Atomic spin low-noise high-bandwidth magnetic field measurement method and atomic magnetometer

Abstract

The application provides an atomic spin low-noise high-bandwidth magnetic field measurement method and an atomic magnetometer, and comprises the following steps: driving light working current I Q0 The high-frequency current micro-perturbation is superimposed on the top; under the driving light current modulation, the atomic spin optical frequency shift generates a disturbance, and the frequency f1 optical frequency shift modulation is realized; the optical frequency is detected by scanning the detection light current, and the spin precession signal phase disturbance amplitude A is calculated in real time; when A is maximum, the atomic magnetometer sensitivity is optimal; the atomic magnetometer is kept in the state of optimal sensitivity through the closed-loop control of the detection light frequency; the spin precession signal extracted by the detection light is locked at 90° phase in a closed loop, and the atomic spin low-noise high-bandwidth magnetic field measurement is realized. The technical scheme of the application is used to solve the technical problems that there is a lack of small-size atomic magnetometer linearly polarized detection light frequency sensing means in the prior art, and the atomic magnetometer magnetic field noise and measurement bandwidth are easily degraded due to the detection light frequency drift in the actual application environment.

Description

Technical Field

[0001] This invention relates to the field of atomic magnetometer technology, and in particular to a method for measuring low-noise, high-bandwidth magnetic fields of atomic spin and an atomic magnetometer. Background Technology

[0002] An atomic magnetometer is a sensor that measures magnetic fields by utilizing the Larmor precession of atomic spins in an external magnetic field. It features high sensitivity, insensitivity to magnetic field direction, and a stable scaling factor, and has been widely used in various fields of magnetic field measurement.

[0003] There are two main methods for detecting atomic spin: circularly polarized driven beam absorption characteristics detection and linearly polarized beam polarization characteristics detection. Figure 1 , Figure 2 As shown in the figure, the detection method based on circularly polarized beams is simple to implement and is therefore widely used in small-volume atomic magnetometers. However, this method suffers from low sensitivity and poor stability, limiting further performance improvements in small-volume atomic magnetometers. The detection method based on linearly polarized beams offers high sensitivity and is widely used in various ultra-high sensitivity atomic magnetometers. However, small-volume atomic magnetometers use small semiconductor lasers as light sources, which require stable wavelength control through temperature and current. Since small-volume atomic magnetometers lack wavelength sensing capabilities for linearly polarized beams, and the wavelength of a linearly polarized beam must be maintained within a certain narrow range to ensure low-noise, high-bandwidth detection of atomic spins, the precision requirements for light source temperature control are stringent, leading to noise degradation in various practical dynamic applications. Therefore, a method for measuring low-noise, high-bandwidth magnetic fields using atomic spins is urgently needed. Summary of the Invention

[0004] This invention provides a method for measuring low-noise, high-bandwidth magnetic fields of atomic spin and an atomic magnetometer, which can solve the technical problems of the lack of small-volume atomic magnetometers with linear polarization detection light frequency sensing means, and the easy degradation of magnetic field noise and measurement bandwidth of atomic magnetometers due to detection light frequency drift in practical application environments.

[0005] According to one aspect of the present invention, a method for measuring low-noise, high-bandwidth magnetic fields of atomic spin is provided. The method includes: Step 1, under the driving photocurrent I... Q0 The superimposed high-frequency current perturbation, i.e., I Q =I Q0 +I1·sin2πf1t, where I1 is the amplitude of the driving photocurrent perturbation, f1 is the frequency of the driving photocurrent perturbation, f1 is greater than the measurement bandwidth of the atomic magnetometer and less than the atomic spin magnetic resonance linewidth, I QThe process involves three steps: First, a driving photocurrent is superimposed after high-frequency current perturbation. Under the modulation of the driving photocurrent, the atomic spin optical frequency shift is disturbed, achieving optical frequency shift modulation at a frequency of f1. Second, since the optical frequency shift modulation frequency f1 is greater than the magnetic field measurement bandwidth of the atomic magnetometer, the phase of the spin precession signal extracted by the detection light is disturbed at a frequency of the optical frequency shift modulation frequency f1. The optical frequency is detected by scanning the detection photocurrent, and the amplitude A of the spin precession signal phase disturbance is calculated in real time. When A is at its maximum, the atomic magnetometer has the optimal sensitivity. The atomic magnetometer is kept in the optimal sensitivity state by closed-loop control of the detection light frequency. Third, the spin precession signal extracted by the detection light is locked at a 90° phase in the closed loop to achieve low-noise, high-bandwidth magnetic field measurement of atomic spin.

[0006] Furthermore, step two specifically includes: detecting the operating current I. J0 The superimposed high-frequency current perturbation, i.e., I J =I J0 +I2·sin2πf2t, where I2 is the amplitude of the detected photocurrent perturbation and f2 is the frequency of the detected photocurrent perturbation; the phase perturbation amplitude A of the spin precession signal is calculated in real time; the operating temperature of the detection light is dynamically adjusted so that I J =I J0 At the same time point ±I2, the amplitude of the spin precession signal phase disturbance A is the largest, and the atomic magnetometer has the best sensitivity.

[0007] Furthermore, the detection frequency of the photocurrent perturbation, f2, is f2 = 0.5f1.

[0008] Furthermore, the optical frequency shift is Among them, B LS For optical frequency shift, r e Let be the electron radius, c be the speed of light, and φ be the photon flux. For circular polarization degree, γ e V is the electron gyromagnetic ratio, V(ν-ν0) is the spectral type, ν is the driving light frequency, and ν0 is the light frequency corresponding to the atomic energy level transition.

[0009] Furthermore, in step two, the phase of the spin precession signal is disturbed at a frequency equal to the optical frequency shift modulation frequency f1. The phase of the disturbance.

[0010] According to another aspect of the present invention, an atomic magnetometer is provided, which performs atomic spin low-noise high-bandwidth magnetic field measurement using the atomic spin low-noise high-bandwidth magnetic field measurement method described above.

[0011] The present invention provides a method for measuring low-noise, high-bandwidth magnetic fields of atomic spins. This method modulates a circularly polarized driving photocurrent and actively applies a light frequency shift characteristic signal to achieve real-time sensing of the atomic spin detection frequency. It locks the detection light at the state of optimal spin detection sensitivity, thus realizing the measurement of low-noise, high-bandwidth magnetic fields of atomic spins. This invention does not introduce additional structures or components and is particularly suitable for small-volume atomic magnetometers. Attached Figure Description

[0012] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0013] Figure 1 A schematic diagram illustrating the principle of detecting the absorption characteristics of a circularly polarized driven beam is shown.

[0014] Figure 2 A schematic diagram illustrating the principle of linear polarization detection beam polarization characteristics is shown. Detailed Implementation

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0017] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0018] According to a specific embodiment of the present invention, a method for measuring low-noise, high-bandwidth magnetic fields of atomic spin is provided. This method includes: Step 1, under a driving photocurrent I... Q0 The superimposed high-frequency current perturbation, i.e., I Q =I Q0 +I1·sin2πf1t, where I1 is the amplitude of the driving photocurrent perturbation, f1 is the frequency of the driving photocurrent perturbation, f1 is greater than the measurement bandwidth of the atomic magnetometer and less than the atomic spin magnetic resonance linewidth, I Q The process involves three steps: First, a driving photocurrent is superimposed after high-frequency current perturbation. Under the modulation of the driving photocurrent, the atomic spin optical frequency shift is disturbed, achieving optical frequency shift modulation at a frequency of f1. Second, since the optical frequency shift modulation frequency f1 is greater than the magnetic field measurement bandwidth of the atomic magnetometer, the phase of the spin precession signal extracted by the detection light is disturbed at a frequency of the optical frequency shift modulation frequency f1. The optical frequency is detected by scanning the detection photocurrent, and the amplitude A of the spin precession signal phase disturbance is calculated in real time. When A is at its maximum, the atomic magnetometer has the optimal sensitivity. The atomic magnetometer is kept in the optimal sensitivity state by closed-loop control of the detection light frequency. Third, the spin precession signal extracted by the detection light is locked at a 90° phase in the closed loop to achieve low-noise, high-bandwidth magnetic field measurement of atomic spin.

[0019] This configuration provides a method for measuring low-noise, high-bandwidth magnetic fields of atomic spins. This method modulates a circularly polarized driving photocurrent to actively apply a light frequency shift characteristic signal, achieving real-time sensing of the atomic spin detection frequency. It locks the detection light at the optimal spin detection sensitivity, thus realizing low-noise, high-bandwidth magnetic field measurement of atomic spins. This invention does not introduce additional structures or components, making it particularly suitable for small-volume atomic magnetometers.

[0020] Specifically, in this invention, the interaction between the driving light and the atomic spin causes the atom to experience a spurious magnetic field, known as optical frequency shift, which is... Among them, B LS For optical frequency shift, r e Let be the electron radius, c be the speed of light, and φ be the photon flux. For circular polarization degree, γ e Here, V(ν-ν0) represents the electron gyromagnetic ratio, ν is the spectral type, ν is the driving light frequency, and ν0 is the light frequency corresponding to the atomic energy level transition. The optical frequency shift formula indicates that the optical frequency shift varies with parameters such as the driving light frequency and intensity; fluctuations in these parameters will cause perturbations in the optical frequency shift. Therefore, by modulating the driving photocurrent, the frequency and power of the driving light are perturbed, thereby generating an optical frequency shift signal for real-time sensing of atomic spin detection sensitivity.

[0021] Since the optical frequency shift modulation frequency f1 is greater than the magnetic field measurement bandwidth of the atomic magnetometer, the phase of the spin precession signal extracted by the detection light is disturbed at a frequency of the optical frequency shift modulation frequency f1. The optical frequency is detected by scanning the photocurrent, and the amplitude A of the spin precession signal phase disturbance is calculated in real time. When A is the maximum, the atomic magnetometer has the optimal sensitivity. By controlling the detection light frequency in a closed loop, the atomic magnetometer is kept in the state of optimal sensitivity.

[0022] In this invention, step two specifically includes: detecting the operating current I. J0 The superimposed high-frequency current perturbation, i.e., I J =I J0 +I2·sin2πf2t, where I2 is the amplitude of the detected photocurrent perturbation and f2 is the frequency of the detected photocurrent perturbation; the phase perturbation amplitude A of the spin precession signal is calculated in real time; the operating temperature of the detection light is dynamically adjusted so that I J =I J0 At the same time (±I2), the amplitude of the spin precession signal phase perturbation A is the largest, and the atomic magnetometer sensitivity is optimal. In a specific embodiment of the invention, the photocurrent perturbation frequency f2 is f2 = 0.5f1. In step two, the spin precession signal phase is perturbed at a frequency equal to the optical frequency shift modulation frequency f1. The phase of the disturbance.

[0023] According to another aspect of the present invention, an atomic magnetometer is provided that performs atomic spin low-noise high-bandwidth magnetic field measurement using the atomic spin low-noise high-bandwidth magnetic field measurement method described above.

[0024] This configuration provides an atomic magnetometer that uses the atomic spin low-noise, high-bandwidth magnetic field measurement method provided in this invention to measure atomic spin low-noise, high-bandwidth magnetic fields. This method modulates a circularly polarized driving photocurrent and actively applies a light frequency shift characteristic signal to achieve real-time sensing of the atomic spin detection frequency, locking the detection light at the optimal spin detection sensitivity, thus realizing the measurement of atomic spin low-noise, high-bandwidth magnetic fields. This invention does not introduce additional structures or components, making it particularly suitable for small-volume atomic magnetometers. Therefore, applying the atomic spin low-noise, high-bandwidth magnetic field measurement method provided in this invention to atomic magnetometers can greatly improve their performance.

[0025] To gain a further understanding of the present invention, the method for measuring low-noise, high-bandwidth atomic spin magnetic fields provided by the present invention will be described in detail below.

[0026] This invention achieves real-time sensing of atomic spin detection sensitivity by modulating a circularly polarized driving photocurrent and actively applying a light frequency shift characteristic signal. Furthermore, by modulating the detection light source current, the detection light is locked at the state with optimal spin detection sensitivity. The specific implementation steps are as follows:

[0027] Step 1: Optical Frequency Shift Modulation

[0028] The interaction between driving light and atomic spins causes the atoms to experience a spurious magnetic field, known as a light frequency shift.

[0029]

[0030] In equation (1), B LS For optical frequency shift, r e Let be the electron radius, c be the speed of light, and φ be the photon flux. For circular polarization degree, γ e Let V(ν-ν0) be the electron gyromagnetic ratio, V(ν-ν0) be the spectral type, ν be the driving light frequency, and ν0 be the light frequency corresponding to the atomic energy level transition. Equation (1) indicates that the optical frequency shift changes with parameters such as the driving light frequency and light intensity, and fluctuations in these parameters will cause disturbances in the optical frequency shift. Therefore, by modulating the driving photocurrent, the frequency and power of the driving light are disturbed, thereby generating an optical frequency shift signal for real-time sensing of atomic spin detection sensitivity. The specific steps are as follows:

[0031] (1.1) In the driving light operating current I Q0 The superimposed high-frequency current perturbation, i.e., I Q =I Q0 +I1·sin2πf1t, where I1 is the amplitude of the driving photocurrent perturbation, f1 is the frequency of the driving photocurrent perturbation, and f1 should be greater than the measurement bandwidth of the atomic magnetometer and less than the atomic spin magnetic resonance linewidth.

[0032] (1.2) Under the modulation of the driving photocurrent, the atomic spin optical frequency shift generates a disturbance, realizing optical frequency shift modulation with a frequency of f1.

[0033] Step 2: Detect optical frequency closed loop

[0034] An atomic magnetometer achieves closed-loop magnetic resonance by locking the spin precession signal extracted from the detection light at a 90° phase. Because the optical frequency shift modulation frequency f1 is greater than the magnetic field measurement bandwidth of the atomic magnetometer, the phase of the spin precession signal extracted from the detection light is perturbed by a frequency equal to the optical frequency shift modulation frequency f1. The atomic magnetometer's sensitivity is optimal when the photocurrent is detected and the optical frequency is scanned, and the phase perturbation amplitude A of the spin precession signal is calculated in real time. Closed-loop control based on the detected optical frequency can maintain the atomic magnetometer in its optimal sensitivity state. The specific steps are as follows:

[0035] (2.1) Detecting the operating current I J0 The superimposed high-frequency current perturbation, i.e., I J =I J0 +I2·sin2πf2t, where I2 is the amplitude of the detected photocurrent perturbation and f2 is the frequency of the detected photocurrent perturbation, which can be set to f2=0.5f1;

[0036] (2.2) Calculate the phase perturbation amplitude A of the spin precession signal in real time;

[0037] (2.3) Dynamically adjust the working temperature of the detection light to make I J =I J0 At the same time point ±I2, the amplitude of the spin precession signal phase disturbance A is the largest, and the atomic magnetometer has the best sensitivity.

[0038] Step 3: Measurement of low-noise, high-bandwidth magnetic fields of atomic spins

[0039] By locking the spin precession signal extracted by the detection light in a closed loop at a 90° phase, low-noise, high-bandwidth magnetic field measurement of atomic spins can be achieved.

[0040] The beneficial effects of this invention compared to the prior art are as follows:

[0041] Currently, there is a lack of methods for detecting the frequency of light polarization in small-volume atomic magnetometers. In practical applications, the frequency drift of the detected light can easily lead to magnetic field noise and degradation of the measurement bandwidth of the atomic magnetometer.

[0042] This invention achieves real-time sensing of atomic spin detection frequencies by modulating a circularly polarized driving photocurrent and actively applying a light frequency shift characteristic signal. It locks the detection light at the optimal spin detection sensitivity, enabling low-noise, high-bandwidth magnetic field measurement of atomic spins. This invention does not introduce additional structures or components, making it particularly suitable for small-volume atomic magnetometers.

[0043] In summary, this invention provides a method for measuring low-noise, high-bandwidth magnetic fields using atomic spin, applicable to various high-sensitivity, small-volume atomic magnetometers. This method employs circularly polarized driving light and linearly polarized detection light, combined with a closed-loop control method for the detection light frequency based on optical frequency shift modulation. This allows for optimal low-noise, high-bandwidth magnetic field measurement capabilities of atomic spin in practical applications.

[0044] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0045] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring low-noise, high-bandwidth magnetic fields of atomic spin, characterized in that, The method for measuring low-noise, high-bandwidth magnetic fields of atomic spin includes: Step 1, in the driving optical operating current I Q0 The superimposed high-frequency current perturbation, i.e., I Q =I Q0 +I1·sin2πf1t, where I1 is the amplitude of the driving photocurrent perturbation, f1 is the frequency of the driving photocurrent perturbation, f1 is greater than the measurement bandwidth of the atomic magnetometer and less than the atomic spin magnetic resonance linewidth, I Q The driving photocurrent is superimposed with a high-frequency current perturbation; under the modulation of the driving photocurrent, the atomic spin optical frequency shift is perturbed, realizing optical frequency shift modulation with a frequency of f1; Step 2: Since the optical frequency shift modulation frequency f1 is greater than the magnetic field measurement bandwidth of the atomic magnetometer, the phase of the spin precession signal extracted by the detection light has a disturbance with a frequency of the optical frequency shift modulation frequency f1. The optical frequency is detected by scanning the photocurrent, and the amplitude A of the spin precession signal phase disturbance is calculated in real time. When A is the maximum, the atomic magnetometer has the optimal sensitivity. The atomic magnetometer is kept in the optimal sensitivity state by closed-loop control of the detection light frequency. Step 3: The spin precession signal extracted by the detection light is closed-loop locked at 90° phase to achieve low-noise, high-bandwidth magnetic field measurement of atomic spin.

2. The atomic spin low-noise high-bandwidth magnetic field measurement method according to claim 1, characterized in that, Step two specifically includes: Detecting the operating current I J0 The superimposed high-frequency current perturbation, i.e., I J =I J0 +I2·sin2πf2t, where I2 is the amplitude of the detected photocurrent perturbation and f2 is the frequency of the detected photocurrent perturbation; Real-time calculation of the phase perturbation amplitude A of the spin precession signal; Dynamically adjust the operating temperature of the detection light to make I J =I J0 At the same time point ±I2, the amplitude of the spin precession signal phase disturbance A is the largest, and the atomic magnetometer has the best sensitivity.

3. The atomic spin low-noise high-bandwidth magnetic field measurement method according to claim 2, characterized in that, The frequency f2 for detecting photocurrent perturbation is f2 = 0.5f1.

4. The method for measuring low-noise, high-bandwidth atomic spin magnetic fields according to claim 3, characterized in that, The optical frequency shift is Among them, B LS For optical frequency shift, r e Let be the electron radius, c be the speed of light, and φ be the photon flux. For circular polarization degree, γ e V is the electron gyromagnetic ratio, V(ν-ν0) is the spectral type, ν is the driving light frequency, and ν0 is the light frequency corresponding to the atomic energy level transition.

5. The method for measuring low-noise, high-bandwidth atomic spin magnetic fields according to claim 4, characterized in that, In step two, the spin precession signal phase is disturbed at a frequency of the optical frequency shift modulation frequency f1. The phase of the disturbance.

6. An atomic magnetometer, characterized in that, The atomic magnetometer performs atomic spin low-noise high-bandwidth magnetic field measurement using the atomic spin low-noise high-bandwidth magnetic field measurement method as described in any one of claims 1 to 5.

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