidium atomic vapor pool to achieve interference, and measuring the beat frequency signal formed by the interference through the Rydberg atomic microwave electric field sensor;

[0035] Specifically, two microwave antennas radiate the signal microwave and the localized microwave into a rubidium atomic vapor cell, where they interfere with each other. The resulting beat frequency signal is measured using a Rydberg atomic microwave electric field sensor. This signal is obtained by measuring the periodic sinusoidal variation of the detection light intensity over time. The localized microwaves are linearly polarized, and their polarization direction remains constant.

[0036] As an example, a rectangular horn antenna is used to transmit a microwave electric field to a rubidium atomic vapor pool. This rectangular horn antenna can provide a very good linearly polarized microwave signal under far-field conditions. The interferometric beat frequency signal is measured by a Rydberg atomic microwave electric field sensor, which is a periodic sinusoidal variation of the detection light intensity over time. The beat frequency is equal to the frequency difference Δ between the two microwave electric fields. MW When the amplitude of the local microwave electric field E LO Much larger than the amplitude E of the signal microwave electric field SIG When the detection light intensity T p The relationship with the signal microwave electric field amplitude is as follows:

[0037] T p ∝E LO +E SIG sin(Δ MW t)

[0038] It can be understood that this embodiment only focuses on the change in amplitude, and thus ignores the phase information of the local microwave electric field and the signal microwave electric field.

[0039] In a specific embodiment, the frequency difference between the two microwave electric fields, that is, the frequency difference between the signal microwave and the local microwave electric field is 1 kHz, and the amplitude E of the local microwave electric field is LO =6.43mV / cm, the amplitude of the signal microwave electric field E SIG =1.73mV / cm, and the gain of the two antennas is 10dB. During the experiment, the field strengths of the signal microwave and the local microwave electric field can be adjusted to obtain a clear beat signal. The peak-to-peak oscillation of the transmitted probe light intensity caused by the beat signal can be adjusted according to actual measurement requirements. The requirement is to have a clear 1kHz beat signal after the probe light passes through the rubidium cell. In practice, the frequency difference between the two microwave electric fields can reach 100kHz, primarily due to the 100kHz bandwidth of the lock-in amplifier used in the experiment.

[0040] S3, adjusting the polarization direction of the signal microwave electric field to convert the measurement of microwave polarization into the measurement of beat frequency amplitude;

[0041] Specifically, by introducing the change in the polarization direction of the signal microwave electric field, this change is defined as the projection of the signal microwave electric field polarization on the polarization direction of the local microwave electric field. At this time, the detection light intensity T p Amplitude A p The relationship between the signal microwave electric field amplitude and the polarization direction angle θ is as follows:

[0042] A p ∝|E LO +E SIG cosθ|

[0043] Therefore, when the polarization direction of the signal microwave electric field changes, the amplitude of the probe light intensity will also change. In other words, the measurement of microwave polarization can be converted into the measurement of beat frequency amplitude. By measuring the amplitude of the beat frequency signal, the intensity of the microwave electric field can be measured.

[0044] In this embodiment, the rectangular horn antenna of the signal microwave electric field is fixed on an electric rotating table, which can rotate continuously within a range of 360 degrees with a step accuracy of less than 0.05 degrees. Therefore, the polarization direction of the signal microwave electric field line can be continuously changed within a range of 360 degrees. At the same time, the rectangular horn antenna of the local microwave electric field is fixed, that is, the polarization direction of the local microwave electric field is guaranteed to remain unchanged. The polarization direction of the signal microwave electric field is changed by using the electric rotating table every 5 degrees (or 10 degrees), and then the amplitude of the corresponding beat frequency signal is read on the oscilloscope, thereby realizing the measurement of the polarization direction of the signal microwave electric field. The results are shown as follows: Figure 4 shown.

[0045] In this embodiment, the theoretically calculated data is multiplied by a coefficient representing the effect of the amplification gain of the photodetector and the lock-in amplifier on the amplitude A of the detected light intensity. p The relationship between the signal microwave electric field amplitude and the polarization direction angle θ is geometrically amplified, and it can be clearly seen that the amplitude of the beat signal oscillates periodically with the change of the polarization direction of the signal microwave electric field.

[0046] It is understood that in other embodiments, the polarization direction of the signal microwave electric field can be adjusted in any manner, not limited to the rotation of the electric rotary table, as long as the polarization direction of the signal microwave electric field line can be changed.

[0047] Furthermore, in the relatively good linear region of 50 to 70 degrees, the polarization direction of the signal microwave electric field is changed every 2 degrees. The results are as follows: Figure 5 As shown, the amplitude of the beat signal exhibits a linear, monotonic downward trend as the polarization direction of the microwave electric field changes. Using the experimental signal, a linear fit was performed, yielding a slope of 0.03359 V / degree. Using the typical statistical error of 0.01409 V, the resolvable polarization angle was determined to be 0.42 degrees.

[0048] To verify the above steps, the polarization insensitivity of the probe light and coupling light to form Rydberg electromagnetically induced transparency was tested. The polarization of the probe light and coupling light was changed by using a quarter-wave plate. The tests were performed under the following conditions: the probe light was circularly polarized, the coupling light was polarized, and both the probe light and coupling light were circularly polarized:

[0049] Figure 6 The figure shows the relationship between the mixer output amplitude and the polarization of the microwave electric field to be measured when the probe light is circularly polarized and the coupled light is linearly polarized. It can be seen that the amplitude of the beat signal is lower than when both the probe light and the coupled light are linearly polarized. This is because the Rabi frequencies corresponding to different polarization combinations of the probe light and the coupled light vary, causing the intensity of the Rydberg EIT to change, thus affecting the overall amplitude variation of the beat signal. However, importantly, the overall trend of the beat signal amplitude and the change in the polarization direction of the signal microwave electric field remains unchanged. In other words, the amplitude of the beat signal can still be characterized by the projection of the measured microwave polarization onto the local microwave electric field polarization. Similarly, the linear fit and statistical error in the linear region yield a resolvable polarization direction of 0.52 degrees.

[0050] Figure 7 The relationship between the mixer output amplitude and the polarization of the microwave electric field to be measured when both the probe light and the coupled light are circularly polarized is shown in the figure. The specific analysis process and results are similar to those in the figure. Figure 6 The conclusion is similar to that shown in the figure: the linear fitting and statistical error in the linear region give a resolvable polarization angle of 0.49 degrees.

[0051] The above verification shows that the overall trend of the change in the amplitude of the beat signal and the polarization direction of the signal microwave electric field remains unchanged. The amplitude of the beat signal can still be characterized by the projection of the polarization of the microwave to be measured on the LO field polarization. Similarly, through linear fitting and statistical error in the linear region, we obtained the resolvable polarization angles of 0.52 degrees and 0.49 degrees, reaching the current best level of microwave polarization measurement by Rydberg atom sensors.

[0052] The present invention also provides a storage medium storing a computer program, which, when executed by a processor, implements the steps of a method for measuring the polarization direction of microwaves.

[0053] It should be noted that the storage medium shown in this application can be a computer-readable signal medium or a storage medium or any combination of the above. The storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, system or device, or any combination of the above. More specific examples of storage media can include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this application, a storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, system or device. In this application, a storage medium can include a data signal propagated in baseband or as part of a carrier wave, which carries computer-readable program code. This propagated data signal can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The storage medium may also be any computer-readable medium other than a storage medium that can transmit, propagate, or transfer a program for use by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable medium may be transmitted using any suitable medium, including but not limited to wireless, wire, optical cable, RF, etc., or any suitable combination thereof.

[0054] The present invention also provides a system for measuring microwave polarization direction, comprising:

[0055] Rydberg atom microwave electric field sensor building block, used to build a Rydberg atom microwave electric field sensor to measure beat frequency signals;

[0056] The microwave adjustment module is used to generate local microwaves with constant phase and signal microwaves with adjustable polarization direction, and radiate the local microwaves and signal microwaves into the rubidium atomic vapor pool to achieve interference;

[0057] The conversion module is used to convert the measurement of microwave polarization into the measurement of beat frequency amplitude.

[0058] As can be seen from the above embodiments, the present invention can establish a relationship between the amplitude of the beat signal and the polarization direction of the signal microwave electric field by changing the polarization direction of the signal microwave electric field and statistically analyzing the resulting changes in the beat signal. This allows the polarization of the signal microwave electric field to be measured directly using the amplitude of the beat signal. This ensures that the amplitude of the output beat signal is solely related to the projection of the signal microwave polarization onto the local microwave polarization, making it immune to the polarization of the light field that forms Rydberg electromagnetic induction transparency. This greatly simplifies the theoretical analysis and experimental system for measuring microwave polarization using Rydberg atoms.

[0059] The method and system of the present invention are not limited to the embodiments described in the specific implementation manner. Those skilled in the art may derive other implementation manners based on the technical solution of the present invention, which also fall within the scope of the technical innovation of the present invention.

Claims

1. A method for measuring the polarization direction of microwaves, characterized in that: Including steps: Constructing a Rydberg atom microwave electric field sensor; The signal microwave and the local microwave are radiated into the rubidium atomic vapor pool to achieve interference, and the beat frequency signal formed by the interference is measured by a Rydberg atomic microwave electric field sensor; The polarization direction of the signal microwave electric field is adjusted to convert the measurement of microwave polarization into the measurement of beat frequency amplitude.

2. The method for measuring the polarization direction of microwaves according to claim 1, wherein: The signal microwave and the local microwave are radiated into the rubidium atomic vapor pool through two microwave antennas respectively, wherein the polarization of the local microwave is linear polarization and constant.

3. The method for measuring the polarization direction of microwaves according to claim 2, wherein: The microwave antenna is a rectangular horn antenna.

4. The method for measuring the polarization direction of microwaves according to claim 2, wherein: The rectangular horn antenna of the signal microwave electric field is fixed on an electric rotating platform so that the polarization direction of the signal microwave can be adjusted by rotating the electric rotating platform.

5. The method for measuring the polarization direction of microwaves according to claim 4, wherein: The electric rotating platform can rotate continuously within a range of 360 degrees, and the step accuracy is less than 0.05 degrees.

6. A method for measuring the polarization direction of microwaves according to claim 1, characterized in that The beat frequency signal is measured by the Rydberg atomic microwave electric field sensor to obtain a periodic sinusoidal change in the detection light intensity over time. The relationship between the detection light intensity and the signal microwave electric field amplitude is: T p ∝E LO +E SIGs in(Δ MW t) Among them, T p is the detection light intensity; E LO is the amplitude of the local microwave electric field; E SIG is the amplitude of the signal microwave electric field; Δ MW is the beat frequency.

7. A method for measuring microwave polarization direction according to claim 6, characterized in that : The change in the polarization direction of the signal microwave electric field is used as the projection on the polarization direction of the local microwave electric field, and the relationship between the amplitude of the detection light intensity and the angle between the amplitude of the signal microwave electric field and the polarization direction is obtained as follows: TO p ∝|E LO +E SIG cosθ| Among them, A p is the amplitude of the detected light intensity; E LO is the amplitude of the local microwave electric field; E SIG is the amplitude of the signal microwave electric field; θ is the polarization angle.

8. A method for measuring the polarization direction of microwaves according to claim 7, characterized in that : The frequency of the beat frequency is 1 kHz, the amplitude of the local microwave electric field is 6.43 mV / cm, and the amplitude of the signal microwave electric field is 1.73 mV / cm.

9. A storage medium, characterized in that: The storage medium stores a computer program, wherein the computer program is configured to execute the method for measuring the polarization direction of microwaves as described in any one of claims 1 to 8 when running.

10. A system for measuring microwave polarization direction, characterized in that: include: Rydberg atom microwave electric field sensor building block, used to build a Rydberg atom microwave electric field sensor to measure beat frequency signals; The microwave adjustment module is used to generate local microwaves with constant phase and signal microwaves with adjustable polarization direction, and radiate the local microwaves and signal microwaves into the rubidium atomic vapor pool to achieve interference; The conversion module is used to convert the measurement of microwave polarization into the measurement of beat frequency amplitude.

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