Rydberg atom microwave electric field sensing system and method based on coupling light modulation

Abstract

The invention discloses a Rydberg atom microwave electric field sensing system and method based on coupling light modulation, and belongs to the technical field of microwave electric field sensing. In the system, a Rydberg atom preparation module excites alkali metal atoms to a Rydberg state; the radio frequency module provides a local oscillator signal for the Rydberg atom preparation module; the coupling light modulation module modulates the broadband pulse signal to the coupling light through an acousto-optic modulator so as to change the intensity of the coupling light entering the Rydberg atom preparation module; the signal receiving and processing module collects transmission light signals passing through the Rydberg atom preparation module, matched filtering processing is carried out, microwave electric field information is extracted, and the transmission light signals are generated by alkali metal atoms under the combined action of to-be-detected signals, detection light, local oscillation signals and coupling light with changed intensity. According to the method, the measurement sensitivity and the signal-to-noise ratio are improved, higher environmental adaptability is achieved, and stable measurement performance can be kept under complex conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave electric field sensing, and in particular relates to a Rydberg atom microwave electric field sensing system and method based on coupled light modulation. Background Art

[0002] Microwave sensing technology has extensive and important applications in the fields of communications, radar detection, aerospace, and national defense security. High-sensitivity, high-precision, and high-applicability microwave sensing technology has always been a research hotspot in related fields. Rydberg atoms are atoms in a highly excited state, whose adjacent energy level transition frequencies are in the microwave frequency band and have extremely high transition dipole moments, making them highly sensitive to microwave electric fields. Using Rydberg atoms to detect microwave fields can break through the limitations of thermal noise in traditional electronic circuits, and show great potential in the field of high-sensitivity microwave electric field sensing.

[0003] In the existing Rydberg atom microwave electric field sensing technology, the sensitivity of the system is severely restricted by the stability of the laser light source. Weak signals are often annihilated in the background noise introduced by the light source noise, thus limiting the detection accuracy of the system. Due to the need for a highly stable laser light source, the existing technology has high requirements for experimental conditions in applications and is difficult to be widely promoted and applied in complex environments. Although some studies have improved the sensitivity by introducing a superheterodyne structure, the detection of weak changes in microwave signals is still limited by the noise environment, making it difficult to achieve higher precision detection.

[0004] Therefore, how to further improve sensitivity and applicability is a technical problem that needs to be urgently solved in the technological development of this field. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a Rydberg atom microwave electric field sensing system and method based on coupled light modulation, which achieves signal amplification and noise suppression by modulating the coupled light into a broadband frequency modulation signal on the basis of a superheterodyne structure and combining matched filtering processing, thereby significantly improving the sensitivity of the sensing system. By introducing broadband frequency modulation, a breakthrough has been made in the frequency dimension of signal gain, allowing signal amplification at a longer measurement time or a wider modulation bandwidth, significantly improving the adaptability of the system in complex and changeable environments, and enabling the sensing system to maintain high performance in a noisy environment.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A Rydberg atom microwave electric field sensing system based on coupled light modulation, comprising:

[0008] Rydberg atom preparation module, used to excite alkali metal atoms to Rydberg states;

[0009] The radio frequency module is used to provide a local oscillator signal to the Rydberg atom preparation module;

[0010] The coupling light modulation module is used to modulate a broadband pulse signal onto the coupling light through an acousto-optic modulator to change the intensity of the coupling light entering the Rydberg atom preparation module;

[0011] The signal receiving and processing module is used to collect the transmitted light signal passing through the Rydberg atom preparation module and perform matched filtering processing to extract microwave electric field information. The transmitted light signal is generated by alkali metal atoms under the combined action of a signal to be measured, a probe light, a local oscillator signal, and a coupling light with changed intensity.

[0012] On the other hand, the present invention provides a Rydberg atom microwave electric field sensing method based on coupling light modulation, including:

[0013] Using the Rydberg atom preparation module to excite alkali metal atoms to the Rydberg state;

[0014] Providing a local oscillator signal to the Rydberg atom preparation module;

[0015] Modulating a broadband pulse signal onto the coupling light through an acousto-optic modulator to change the intensity of the coupling light entering the Rydberg atom preparation module;

[0016] Collecting the transmitted light signal passing through the Rydberg atom preparation module and performing matched filtering processing to extract microwave electric field information. The transmitted light signal is generated by alkali metal atoms under the combined action of a signal to be measured, a probe light, a local oscillator signal, and a coupling light with changed intensity.

[0017] In a third aspect, the present invention provides an electronic device, including: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the foregoing Rydberg atom microwave electric field sensing method based on coupling light modulation.

[0018] In a fourth aspect, the present invention provides a computer-readable storage medium, on which executable instructions are stored, and when the instructions are executed by a processor, the processor can implement the foregoing Rydberg atom microwave electric field sensing method based on coupling light modulation.

[0019] The beneficial effects of the present invention are as follows:

[0020] By applying broadband signal modulation to the coupling light and combining the method of matched filtering, the present invention realizes sensitivity gain in both the time and frequency dimensions. Through pulse compression technology, the signal-to-noise ratio after matched filtering is related to the bandwidth, thus significantly improving the detection ability of the system. Compared with the prior art, the present invention can detect weaker electric field signals within the same measurement time, further improving the measurement sensitivity.

[0021] The present invention processes the pulse signal through matched filtering, and improves the signal-to-noise ratio by utilizing the characteristic that the pulse height after matched filtering is proportional to the amplitude of the sum mixing signal.

[0022] The present invention reduces the dependence on the high stability of the laser light source to a certain extent by modulating the coupling light. Compared with the prior art, the measurement system of the present invention has lower requirements for the stability of the light source, thus having higher environmental adaptability and being able to further maintain stable measurement performance under complex conditions. Brief Description of the Drawings

[0023] Figure 1 is the schematic diagram of the Rydberg atom microwave electric field sensing system based on coupling light modulation of the present invention;

[0024] Figure 2 is the schematic diagram of the coupling light modulation signal;

[0025] Figure 3 is the curve of the sensitivity of the present invention varying with the bandwidth. Detailed Embodiments

[0026] The present invention will be further described below in conjunction with the drawings and embodiments.

[0027] The present invention provides a Rydberg atom microwave electric field sensing system based on coupling light modulation, as Figure 1 shown, including:

[0028] Rydberg atom preparation module: used to excite alkali metal atoms to the Rydberg state. This module mainly includes an atomic gas cell, a probe light laser and a frequency stabilization component, and a coupling light laser and a frequency locking component. The atomic gas cell is a cylindrical glass bulb containing saturated vapor of alkali metal atoms, such as rubidium and cesium, and both ends are as flat as possible to reduce the influence on the laser beam. The probe light is generally near-infrared light (rubidium: 780 nm, cesium: 852 nm), and a semiconductor laser can be selected as the probe light laser to generate the probe light. The coupling light is generally green light (rubidium: 480 nm, cesium: 510 nm), which can be achieved by frequency doubling. Since the linewidth of the commercial coupling light laser is relatively wide, a corresponding frequency locking component is required to lock the frequency of the coupling light laser.

[0029] Radio frequency module: used to provide a local oscillator signal to the Rydberg atom preparation module;

[0030] The radio frequency module mainly includes a radio frequency microwave source and a radiation antenna. The radio frequency microwave source provides a local reference microwave signal (local oscillator), and the local oscillator signal is radiated onto the Rydberg atom preparation module through the radiation antenna. When testing, the local oscillator signal and the signal to be measured are irradiated onto the atomic gas cell together.

[0031] Coupled optical modulation module: It is used to modulate the acousto-optic modulator drive signal with envelope modulation onto the coupled light to change the intensity of the coupled light entering the Rydberg atom preparation module. The coupled optical modulation module mainly includes a function generator, a mixer, an amplifier, an acousto-optic modulator (AOM), etc. cascaded in sequence. The function generator generates two signals, one is a broadband pulse signal containing a DC bias, denoted as S A , and the other is the AOM drive signal, denoted as S B . The role of the DC bias is to ensure that the mixed signal is an envelope modulation signal. After signals S A and S B pass through the mixer, the output signal is the AOM drive signal with envelope modulation, denoted as S C , and its envelope signal is a broadband pulse signal. According to the relevant knowledge of acousto-optic modulators, when the AOM works in the Bragg diffraction state, the ratio of the intensity of its first-order diffracted light to the incident light, that is, the diffraction efficiency is:

[0032]

[0033] Among them, is a characteristic parameter of the AOM, is the incident light wavelength, and P a is the driving power of the transducer. In the Bragg diffraction state, the output optical signal of the AOM only contains the zero-order diffracted light and the first-order diffracted light. Selecting an appropriate working point can make the diffraction efficiency and approximately linearly related, that is, the diffraction efficiency and the amplitude of the drive signal are approximately linearly related:

[0034]

[0035] Among them, is the envelope amplitude of the AOM drive signal with envelope modulation, and the coefficients and can be calibrated through experiments. The AOM drive signal with envelope modulation is modulated onto the coupled light through an amplifier and an acousto-optic modulator. After modulation, the intensity of the zero-order diffracted light is:

[0036]

[0037] Among them, is the zero-order light intensity-driving voltage proportionality coefficient, is the ratio of the zero-order diffracted light intensity to the incident light intensity without driving voltage, and both can be calibrated through experiments, is the intensity of the coupled light before entering the AOM. To avoid the influence of modulation on the beam direction, this scheme takes the zero-order diffracted component of the coupled light to enter the Rydberg atom preparation module.

[0038] Signal reception and processing module: It is used to collect the transmitted light signal passing through the Rydberg atom preparation module and perform matched filtering processing to extract microwave electric field information. The transmitted light signal is generated by the interaction of alkali metal atoms under the action of the signal to be measured, probe light, local oscillator signal, and coupling light with variable intensity. It mainly includes a photodetector, a transimpedance amplifier, an oscilloscope, a matched filter, etc. The transmitted light signal passing through the atomic cell is received by the photodetector, converted into a voltage signal by the transimpedance amplifier, observed and collected by the oscilloscope, and the broadband signal in the collected signal is filtered and amplified by the matched filter. Based on the research foundation of the superheterodyne atomic receiver, it can be known that the field to be measured changes the transmittance of the probe light through the atomic cell by coupling with the Rydberg energy level, so that the optical power of the probe light after passing through the atomic cell Satisfies:

[0039]

[0040] Among them, Is the incident power, Is the average transmittance, Is the transmittance gain coefficient, And Are the frequency difference and phase difference between the signal to be measured and the local oscillator signal respectively, corresponding to the signal frequency and phase received by the signal reception and processing module, Represents time. Is the Rabi frequency of the signal to be measured, and there is:

[0041]

[0042] Among them, Is the transition dipole moment, Is the reduced Planck constant, Is the electric field strength of the signal to be measured.

[0043] The role of the coupling light is to couple the atoms to the Rydberg energy level. Therefore, the higher the power of the coupling light, the more atoms can participate in the electromagnetically induced transparency (EIT) effect, and the stronger the EIT effect. It is reflected in the average transmittance Of the probe light of the superheterodyne atomic receiver,

[0044]

[0045] Among them, Is the transmittance-coupling light intensity proportionality coefficient, Is the transmittance without coupling light, and both can be determined through experiments, Represents the coupling light intensity variable.

[0046] In this system, taking the chirp signal as an example of the broadband pulse signal to modulate the coupled light, the envelope amplitude of the AOM drive signal with envelope modulation after mixing and amplification is as follows. Using to represent the chirp signal, only write the expression within one period as follows:

[0047]

[0048] where is the DC bias, is the amplitude of the chirp signal, f0 is the center frequency, k is the chirp rate, is the phase of the chirp signal.

[0049] Substituting equations (3), (6), and (7) into equation (4) together, the optical power P(t) of the probe light after passing through the atomic cell (i.e., the transmitted light) satisfies:

[0050]

[0051] where is the average transmittance only under the action of the coupled light modulation, is the drive signal control term, which is proportional to proportional.

[0052] Equation (8) contains four terms, denoted as M1, M2, M3, and M4 respectively, corresponding to the four influencing factors of the transmittance:

[0053]

[0054] The mixed-frequency signal M1 is the main signal to be detected in this scheme, that is, the transmitted light, whose amplitude is proportional to and thus also proportional to the electric field strength of the signal to be measured proportional. M2 is the superheterodyne signal term, which is not detected in this scheme. M3 is the drive signal control term, and M4 is the average transmittance only under the action of the coupled light modulation.

[0055] Using the product-to-sum formula to decompose the sum-frequency signal and difference-frequency signal respectively included in M1:

[0056]

[0057]

[0058] In this scheme, the transmitted detection optical signal received by the photodetector contains the chirp signal introduced by the coupled optical modulation module and the radio frequency signal of the Rydberg atom part. The mixed-frequency signal of the two can be decomposed into the sum-frequency signal and the difference-frequency signal through the product-to-sum and difference formulas.

[0059] By performing matched filtering on the signal, a broadband signal within one period can be converted into a pulse signal to achieve pulse compression. Taking the sum-frequency signal as an example, the impulse response of the matched filter is:

[0060]

[0061] The pulse height after matched filtering is proportional to the amplitude of the sum-frequency signal. Further, the electric field strength to be measured can be calculated based on the pulse height and Equation (5). Since the signal-to-noise ratio gain after matched filtering is related to the time-bandwidth product (TBP), the system signal-to-noise ratio can be improved by increasing the measurement time or the modulation bandwidth, enhancing the adaptability of the sensing system to the noise environment.

[0062] The signal flow of the coupled optical modulation module is as Figure 2 shown. The driving signal of the acousto-optic modulator is a single-frequency signal, which is mixed with a broadband signal with a DC bias to obtain an envelope-modulated driving signal. In Figure 2 , taking the chirp signal as an example, the frequency-domain and time-domain images of the envelope-modulated driving signal are respectively shown. The information of the broadband signal is carried in the envelope. After passing through the acousto-optic modulator, the information of the broadband signal is transferred to the coupled optical intensity, realizing the modulation of the coupled light.

[0063] In the superheterodyne scheme, the minimum detectable electric field is affected by the measurement time. As the measurement time increases, the minimum detectable electric field becomes smaller and the measurement accuracy is higher. The minimum detectable electric field decreases at a rate of with the measurement time. This scheme further explores the characteristics of the system. Through the broadband modulation of the coupled light, a signal gain in the frequency dimension is constructed by the method of pulse compression and filter matching.

[0064] In this scheme, the minimum detectable electric field is affected by the measurement time and the modulation bandwidth. As the measurement time T and the bandwidth increase, Figure 3 shows the variation of the electric field measurement sensitivity of this scheme (solid line) and the superheterodyne scheme (dashed line) with the bandwidth. Considering the improvement of the signal-to-noise ratio by pulse compression, the variation relationship of the sensitivity with the bandwidth is calculated. The intensity of the pulse-compressed signal is proportional to the time-bandwidth product TBP. Therefore, the signal-to-noise ratio is proportional to TBP, and the corresponding electric field strength is inversely proportional to The minimum detectable electric field decreases at a rate of The rate decreases with the measurement time. Therefore, for the same detection time, this method can detect weaker electric fields by increasing the modulation bandwidth, amplifying the signal further in the frequency dimension.

[0065] On the other hand, the present invention provides a Rydberg atom microwave electric field sensing method based on coupled optical modulation, which is applied to the aforementioned system. Specifically, it includes:

[0066] Using a Rydberg atom preparation module to excite alkali metal atoms to the Rydberg state;

[0067] Providing a local oscillator signal to the Rydberg atom preparation module;

[0068] Modulating the driving signal of the acousto-optic modulator with envelope modulation onto the coupled light to change the intensity of the coupled light entering the Rydberg atom preparation module;

[0069] Collecting the transmitted light signal passing through the Rydberg atom preparation module and performing matched filtering processing to extract microwave electric field information, where the transmitted light signal is generated by the alkali metal atoms under the combined action of the signal to be measured, the probe light, the local oscillator signal, and the coupled light with changed intensity.

[0070] In a third aspect, the present invention provides an electronic device, including: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned Rydberg atom microwave electric field sensing method based on coupled optical modulation.

[0071] In a fourth aspect, the present invention provides a computer-readable storage medium, on which executable instructions are stored, and when the instructions are executed by a processor, the processor can implement the aforementioned Rydberg atom microwave electric field sensing method based on coupled optical modulation.

[0072] The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A Rydberg atom microwave electric field sensing system based on coupled light modulation, characterized in that: include: Rydberg atom preparation module, used to excite alkali metal atoms to Rydberg states; A radio frequency module, used for providing a local oscillator signal to a Rydberg atom preparation module; A coupled light modulation module, used to modulate a broadband pulse signal onto the coupled light through an acousto-optic modulator, so as to change the intensity of the coupled light entering the Rydberg atom preparation module; Signal receiving and processing module: used to collect the transmitted light signal passing through the Rydberg atom preparation module and perform matched filtering processing to extract microwave electric field information. The transmitted light signal is generated by alkali metal atoms under the combined action of the signal to be measured, the detection light, the local oscillator signal, and the coupled light with changed intensity.

2. The Rydberg atom microwave electric field sensing system based on coupled light modulation according to claim 1, characterized in that: The radio frequency module includes a radio frequency microwave source and a radiation antenna. The local oscillator signal provided by the radio frequency microwave source is radiated to the Rydberg atom preparation module via the radiation antenna.

3. The Rydberg atom microwave electric field sensing system based on coupled light modulation according to claim 1, characterized in that: The coupled light modulation module comprises a function generator, a mixer, an amplifier and an acousto-optic modulator which are cascaded in sequence.

4. The Rydberg atom microwave electric field sensing system based on coupled light modulation according to claim 3 is characterized in that: The function generator generates two signals, one is a broadband pulse signal containing a DC bias, and the other is an AOM drive signal. After the two signals pass through a mixer, an envelope-modulated AOM drive signal is output. The envelope of the envelope-modulated AOM drive signal is a broadband pulse signal. The broadband pulse signal acts on the broadband modulation of the coupled light through an amplifier and an acousto-optic modulator.

5. The Rydberg atom microwave electric field sensing system based on coupled light modulation according to claim 4, characterized in that: The envelope amplitude of the envelope modulated AOM driving signal The expression is: in, is the DC bias, represents a broadband pulse signal, Indicates time.

6. The Rydberg atom microwave electric field sensing system based on coupled light modulation according to claim 5, characterized in that: The transmitted light signal power satisfy: in, is the incident power, is the transmittance-coupled light intensity ratio coefficient, is the coupled light intensity before entering the AOM, is the 0-level light intensity-driving voltage proportionality coefficient, It is the 0-level light intensity when there is no driving voltage. is the transmittance without coupled light, is the transmittance gain coefficient, is the Rabi frequency of the signal to be measured, and are the frequency difference and phase difference between the signal to be measured and the local oscillator signal, is the average transmittance under the effect of coupled light modulation only, is the driving signal control term, and is proportional to; Formula (8) is decomposed into four terms, recorded as M1, M2, M3, and M4, corresponding to the four factors affecting transmittance: Where, the mixing signal M1 is the transmitted light signal term, and its amplitude and Proportional to the transmission rate, M2 is the superheterodyne signal term, M3 is the driving signal control term, and M4 is the average transmittance under the coupling light modulation only.

7. The Rydberg atom microwave electric field sensing system based on coupled light modulation according to claim 1, characterized in that: The signal receiving and processing module includes a photodetector, a transimpedance amplifier, an oscilloscope, and a matched filter. The transmitted light signal passing through the atomic gas chamber is received by the photodetector, converted into a voltage signal by the transimpedance amplifier, and enters the matched filter after being observed and collected by the oscilloscope.

8. A Rydberg atom microwave electric field sensing method based on coupled light modulation, characterized in that: include: Use the Rydberg atom preparation module to excite alkali metal atoms to Rydberg states; Provide local oscillator signal to the Rydberg atom preparation module; The broadband pulse signal is modulated onto the coupling light through an acousto-optic modulator to change the intensity of the coupling light entering the Rydberg atom preparation module; The transmitted light signal passing through the Rydberg atom preparation module is collected and matched filtering is performed to extract the microwave electric field information. The transmitted light signal is generated by the alkali metal atoms under the combined action of the signal to be measured, the detection light, the local oscillator signal, and the coupled light with changed intensity.

9. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; Wherein, when one or more programs are executed by the one or more processors, the one or more processors implement the Rydberg atom microwave electric field sensing method based on coupled light modulation as described in claim 8.

10. A computer-readable storage medium, characterized in that: Executable instructions are stored thereon, and when the instructions are executed by the processor, the processor can implement the Rydberg atom microwave electric field sensing method based on coupled light modulation as described in claim 8.

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