Atomic oscillator

Abstract

It is difficult to further improve the stability of the resonance frequency against magnetic field fluctuations in atomic oscillators. [Solution] The atomic oscillator of the present disclosure comprises two gas cells, each containing alkali metal atoms and having bias magnetic fields applied in opposite directions to each other; a light generating unit that irradiates the two gas cells with light having at least two different frequency components; a light detection unit that detects the transmitted light that has passed through the two gas cells; and a control unit that determines a resonance frequency based on detection signals corresponding to the transmitted light detected from the two gas cells and controls the oscillation frequency of an oscillation signal output to the outside based on the determined resonance frequency.

Description

[Technical Field]

[0001] This disclosure relates to atomic oscillators. [Background technology]

[0002] As an oscillator with long-term high-precision oscillation characteristics, atomic oscillators that oscillate based on the energy transitions of alkali metal atoms are known. In atomic oscillators, the resonance frequency is determined by detecting the amount of light transmitted through the atom, and the oscillation frequency is controlled based on this. In this case, atomic oscillators are generally operated by applying a bias magnetic field of several tens to several hundred μT in order to obtain a clear resonance signal.

[0003] On the other hand, in an atomic oscillator, if the magnetic field fluctuates due to an external magnetic field, the resonance frequency fluctuates, making it difficult to improve the stability of the resonance frequency. For this reason, in atomic oscillators, methods such as shielding the magnetic field or canceling it out are employed, as described in Patent Document 1. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-21719 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, it is difficult to completely shield or cancel out an external magnetic field in an atomic oscillator. Therefore, a problem arises in that it is difficult to further improve the stability of the resonance frequency in the atomic oscillator by reducing magnetic field fluctuations.

[0006] One of the purposes of this disclosure is to solve the aforementioned problem, which is the difficulty in further improving the stability of the resonance frequency with respect to magnetic field fluctuations in atomic oscillators.

Means for Solving the Problem

[0007] An atomic oscillator according to one embodiment of the present invention includes two gas cells in which alkali metal atoms are enclosed and bias magnetic fields are applied in opposite directions to each other, a light generation unit that irradiates the two gas cells with irradiation light having at least two different frequency components, respectively, a light detection unit that detects the transmitted light transmitted through the two gas cells, respectively, a control unit that determines a resonance frequency based on detection signals corresponding to the transmitted light detected from the two gas cells, respectively, and controls the oscillation frequency of an oscillation signal output externally based on the determined resonance frequency, and has such a configuration. Also, a control method for an atomic oscillator according to one embodiment of the present invention is two gas cells in which alkali metal atoms are enclosed, a light generation unit that irradiates the two gas cells with irradiation light having at least two different frequency components, respectively, a light detection unit that detects the transmitted light transmitted through the two gas cells, respectively, and is a control method in an atomic oscillator including applying bias magnetic fields in opposite directions to the two gas cells, determining a resonance frequency based on detection signals corresponding to the transmitted light detected from the two gas cells, respectively, and controlling the oscillation frequency of an oscillation signal output externally based on the determined resonance frequency, and has

Advantages of the Invention

[0008] With the present disclosure configured as described above, in an atomic oscillator, it is possible to further improve the stability of the resonance frequency with respect to magnetic field fluctuations.

Brief Description of the Drawings

[0009] [Figure 1]This diagram shows the configuration of an atomic oscillator in this disclosure. [Figure 2] This figure shows the processing performed by the atomic oscillator in this disclosure. [Figure 3] This figure shows the processing performed by the atomic oscillator in this disclosure. [Figure 4] This flowchart shows the processing operation by the atomic oscillator in this disclosure. [Figure 5] This diagram shows the configuration of an atomic oscillator in this disclosure. [Figure 6] This flowchart shows the processing operation by the atomic oscillator in this disclosure. [Figure 7] This diagram shows the configuration of an atomic oscillator in this disclosure. [Figure 8] This figure shows the processing performed by the atomic oscillator in this disclosure. [Figure 9] This flowchart shows the processing operation by the atomic oscillator in this disclosure. [Figure 10] This diagram shows the configuration of the atomic oscillator in this disclosure. [Modes for carrying out the invention]

[0010] <Embodiment 1> A first embodiment of this disclosure will be described with reference to the drawings. The drawings may be relevant to any of the embodiments.

[0011] [composition] First, let's explain the basics of atomic oscillators. An atomic oscillator is a device that uses atomic gases, such as alkali metal atoms, to achieve stable frequency oscillation. An atomic oscillator has a gas cell containing an atomic gas, and by irradiating the gas cell with light containing at least two different frequencies and measuring the transmitted light, the quantum interference effect (called CPT (Coherent Population Trapping) resonance) that occurs when the difference frequency of the irradiated light matches the transition frequency between specific quantum states of the atomic gas can be detected as a fluctuation in the amount of transmitted light. For example, if the transmitted light spectrum is measured while sweeping the difference frequency of the irradiated light and detecting the transmitted light of cesium atoms, the amount of transmitted light reaches a peak value when the difference frequency matches the transition frequency between specific quantum states, and CPT resonance is detected. The difference frequency of the irradiated light at this time is called the resonance frequency. By detecting the resonance frequency of CPT resonance and controlling the difference frequency of the irradiated light to match the transition frequency between specific quantum states, a high-precision atomic oscillator utilizing the quantum interference effect can be realized. In the atomic oscillator using the CPT method described above, the resonance frequency of CPT resonance is used as the reference for the oscillation frequency.

[0012] The transmitted light spectrum is represented as a Lorentz function centered on the transition frequency between quantum states, and the point where the transmitted light amount is maximum is generally used as the resonance frequency of the CPT resonance, serving as the reference for the oscillation frequency. As an example, by sweeping the difference frequency of the light emitted when starting up an atomic oscillator, an error signal of the transmitted light spectrum, as shown in the schematic diagram in Figure 2(2-1), can be obtained, and the zero-crossing point of the error signal can be used as the resonance frequency, serving as the reference for the oscillation frequency. The error signal of the transmitted light spectrum can be obtained, for example, by modulating the difference frequency with a reference frequency that has a shorter period than the sweep period of the difference frequency when sweeping the difference frequency of the emitted light, and then locking in detection the detected transmitted light amount with the reference frequency.

[0013] The zero-point slope is defined as the amount of change in the error signal at the zero-crossing point, which is the resonance frequency. In other words, it is the ratio of the error signal fluctuation to the deviation between the difference frequency and the resonance frequency. When monitoring the error signal, a larger absolute value of the zero-point slope indicates higher sensitivity to detecting the difference between the difference frequency and the resonance frequency.

[0014] Furthermore, in an atomic oscillator, after detecting the resonance frequency using the zero-crossing point as described above during the initialization process, the zero-crossing point is constantly monitored, and the stability of the output frequency can be improved by feeding back the amount deviated from the zero-crossing point to the control signal of the oscillator.

[0015] In this embodiment, the atomic oscillator is operated in a (0,0) resonance state. The (0,0) resonance frequency is expressed as a quadratic function of the magnetic field parallel to the optical axis, as shown in Figure 2(2-2). In a parallel magnetic field of 0 μT, other quantum levels are not separated, and therefore a clear resonance signal cannot be obtained. For this reason, in the atomic oscillator of this embodiment, a bias magnetic field of several tens to several hundred μT is applied to the gas cell, as will be described later.

[0016] Next, the configuration of the atomic oscillator in this embodiment will be described. As shown in Figure 1, the atomic oscillator comprises a light source 10, magnetic field application devices 20, 21, 22, gas cells 31, 32, detectors 41, 42, a control device 50, and an oscillator 60. Here, the control device 50 is composed of an information processing device equipped with an arithmetic unit and a memory device. The control device 50 comprises a frequency adjustment unit 51 and a frequency correction unit 52, which are constructed by the arithmetic unit executing a program, as shown in Figure 1. In particular, this embodiment is equipped with two gas cells, and the magnetic field application devices 20, 21, 22 and detectors 41, 42 are configured to correspond to these two gas cells 31, 32. The following describes each configuration in detail.

[0017] The light source 10 functions as a light generator and generates light having at least two different frequencies. The light generated by the light source 10 is irradiated onto two gas cells 31 and 32, respectively. The transmitted light that passes through the two gas cells 31 and 32 reaches two detectors 41 and 42, respectively, where it is detected, converted into an electrical signal, and sent to the control device 50. The light source 10 is configured so that the wavelength of the generated light, the intensity of each frequency component of the light, and the difference frequency are controlled based on the control signal from the control device 50.

[0018] The irradiated light, which is light emitted from the light source 10, has at least two different frequency components. The light emitted from the light source 10 may have three or more different frequency components, but the difference frequency of two of these frequency components is approximately equal to the transition frequency between specific quantum states that form CPT resonances of alkali metal atoms. For example, the light emitted from the light generation unit 1 is realized by generating sidebands by modulating single-wavelength light emitted from a semiconductor laser or the like at a frequency approximately equal to the transition frequency of alkali metal atoms or approximately equal to 1 / N times, where N is an integer. In this case, the difference frequency is controlled by a mechanism that controls the modulation frequency. Alternatively, the light emitted from the light generation unit 1 can also be realized by combining two single-wavelength lights emitted from two semiconductor lasers or the like, each having a mechanism for controlling the difference frequency.

[0019] Specifically, in this embodiment, the light source 10 is configured with a vertical cavity surface-emitting laser (VCSEL) as a light source element that generates single-wavelength excitation light, and two excitation beams are generated by frequency modulation from this single-wavelength excitation light. The excitation light generated by the light source 10 is then split and irradiated onto the two gas cells 31 and 32, respectively. In Figure 1, the gray areas show the irradiation of the two gas cells 31 and 32 with excitation light.

[0020] Each of the two gas cells 31 and 32 is constructed by sealing in alkali metal atoms. The alkali metal atoms sealed in the gas cells 31 and 32 may be, for example, cesium atoms, rubidium atoms, sodium atoms, or potassium atoms. The material constituting the containers of the gas cells 31 and 32 is preferably a transparent material such as glass that has a high transmittance of the irradiation light generated from the light source 10. In addition to alkali metal atoms, the gas cells 31 and 32 may also contain a buffer gas that does not contribute to the absorption of irradiation light, in order to reduce the effect of collisions between the container wall and the gaseous alkali metal atoms.

[0021] In this embodiment, one gas cell 31 is referred to as the main gas cell (first gas cell), and the other gas cell 32 is referred to as the sub-gas cell (second gas cell). The system in which the main gas cell 31 is irradiated with excitation light is referred to as the main system, and the system in which the sub-gas cell 32 is irradiated with excitation light is referred to as the sub-system.

[0022] The magnetic field application devices 20, 21, and 22 are configured to include a current source 20 and coils 21 and 22. The coils 21 and 22 are arranged in a main system and a sub-system, respectively, with a main coil 21 positioned to cover the gas cell 31 of the main system and a sub-coil 22 positioned to cover the gas cell 32 of the sub-system. The current source 20 is connected to each coil 21 and 22 and configured to apply current, and the control device 50 adjusts the direction and magnitude of the current. This generates a bias magnetic field parallel or antiparallel to the irradiated light at a predetermined position inside each of the gas cells 31 and 32.

[0023] In this embodiment, by applying currents in opposite directions to the main coil 21 and the sub-coil 22, bias magnetic fields of the same intensity are applied to the main gas cell 31 and the sub-gas cell 32 in opposite directions. As a result, as shown in Figure 1, a +B bias magnetic field is applied to a predetermined position inside the main gas cell 31 at +B bias A bias magnetic field is applied, and at a predetermined position inside the sub-gas cell 32, -B biasThis results in a state where a bias magnetic field is applied.

[0024] Detectors 41 and 42 function as photodetectors and detect transmitted light, which is light that has passed through each gas cell 31 and 32, respectively. Detectors 41 and 42 can be implemented using, for example, photodiodes, but may be implemented using any photodetector that has the function of detecting light. Specifically, in this embodiment, there is a main detector 41 located in the main system that detects transmitted light from the main gas cell 31, and a sub-detector 42 located in the sub-system that detects transmitted light from the sub-gas cell 32. The light information detected by each detector 41 and 42 is converted into an electrical signal or the like and input to the control device 50.

[0025] The frequency adjustment unit 51 of the control device 50 (control unit) determines the resonance frequency from a signal based on the amount of transmitted light input from detectors 41 and 42 as an initialization process, such as when the atomic oscillator is started, and controls the oscillation frequency of the oscillator 60 based on the determined resonance frequency. Specifically, in this embodiment, the frequency adjustment unit 51 sweeps the difference frequency of the irradiated light and, as shown in Figure 2(2-1), determines the resonance frequency as the zero-crossing point at the monitoring position of the error signal of the transmitted light spectrum based on the transmitted light that has passed through the main gas cell 31 of the main system. Once the resonance frequency is determined, it applies feedback to fix the error signal of the lock-in detected transmitted light spectrum at a predetermined signal level, and controls the oscillation frequency by adjusting the control voltage of the oscillator 60. Here, the oscillator 60 is composed of a VCXO (voltage-controlled crystal oscillator) that oscillates at about 10 MHz, and generates an oscillation signal according to the control voltage output from the frequency adjustment unit 51 and applied, and outputs it as the oscillation frequency, which is the external output of the atomic oscillator. As a result, the oscillation frequency is stabilized at 10 MHz as long as the resonance frequency does not change. In addition, the difference frequency of the irradiated light is generated by converting the oscillation signal of the VCXO into a signal of several GHz using a frequency multiplier, and this is input to the light generation unit 1.

[0026] Here, a case where an intrusion magnetic field, which is an external magnetic field other than the bias magnetic field, occurs in the atomic oscillator will be described. The intrusion magnetic field is equally applied to the main gas cell 31 and the sub gas cell 32, and the magnetic field value at the positions of the main gas cell 31 and the sub gas cell 32 where bias magnetic fields of the same intensity are applied in the opposite directions will fluctuate. In the case of circularly polarized light irradiation, the resonance frequency is determined by the absolute value of the parallel magnetic field. For example, if |B bias (bias magnetic field)| > |B ext (intrusion magnetic field)|, then at the position of the main gas cell 31, |B bias +B ext | is applied, and at the position of the sub gas 32, |B bias -B ext | is applied. At this time, the bias magnetic field is several tens to several hundreds of μT, the geomagnetism is several tens of μT, and if the intrusion magnetic field is shielded to about 1 / 1000, the above conditions can be satisfied. As an example, as shown in FIG. 3(3-2), when an intrusion magnetic field of “+B ext ” occurs, at the position of the main gas cell 31, a magnetic field of “+B bias +B ext ” is applied, and at the position of the sub gas cell 32, a magnetic field of “-B bias +B ext ” is applied, and the magnetic fields at the positions of the respective gas cells 31 and 32 fluctuate and are different. Then, as shown in FIG. 3(3-2), the (0,0) resonance frequency is f(B bias +B ext ) in the main gas cell 31 and f(B bias -B ext ) in the sub gas cell 32, and the resonance frequencies in the main system and the sub system are different.

[0027] In the above-described situation, the frequency correction unit 52 monitors the error signal of the transmitted light spectrum that has passed through the main gas cell 31 and the error signal of the transmitted light spectrum that has passed through the sub gas cell 32, and detects whether or not an intrusion magnetic field has occurred. For example, at the zero-crossing point of the error signal of the transmitted light spectrum that has passed through the main gas cell 31, which is the monitor position, the error signal value V of the transmitted light spectrum that has passed through the sub gas cell 32 sIf the signal is not at the zero-crossing point, that is, if the error signal of the main gas cell 31 and the error signal of the sub-gas cell 32 are different, it is possible to detect that an intrusive magnetic field has been generated. However, the frequency correction unit 52 may also detect that the error signals of the main gas cell 31 and the sub-gas cell 32 are different by other means based on the detected values ​​of these signals, or it may detect that an intrusive magnetic field has been generated by measuring the external magnetic field without using the detected values.

[0028] When the frequency correction unit 52 detects the occurrence of an intrusion magnetic field, it corrects the oscillation frequency of the oscillation signal based on the resonance frequency determined based on the error signal of the transmitted light spectrum of the main gas cell 31, based on the error signal of the transmitted light spectrum detected from the sub-gas cell 32. Here, the frequency correction unit 52 calculates the zero-point slope of the error signal value from the sub-gas cell 32 shown in Figure 3(3-1) as shown in Equation 1 below. At this time, the magnetic field fluctuation of the resonance frequency is expressed by Equation 2, and the intrusion magnetic field B ext When this is the case, the variation in the monitor position (main resonance frequency) is given by equation 3, the variation in the sub-resonance frequency is given by equation 4, and the error signal value V of the sub-gas cell 32 at the monitor position. s This becomes equation 5.

[0029]

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[0030] Then, the relative frequency variation of the resonance frequency of the main gas cell 31 is given by equation 6, and the frequency correction unit 52 uses the resonance frequency determined by the frequency adjustment unit 51 to output the frequency f as shown in equation 7. out Correct it to this.

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[0031] With the above configuration, the atomic oscillator in this embodiment can estimate the intrusion magnetic field based on the error signal of the transmitted light spectrum detected from the sub-gas cell 32, which is a sub-system, and output an oscillation signal with an oscillation frequency corrected according to the intrusion magnetic field. In the above, the resonance frequency is corrected by detecting the generation of an intrusion magnetic field from the sub-system, but the frequency correction unit 52 may always correct the resonance frequency based on the error signal from the sub-gas cell 32, regardless of the detection of an intrusion magnetic field.

[0032] [Operation] Next, we will explain the operation of the atomic oscillator described above.

[0033] As an initialization process, such as when the atomic oscillator is started, the control device 50 sweeps the difference frequency of the light emitted from the light source 10 and determines the zero-crossing point at the monitoring position of the error signal of the transmitted light spectrum based on the transmitted light that has passed through the main gas cell 31 of the main system as the resonance frequency (step S1 in Figure 4). The control device 50 also calculates the zero-point slope shown in Equation 1 for the error signal of the transmitted light spectrum based on the transmitted light that has passed through the sub-gas cell 32 of the sub-system, as shown in Figure 3(3-1) (step S2 in Figure 4). Then, as shown in Figure 3(3-1), the control device 50 controls the oscillation frequency by adjusting the control voltage of the oscillator 60 so that the error signal of the transmitted light spectrum detected from the main gas 31 matches the zero point (step S3 in Figure 4).

[0034] Subsequently, the control device 50 detects the error signal V of the transmitted light spectrum transmitted through the sub-gas cell 32. s Based on this, the control unit controls the output to output an oscillation frequency corrected for the resonance frequency according to the intrusion magnetic field (step S4 in Figure 4). Specifically, as shown in Figure 3(3-1), the control unit 50 detects that an intrusion magnetic field has been generated when the error signal of the main gas cell 31 and the error signal of the sub-gas cell 32 are different, and as shown in equations 3 to 7, the slope value of the error signal of the transmitted light spectrum detected from the sub-gas cell 32 and the error signal value V at the monitoring position s Based on this, an oscillation signal with an oscillation frequency corrected from the resonance frequency determined from the error signal of the transmitted light spectrum of the main gas cell 31 is output.

[0035] As described above, in the atomic oscillator of this embodiment, an oscillation signal with an oscillation frequency corrected according to the penetration magnetic field can be output based on the error signal of the transmitted light spectrum detected from the sub-gas cell 32, which is a sub-system. As a result, the stability of the resonance frequency against magnetic field fluctuations can be further improved in the atomic oscillator.

[0036] <Embodiment 2> Next, a second embodiment of this disclosure will be described with reference to the drawings. The drawings may be relevant to any of the embodiments.

[0037] [composition] The atomic oscillator in this embodiment differs in some configurations from the atomic oscillator in Embodiment 1 described above, and the following will mainly describe the differences in these configurations in detail.

[0038] As shown in Figure 5, the atomic oscillator in this embodiment comprises a light source 10, magnetic field application devices 20, 21, 22, gas cells 31, 32, detectors 41, 42, a control device 50, and an oscillator 60. The control device 50, as shown in Figure 1, comprises a frequency adjustment unit 51 and a magnetic field correction unit 53, which are constructed by the arithmetic unit executing a program. The following describes each component in detail.

[0039] As described above, the atomic oscillator is equipped with two gas cells 31 and 32 (main gas cell 31 and sub-gas cell 32), which constitute the main system and sub-system, respectively. Each gas cell 31 and 32 is then subjected to bias magnetic fields of the same intensity in opposite directions by the coils 21 and 22 of the magnetic field application devices 20, 21, and 22, as described above. As a result, a +B magnetic field is applied to a predetermined position inside the main gas cell 31 at a specific location. bias A bias magnetic field is applied, and a predetermined position inside the sub-gas cell 32 is at -B bias This results in a state where a bias magnetic field of +B is applied. Furthermore, when an intrusion magnetic field is applied to the atomic oscillator, a +B magnetic field is applied to a predetermined position inside the main gas cell 31. bias +B ext A magnetic field is applied, and at a predetermined location inside the sub-gas cell 32, -B bias +B ext This results in a state where a magnetic field of that magnitude is applied.

[0040] The frequency adjustment unit 51 of the control device 50 (control unit) sweeps the difference frequency of the irradiated light, as described above, and determines the resonance frequency as the zero-crossing point at the monitoring position of the error signal of the transmitted light spectrum based on the transmitted light that has passed through the main gas cell 31 of the main system. Once the resonance frequency is determined, it applies feedback to fix the error signal of the lock-in detected transmitted light spectrum at a predetermined signal level, and controls the oscillation frequency by adjusting the control voltage of the oscillator 60. Furthermore, as will be described later, even if the bias magnetic field applied to each gas cell 31, 32 is corrected due to the application of an intrusion magnetic field, the control device 50 controls the oscillation frequency by determining the resonance frequency from the error signal of the transmitted light spectrum based on the transmitted light that has passed through the main gas cell 31 of the main system in such a situation.

[0041] The magnetic field correction unit 53 of the control device 50 (control unit) monitors the error signal of the transmitted light spectrum transmitted through the main gas cell 31 and the error signal of the transmitted light spectrum transmitted through the sub-gas cell 32, similar to the embodiment 1 described above, to detect whether or not an intrusive magnetic field has been generated. For example, at the zero-crossing point of the error signal of the transmitted light spectrum transmitted through the main gas cell 31, which is the monitoring position, the magnetic field correction unit 53 checks the error signal value V of the transmitted light spectrum transmitted through the sub-gas cell 32. s If the signal is not at the zero-crossing point, that is, if the error signal of the main gas cell 31 and the error signal of the sub-gas cell 32 are different, it is possible to detect that an intrusive magnetic field has been generated. However, the magnetic field correction unit 53 may also detect that the error signals of the main gas cell 31 and the sub-gas cell 32 are different by other means based on the detected values ​​of these signals, or it may detect that an intrusive magnetic field has been generated by measuring the external magnetic field without using the detected values.

[0042] When the magnetic field correction unit 53 detects that an intrusion magnetic field has been generated, it controls the strength of the bias magnetic field based on the error signal of the transmitted light spectrum detected from the sub-gas cell 32. At this time, the magnetic field correction unit 53 controls the strength of the magnetic field at a predetermined position inside the main gas cell 31 "+B bias +B ext The current value applied to the current source 20 of the magnetic field application devices 20, 21, and 22 is controlled to vary the strength of the magnetic field applied by the coil 21, so that the value of the current remains constant.

[0043] Specifically, the magnetic field correction unit 53 corrects the magnetic field as follows. First, the magnetic field at the start of the atomic oscillator is given by equation 8, and the error signal value of the sub-gas cell 32 when no intrusion magnetic field is applied and there are no magnetic field fluctuations is given by equation 9. Then, when an intrusion magnetic field is applied and the error signal value of the sub-gas cell 32 during magnetic field fluctuations is given by equation 10, the intrusion magnetic field can be estimated by equation 11. For this reason, the magnetic field correction unit 53 corrects the bias magnetic field as shown in equation 12. In addition, as shown in equation 12, in order to correct the bias magnetic field, the slope of the error signal, which is expressed by equation 1 as described above, is calculated in advance, and data representing the magnetic field fluctuation at the resonance frequency, as shown in Figure 2(2-2), is stored in advance, which is expressed by equation 2.

[0044]

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[0045] With the above configuration, the atomic oscillator in this embodiment estimates the intrusion magnetic field based on the error signal of the transmitted light spectrum detected from the sub-gas cell 32, which is a sub-system, and corrects the bias magnetic field to cancel out the intrusion magnetic field. The atomic oscillator then determines the resonance frequency according to the error signal from the main gas cell 31 in the corrected magnetic field and can output an oscillation signal at the oscillation frequency based on the determined resonance frequency. In the above, the magnetic field is corrected by detecting the generation of an intrusion magnetic field from the sub-system, but the magnetic field correction unit 53 may always correct the magnetic field based on the error signal from the sub-gas cell 32, regardless of the detection of an intrusion magnetic field.

[0046] [Operation] Next, we will explain the operation of the atomic oscillator described above.

[0047] As an initialization process, such as when the atomic oscillator is started, the control device 50 sweeps the difference frequency of the light emitted from the light source 10 and determines the zero-crossing point of the error signal of the transmitted light spectrum based on the transmitted light that has passed through the main gas cell 31 of the main system as the resonance frequency (step S11 in Figure 6). In addition, as shown in Figure 3(3-1), the control device 50 calculates the zero-point slope shown in Equation 1 of the error signal of the transmitted light spectrum based on the transmitted light that has passed through the sub-gas cell 32 of the sub-system (step S12 in Figure 6). Furthermore, the control device 50 estimates the initial value of the magnetic field shown in Equation 8 and calculates the magnetic field fluctuation from the magnetic field fluctuation data of the resonance frequency, which is expressed by Equation 2 and shown in Figure 2(2-2) (step S12 in Figure 6). Then, as shown in Figure 3(3-1), the control device 50 controls the oscillation frequency by adjusting the control voltage of the oscillator 60 so that the error signal of the transmitted light spectrum detected from the main gas 31 matches the zero point (step S13 in Figure 6).

[0048] Subsequently, the control device 50 controls the current value applied to the current source 20 of the magnetic field application device to correct the magnetic field according to the intrusion magnetic field, based on the error signal of the transmitted light spectrum transmitted through the sub-gas cell 32 (step S14 in Figure 6). Specifically, as shown in Figure 3(3-1), the control device 50 detects that an intrusion magnetic field has been generated when the error signal of the main gas cell 31 and the error signal of the sub-gas cell 32 are different, and corrects and applies the magnetic field based on the slope value of the error signal of the transmitted light spectrum detected from the sub-gas cell 32 and the magnetic field fluctuation, as shown in equations 9 to 12. Then, the control device 50 outputs an oscillation signal with an oscillation frequency based on the resonance frequency determined from the error signal of the transmitted light spectrum of the main gas cell 31 in the corrected magnetic field.

[0049] As described above, in the atomic oscillator of this embodiment, the magnetic field applied to the main gas cell 31 is corrected according to the intrusion magnetic field based on the error signal of the transmitted light spectrum detected from the sub-gas cell 32, which is a sub-system, and an oscillation signal with an oscillation frequency corresponding to the resonance frequency detected under such corrected magnetic field environment can be output. As a result, the stability of the resonance frequency against magnetic field fluctuations can be further improved in the atomic oscillator.

[0050] <Embodiment 3> Next, a third embodiment of this disclosure will be described with reference to the drawings. The drawings may be relevant to any of the embodiments.

[0051] [composition] The atomic oscillator in this embodiment differs in some configurations from the atomic oscillators in embodiments 1 and 2 described above. The following will mainly describe the differences in these configurations in detail.

[0052] As shown in Figure 7, the atomic oscillator in this embodiment comprises a light source 10, magnetic field application devices 20, 21, 22, gas cells 31, 32, detectors 41, 42, a control device 50, and an oscillator 60. The control device 50 includes a frequency adjustment unit 51 constructed by a computing unit executing a program, as shown in Figure 1. The following describes each component in detail.

[0053] As described above, the atomic oscillator is equipped with two gas cells 31 and 32 (main gas cell 31 and sub-gas cell 32), which constitute the main system and sub-system, respectively. As described above, bias magnetic fields are applied to each gas cell 31 and 32 in opposite directions by the coils 21 and 22 of the magnetic field application device 20, 21, and 22. However, in this embodiment, bias magnetic fields of different strengths are applied to each gas cell 31 and 32. For example, by adding a parallel resistor to the main coil 21 of the magnetic field application device as shown in Figure 7, or by reducing the number of turns of the coil, a difference B1 is created in the strength of the bias magnetic fields applied to each gas cell 31 and 32 by the main coil 21 and the sub-coil 22. As a result, a +B bias A bias magnetic field of -B1 is applied, and a predetermined position inside the sub-gas cell 32 is -B bias This results in a state where a bias magnetic field is applied. However, the method is not limited to the one described above; any method may be used to create a difference in the strength of the magnetic field applied to each gas cell 31, 32.

[0054] In this embodiment, as shown in Figure 7, the atomic oscillator is configured such that a difference signal representing the difference between the error signal of the transmitted light spectrum detected by the detector 41 after passing through the main gas cell 31 and the error signal of the transmitted light spectrum detected by the detector 42 after passing through the sub-gas cell 32 is input to the control device 50. In this embodiment, as described above, even when no intrusion magnetic field is applied to each gas cell 31, 32, bias magnetic fields of different strengths are applied to each. Therefore, as shown in Figure 8, there is a difference in the error signals (main and sub) from each gas cell 31, 32, and differences may occur in the resonance frequencies that can be determined from each error signal. Furthermore, when an intrusion magnetic field is applied, bias magnetic fields are applied to each gas cell 31, 32 in opposite directions, resulting in even greater differences in the resonance frequencies that can be determined from each error signal.

[0055] In the situation described above, the frequency adjustment unit 51 of the control device 50 (control unit) in this embodiment determines the resonance frequency based on the difference signal between the error signal of the transmitted light spectrum transmitted through the main gas cell 31 and the error signal of the transmitted light spectrum transmitted through the sub-gas cell 32, and controls the oscillation frequency of the oscillation signal based on the determined resonance frequency. Specifically, the frequency adjustment unit 51 sweeps the difference frequency of the irradiated light and, as shown in Figure 8, determines the center (peak) of the difference signal between the error signal of the transmitted light spectrum detected from the main gas cell 31 and the error signal of the transmitted light spectrum detected from the sub-gas cell 32 as the resonance frequency. The frequency adjustment unit 51 then locks the center (peak) of the difference signal as the resonance frequency and controls the oscillation frequency by adjusting the control voltage of the oscillator 60. At this time, even if an intrusive magnetic field is applied, the peak of the difference signal is unlikely to move, and the frequency remains stable against magnetic field fluctuations.

[0056] Note that the magnetic field difference B1 is the assumed penetration magnetic field B ext It is desirable that it be greater than a multiple of the maximum value. For example, B ext This is because, in the case of =B1 / 2, the resonance frequencies of the main error signal and the sub-error signal overlap, and there is a risk that the difference signal will disappear.

[0057] [Operation] Next, we will explain the operation of the atomic oscillator described above.

[0058] First, the atomic oscillator is set up so that bias magnetic fields of opposite directions and different intensities are applied to each gas cell 31 and 32 (step S21 in Figure 9). In this configuration, the control device 50 sweeps the difference frequency of the irradiated light and obtains the difference signal between the error signal of the transmitted light spectrum detected from the main gas cell 31 and the error signal of the transmitted light spectrum detected from the sub-gas cell 32 (step S22 in Figure 9). Then, the control device 50 determines the center (peak) of the difference signal as the resonance frequency and controls the oscillation frequency by adjusting the control voltage of the oscillator 60 (step S23 in Figure 9).

[0059] As described above, in the atomic oscillator of this embodiment, a difference is provided in the magnetic fields applied to each gas cell 31 and 32, and the resonance frequency can be determined from the difference signal of the error signals of the transmitted light spectra detected from each gas cell 31 and 32, and an oscillation signal can be output. As a result, the stability of the resonance frequency against magnetic field fluctuations can be further improved in the atomic oscillator.

[0060] <Embodiment 4> Next, a fourth embodiment of this disclosure will be described with reference to the drawings. The drawings may be relevant to any of the embodiments.

[0061] As shown in Figure 10, the atomic oscillator 100 in this embodiment is Two gas cells 101, each containing alkali metal atoms and with bias magnetic fields applied in opposite directions, A light generating unit 102 that irradiates each of the two gas cells with irradiation light having at least two different frequency components, A photodetector 103 detects the transmitted light that has passed through the two gas cells, A control unit 104 determines the resonance frequency based on the detection signal corresponding to the transmitted light detected from each of the two gas cells, and controls the oscillation frequency of the oscillation signal output to the outside based on the determined resonance frequency. It is equipped with.

[0062] With the above configuration, the atomic oscillator 100 determines the resonance frequency and controls the oscillation frequency based on the detection signals of transmitted light from each of the two gas cells 101 to which bias magnetic fields are applied in opposite directions. This allows for the detection of the application of an intrusion magnetic field from the transmitted light, and enables the correction of the resonance frequency or magnetic field according to the intrusion magnetic field, or the determination of the resonance frequency while suppressing the effects of magnetic field fluctuations caused by the intrusion magnetic field. As a result, the stability of the resonance frequency against magnetic field fluctuations can be further improved.

[0063] Although the present disclosure has been described above with reference to the embodiments described above, the present disclosure is not limited to the embodiments described above. Various modifications to the structure of the present disclosure can be made that will be understood by those skilled in the art within the scope of the present disclosure.

[0064] <Note> Some or all of the above embodiments may also be described as follows. The general configuration of the atomic oscillator and control method in this disclosure is described below. However, the present invention is not limited to the following configuration. Furthermore, some or all of the configurations and functions described in Appendices 2 to 7, which are dependent on Appendice 1 below, may also be dependent on other Appendices 8 in the same way as Appendices 2 to 7. Moreover, not limited to Appendices 1 and 8, some or all of the configurations and functions described as appendices may also be dependent on similar hardware, software, various recording means for recording software, or systems, without departing from the embodiments described above. (Note 1) Two gas cells containing alkali metal atoms, with biased magnetic fields applied in opposite directions, A light generating unit that irradiates each of the two gas cells with irradiation light having at least two different frequency components, A photodetector that detects the transmitted light that has passed through the two gas cells, A control unit that determines the resonance frequency based on detection signals corresponding to the transmitted light detected from each of the two gas cells, and controls the oscillation frequency of the oscillation signal output to the outside based on the determined resonance frequency, An atomic oscillator equipped with [a specific feature / equipment]. (Note 2) The atomic oscillator described in Appendix 1, The system is configured to apply the bias magnetic field of the same intensity to the two gas cells in opposite directions. Atomic oscillator. (Note 3) The atomic oscillator described in Appendix 2, The control unit, when the detection signals detected from the two gas cells are different, determines the resonance frequency based on the detection signals detected from the two gas cells and controls the oscillation frequency of the oscillation signal output to the outside based on the determined resonance frequency. Atomic oscillator. (Note 4) The atomic oscillator described in Appendix 2, The control unit determines the resonance frequency based on the detection signal detected from the first gas cell, and corrects the oscillation frequency of the oscillation signal based on the resonance frequency based on the detection signal detected from the second gas cell. Atomic oscillator. (Note 5) The atomic oscillator described in Appendix 2, The control unit corrects the strength of the bias magnetic field based on the detection signal detected from the second gas cell, and determines the resonance frequency based on the detection signal detected from the first gas cell to control the oscillation frequency of the oscillation signal. Atomic oscillator. (Note 6) The atomic oscillator described in Appendix 1, The system is configured to apply bias magnetic fields of different intensities in opposite directions to the two gas cells. Atomic oscillator. (Note 7) The atomic oscillator described in Appendix 6, The control unit determines the resonance frequency based on the difference between the detection signals detected from the two gas cells, and controls the oscillation frequency of the oscillation signal output to the outside based on the determined resonance frequency. Atomic oscillator. (Note 8) Two gas cells containing alkali metal atoms, A light generating unit that irradiates each of the two gas cells with irradiation light having at least two different frequency components, A photodetector that detects the transmitted light that has passed through the two gas cells, A control method for an atomic oscillator equipped with, By applying bias magnetic fields in opposite directions to the two gas cells, Based on the detection signals corresponding to the transmitted light detected from each of the two gas cells, the resonance frequency is determined, and the oscillation frequency of the oscillation signal output to the outside is controlled based on the determined resonance frequency. Control method. (Note 9) The control method described in Appendix 8, Apply the bias magnetic field of the same intensity to the two gas cells in opposite directions. Control method. (Note 10) The control method described in Appendix 9, When the detection signals detected from the two gas cells are different, the resonance frequency is determined based on the detection signals detected from the two gas cells, and the oscillation frequency of the externally output oscillation signal is controlled based on the determined resonance frequency. Control method. (Note 11) The control method described in Appendix 9, The resonance frequency is determined based on the detection signal detected from the first gas cell, and the oscillation frequency of the oscillation signal based on the resonance frequency is corrected based on the detection signal detected from the second gas cell. Control method. (Note 12) The control method described in Appendix 9, The strength of the bias magnetic field is corrected based on the detection signal detected from the second gas cell, and the resonance frequency is determined based on the detection signal detected from the first gas cell to control the oscillation frequency of the oscillation signal. Control method. (Note 13) The control method described in Appendix 8, The system is configured to apply bias magnetic fields of different intensities in opposite directions to the two gas cells. Control method. (Note 14) The control method described in Appendix 13, Based on the difference between the detection signals detected from the two gas cells, the resonance frequency is determined, and the oscillation frequency of the externally output oscillation signal is controlled based on the determined resonance frequency. Control method. [Explanation of symbols]

[0065] 10 light source 20 Current source 21,22 coils 31,32 gas cells 41,42 detectors 50 Control device 51 Frequency adjustment section 52 Frequency Correction Section 53 Magnetic field correction unit 60 Oscillator 100 Atomic Oscillators 101 Gas Cell 102 Light generating unit 103 Light detection unit 104 Control Unit

Claims

1. Two gas cells containing alkali metal atoms, with bias magnetic fields applied in opposite directions, A light generating unit that irradiates each of the two gas cells with irradiation light having at least two different frequency components, A photodetector that detects the transmitted light that has passed through the two gas cells, A control unit that determines the resonance frequency based on detection signals corresponding to the transmitted light detected from each of the two gas cells, and controls the oscillation frequency of the oscillation signal output to the outside based on the determined resonance frequency, An atomic oscillator equipped with [a specific feature / equipment].

2. The atomic oscillator according to claim 1, The system is configured to apply the same strength of bias magnetic fields in opposite directions to the two gas cells. Atomic oscillator.

3. The atomic oscillator according to claim 2, The control unit, when the detection signals detected from the two gas cells are different, determines the resonance frequency based on the detection signals detected from the two gas cells and controls the oscillation frequency of the oscillation signal output to the outside based on the determined resonance frequency. Atomic oscillator.

4. The atomic oscillator according to claim 2, The control unit determines the resonance frequency based on the detection signal detected from the first gas cell, and corrects the oscillation frequency of the oscillation signal based on the resonance frequency based on the detection signal detected from the second gas cell. Atomic oscillator.

5. The atomic oscillator according to claim 2, The control unit corrects the strength of the bias magnetic field based on the detection signal detected from the second gas cell, and controls the oscillation frequency of the oscillation signal by determining the resonance frequency based on the detection signal detected from the first gas cell. Atomic oscillator.

6. The atomic oscillator according to claim 1, The system is configured to apply bias magnetic fields of different intensities in opposite directions to the two gas cells. Atomic oscillator.

7. The atomic oscillator according to claim 6, The control unit determines the resonance frequency based on the difference between the detection signals detected from the two gas cells, and controls the oscillation frequency of the oscillation signal output to the outside based on the determined resonance frequency. Atomic oscillator.

8. Two gas cells containing alkali metal atoms, A light generating unit that irradiates each of the two gas cells with irradiation light having at least two different frequency components, A photodetector that detects the transmitted light that has passed through the two gas cells, A control method for an atomic oscillator equipped with, By applying bias magnetic fields in opposite directions to the two gas cells, Based on the detection signals corresponding to the transmitted light detected from each of the two gas cells, the resonance frequency is determined, and the oscillation frequency of the externally output oscillation signal is controlled based on the determined resonance frequency. Control method.

9. A control method according to claim 8, Apply the bias magnetic field of the same intensity to the two gas cells in opposite directions. Control method.

10. A control method according to claim 8, The system is configured to apply bias magnetic fields of different intensities in opposite directions to the two gas cells. Control method.

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