A microwave precision detection method based on transmission-enhanced spectroscopy without population inversion

Abstract

The present invention discloses a microwave precision detection method based on the transmission enhancement spectrum without particle number inversion, which belongs to the field of microwave quantum detection technology. This method abandons the electromagnetic induced transparency mechanism that traditional atomic microwave electric field meters rely on, and realizes the transmission field enhancement effect without particle number inversion conditions through periodic coupling of pulsed light, thereby generating a transmission spectrum. The linear relationship between the peak-to-peak spacing of the medium transmission spectrum and the microwave field intensity is utilized to achieve precise detection of the microwave field. Compared with traditional technologies, the present invention significantly compresses the spectral line width of the transmitted light, greatly improves the sensitivity and accuracy of the measurement, and shows broad application potential. In addition, the present invention provides a new generation mechanism for the design of atomic microwave electric field meters, opening up a new path for the development of microwave electric field precision detection technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave quantum detection, and in particular relates to a microwave precision detection method based on transmission enhancement spectroscopy without population inversion. Background Art

[0002] Traditionally, microwave electric field measurements have relied on dipole antennas, but this approach has several limitations. Dipole antennas are typically made of metal and utilize metal transmission lines, which can cause interference between the microwave field being measured and the conductive material involved. While spatial resolution can be improved by reducing probe size, this approach still cannot achieve subwavelength measurements.

[0003] Rydberg atoms are extremely sensitive to external electromagnetic fields and therefore show great potential in achieving high-precision measurements of microwave electric fields. Traditional microwave electric field meters based on Rydberg atoms mainly rely on the electromagnetically induced transparency spectrum generated by the interaction of continuous detection fields and coupling fields with Rydberg atoms. When a microwave field is applied on this basis, the electromagnetically induced transparency spectrum will undergo peak-to-peak splitting, and the peak-to-peak spacing between the two transmission spectra is proportional to the microwave field intensity, thereby achieving precise measurement of the microwave field. However, the spectral line width of the electromagnetically induced transparency spectrum is relatively wide, which limits the accuracy and sensitivity of the measurement. Therefore, researchers usually need to use the resonant cavity method, grating method or superheterodyne method to further compress the spectral line width.

[0004] The Rydberg atom microwave electric field precision detection scheme disclosed in this invention differs significantly from conventional Rydberg atom electric field meters in its operating principle. Instead of relying on the electromagnetically induced transparency effect, the present invention utilizes the population-inversion-free transmission enhancement spectrum induced by the coherence of the sideband radiation field and the detection field to achieve microwave electric field quantum precision measurement. Compared with conventional Rydberg atom electric field meters, the present invention achieves a narrower transmission spectrum linewidth, significantly improving the accuracy and sensitivity of microwave field detection. This improvement not only enhances measurement accuracy but also broadens the application prospects of microwave quantum precision detection technology. Summary of the Invention

[0005] In response to the above-mentioned problems existing in the prior art, the present invention proposes a microwave precision detection method based on transmission enhancement spectroscopy without population inversion, which has a reasonable design, solves the shortcomings of the prior art and has good effects.

[0006] A microwave precision detection method based on transmission enhancement spectroscopy without population inversion comprises the following steps:

[0007] Step 1: Build a detection system, which includes An atomic gas cell, a frequency-stabilized laser system, a microwave horn antenna, a signal generator, a photodetector, a spectrum analyzer, an electro-optical modulator, two lenses, and a half-wave plate. The frequency-stabilized laser system includes a detection field laser and a coupling field laser.

[0008] Step 2: The output end of the detection field laser is connected to the electro-optical modulator through an optical fiber, and the output end of the coupling field laser is connected to the signal generator through an optical fiber. The detection light and the coupling light are The atoms pass through the gas chamber in opposite directions to form a detection field and a coupling field. The microwave horn antenna is used to generate the microwave field to be measured;

[0009] Step 3: modulate the detection field detuning through an electro-optical modulator, and detect the detection field transmission spectrum using a photodetector and a spectrum analyzer;

[0010] Step 4: Use the linear relationship between the peak-to-peak spacing of the detection field enhancement transmission spectrum and the microwave electric field intensity to achieve precise detection of the microwave field.

[0011] Furthermore, in the step 2, the detection light emitted by the detection field laser passes through the electro-optic modulator, the first lens, the first half-wave plate, The atomic gas chamber and the second lens are then input to the photoelectric detector, which performs photoelectric conversion and then inputs it to the spectrum analyzer; the coupling light emitted by the coupling field laser passes through the signal generator and the second half-wave plate, the second lens, Atomic gas cell, first half-wave plate and first lens.

[0012] Furthermore, the lasers output by the detection field laser and the coupling field laser are both continuous light with wavelengths of 480 nm and 780 nm, respectively. The continuous coupling light is modulated into a periodic laser pulse chain by a signal generator, and its pulse waveform, single pulse height and half-maximum full width, and the distance between two adjacent pulses are all adjustable.

[0013] Furthermore, the microwaves generated by the horn antenna pass through the Atomic gas chamber, detecting fields and states 、 Phase coupling, coupled field and state 、 Phase coupling, microwave field and state 、 Phase coupling.

[0014] Furthermore, in the step 4, a linear relationship between the peak-to-peak spacing of the detection field enhanced transmission spectrum and the microwave electric field intensity is obtained by pre-calibration, thereby realizing the detection of the microwave electric field intensity.

[0015] Beneficial technical effects brought about by the present invention:

[0016] The microwave quantum precision detection method based on Rydberg atoms involved in this invention fundamentally differs from the operating principle of traditional Rydberg atom microwave electric field meters. Its operating mechanism is not based on electromagnetically induced transparency, but rather on the population inversion-free transmission enhancement spectrum caused by the coherence of the sideband radiation field and the detection field. The beneficial technical effects brought about by this invention are as follows:

[0017] 1. High-sensitivity detection: This method significantly improves the detection sensitivity of microwave electric fields through the non-particle number inversion transmission spectrum enhancement technology, and can detect very weak microwave electric fields.

[0018] 2. High-precision measurement: By utilizing the linear relationship between the peak-to-peak spacing of the transmission enhancement spectrum and the microwave electric field intensity, this method can achieve high-precision measurement of the microwave electric field intensity.

[0019] 3. Wide-band measurement capability: The present invention does not rely on a specific frequency, so it can achieve wide-band microwave electric field measurement, covering a wide range of applications from low frequency to high frequency.

[0020] 4. Strong anti-interference ability: Due to the high sensitivity of Rydberg atoms to external fields, the present invention can reduce the interference of conductive materials on the measurement and improve the accuracy of the measurement.

[0021] 5. Self-calibration capability: The Rydberg atomic electric field meter can be traced back to basic physical constants and can use atomic parameters for self-calibration, reducing the complexity and uncertainty of the calibration process.

[0022] 6. Sub-wavelength electric field imaging: The present invention can also measure the polarization direction of the microwave electric field, realize sub-wavelength electric field imaging, and provide more precise measurement of the spatial distribution of the microwave field.

[0023] 7. System stability and repeatability: Through regular calibration and digital signal processing, the present invention improves the measurement accuracy and stability of the system and ensures the repeatability of the measurement results.

[0024] 8. Flexibility and adjustability: The pulse shape, modulation depth and frequency of the periodic laser pulse train can be adjusted according to actual detection requirements, making this method highly flexible and adaptable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the detection system of the present invention;

[0026] Among them, 1- Atomic gas chamber; 2-detection field laser; 3-coupled field laser; 4-microwave horn antenna; 5-signal generator; 6-photodetector; 7-spectrum analyzer; 8-electro-optic modulator; 9-first lens; 10-second lens; 11-first half-wave plate; 12-second half-wave plate;

[0027] Figure 2 is the microwave field intensity Set to 0, and the detection field and coupling field are detuned and Under the condition that both are 0, the imaginary part of the dielectric polarizability Over time A graph showing the relationship between changes;

[0028] Figure 3 The microwave field intensity is 0, the coupling field is detuned When the medium transmission spectrum is 0, Detuning with the detection field and time Change relationship diagram;

[0029] Figure 4 The microwave field intensity Set to 0.5×2π MHz, the coupling field is detuned When the medium transmission spectrum is detuned with the detection field, and time Change relationship diagram;

[0030] Figure 5 The peak spacing of the enhanced spectrum is the medium transmission and microwave field strength Linear relationship diagram between

[0031] Figure 6 is the medium transmission spectrum T detuned with the detection field Change relationship diagram; DETAILED DESCRIPTION

[0032] The specific implementation of the present invention will be further described below with reference to specific embodiments:

[0033] Traditional atomic microwave electric field meters based on Rydberg atoms mostly use continuous light or long-pulsed lasers as the probe and coupling fields. For a three-level ladder-shaped atomic system, when the transition between the two lower energy levels (the ground state and the excited state) matches the frequency of the probe light, the atoms absorb the light and become opaque. When a strong coupling light field acts on the transition between the excited and Rydberg states, it causes electrons to transition back and forth between the two energy levels, forming a coherent state. This coherence effect prevents the probe light, which would otherwise be absorbed, from being absorbed, rendering the medium transparent to light of that frequency. This phenomenon is known as electromagnetically induced transparency. Traditional atomic microwave electric field meters rely on electromagnetically induced transparency to achieve precise measurements of microwave electric fields.

[0034] The present invention uses a pulse laser chain with adjustable pulse width, pulse spacing and pulse shape as the coupling field. When the coupling field is turned off, the ground state Some particles on the surface are excited to excited states through single photon resonant transitions. When the strong coupling field is turned on, the coupled excited state and Rydberg states , and two new dressed states are generated. At this time, the ground state The particles on the 、 Particles on the energy level will return to the ground state due to the sideband effect The sideband radiation is coherently enhanced with the detection field, producing a transmission enhancement spectrum without population inversion. The present invention utilizes this enhanced transmission spectrum to achieve quantum precision detection of microwave electric fields. A microwave precision detection method based on the transmission enhancement spectrum without population inversion includes the following steps:

[0035] Step 1: Build a detection system, such as Figure 1 As shown, the detection system includes The atomic gas cell 1, the frequency-stabilized laser system, the microwave horn antenna 4, the signal generator 5, the photodetector 6, the spectrum analyzer 7, the electro-optical modulator 8, two lenses and a half-wave plate. The frequency-stabilized laser system includes a detection field laser 2 and a coupling field laser 3. These components together constitute the experimental platform of the present invention, which is used to achieve precise detection of microwave electric fields.

[0036] Step 2: The output end of the detection field laser 2 is connected to the electro-optical modulator 8 through an optical fiber, and the output end of the coupling field laser 3 is connected to the signal generator 5 through an optical fiber. The detection light and the coupling light are connected in The atoms pass through the gas chamber 1 in opposite directions to form a detection field and a coupling field. The microwave horn antenna 4 is used to generate the microwave field to be measured;

[0037] Step 3: The detection field is detuned by the electro-optical modulator 8, and the transmission spectrum of the detection field is detected using the photodetector 6 and the spectrum analyzer 7. This step is the key to achieving precise detection of the microwave electric field. By adjusting the detuning amount, the detection effect of the detection light transmission spectrum can be optimized.

[0038] Step 4: Utilize the linear relationship between the peak-to-peak spacing of the detection field enhancement transmission spectrum and the microwave electric field intensity to achieve precise detection of the microwave field. This step embodies the core advantage of the present invention, namely, achieving high-precision measurement of microwave electric field intensity by precisely controlling the detuning amount.

[0039] The physical mechanism of this microwave quantum precision detection method is the transmission enhancement spectrum without particle number inversion caused by the coherence of the sideband radiation field and the detection field. This mechanism is different from the traditional Rydberg atomic electric field meter.

[0040] Specifically, in the detection system, photodetectors and spectrum analyzers are used as detection tools. Other detection tools such as oscilloscopes and single-photon detectors can also be selected. In actual use, the detection system is calibrated regularly to maintain the measurement accuracy and stability of the system.

[0041] Specifically, in step 2, the detection light emitted by the detection field laser 2 passes through the electro-optic modulator 8, the first lens 9, the first half-wave plate 11, The atomic gas chamber 1 and the second lens 10 are then input to the photodetector 6, which performs photoelectric conversion and then inputs the light to the spectrum analyzer 7; the coupled light emitted by the coupled field laser 3 passes through the signal generator 5 and the second half-wave plate 12, the second lens 10, Atomic gas cell 1, first half-wave plate 11 and first lens 9.

[0042] Specifically, the lasers output by the detection field laser 2 and the coupling field laser 3 are both continuous light with wavelengths of 480 nm and 780 nm, respectively. The continuous coupling light is modulated by the signal generator 5 into a periodic laser pulse chain. Its pulse waveform (such as Gaussian, step type, etc.), single pulse height and half-maximum full width, the distance between two adjacent pulses and other parameters are all adjustable. This modulation method provides the necessary time structure for subsequent detection.

[0043] Specifically, The atomic gas chamber is used to provide the detection medium for the microwave electric field to be measured. Atomic gas chamber 1 87 Rb atoms adopt four energy levels Atom, its state 、 、 and Respectively represent Atomic 、 、 and Four energy levels, energy levels Adjust according to the frequency of the microwave field to be measured. The detection light and the coupling light pass through the atomic gas chamber in opposite directions, while the microwaves generated by the horn antenna pass through the atomic gas chamber perpendicular to the light path. and Phase coupling, coupled field and state and Phase coupling, microwave field and state and Phase coupling. Detuning of detection field, coupling field and microwave field ( , and ) and intensity ( , and ) are characterized. Under such conditions, the atomic medium polarizability It can be expressed as:

[0044]

[0045] In the above formula, is the atomic density, is the dielectric constant of vacuum, , and ,in Represents atoms Under this condition, the atomic medium transmission spectrum function It can be expressed as:

[0046]

[0047] in, is the frequency of the detection field, is the length of the atomic gas cell, is the imaginary part of the dielectric polarizability, is the speed of light in free space.

[0048] In the simulation of this embodiment, the detection field strength is set to , the coupled light intensity changes with time, given by Given, where represents the amplitude of the coupled pulse light, and is the duration of a single pulse. The atomic gas chamber, whose spatial length is set to , atomic 、 、 The decay rates of the energy levels are set as 、 、 The simulation results reveal the following phenomena:

[0049] When the microwave field is off: When the detection field and the coupling field are in resonance (i.e. ), the imaginary part of the dielectric polarizability As time evolves, periodic negative values ​​will appear, such as Figure 2 This indicates that negative absorption of the detection field can be observed in a specific time period. The corresponding atomic medium transmission enhancement spectrum distribution is shown in Figure 3 As shown in the figure, it can be clearly seen that when the detection field resonates (i.e. ), a periodic transmission enhancement spectrum without population inversion will appear.

[0050] When the microwave field is turned on: When the microwave field acts between two Rydberg energy levels of an atom, it will cause the corresponding Rydberg energy levels to undergo Autler-Townes (AT) splitting. This AT splitting phenomenon of energy levels will induce the non-particle inversion transmission enhancement spectrum at the resonant excitation of the detection field to split. Specifically, Figure 4 As shown, when the microwave field intensity is set to When the coupling field is detuned When is 0, the transmission enhancement spectrum originally at the resonance excitation of the detection field splits into two transmission spectra, and the peak-to-peak spacing of the two transmission spectra is 0.5×2π MHz. By changing the intensity of the microwave field, it can be observed that the peak-to-peak spacing of the two transmission enhancement spectra without population inversion is proportional to the microwave field intensity, as shown in Figure 2. Figure 5 This figure not only intuitively presents the direct connection between the two, but also provides a theoretical basis for using this linear relationship for quantum precision detection of microwave electric fields. By precisely measuring the peak-to-peak spacing of the medium transmission spectrum, the intensity of the microwave field can be accurately inferred, thereby achieving high-precision quantum detection of the microwave electric field intensity.

[0051] Further simulation results show that the microwave field intensity Set to 0.5×2π MHz, and the coupling field is detuned When is 0, Figure 6 As shown, the full-width at half-maximum (FWHM) of the transmission enhancement spectrum in this scheme is significantly reduced compared to the FWHM of the transmission spectrum in a conventional Rydberg atom-based microwave detection scheme under the same conditions (when the coupling field is replaced with continuous light and the maximum amplitude is maintained unchanged), becoming only one-third of the latter. Under the same conditions, that is, when the coupling field is replaced with continuous light and the maximum amplitude is maintained unchanged, this invention can significantly improve the accuracy and sensitivity of microwave quantum precision detection. This improvement not only enhances measurement accuracy but also broadens the application prospects of microwave quantum precision detection technology.

[0052] In step 4, the linear relationship is obtained through pre-calibration to ensure the measurement accuracy of the microwave electric field intensity. The linear relationship between the peak-to-peak distance between the two non-particle population inversion transmission enhancement spectra and the microwave electric field intensity is expressed as: ,in is the peak spacing of the medium transmission enhancement spectrum, is the proportionality coefficient, is the intensity of the microwave field to be measured.

[0053] In summary, this embodiment achieves high-sensitivity and high-precision detection of microwave electric fields by precisely controlling the intensity and time characteristics of the detection field and the coupling field, and utilizing the characteristics of Rydberg atoms, demonstrating the significant advantages of the present invention in the field of microwave quantum precision measurement.

[0054] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A microwave precision detection method based on transmission enhancement spectroscopy without population inversion, characterized in that: The following steps are involved: Step 1: Build a detection system, which includes An atomic gas cell, a frequency-stabilized laser system, a microwave horn antenna, a signal generator, a photodetector, a spectrum analyzer, an electro-optical modulator, two lenses, and a half-wave plate. The frequency-stabilized laser system includes a detection field laser and a coupling field laser. Step 2: The output end of the detection field laser is connected to the electro-optical modulator through an optical fiber, and the output end of the coupling field laser is connected to the signal generator through an optical fiber. The detection light and the coupling light are The atoms pass through the gas chamber in opposite directions to form a detection field and a coupling field. The microwave horn antenna is used to generate the microwave field to be measured; Step 3: modulate the detection field detuning through an electro-optical modulator, and detect the detection field transmission spectrum using a photodetector and a spectrum analyzer; Step 4: Utilize the linear relationship between the peak-to-peak spacing of the detection field enhancement transmission spectrum and the microwave electric field intensity to achieve precise detection of the microwave field; The lasers output by the detection field laser and the coupling field laser are both continuous light with wavelengths of 480 nm and 780 nm respectively. The continuous coupling light is modulated by a signal generator into a periodic laser pulse train, and its pulse waveform, single pulse height and half-maximum full width, and the distance between two adjacent pulses are all adjustable; When the coupling field is turned off, the ground state Some particles on the surface are excited to excited states through single photon resonant transitions. , when the strong coupling field is turned on, its coupled excited state and Rydberg states , and two new dressed states are generated. At this time, the ground state The particles on the 、 Particles on the energy level will return to the ground state due to the sideband effect , the sideband radiation is coherently enhanced with the detection field, producing a transmission enhancement spectrum without population inversion; Atomic gas chamber 1 87 Rb atoms adopt four energy levels Atom, its state 、 、 and Respectively represent Atomic 、 、 and Four energy levels.

2. The microwave precision detection method based on transmission enhancement spectroscopy without population inversion according to claim 1 is characterized in that: In the step 2, the detection light emitted by the detection field laser passes through the electro-optic modulator, the first lens, the first half-wave plate, The atomic gas chamber and the second lens are then input to the photoelectric detector, which performs photoelectric conversion and then inputs it to the spectrum analyzer; the coupling light emitted by the coupling field laser passes through the signal generator and the second half-wave plate, the second lens, Atomic gas cell, first half-wave plate and first lens.

3. The microwave precision detection method based on transmission enhancement spectroscopy without population inversion according to claim 2 is characterized in that: The microwaves generated by the horn antenna pass through the Atomic gas chamber, detecting fields and states 、 Phase coupling, coupled field and state 、 Phase coupling, microwave field and state 、 Phase coupling.

4. The microwave precision detection method based on transmission enhancement spectroscopy without population inversion according to claim 3 is characterized in that: In the step 4, a linear relationship between the peak-to-peak spacing of the detection field enhanced transmission spectrum and the microwave electric field intensity is obtained through pre-calibration, thereby realizing the detection of the microwave electric field intensity.

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