An all-optical atomic magnetometer device

Abstract

An all-optical atomic magnetometer device comprises: a laser driving circuit for outputting a pumping light driving signal and a probe light driving signal; a laser generating assembly for generating parallel light; wherein the parallel light generated by the laser generating assembly under the driving of the pumping light driving signal is monochromatic linearly polarized light, and the parallel light generated by the laser generating assembly under the driving of the probe light driving signal is polychromatic linearly polarized light; a polarization converter for emitting monochromatic circularly polarized light as pumping light; an atomic cell filled with working atoms; the working atoms in the atomic cell resonate in a magnetic field to be measured under the action of the pumping light to achieve coherent pumping; a second PBS for separating the probe light carrying magnetic field information emitted by the atomic cell into first probe light and second probe light; a first detector for receiving the first probe light and converting it into a first electric signal; and a second detector for receiving the first probe light and converting it into a second electric signal.

Description

Technical Field

[0001] This application relates to the field of magnetic measurement, and more particularly to an all-optical atomic magnetometer device. Background Technology

[0002] An atomic magnetometer is a high-precision weak magnetic sensor with advantages such as high sensitivity in magnetic field measurement, low power consumption, and easy integration. It can be widely used in basic scientific research, mineral resource exploration, military anti-submarine warfare, and biomagnetic imaging.

[0003] To obtain information about the magnetic field being measured, atomic magnetometers typically use pump light resonating with the atomic transition frequency to macroscopically polarize the atoms, and then detect the paramagnetic resonance signal of the polarized atoms in the magnetic field. Currently, there are two ways to drive atoms to generate paramagnetic resonance. One is to apply an external radio frequency field perpendicular to the pump light; when the frequency of the radio frequency equals the precession frequency of the atomic magnetic moment around the magnetic field being measured, the atoms can be driven to generate paramagnetic resonance. The other is to change the interaction period between the pump light and the atoms, for example, by modulating the amplitude, frequency, or polarization of the pump light; when the modulation frequency equals the precession frequency of the atomic magnetic moment around the magnetic field being measured, paramagnetic resonance can also be generated. This type of atomic magnetometer, which utilizes modulated pump light technology, is called an all-optical magnetometer because it does not require providing a radio frequency field to the probe when measuring the magnetic field. Therefore, all-optical magnetometers are particularly suitable for the development of magnetic field gradiometers and magnetic measurement arrays.

[0004] Existing all-optical magnetometers have low pumping and detection efficiency and high noise, which cannot meet the increasingly demanding requirements for high-precision measurement. Summary of the Invention

[0005] The main technical problem addressed in this application is how to improve the pumping and detection efficiency of lasers.

[0006] According to a first aspect, one embodiment provides an all-optical atomic magnetometer device, comprising: a laser driving circuit for alternately outputting a pump light driving signal and a probe light driving signal at a preset switching frequency; a laser generating component for generating parallel light; wherein the parallel light generated by the laser generating component under the drive of the pump light driving signal is monochromatic linearly polarized light, and the parallel light generated under the drive of the probe light driving signal is polychromatic linearly polarized light; a polarization converter for performing beam splitting and recombining optical interference on the monochromatic linearly polarized light to output monochromatic circularly polarized light as pump light, and for performing beam splitting and recombining optical interference on the polychromatic linearly polarized light to obtain linearly polarized light with mutually perpendicular polarization directions as probe light; and atomic gas... The system comprises a chamber filled with working atoms; the atomic gas chamber is located in the optical path of the pump light and the probe light; the working atoms in the atomic gas chamber resonate in the magnetic field to be measured under the action of the pump light to achieve coherent pumping; the probe light carries the magnetic field information of the magnetic field to be measured after passing through the atomic gas chamber and being emitted again; a second PBS (polarized beam splitter) is used to split the probe light carrying the magnetic field information emitted from the atomic gas chamber into a first probe light and a second probe light; a first detector is used to receive the first probe light and convert it into a first electrical signal; a second detector is used to receive the first probe light and convert it into a second electrical signal; the first electrical signal and the second electrical signal are used to calculate the magnetic field information of the magnetic field to be measured.

[0007] In one embodiment, the laser driving circuit includes a current source, a microwave source, a signal source, a microwave switch, and a coupler. The microwave signal generated by the microwave source is controlled by a square wave signal generated by the signal source. When the square wave signal controls the microwave switch to disconnect, the microwave signal cannot pass through the microwave switch, and the microwave source outputs a pump light driving signal to drive the laser generating component to generate monochromatic linearly polarized light for pumping. When the square wave signal controls the microwave switch to connect, the microwave signal and the DC signal generated by the current source are coupled through the coupler to form a probe light driving signal, which drives the laser generating component to generate multicolor linearly polarized light for detection.

[0008] In one embodiment, the laser generating assembly includes a tunable semiconductor laser and a plano lens.

[0009] In one embodiment, the polarization converter includes a first quarter-wave plate, a second quarter-wave plate, a first PBS, a first reflector, and a second reflector. Monochromatic linearly polarized light or multichromatic linearly polarized light enters the polarization converter and is split into first PBS refracted light and first PBS transmitted light by the first PBS. The first PBS refracted light passes through the first quarter-wave plate and is reflected by the first reflector, and then passes through the first quarter-wave plate again to become first reflected light. The first PBS transmitted light passes through the second quarter-wave plate and is reflected by the second reflector, and then passes through the second quarter-wave plate again to become second reflected light. The first reflected light and the second reflected light are combined at the first PBS and interfere to produce the output monochromatic circularly polarized light as pump light for the atomic gas cell or to produce the output linearly polarized light with mutually perpendicular polarization directions as probe light.

[0010] In one embodiment, the frequency f0 of the monochromatic linearly polarized laser light is equal to the transition frequency of the atom.

[0011] In one embodiment, the frequency f of the polychromatic linearly polarized light ±1st order sideband light +1 and f -1 It maintains symmetric detuning with the atomic transition frequency f0.

[0012] In one embodiment, during pumping, the monochromatic circularly polarized light resonates with the atomic transitions, causing the atoms to polarize. During detection, the intensity ratio of the ±1st order sidebands of the multicolor linearly polarized light is adjusted to the maximum.

[0013] In one embodiment, the microwave frequency of the microwave signal is f. w The frequency difference between the ±1st order sideband light of the polychromatic linearly polarized light is Δf = f +1 -f -1 =2f w .

[0014] In one embodiment, the frequency f of the square wave signal generated by the signal source m It is equal to the precession frequency of the atom around the magnetic field, and the duty cycle of the square wave signal represents the ratio of pumping time to detection time.

[0015] In one embodiment, the working atom is an alkali metal atom.

[0016] According to the apparatus of the above embodiments, the pumping of atoms and the detection of signals are completely separated by time-division modulation and polarization conversion techniques. During the pumping process, all light intensity is concentrated in monochromatic circularly polarized light, and during the detection process, the power proportion of monochromatic circularly polarized light is minimized. Theoretically, the laser power utilization rate of this scheme is twice that of the elliptical light scheme, and the intensity noise of the detection signal is further reduced, thereby improving the pumping and detection efficiency of the laser. Attached Figure Description

[0017] Figure 1 A schematic diagram of an all-optical atomic magnetometer device provided in an embodiment of this application;

[0018] Figure 2 A schematic diagram illustrating the working process of an all-optical atomic magnetometer device provided in this application embodiment;

[0019] Figure 3 A schematic diagram illustrating the principle of a polarization converter and the laser polarization conversion process provided in this application embodiment;

[0020] Figure 4 This is a schematic diagram illustrating the generation process and frequency variation of monochromatic linearly polarized light and polychromatic linearly polarized light, provided for embodiments of this application. Detailed Implementation

[0021] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0022] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0023] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0024] There are two main approaches to detecting paramagnetic resonance signals using all-optical magnetometers. One approach directly detects the change in absorption intensity of a single pump beam by atoms (referred to as the "single-beam approach"). The other approach involves adding a linearly polarized beam, appropriately detuned to the atomic transition frequency, to interact with the atoms. The magnetic field is measured by detecting the change in the Faraday rotation angle of the linearly polarized beam when paramagnetic resonance occurs (referred to as the "double-beam approach"). Of these two approaches, the single-beam approach requires only one laser, resulting in a simple optical path structure. Magnetometers developed using this approach can easily achieve small size and low power consumption. However, because the frequency jitter noise of the probe light is directly converted into intensity noise (FM-AM noise) of the probe signal, the sensitivity achieved by this approach is generally not high. The double-beam approach, on the other hand, can effectively suppress common-mode noise of the probe signal through differential detection, thus achieving extremely high sensitivity. However, the double-beam structure increases the probe size, and using two lasers also increases the power consumption and cost of the magnetometer.

[0025] To obtain a highly sensitive, compact, all-optical magnetometer probe, using a single beam of elliptically polarized light interacting with atoms is a feasible approach (referred to as the "single-beam elliptically polarized light scheme"). As an optimization of the two-beam scheme, elliptically polarized light can be considered a combination of circularly polarized and linearly polarized light. During pumping, frequency modulation can be used to make the light resonate with the transition frequencies of the atoms. During detection, the linearly polarized light, detuned to the atoms, records the Faraday rotation signal. By changing the period of the modulation signal, making the alternation frequency of pumping and detection equal to the precession frequency of the atoms around the magnetic field, paramagnetic resonance can be achieved. However, since only the circularly polarized component contributes to the pumping effect during pumping and only the linearly polarized component contributes to the detection signal during detection, only half of the optical power is effectively utilized in the elliptically polarized light scheme, with the remainder converted into laser intensity noise. This, to some extent, limits the sensitivity of the single-beam elliptically polarized light magnetometer.

[0026] In the embodiments of this application, the following are provided: Figure 1 The image shows an all-optical atomic magnetometer device.

[0027] The reference numerals in this application are explained below: 1-Tunable Semiconductor Laser (VCSEL); 2-Plan-convex lens; 3a-First PBS (Polarization Beam Splitter); 3b-Second PBS (Polarization Beam Splitter); 4a-First Reflector; 4b-Second Reflector; 5a-First Quarter-Wave Plate; 5b-Second Quarter-Wave Plate; 6-Atomic Gas Cell; 7a-First Detector; 7b-Second Detector; 8-Polarization Converter; 9-Current Source; 10-Microwave Source; 11-Signal Source; 12-Microwave 13-Switch; 14-Coupled; 15-Laser drive circuit; 16-Laser generating component; S1-DC signal; S2-Microwave signal; S3-Square wave signal; S4-Microwave on / off signal; S5-Laser drive signal; L1-Initial diverging light; L2-Initial parallel light; L3-First PBS refracted light; L4-First PBS transmitted light; L5-First reflected light; L6-Second reflected light; L7-Atomic gas cell incident light; L8-Atomic gas cell exit light; L9-First probe beam; L10-Second probe beam.

[0028] Figure 1 The illustrated all-optical atomic magnetometer device includes: a laser driving circuit 14, used to alternately output pump light driving signals and probe light driving signals according to a preset switching frequency; a laser generating component 15, used to generate parallel light; wherein the parallel light generated by the laser generating component 15 under the drive of the pump light driving signal is monochromatic linearly polarized light, and the parallel light generated under the drive of the probe light driving signal is polychromatic linearly polarized light; a polarization converter 8, used to split and recombine the monochromatic linearly polarized light for optical interference to output monochromatic circularly polarized light as pump light, and used to split and recombine the polychromatic linearly polarized light for optical interference to obtain linearly polarized light with mutually perpendicular polarization directions as probe light; and atomic gas... Chamber 6 is filled with working atoms. The atomic gas chamber 6 is located in the optical path of the pump light and the probe light. The working atoms in the atomic gas chamber 6 resonate in the magnetic field to be measured under the action of the pump light to achieve coherent pumping. The probe light, after passing through the atomic gas chamber 6 and exiting, carries the magnetic field information of the magnetic field to be measured. A second PBS3b (polarization beam splitter) is used to split the probe light carrying the magnetic field information emitted from the atomic gas chamber 6 into a first probe light and a second probe light. A first detector 7a is used to receive the first probe light and convert it into a first electrical signal. A second detector 7b is used to receive the first probe light and convert it into a second electrical signal. The first and second electrical signals are used to calculate the magnetic field information of the magnetic field to be measured.

[0029] In one embodiment, the magnetic field information is a Faraday rotation signal. In one embodiment, the laser generating assembly 15 includes a tunable semiconductor laser 1 and a plano lens 2.

[0030] In some embodiments, the first detection light is a first detection beam L9, and the second detection light is a second detection beam L10.

[0031] Figure 2 This is a schematic diagram illustrating the operation of an all-optical atomic magnetometer device in one embodiment. In one embodiment, as shown... Figure 2 As shown, the laser generating assembly 15 includes a tunable semiconductor laser 1 and a plano-convex lens 2. The initial diverging light L1 emitted by the tunable semiconductor laser 1 is focused by the plano-convex lens 2 to become a parallel-propagating initial parallel light L2. The initial parallel light L2 enters the polarization converter 8 and is split into a first PBS refracted light L3 and a first PBS transmitted light L4 by the first PBS 3a. The first PBS refracted light L3 passes through the first quarter-wave plate 5a and is reflected by the first reflecting mirror 4a, and then passes through the first quarter-wave plate 5a again to become the first reflected light L5. The first PBS transmitted light L4 passes through the second quarter-wave plate 5b and is reflected by the second reflecting mirror 4b, and then passes through the second quarter-wave plate 5b again to become the second reflected light L6. The first reflected light L5 and the second reflected light L6 are combined at the first PBS 3a and interfere to become the atomic gas cell incident light L7. The atomic gas cell exit light L8, which carries magnetic field information, is split into a first detection beam L9 and a second detection beam L10 by the second PBS3b, and is finally detected by the first detector 7a and the second detector 7b, respectively.

[0032] like Figure 2 As shown, the laser driving circuit 14 includes a current source 9, a microwave source 10, a signal source 11, a microwave switch 12, and a coupler 13. The microwave signal S2 generated by the microwave source 10 is controlled by the square wave signal S3 generated by the signal source 11. When the square wave signal S3 controls the microwave switch 12 to disconnect, the microwave signal S2 cannot pass through the microwave switch 12, and the microwave source 10 outputs a pump light driving signal to drive the laser generating component 15 to generate monochromatic linearly polarized light for pumping. When the square wave signal S3 controls the microwave switch 12 to connect, the microwave signal S2 and the DC signal S1 generated by the current source 9 are coupled through the coupler 13 to form a probe light driving signal, which drives the laser generating component 15 to generate multicolor linearly polarized light.

[0033] The microwave source 10 can control the laser generating component to generate monochromatic or polychromatic linearly polarized light through the microwave on / off signal S4.

[0034] In one embodiment, during pumping, the monochromatic circularly polarized light resonates with the atomic transitions, causing the atoms to polarize. During detection, the intensity ratio of the ±1st order sidebands of the multicolor linearly polarized light is adjusted to the maximum.

[0035] Taking rubidium-87 atoms as an example, the laser driving circuit 14 consists of a DC signal S1 and a microwave signal S2. The microwave signal S2 is controlled by a square wave signal S3 to open and close under the action of the microwave switch 12. When the microwave switch 12 is open, only the DC signal S1 drives the tunable semiconductor laser 1. The tunable semiconductor laser 1 outputs monochromatic linearly polarized light that undergoes a linear transition with the rubidium-87 atom. This light is then converted into monochromatic circularly polarized light by the polarization converter 8 to pump the rubidium-87 atoms in the atomic gas chamber 6. When the microwave switch 12 is closed, the microwave signal S2 is coupled with the DC signal S1 to jointly drive the tunable semiconductor laser 1. At this time, the intensity of the ±1st order sidebands in the multicolor linearly polarized light output by the tunable semiconductor laser 1 reaches its maximum. After passing through the polarization converter 8, the polarization directions of the ±1st order sidebands become perpendicular to each other. After exiting the atomic gas chamber 6, the magnetic field information carried by the ±1st order sidebands is collected by the differential detection module.

[0036] The DC signal S1 generated by current source 9, after passing through coupler 13, can directly drive tunable semiconductor laser 1 to generate monochromatic linearly polarized light resonating with the D1 line transition of rubidium 87 atoms. The microwave signal S2 generated by microwave source 10 has a frequency of approximately 2 GHz. When microwave switch 12 is connected, the DC signal S1 and microwave signal S2 are coupled by coupler 13 into a laser driving signal S5, which drives tunable semiconductor laser 1 to generate polychromatic linearly polarized light. The ±1st order sidebands of the polychromatic linearly polarized light maintain approximately 2 GHz of symmetrical detuning with the D1 line of rubidium 87 atoms. In one embodiment, the laser driving signal S5 includes a pump light driving signal and a probe light driving signal.

[0037] In one embodiment, the frequency f0 of the monochromatic linearly polarized laser light is equal to the transition frequency of the atoms, and the frequency f of the ±1st order sideband light of the polychromatic linearly polarized light is... +1 and f -1 It maintains symmetric detuning with the atomic transition frequency f0.

[0038] In one embodiment, the microwave frequency of microwave signal S2 is f w The frequency difference between the ±1st order sideband light of polychromatic linearly polarized light is Δf = f +1 -f -1 =2f w .

[0039] In one embodiment, the DC signal S1 generated by current source 9 and the microwave signal S2 generated by microwave source 10 are coupled into a laser driving signal S5 through coupler 13. When the square wave signal S3 provided by signal source 11 is at a high level, the microwave signal S2 can pass through microwave switch 12, and the laser driving signal S5 contains the modulation signal; when the square wave signal S3 is at a low level, the microwave signal S2 is disconnected by microwave switch 12, and the laser driving signal S5 is the same as the DC signal S1. The switching frequency of the microwave signal S2 is determined by the frequency of the square wave signal S3. In one embodiment, the frequency f of the square wave signal S3 generated by signal source 11 is... m It is equal to the precession frequency of the atom around the magnetic field, and the duty cycle of the square wave signal S3 represents the ratio of pumping time to detection time.

[0040] like Figure 2 As shown, the polarization converter 8 includes a first quarter-wave plate 5a, a second quarter-wave plate 5b, a first PBS 3a, a first reflector 4a, and a second reflector 4b. Monochromatic or polychromatic linearly polarized light enters the polarization converter 8 and is split by the first PBS 3a into a first PBS refracted light L3 and a first PBS transmitted light L4. The first PBS refracted light L3 passes through the first quarter-wave plate 5a, is reflected by the first reflector, and passes through the first quarter-wave plate 5a again to become the first reflected light L5. The first PBS transmitted light L4 passes through the second quarter-wave plate 5b, is reflected by the second reflector, and passes through the second quarter-wave plate 5b again to become the second reflected light L6. The first reflected light L5 and the second reflected light L6 are combined at the first PBS 3a and interfere, resulting in either the output monochromatic circularly polarized light becoming the pump light of the atomic gas cell 6 or the output linearly polarized light with mutually perpendicular polarization directions becoming the probe light. The polarization directions of the first PBS refracted light L3 and the first PBS transmitted light L4 will rotate by 90 degrees after passing through the first quarter-wave plate 5a and the second quarter-wave plate 5b twice, respectively.

[0041] The combined beam is the incident light L7 of the atomic gas cell. When the incident light L7 passes through the atomic gas cell 6, it will pump and detect the Faraday rotation of rubidium 87 atoms. The outgoing light L8 of the atomic gas cell carrying the Faraday rotation signal is split into the first detection beam L9 and the second detection beam L10 by the second PBS3b. Then, it is converted into electrical signals by the first detector 7a and the second detector 7b respectively and then differentially calculated.

[0042] Except for the initial diverging light L1, which is a diverging light, the initial parallel light L2, the first PBS refracted light L3, the first PBS transmitted light L4, the first reflected light L5, the second reflected light L6, the atomic gas cell incident light L7, the atomic gas cell exit light L8, the first probe beam L9, and the second probe beam L10 are all parallel propagating beams.

[0043] The initial divergent light L1 and the initial parallel light L2 are linearly polarized, with their polarization directions forming a 45-degree angle with the transmission axis of the first PBS3a. The light intensities of the first PBS refracted light L3 and the first PBS transmitted light L4, after being split by the first PBS3a, are equal. The polarization direction of the atomic gas cell emitted light L8 depends on the magnitude of the magnetic field to be measured. The light intensities of the first detector beam L9 and the second detector beam L10, after being split by the second PBS3b, are not equal, and the difference is calculated from the detection signals of the first detector 7a and the second detector 7b.

[0044] The driving signal S5 provided by the laser driving circuit 14 drives the tunable semiconductor laser 1 to switch between pump and probe light. The switching frequency depends on the frequency of the square wave signal S3 provided by the signal source 11 and is equal to the precession frequency of the working atoms around the magnetic field in the atomic gas cell 6. The low level of the square wave signal S3 triggers the microwave switch 12 to open, and the DC signal S1 drives the tunable semiconductor laser 1 to generate an initial diverging light L1 with a frequency of f0. At this time, the incident light L7 from the atomic gas cell after exiting the polarization converter 8 is circularly polarized. The high level of the square wave signal S3 triggers the microwave switch 12 to open, and the DC signal S1 and the microwave signal S2 couple to drive the tunable semiconductor laser 1 to generate light with a frequency of f0. +1 and f -1 The initial diverging light L1 of the ±1st order sideband, at this time the incident light L7 of the atomic gas cell after exiting the polarization converter 8 is linearly polarized.

[0045] During pumping, the frequency f0 of the monochromatic linearly polarized light resonates with the transition frequency of the working atoms in atomic cell 6. At this time, the incident light L7 in the atomic cell is monochromatic circularly polarized light, and the atoms are effectively polarized under the action of the monochromatic pump light. During detection, the frequency difference Δf = f0 between the ±1st order sidebands of the multicolor linearly polarized light. +1 -f -1 Equal to the frequency f of microwave signal S2 w Twice that of the atomic gas cell, at this time the incident light L7 is polychromatic linearly polarized light, and the detuning of the polychromatic linearly polarized light is controlled by microwave signal S2 to obtain the optimal Faraday rotation signal.

[0046] The interference effect of the first reflected light L5 and the second reflected light L6 after being combined in the polarization converter 8 depends on the distance difference Δl between the first quarter-wave plate 5a and the second quarter-wave plate 5b and the first PBS3a. By appropriately adjusting the value of Δl, a pump light with frequency f0 will produce a phase difference of π / 4, with a frequency of f... +1 and f -1 The phase difference of the probe light is an odd multiple of π / 2.

[0047] The interior of the atomic gas chamber 6 needs to be filled with working atoms with a high gyromagnetic ratio. In one embodiment, the working atoms are alkali metal atoms, such as rubidium or cesium, to obtain a high-quality magnetic resonance signal. The modulated pump light generated by the tunable semiconductor laser 1 can drive the working atoms to resonate in the magnetic field to achieve coherent pumping.

[0048] Figure 3 This is a schematic diagram illustrating the principle of the polarization converter 8 of the present invention and the laser polarization conversion process. The initial parallel light L2 has a 45-degree angle between its polarization direction and the optical transmission axis of the first PBS3a, and is therefore split by the first PBS3a into a first PBS refracted light L3 and a first PBS transmitted light L4, both of equal power. According to the PBS's beam splitting principle... Figure 3 The polarization direction of the first PBS refracted light L3 is perpendicular to the plane of the paper (e.g., Figure 3 In the front-to-back direction, the polarization direction of the first PBS transmitted light L4 is parallel to the horizontal plane of the paper (e.g., ...). Figure 3 (Horizontal) direction. The first PBS refracted light L3 passes through the first quarter-wave plate 5a and is reflected by the first reflecting mirror 4a, then passes through the first quarter-wave plate 5a again to become the first reflected light L5. The polarization direction of the first reflected light L5 is parallel to the plane of the paper (e.g., horizontal). Figure 3 In the vertical direction, the light L4 is rotated 90 degrees relative to the first PBS refracted light L3; similarly, the first PBS transmitted light L4 passes through the second quarter-wave plate 5b and is reflected by the second reflecting mirror 5a, then passes through the second quarter-wave plate 5b again to become the second reflected light L6. The polarization direction of the second reflected light L6 is perpendicular to the front and back of the paper (e.g., in the vertical direction). Figure 3 In the front-to-back direction, it is rotated 90 degrees relative to the first PBS transmitted light L4. The distances between the first quarter-wave plate 5a and the second quarter-wave plate 5b and the first PBS 3a are l1 and l2, respectively. Therefore, the optical path difference experienced by the first reflected light L5 and the second reflected light L6 before beam combining is: 2Δl=2(l1-l2). In order to satisfy the requirement that the pump light with frequency f0 becomes circularly polarized light after passing through the polarization converter 8 ( Figure 3 (Left side) with frequency f +1 and f -1 The ±1st order sidebands are converted into linearly polarized light with mutually perpendicular polarizations after passing through polarization converter 8. Figure 3 (On the right), the conditions that Δl should satisfy are: 1. Δl = (n + 1 / 2)c / (4f0); 2. Δl = c / (4Δf), where c is the speed of light, n is an integer, and Δf = 2f w .

[0049] Figure 4This diagram illustrates the generation process and frequency variation of monochromatic and polychromatic linearly polarized light. During the period when the square wave signal S3 generated by signal source 11 is at a low level, microwave switch 12 is disconnected, and microwave signal S2 cannot pass through. At this time, the DC signal S1 generated by current source 9... Figure 4 The DC will directly drive the tunable semiconductor laser 1 ( Figure 4 A VCSEL (Variable Cathode Laser Separator) generates monochromatic linearly polarized light with a frequency of f0. After exiting the polarization converter 8, the beam is converted into right-hand circularly polarized light, and the atoms will achieve macroscopic polarization under the action of the circularly polarized pump light. Figure 4 The polarization direction shown in the neutral polarization state is the direction of the electric field vibration of the electromagnetic wave when viewed from the direction of the light vector. During the high-level period of the square wave signal S3, the microwave signal S2 can be coupled to the DC signal S1 through the microwave switch 12. Figure 4 A DC+WAVE microwave is used to drive a tunable semiconductor laser 1 to generate polychromatic linearly polarized light. By adjusting the power of the microwave, the proportion of ±1st order sidebands of the polychromatic linearly polarized light is maximized. Figure 4 Other frequency components of light are not shown due to their small proportion. After exiting the polarization converter 8, the ±1st order sidebands of the polychromatic linearly polarized light are converted into linearly polarized light with mutually perpendicular polarization directions. Figure 4 (Positive π / 4 and negative π / 4) After exiting atomic gas chamber 6, the Faraday rotation directions of the ±1st order sidebands are opposite, and the rotation signal of the beam will be received by the differential system in the form of intensity superposition.

[0050] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0051] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0052] Furthermore, unless expressly stated in the claims, the order of elements and sequences, the use of numbers and letters, or other names in this specification are not intended to limit the order of the processes and methods described herein. Although various examples have been discussed in the foregoing disclosure of some embodiments of the invention that are currently considered useful, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the spirit and scope of the embodiments described herein. For example, while the system components described above can be implemented using hardware devices, they can also be implemented solely using software solutions, such as installing the described system on an existing server or mobile device.

[0053] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0054] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0055] For each patent, patent application, patent application publication, and other material, such as articles, books, specifications, publications, and documents, referenced in this specification, the entire contents of which are incorporated herein by reference. This excludes historical application documents that are inconsistent with or conflict with the content of this specification, as well as documents that limit the broadest scope of the claims in this specification (currently or subsequently appended to this specification). It should be noted that in the event of any inconsistency or conflict between the descriptions, definitions, and / or terminology used in the supplementary materials and the content of this specification, the descriptions, definitions, and / or terminology used in this specification shall prevail.

[0056] Finally, it should be understood that the embodiments in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments in this specification are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments in this specification are not limited to those explicitly described and illustrated herein.

Claims

1. A fully optical atomic magnetometer device, characterized in that, include: The laser driving circuit is used to alternately output pump light driving signals and probe light driving signals according to a preset switching frequency; Laser generating components are used to generate parallel light; The parallel light generated by the laser generating component under the drive of the pump light driving signal is monochromatic linearly polarized light, and the parallel light generated under the drive of the probe light driving signal is polychromatic linearly polarized light. A polarization converter is used to split and recombine the monochromatic linearly polarized light through optical interference to output monochromatic circularly polarized light as pump light, and to split and recombine the multicolor linearly polarized light through optical interference to obtain linearly polarized light with mutually perpendicular polarization directions as probe light. An atomic gas chamber is filled with working atoms. The atomic gas chamber is located in the optical path of the pump light and the probe light. The working atoms in the atomic gas chamber resonate in the magnetic field to be measured under the action of the pump light to achieve coherent pumping. The probe light carries the magnetic field information of the magnetic field to be measured after passing through the atomic gas chamber and being emitted again. The second PBS is used to divide the probe light carrying magnetic field information emitted from the atomic gas cell into a first probe light and a second probe light. A first detector is used to receive the first detection light and convert it into a first electrical signal; The second detector is used to receive the first detection light and convert it into a second electrical signal; the first electrical signal and the second electrical signal are used to calculate the magnetic field information of the magnetic field to be measured. The polarization converter includes a first quarter-wave plate, a second quarter-wave plate, a first PBS, a first reflector, and a second reflector. After entering the polarization converter, the monochromatic linearly polarized light or the polychromatic linearly polarized light is split into first PBS refracted light and first PBS transmitted light by the first PBS. The first PBS refracted light passes through the first quarter-wave plate and is reflected by the first reflector, and then passes through the first quarter-wave plate again to become the first reflected light. The first PBS transmitted light passes through the second quarter-wave plate and is reflected by the second reflector, and then passes through the second quarter-wave plate again to become the second reflected light. The first reflected light and the second reflected light are combined at the first PBS and interfere to produce the output monochromatic circularly polarized light as the pump light of the atomic gas cell or to produce the output linearly polarized light with mutually perpendicular polarization directions as the probe light.

2. The all-optical atomic magnetometer device as described in claim 1, characterized in that, The laser driving circuit includes a current source, a microwave source, a signal source, a microwave switch, and a coupler. The microwave signal generated by the microwave source is controlled by a square wave signal generated by the signal source. When the square wave signal controls the microwave switch to disconnect, the microwave signal cannot pass through the microwave switch, and the microwave source outputs the pump light driving signal to drive the laser generating component to generate the monochromatic linearly polarized light for pumping. When the square wave signal controls the microwave switch to connect, the microwave signal and the DC signal generated by the current source are coupled through the coupler to form a probe light driving signal to drive the laser generating component to generate multicolor linearly polarized light.

3. The all-optical atomic magnetometer device as described in any one of claims 1 or 2, characterized in that, The laser generating assembly includes a tunable semiconductor laser and a plano lens.

4. The all-optical atomic magnetometer device as described in claim 1, characterized in that, The frequency f0 of the monochromatic linearly polarized laser light is equal to the transition frequency of the atoms.

5. The all-optical atomic magnetometer device as described in claim 1, characterized in that, The frequency f of the ±1st order sideband light of the polychromatic linearly polarized light +1 and f -1 It maintains symmetric detuning with the atomic transition frequency f0.

6. The all-optical atomic magnetometer device as described in claim 2, characterized in that, During pumping, the monochromatic circularly polarized light resonates with the atomic transitions, causing the atoms to polarize. During detection, the intensity ratio of the ±1st order sidebands of the polychromatic linearly polarized light is adjusted to the maximum.

7. The all-optical atomic magnetometer device as described in claim 6, characterized in that, The microwave frequency of the microwave signal is f w The frequency difference between the ±1st order sideband light of the polychromatic linearly polarized light is Δf=f +1 -f -1 =2f w .

8. The all-optical atomic magnetometer device as described in claim 2, characterized in that, The frequency f of the square wave signal generated by the signal source m It is equal to the precession frequency of the atom around the magnetic field, and the duty cycle of the square wave signal represents the ratio of pumping time to detection time.

9. The all-optical atomic magnetometer device as described in claim 1, characterized in that, The working atom is an alkali metal atom.

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