Atomic oscillator

Abstract

To solve a problem of difficulty in preventing a light shift from occurring to an atomic oscillator.SOLUTION: An atomic oscillator 100 comprises: a light generator 101 which generates two exciting light beams; an alkali metal atomic gas cell 102 which is irradiated with the two exciting light beams having their frequency difference varied; a detection part 103 which detects the quantity of transmitted light transmitted through the alkali metal atomic gas cell; and a control part 104 which measures the resonance frequency of an alkali metal atomic gas based upon the detected quantity of the transmitted light, and controls the intensity ratio of the two exciting light beams irradiating the alkali metal gas cell based upon the measured resonance frequency.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present disclosure relates to an atomic oscillator, a control method, a control device, and a program.

Background Art

[0002] An atomic oscillator is a device that measures accurate time based on the natural frequency of an atom. In a small atomic clock, the CPT (Coherent Population Trapping), which is a quantum interference effect that occurs when two frequencies of excitation light are irradiated on an alkali metal atom gas, is used as the oscillation principle of the atomic oscillator to measure the natural frequency of the atom. In CPT, when the difference between the frequencies of the two excitation lights matches the transition frequency between the ground levels of the alkali metal, the absorption of the excitation light does not occur and the amount of transmitted light increases. In an atomic oscillator that operates on the principle of CPT, the difference in the frequencies of the excitation lights is swept, and the difference in the frequencies at which the amount of transmitted light is maximized is regarded as the natural frequency of the atom. Whether the natural frequency of this atom can be stably acquired over a long period (long-term stability) is one of the performance indicators of the atomic oscillator.

[0003] In the measurement of the natural frequency of an atom using CPT, the main factor that reduces the above-described long-term stability is the change over time of the light shift. The light shift is a phenomenon in which the natural frequency of an atom shifts due to the interaction between the excitation light and the atom. For example, it is known that the light shift occurs due to the change over time of the intensity of the excitation light.

[0004] Regarding the above-described problem of the light shift, Patent Document 1 describes suppressing the light shift by correcting the change in the intensity of all the excitation lights. Specifically, in Patent Document 1, the intensity of all the excitation lights is corrected to a constant value by using two types of light sources, thereby suppressing the occurrence of the light shift.

Prior Art Documents

Patent Documents

[0005]

Patent Document

[0006] However, it is difficult to keep the intensity of all excitation light perfectly constant, and it remains difficult to suppress the occurrence of light shift.

[0007] Therefore, the purpose of this disclosure is to provide an atomic oscillator that can solve the above-mentioned problem of difficulty in suppressing the occurrence of light shift. [Means for solving the problem]

[0008] One form of the atomic oscillator in this disclosure is A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A control unit measures the resonance frequency of the alkali metal atomic gas based on the detected amount of transmitted light, and controls the intensity ratio of two excitation lights irradiated onto the alkali metal atomic gas cell based on the measured resonance frequency. Equipped with, This is the structure it takes.

[0009] Furthermore, a control method which is one form of this disclosure is A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A method for controlling an atomic oscillator equipped with, The resonance frequency of the alkali metal atomic gas is measured based on the detected amount of transmitted light, and the intensity ratio of the two excitation lights irradiated onto the alkali metal atomic gas cell is controlled based on the measured resonance frequency. adopts the following structure.

[0010] Also, a control device according to one embodiment of the present disclosure includes a light generator that generates two excitation lights, an alkali metal atomic gas cell irradiated with a changed frequency difference between the two excitation lights, a detection unit that detects the amount of light of the transmitted light that has passed through the alkali metal atomic gas cell, and is a control device that controls an atomic oscillator including these components, measures the resonance frequency of the alkali metal atomic gas based on the detected amount of light of the transmitted light, and controls the intensity ratio of the two excitation lights irradiated to the alkali metal atomic gas cell based on the measured resonance frequency. adopts the following structure.

[0011] Also, a program according to one embodiment of the present disclosure causes a control device including a light generator that generates two excitation lights, an alkali metal atomic gas cell irradiated with a changed frequency difference between the two excitation lights, a detection unit that detects the amount of light of the transmitted light that has passed through the alkali metal atomic gas cell, and that controls an atomic oscillator including these components to measure the resonance frequency of the alkali metal atomic gas based on the detected amount of light of the transmitted light, and to control the intensity ratio of the two excitation lights irradiated to the alkali metal atomic gas cell based on the measured resonance frequency. execute the process. adopts the following structure.

Advantages of the Invention

[0012] The present disclosure configured as described above can provide an atomic oscillator that can suppress the occurrence of light shift.

Brief Description of the Drawings

[0013] [Figure 1] It is a block diagram showing the configuration of an atomic oscillator in a first embodiment of the present disclosure. [Figure 2]It is a diagram showing the state of processing by the atomic oscillator disclosed in FIG. 1. [Figure 3] It is a diagram showing the state of processing by the atomic oscillator disclosed in FIG. 1. [Figure 4] It is a diagram showing the state of processing by the atomic oscillator disclosed in FIG. 1. [Figure 5] It is a diagram showing the state of processing by the atomic oscillator disclosed in FIG. 1. [Figure 6] It is a diagram showing the state of processing by the atomic oscillator disclosed in FIG. 1. [Figure 7] It is a flowchart showing the processing operation of the atomic oscillator disclosed in FIG. 1. It is a diagram showing the state of processing. [Figure 8] It is a block diagram showing the configuration of the atomic oscillator in the second embodiment of the present disclosure. [Figure 9] It is a flowchart showing the processing operation of the atomic oscillator disclosed in FIG. 8. [Figure 10] It is a block diagram showing the configuration of the atomic oscillator in the third embodiment of the present disclosure. [Figure 11] It is a flowchart showing the processing operation of the atomic oscillator disclosed in FIG. 10. [Figure 12] It is a block diagram showing the configuration of the atomic oscillator in Embodiment 4 of the present disclosure. [Figure 13] It is a flowchart showing the operation of the atomic oscillator in Embodiment 4 of the present disclosure.

Mode for Carrying Out the Invention

[0014] <Embodiment 1> The first embodiment of the present disclosure will be described with reference to FIGS. 1 to 7. FIGS. 1 to 6 are diagrams for explaining the configuration of the atomic oscillator in the present embodiment, and FIG. 7 is a diagram for explaining the operation of the atomic oscillator.

[0015] [Configuration] As shown in Figure 1, the atomic oscillator in this embodiment mainly comprises a photogenerator 1, a cesium metal atomic gas cell 2, a photodetector 3, a controller 4, and a spectrometer 5. The photogenerator 1 comprises a laser 11, an optical frequency modulator 12, and an optical attenuator 13. The controller 4 comprises a laser control unit 41, a signal generator control unit 42, an optical attenuator control unit 43, and a calculation unit 44. The controller 4 is composed of an information processing device (control device) equipped with an arithmetic unit and a memory device, and each of the units 41 to 44 of the controller 4 is realized by the execution of a program by the arithmetic unit.

[0016] The photogenerator 1 generates excitation light of a single wavelength and also generates two excitation lights by frequency modulation from this single wavelength excitation light, which are then irradiated onto the cesium metal atomic gas cell 2. Specifically, first, the laser 11 of the photogenerator 1 generates excitation light of a single wavelength, for example, 894.5812 nm (first excitation light), based on a setting value specified by the laser control unit 41 of the controller 4. This single wavelength excitation light is sent to the optical frequency modulator 12.

[0017] The optical frequency modulator 12 generates two excitation beams (second excitation beams) to irradiate the cesium metal atom gas cell by frequency modulating single-wavelength excitation beams. Specifically, the signal generator control unit 42 of the controller 4 sets the frequency modulation power and modulation frequency, which are the set values ​​of the equipped signal generator 42a. The signal generator 42a then controls the optical frequency modulator 12 with the set frequency modulation power and modulation frequency fmod to generate excitation beams containing multiple frequency components consisting of a main band (f0) and sidebands (f0±fmod, f0±2fmod, f0±3fmod, ...) as shown in Figure 2. In particular, in this embodiment, excitation beams are generated that use two frequency components, 0th-order light and -1st-order light, as the main light sources for resonance generation. However, the two excitation beams generated by the optical frequency modulator 12 and used as the main light sources for resonance generation are not limited to 0th-order light and -1st-order light; they may also be 0th-order light and +1st-order light, or excitation beams of other bands may be used.

[0018] In this embodiment, the signal generator control unit 42 generates excitation light for each changed setting by varying the frequency modulation power and modulation frequency to multiple values. In other words, each time the setting values ​​of the frequency modulation power and modulation frequency are changed, the atomic oscillator irradiates the cesium metal atom gas cell 2 with two generated excitation lights. For example, the modulation frequency is set to sweep through 1000 values ​​around 9.19 GHz, which corresponds to the transition frequency between the ground states of cesium atoms. The frequency modulation power is set to vary when the value of the frequency modulation power is converted to a modulation index m, so that the modulation index m takes on 10 values ​​in the range of 0.88 to 2.5, as shown in Figure 3.

[0019] Figure 4 shows the relationship between the modulation index m, which is obtained by converting the value of the frequency modulation power, and the intensity of the excitation light. As shown in this figure, changing the modulation index m changes the intensity of the two excitation lights. In particular, increasing the value of the modulation index m, that is, increasing the value of the frequency modulation power, decreases the intensity of the 0th-order light, which is the main band, and increases the intensity of the sidebands, such as the -1st-order light. Therefore, by changing the modulation index, that is, the value of the frequency modulation power, the intensity ratio of the two excitation lights, which are the 0th-order light and the -1st-order light, can be changed. In this way, the signal generator control unit 42 sets the intensity ratio of the two excitation lights to take on 10 values ​​by changing the modulation index to take on 10 values ​​in the range of 0.88 to 2.5. Then, as described above, the two excitation lights generated by frequency modulation are sent to the optical attenuator 13.

[0020] The optical attenuator 13 controls the intensity of the irradiated excitation light to an intensity set by the optical attenuator control unit 43 of the controller 4. In this embodiment, the optical attenuator control unit 43 generates excitation light for each changed setting value by changing the sum of the intensities of the excitation light of all frequency components, including the two frequency components that are the main light sources for resonance generation, to multiple values. For example, the optical attenuator control unit 43 sets the sum of the intensities of the excitation light to 2.0 to 11.0 μW / mm². 2The intensity is set to vary by 8 values ​​within that range. The excitation light with the set intensity is then converted to linear polarization by a polarizer 15, such as a λ / 2 plate, and then irradiated onto the cesium metal atom gas cell 2. Simultaneously, the excitation light is also incident on a spectrometer 5, which detects the sum of the intensities of all the excitation light and notifies the controller 4. Note that the polarizer 15 may be a polarizer that converts to circular polarization.

[0021] In this way, the photogenerator 1, in response to commands from the controller 4, generates two excitation beams of light and irradiates the cesium metal atom gas cell 2 while changing the modulation index, that is, the ratio of the intensities of the two excitation beams and the sum of the intensities of the two excitation beams, and sweeping the modulation frequency around 9.19 GHz, which is near the resonance frequency.

[0022] Specifically, the photogenerator 1 first sets the modulation index, i.e., the intensity ratio, to a first value, and also sets the excitation light intensity to a first value, and then sweeps the modulation frequency around the resonance frequency to obtain the resonance frequency for the set modulation index and excitation light intensity, as will be described later. Subsequently, the photogenerator 1 keeps the modulation index at the first value and, for example, changes the value of the total excitation light intensity, which is the sum of the intensities of the excitation light for all frequency components, to a total of eight values, and repeats the process of sweeping the modulation frequency around the resonance frequency each time, thereby obtaining the resonance frequency for the first value of the modulation index for the eight set values ​​of the total excitation light intensity. Furthermore, the photogenerator 1 changes the modulation index to a second value and, as described above, changes the value of the total excitation light intensity to eight values ​​each time, and repeats the process of sweeping the modulation frequency around the resonance frequency each time, thereby obtaining the resonance frequency for the second value of the modulation index for the eight set values ​​of the excitation light intensity. Then, each time the modulation index is changed to, for example, a total of 10 values, the light generator 1 repeats the irradiation as described above, thereby obtaining the resonance frequencies for each of the 10 modulation index values ​​and the 8 set values ​​of the excitation light intensity. The processing of the obtained resonance frequencies will be described later.

[0023] The cesium metal atom gas cell 2 contains alkali metal atoms such as cesium atoms, rubidium atoms, sodium atoms, and potassium atoms. In Embodiment 1, cesium atoms are sealed inside the gas cell. The cesium metal atom gas cell 2 is placed in a magnetic field applied space, and as described above, excitation light from the photogenerator 1 is incident on it, with a portion of it being transmitted.

[0024] The photodetector 3 (detection unit) detects the transmitted light that has passed through the cesium metal atom gas cell 2 and measures the transmitted light quantity, which is the amount of light of the transmitted light. At this time, as described above, the excitation light is irradiated while the setting values ​​of the modulation index, i.e., intensity ratio, total excitation light intensity, and modulation frequency are changed, so the measured transmitted light quantity is transmitted to the controller 4 in correspondence with each of the changed setting values.

[0025] The calculation unit 44 of the controller 4 has the function of calculating a modulation index, or intensity ratio, that can suppress the occurrence of light shift from the transmitted light amount measured as described above. Specifically, the calculation unit 44 first plots the resonance frequency values ​​for each value of the modulation index against eight set values ​​of the total excitation light intensity, and then linearly fits these plots. This allows the slope of the resonance frequency with respect to the change in total excitation light intensity to be obtained for each value of the modulation index. In other words, 10 pairs of the modulation index and the slope of the resonance frequency with respect to the change in total excitation light intensity can be obtained. The obtained slope can be said to be the frequency shift with respect to the total excitation light intensity for each modulation index. Then, as shown in Figure 5, the calculation unit 44 plots the frequency shift, which is the slope with respect to the modulation index, and generates a graph fitted with a polynomial. Furthermore, the calculation unit 44 calculates the modulation index for which the frequency shift is 0 on the graph and determines it as the modulation index to be set later. In the example in Figure 5, the modulation index is calculated to be 1.56 ± 0.03. The calculation unit 44 is not necessarily limited to calculating the modulation index using the method described above. For example, the calculation unit 44 may calculate and determine the value of the modulation index based on a graph plotting the frequency shift, which is the slope with respect to the modulation index, so that the value of the frequency shift approaches 0.

[0026] Figure 6 shows a graph of the frequency shift measured when the total excitation light intensity is changed for each change in the modulation index, i.e., the ratio of the intensities of the two excitation lights. Each straight line in this figure represents the relationship between the frequency shift and the total excitation light intensity for each modulation index, i.e., each intensity ratio. From this graph, it can be seen that there are modulation indices, i.e., intensity ratios, for which no frequency shift occurs even when the total excitation light intensity changes. For example, in the example in Figure 6, it can be seen that no frequency shift occurs when the intensity ratio is 1.3, even when the total excitation light intensity changes. For this reason, as described above, the calculation unit 44 calculates the modulation index for which the frequency shift is 0 in the graph of Figure 5.

[0027] The calculation unit 44 notifies the signal generator control unit 42 of the modulation index calculated and determined as described above. The signal generator control unit 42 sets the value of the frequency modulation power corresponding to the determined modulation index as the set value for the signal generator 42a. As a result, the signal generator 42a controls the optical frequency modulator 12 with the set frequency modulation power, thereby generating excitation light that suppresses the occurrence of frequency shifts.

[0028] [Operation] Next, the operation of the atomic oscillator described above, in particular, the operation when calculating a modulation index that can suppress the occurrence of frequency shifts, will be explained with reference to the flowchart in Figure 7.

[0029] First, the controller 4 sets the setting values ​​of the photogenerator 1 in each control unit 41, 42, and 43 as follows, and generates excitation light (step S1). Specifically, the laser 11 generates excitation light of a single wavelength, for example, 894.5812 nm. Then, the optical frequency modulator 12 generates two excitation beams of light that are irradiated onto the cesium metal atom gas cell by frequency modulating the single-wavelength excitation light. At this time, the optical frequency modulator 12 changes the modulation index corresponding to the frequency modulation power to take 10 values ​​in the range of, for example, 0.88 to 2.5. The optical frequency modulator 12 also changes the modulation frequency to 1000 values ​​around 9.19 GHz, which corresponds to the transition frequency between ground levels of cesium atoms. Furthermore, the optical attenuator control unit 43 sets the total excitation light intensity to, for example, 2.0 to 11.0 μW / mm². 2 The value is changed to eight values ​​within this range. In this way, the controller 4 changes the modulation frequency to sweep around the transition frequency for each value of the modulation index and excitation light intensity.

[0030] Then, the light generator 1 generates two excitation beams of light while changing the modulation index (i.e., the ratio of the intensities of the two excitation beams) and the total excitation light intensity, and sweeps the modulation frequency around 9.19 GHz, which is near the resonance frequency. These beams are then irradiated onto the cesium metal atom gas cell 2, and the photodetector 3 detects the transmitted light that has passed through the cesium metal atom gas cell 2 (step S2). The measured amount of transmitted light is then transmitted to the controller 4 in correspondence with the changed set values ​​of the modulation index, total excitation light intensity, and modulation frequency.

[0031] Next, the controller 4 calculates the resonance frequency for the set modulation index and total excitation light intensity from the measured transmitted light amount, and stores the relationship between this resonance frequency and the set modulation frequency and total excitation light intensity values ​​(step S3). At this time, the above process is repeated until the measurement of transmitted light amount is completed for all set values ​​of modulation index and total excitation light intensity (step S4 is No, step S7).

[0032] Once the controller 4 has completed measuring the transmitted light amount for all modulation indices and total excitation light intensity settings (Yes in step S4), it calculates a modulation index, or intensity ratio, that can suppress the occurrence of light shift and determines it as a subsequent setting value, as follows. First, the controller 4 plots the resonance frequency values ​​for each modulation index value against eight setting values ​​of total excitation light intensity and performs linear fitting on these plots. Then, the controller 4 obtains the slope of the resonance frequency with respect to the change in total excitation light intensity from the fitted line (step S5). In this way, the controller 4 obtains 10 pairs of modulation indices and the slope of the resonance frequency with respect to the change in total excitation light intensity. Subsequently, as shown in Figure 5, the controller 4 plots the frequency shift, which is the slope with respect to the modulation index, generates a graph fitted with a polynomial, and calculates the modulation index for which the frequency shift is 0 on this graph (step S6). In the example in Figure 5, the modulation index is calculated to be 1.56 ± 0.03 and can be determined as a subsequent setting value.

[0033] Subsequently, the controller 4 can generate excitation light with suppressed frequency shift by setting the frequency modulation power corresponding to the modulation index calculated and determined as described above as the set value of the signal generator 42a.

[0034] <Embodiment 2> Next, a second embodiment of the present disclosure will be described with reference to Figures 8 and 9. Figure 8 is a block diagram showing the configuration of the atomic oscillator in Embodiment 2, and Figure 9 is a flowchart showing the operation of the atomic oscillator.

[0035] [composition] The atomic oscillator in this embodiment has a configuration almost identical to that of the atomic oscillator in Embodiment 1 described above, but the configuration for generating the two excitation beams is different. The differences in this embodiment will be mainly described below.

[0036] As shown in Figure 8, the atomic oscillator is equipped with a current modulator 45a that inputs a drive current to the laser 11 of the photogenerator 1. The current modulator 45a allows setting of the frequency modulation power and modulation frequency of the drive current. The atomic oscillator controller 4 is equipped with a current modulator control unit 45 that sets the setting value of the current modulator 45a. At this time, the current modulator control unit 45 changes the setting value of the frequency modulation power of the drive current of the laser 11, thereby generating excitation light from the laser 11 that includes multiple frequency components consisting of a main band (f0) and sidebands (f0±fmod, f0±2fmod, f0±3fmod, ...) as shown in Figure 2, as described above. In particular, in this embodiment, excitation light is generated that uses two frequency components, the 0th-order light and the -1st-order light, as the main light source for resonance generation. Here, as described above, the frequency modulation power can be converted to a modulation index, and changing the modulation index changes the intensity of the excitation light. Therefore, the current modulator control unit 45 can change the intensity ratio of the two excitation lights generated by changing the setting value of the frequency modulation power of the drive current of the laser 11. In this way, the current modulator control unit 45 sets the intensity ratio of the two excitation lights to take on 10 values ​​by changing the modulation index to take on 10 values ​​in the range of 0.88 to 2.5. Then, as described above, the two excitation lights generated by frequency modulation are sent to the optical attenuator 13.

[0037] [Operation] Next, the operation of the atomic oscillator described above, in particular, the operation when calculating a modulation index that can suppress the occurrence of frequency shifts, will be explained with reference to the flowchart in Figure 9.

[0038] First, the controller 4 sets the setting values ​​for the photogenerator 1 in each control unit 41, 45, and 43 as follows, and generates excitation light (step S1'). Specifically, first, the laser control unit 41 sets the laser 11 to generate excitation light of a single wavelength, for example, 894.5812 nm, when no modulation is applied to the drive current. Then, the current modulator control unit 45 sets the frequency modulation power of the drive current of the laser 11 and frequency modulates the excitation light, thereby generating two excitation beams of light to irradiate the cesium metal atom gas cell. At this time, the current modulator control unit 45 changes the value of the modulation index corresponding to the value of the frequency modulation power to take on 10 values ​​in the range of, for example, 0.88 to 2.5. The current modulator control unit 45 also changes the modulation frequency to 1000 values ​​around 9.19 GHz, which corresponds to the transition frequency between the ground levels of cesium atoms. Furthermore, the optical attenuator control unit 43 sets the total excitation light intensity, which is the sum of the intensities of the excitation light for all frequency components, to, for example, 2.0 to 11.0 μW / mm². 2 The value is changed to eight values ​​within this range. In this way, the controller 4 changes the modulation frequency to sweep around the transition frequency for each value of the modulation index and total excitation light intensity.

[0039] Then, as described above, the photogenerator 1 generates two excitation beams of light while changing the modulation index (i.e., the ratio of the intensities of the two excitation beams) and the total excitation light intensity, and sweeps the modulation frequency around 9.19 GHz, which is near the resonance frequency. These beams are then irradiated onto the cesium metal atom gas cell 2, and the photodetector 3 detects the transmitted light that has passed through the cesium metal atom gas cell 2 (step S2). As a result, the measured amount of transmitted light is transmitted to the controller 4 in correspondence with the changed set values ​​of the modulation index, total excitation light intensity, and modulation frequency.

[0040] Next, the controller 4 calculates the resonance frequency for the set modulation index and total excitation light intensity from the measured transmitted light amount, and stores the relationship between this resonance frequency and the set modulation frequency and total excitation light intensity values ​​(step S3). At this time, the above process is repeated until the measurement of transmitted light amount is completed for all set values ​​of modulation index and total excitation light intensity (step S4 is No, step S7).

[0041] Once the controller 4 has completed the measurement of transmitted light at all set values ​​for modulation indices and total excitation light intensity (Yes in step S4), it calculates a modulation index, or intensity ratio, that can suppress the occurrence of light shift as follows. First, the controller 4 plots the resonance frequency values ​​for each value of the modulation index against eight set values ​​of total excitation light intensity, and then linearly fits these plots. Then, the controller 4 obtains the slope of the resonance frequency with respect to the change in total excitation light intensity from the fitted line (step S5). In this way, the controller 4 obtains 10 pairs of modulation indices and the slope of the resonance frequency with respect to the change in total excitation light intensity. Subsequently, as shown in Figure 5, the controller 4 plots the frequency shift, which is the slope with respect to the modulation index, generates a graph fitted with a polynomial, and calculates the modulation index for which the frequency shift is 0 on this graph (step S6).

[0042] The current modulator control unit 45 of the controller 4 can generate excitation light with suppressed frequency shift by setting the frequency modulation power corresponding to the modulation index calculated as described above to the set value of the current modulator 45a.

[0043] <Embodiment 3> Next, a third embodiment of the present disclosure will be described with reference to Figures 10 and 11. Figure 10 is a block diagram showing the configuration of the atomic oscillator in Embodiment 3, and Figure 11 is a flowchart showing the operation of the atomic oscillator.

[0044] [composition] The atomic oscillator in this embodiment has a configuration almost identical to that of the atomic oscillator in Embodiment 1 described above, but the configuration for generating the two excitation beams is different. The differences in this embodiment will be mainly described below.

[0045] As shown in Figure 10, the atomic oscillator includes a first laser 11a and a second laser 11b, which are two light sources that generate excitation light with different frequency components. Corresponding to the first laser 11a and the second laser 11b, it also includes a first optical attenuator 13a and a second optical attenuator 13b, a first spectrometer 5a and a second spectrometer 5b. It also includes a mixer 14 that mixes the excitation light generated from the first laser 11a and the second laser 11b. Furthermore, the controller 4 includes a first laser control unit 41a and a second laser control unit 41b, corresponding to the first laser 11a and the second laser 11b, respectively, and a first optical attenuator control unit 43a and a second optical attenuator control unit 43b, corresponding to the first optical attenuator 13a and the second optical attenuator 13b, respectively.

[0046] Then, the first laser 11a and the second laser 11b are each controlled by the first laser control unit 41a and the second laser control unit 41b, respectively, to generate excitation light of a single wavelength, for example, 894.5812 nm. At this time, the first laser control unit 41a and the second laser control unit 41b set the frequency difference of the excitation light from the first laser 11a and the second laser 11b to 1000 values ​​around 9.19 GHz, which corresponds to the transition frequency between the ground levels of a cesium atom. For example, the first laser control unit 41a and the second laser control unit 41b set the frequency of the excitation light from either the first laser 11a or the second laser 11b to around 9.19 GHz, which corresponds to the transition frequency between the ground levels of a cesium atom, and set the frequency of the excitation light from the other laser so that the frequency difference between the two lasers is around 9.19 GHz, which corresponds to the transition frequency between the ground levels of a cesium atom.

[0047] Furthermore, the first optical attenuator control unit 43a and the second optical attenuator control unit 43b change the intensity ratio of the excitation light from the first laser 11a and the second laser 11b, respectively, in the first optical attenuator 13a and the second optical attenuator 13b, while referring to the measured values ​​of the first spectrometer 5a and the second spectrometer 5b. For example, the intensity ratio is set to take 10 values ​​in the range of 0.5 to 3.0. In addition, the first optical attenuator control unit 43a and the second optical attenuator control unit 43b change the sum of the intensities of the excitation light from the first laser 11a and the second laser 11b, respectively, in the first optical attenuator 13a and the second optical attenuator 13b, respectively, to multiple values, thereby generating excitation light for each changed setting value. For example, the total excitation light intensity, which is the sum of the intensities of the two excitation lights, is set to 2.0 to 11.0 μW / mm². 2 Set it to change to 8 different values ​​within that range.

[0048] [Operation] Next, the operation of the atomic oscillator described above, in particular, the operation when calculating a modulation index that can suppress the occurrence of frequency shifts, will be explained with reference to the flowchart in Figure 11.

[0049] First, the controller 4 sets the setting values ​​for the photogenerator 1 in each control unit 41a, 41b, 43a, and 43b as follows to generate excitation light (step S1). Specifically, first, while referring to the measurement value of the first spectrometer 5a, the first laser control unit 41a is set to generate excitation light of a single wavelength, for example, 894.5812 nm, in which case the second laser control unit 41b is set to generate excitation light in which the frequency difference between the excitation light of the first laser 11a and the second laser 11b changes to 1000 values ​​around 9.19 GHz. In the first optical attenuator control unit 43a and the second optical attenuator control unit 43b, while referring to the measured values ​​of the first spectrometer 5a and the second spectrometer 5b, the first optical attenuator 13a and the second optical attenuator 13b are set so that the intensity ratio of the excitation light from the first laser 11a and the second laser 11b, respectively, takes 10 values ​​in the range of, for example, 0.5 to 3.0. Furthermore, the first optical attenuator control unit 43a and the second optical attenuator control unit 43b set the total excitation light intensity, which is the sum of the intensity of the excitation light from the first laser 11a and the second laser 11b, respectively, to 2.0 to 11.0 μW / mm². 2 Set it by changing it to 8 different values ​​within that range.

[0050] Then, as described above, the photogenerator 1 generates two excitation beams of light while changing the intensity ratio of the two excitation beams and the total excitation beam intensity, and sweeping the frequency difference around 9.19 GHz, which is near the resonance frequency. These beams are then irradiated onto the cesium metal atom gas cell 2, and the photodetector 3 detects the transmitted light that has passed through the cesium metal atom gas cell 2 (step S2). The measured amount of transmitted light is then transmitted to the controller 4 in correspondence with the changed set values ​​of the intensity ratio, total excitation beam intensity, and modulation frequency.

[0051] Next, the controller 4 calculates the resonance frequency for the set intensity ratio and total excitation light intensity from the measured transmitted light amount, and stores the relationship between this resonance frequency and the set intensity ratio and total excitation light intensity values ​​(step S3'). At this time, the above process is repeated until the measurement of transmitted light amount is completed for all set values ​​of intensity ratio and total excitation light intensity (step S4, step S7).

[0052] Once the controller 4 has completed the measurement of transmitted light at all intensity ratio and total excitation light intensity settings (Yes in step S4), it calculates an intensity ratio that can suppress the occurrence of light shift as follows. First, the controller 4 plots the resonance frequency values ​​for each intensity ratio value against eight setting values ​​of total excitation light intensity and performs linear fitting on these plots. Then, the controller 4 obtains the slope of the resonance frequency with respect to the change in total excitation light intensity from the fitted line (step S5'). In this way, the controller 4 obtains 10 pairs of intensity ratios and the slope of the resonance frequency with respect to the change in total excitation light intensity. Next, the controller 4 plots the frequency shift, which is the slope with respect to the intensity ratio, generates a graph fitted with a polynomial, and calculates the intensity ratio for which the frequency shift is 0 on this graph (step S6').

[0053] The controller 4 can generate excitation light with suppressed frequency shift by setting the intensity ratio calculated as described above as the setting value for the first optical attenuator 13a and the second optical attenuator 13b in the first optical attenuator control unit 43a and the second optical attenuator control unit 43b.

[0054] <Embodiment 4> Next, a fourth embodiment of this disclosure will be described with reference to Figures 12 and 13. Figure 12 is a block diagram showing the configuration of the atomic oscillator in Embodiment 4, and Figure 13 is a flowchart showing the operation of the atomic oscillator. In this embodiment, the configuration of the atomic oscillator and control method described in the above-described embodiments is shown in outline.

[0055] As shown in Figure 12, the atomic oscillator 100 in this embodiment comprises a photogenerator 101 that generates two excitation beams, an alkali metal atomic gas cell 102 that is irradiated with the two excitation beams with a changed frequency difference, a detection unit 103 that detects the amount of transmitted light that has passed through the alkali metal atomic gas cell, and a control unit 104 that measures the resonance frequency of the alkali metal atomic gas based on the detected amount of transmitted light and controls the intensity ratio of the two excitation beams irradiated onto the alkali metal atomic gas cell based on the measured resonance frequency.

[0056] Then, as shown in Figure 13, the control unit 104 (control device) in the above configuration measures the resonance frequency of the alkali metal atomic gas based on the detected amount of transmitted light (step S101), and controls the intensity ratio of the two excitation lights irradiated onto the alkali metal gas cell based on the measured resonance frequency (step S102), and performs the following processing. The processing by the control unit 104 is realized by the execution of a program by the arithmetic unit that constitutes the control unit 104.

[0057] As described above, in this disclosure, the occurrence of light shift can be suppressed by controlling the intensity ratio of two excitation lights irradiated onto an alkali metal gas cell based on the measured resonance frequencies of the two excitation lights.

[0058] 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 and details of the present disclosure can be made that will be understood by those skilled in the art within the scope of the present disclosure.

[0059] <Note> Some or all of the above embodiments may also be described as follows. The following outlines the configurations of the atomic oscillator, control method, control device, and program in this disclosure. However, this disclosure is not limited to the following configurations. (Note 1) A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A control unit measures the resonance frequency of the alkali metal atomic gas based on the detected amount of transmitted light, and controls the intensity ratio of two excitation lights irradiated onto the alkali metal atomic gas cell based on the measured resonance frequency. An atomic oscillator equipped with [a specific feature / equipment]. (Note 2) The atomic oscillator described in Appendix 1, The control unit measures the resonance frequency when the alkali metal atom gas cell is irradiated with varying intensity ratios of the two excitation lights, and determines the intensity ratio of the two excitation lights based on the measurement results. Atomic oscillator. (Note 3) The atomic oscillator described in Appendix 2, The control unit changes the intensity ratio of the two excitation lights and the sum of the excitation light intensities to measure the resonance frequency when irradiated onto the alkali metal atom gas cell, and determines the intensity ratio of the two excitation lights based on the measurement results. Atomic oscillator. (Note 4) The atomic oscillator described in Appendix 3, The control unit measures the resonance frequency when the sum of the intensities of the two excitation lights is changed and irradiated onto the alkali metal atom gas cell, and determines the intensity ratio of the two excitation lights based on the change in the resonance frequency in response to the change in the sum of the intensities of the excitation lights. Atomic oscillator. (Note 5) The atomic oscillator described in Appendix 4, The control unit determines the intensity ratio of the two excitation lights such that the change in the resonance frequency with respect to the change in the sum of the excitation light intensities approaches zero. Atomic oscillator. (Note 6) The atomic oscillator described in Appendix 4, The light generator generates excitation light consisting of two frequency components by frequency modulating one excitation light with a predetermined frequency modulation power. The control unit changes the intensity ratio of the two excitation lights by changing the frequency modulation power. Atomic oscillator. (Note 7) The atomic oscillator described in Appendix 4, The aforementioned light generator generates excitation light consisting of two frequencies by frequency modulating the drive current with a predetermined frequency modulation power. The control unit changes the intensity ratio of the two excitation lights by changing the frequency modulation power. Atomic oscillator. (Note 8) The atomic oscillator described in Appendix 4, The aforementioned light generator has two light sources that each generate excitation light with different frequency components, The control unit changes the intensity ratio of the excitation light generated from each of the two light sources. Atomic oscillator. (Note 9) An atomic oscillator as described in any of the appendices 6 to 8, The light generator sets the frequency of one of the two excitation beams to near the resonance frequency. Atomic oscillator. (Note 10) A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A method for controlling an atomic oscillator equipped with, The resonance frequency of the alkali metal atomic gas is measured based on the detected amount of transmitted light, and the intensity ratio of the two excitation lights irradiated onto the alkali metal atomic gas cell is controlled based on the measured resonance frequency. Control method. (Note 11) A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A control device for controlling an atomic oscillator equipped with the following: The resonance frequency of the alkali metal atomic gas is measured based on the detected amount of transmitted light, and the intensity ratio of the two excitation lights irradiated onto the alkali metal atomic gas cell is controlled based on the measured resonance frequency. Control device. (Note 12) A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A control device for controlling an atomic oscillator equipped with the following: The resonance frequency of the alkali metal atomic gas is measured based on the detected amount of transmitted light, and the intensity ratio of the two excitation lights irradiated onto the alkali metal atomic gas cell is controlled based on the measured resonance frequency. A program to execute a process. [Explanation of Symbols]

[0060] 1. Light generator 2 Cesium metal atom gas cell 3. Photodetector 4. Controller 5 Spectrometer 5a 1st spectrometer 5b 2nd spectrometer 11 Lasers 11a First laser 11b Second laser 12 Optical frequency modulators 13. Optical attenuator 13a First Optical Attenuator 13b Second Optical Attenuator 14 Mixer 15 Polarizing plates 41 Laser Control Unit 41a First Laser Control Unit 41b Second Laser Control Unit 42 Signal Generator Control Unit 42a Signal Generator 43 Optical attenuator control unit 43a First Optical Attenuator Control Unit 43b Second Optical Attenuator Control Unit 44 Calculation section 45 Current Modulator Control Unit 45A current modulator 100 Atomic Oscillators 101 Light Generator 102 Alkali metal atom gas cell 103 Detection unit 104 Control Unit

Claims

1. A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A control unit measures the resonance frequency of the alkali metal atomic gas based on the detected amount of transmitted light, and controls the intensity ratio of two excitation lights irradiated onto the alkali metal atomic gas cell based on the measured resonance frequency. Equipped with, The control unit measures the resonance frequency when the sum of the intensities of the two excitation lights is changed and irradiated onto the alkali metal atom gas cell, and determines the intensity ratio of the two excitation lights based on the change in the resonance frequency in response to the change in the sum of the intensities of the two excitation lights. Atomic oscillator.

2. The atomic oscillator according to claim 1, The control unit determines the intensity ratio of the two excitation lights such that the change in the resonance frequency with respect to the change in the sum of the intensity of the excitation lights approaches zero. Atomic oscillator.

3. The atomic oscillator according to claim 1, The light generator generates excitation light consisting of two frequency components by frequency modulating one excitation light with a predetermined frequency modulation power. The control unit changes the intensity ratio of the two excitation lights by changing the frequency modulation power. Atomic oscillator.

4. The atomic oscillator according to claim 1, The aforementioned light generator generates excitation light consisting of two frequencies by frequency modulating the drive current with a predetermined frequency modulation power. The control unit changes the intensity ratio of the two excitation lights by changing the frequency modulation power. Atomic oscillator.

5. The atomic oscillator according to claim 1, The aforementioned light generator has two light sources that each generate excitation light with different frequency components, The control unit changes the intensity ratio of the excitation light generated from each of the two light sources. Atomic oscillator.

6. An atomic oscillator according to any one of claims 3 to 5, The light generator sets the frequency of one of the two excitation beams to near the resonance frequency. Atomic oscillator.

7. A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A method for controlling an atomic oscillator equipped with, The resonance frequency of the alkali metal atomic gas is measured based on the amount of transmitted light detected, and the intensity ratio of the two excitation lights irradiated onto the alkali metal atomic gas cell is controlled based on the measured resonance frequency. Each time the value of the intensity ratio of the two excitation lights is changed, the resonance frequency is measured when the sum of the intensities of the excitation lights is changed and irradiated onto the alkali metal atomic gas cell, and the intensity ratio of the two excitation lights is determined based on the change in the resonance frequency in response to the change in the sum of the intensities of the excitation lights. Control method.

8. A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A control device for controlling an atomic oscillator equipped with the following: The resonance frequency of the alkali metal atomic gas is measured based on the amount of transmitted light detected, and the intensity ratio of the two excitation lights irradiated onto the alkali metal atomic gas cell is controlled based on the measured resonance frequency. Each time the value of the intensity ratio of the two excitation lights is changed, the resonance frequency is measured when the sum of the intensities of the excitation lights is changed and irradiated onto the alkali metal atomic gas cell, and the intensity ratio of the two excitation lights is determined based on the change in the resonance frequency in response to the change in the sum of the intensities of the excitation lights. Control device.

9. A photogenerator that generates two excitation beams, An alkali metal atom gas cell is irradiated with two excitation lights whose frequency difference is changed, A detection unit for detecting the amount of light transmitted through the alkali metal atom gas cell, A control device for controlling an atomic oscillator equipped with the following: The resonance frequency of the alkali metal atomic gas is measured based on the amount of transmitted light detected, and the intensity ratio of the two excitation lights irradiated onto the alkali metal atomic gas cell is controlled based on the measured resonance frequency. Each time the value of the intensity ratio of the two excitation lights is changed, the resonance frequency is measured when the sum of the intensities of the excitation lights is changed and irradiated onto the alkali metal atomic gas cell, and the intensity ratio of the two excitation lights is determined based on the change in the resonance frequency in response to the change in the sum of the intensities of the excitation lights. A program to execute a process.

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