Atomic oscillator, control method, control apparatus, and program

Abstract

To solve the problem that it is difficult to further enhance frequency stability in an atomic oscillator.SOLUTION: An atomic oscillator 100 of the present disclosure, comprises: a gas cell 101 in which alkali metal atoms are encapsulated; a light generator 102 that applies an irradiation light having at least two different frequency components to the gas cell; a light detector 103 that detects transmitted light having transmitted through the gas cell; and a controller 104 that determines a resonance frequency of the alkali metal atoms based on a light amount of the transmitted light by the gas cell and controls an oscillation frequency on the basis of the determined resonance frequency. Irradiation light is applied by two irradiation methods in which characteristics of change in the resonance frequency due to change in intensity of the irradiation light are mutually different. The controller 104 controls the oscillation frequency on the basis of a result of comparison between the resonance frequencies when the irradiation light is applied to the gas cell by the two irradiation methods, respectively.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] An atomic oscillator is a device that measures precise time based on the natural frequency of an atom. In small atomic clocks, the mainstream method is to measure the natural frequency of an atom by using coherent population trapping (CPT), a quantum interference effect that occurs when an alkali metal atomic gas is irradiated with excitation light of two frequencies, as the oscillation principle of the atomic oscillator. In CPT, when the difference in frequency between the two excitation lights matches the transition frequency between the ground levels of the alkali metal, the amount of transmitted light increases without absorption of the excitation light. In an atomic oscillator that uses CPT as its operating principle, the difference in frequency between the two excitation lights is swept, and the resonance frequency, which is the difference in frequency at which the amount of transmitted light is maximized, is taken as the natural frequency of the atom. Whether or not this natural frequency of the atom can be stably obtained over a long period of time is one of the performance indicators of an atomic oscillator.

[0003] In atomic frequency measurements using CPT, the main factor that reduces the long-term stability described above is the change in light shift over time. Light shift is a phenomenon in which the atomic frequency shifts due to the interaction between the excitation light and the atom. For example, it is known that light shifts occur due to changes in the intensity of the excitation light over time caused by the aging of the laser.

[0004] Regarding the above-mentioned problem of light shift, Patent Document 1 describes a method of suppressing the light shift by correcting the change in the intensity of the total excitation light. Specifically, Patent Document 1 describes a method of correcting the total excitation light intensity 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 1] JP 2016-72371 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, as described in the above-mentioned Patent Document 1, it is difficult to keep the intensity of all pump light completely constant, and it is still difficult to suppress the occurrence of light shifts. As a result, there is a problem that it is not possible to further improve the frequency stability of the atomic oscillator.

[0007] Therefore, an object of the present disclosure is to solve the above-mentioned problem that the frequency stability of an atomic oscillator cannot be further improved. [Means for solving the problem]

[0008] An atomic oscillator according to one embodiment of the present disclosure includes: a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a controller that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The irradiation light is irradiated by two irradiation methods each having different characteristics of a change in the resonance frequency due to a change in the intensity of the irradiation light, The controller controls the oscillation frequency based on a comparison result of the resonance frequency when the gas cell is irradiated with the irradiation light by each of the two irradiation methods. The structure is as follows. In addition, a control method according to an embodiment of the present disclosure includes: a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a controller that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; A method for controlling an atomic oscillator comprising: Irradiating the irradiation light using two irradiation methods each having different characteristics of change in the resonance frequency due to change in intensity of the irradiation light; The controller controls the oscillation frequency based on a comparison result of the resonance frequency when the gas cell is irradiated with the irradiation light by each of the two irradiation methods. The structure is as follows. Further, a control device according to an embodiment of the present disclosure includes: a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a control device that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The control device for an atomic oscillator comprising: the control device irradiates the irradiation light by two irradiation methods having different characteristics of a change in the resonance frequency due to a change in intensity of the irradiation light, and controls the oscillation frequency based on a comparison result of the resonance frequency when the irradiation light is irradiated to the gas cell by each of the two irradiation methods. The structure is as follows. In addition, a program according to an embodiment of the present disclosure includes: a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a control device that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The atomic oscillator is equipped with the control device irradiates the irradiation light by two irradiation methods each having a different characteristic of a change in the resonance frequency due to a change in intensity of the irradiation light, and controls the oscillation frequency based on a comparison result of the resonance frequency when the irradiation light is irradiated to the gas cell by each of the two irradiation methods. Execute the process, The structure is as follows. Effect of the Invention

[0009] By being configured as described above, the present disclosure can further improve the frequency stability of the atomic oscillator. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a configuration of an atomic oscillator according to the present disclosure. [Diagram 2] FIG. 2 is a diagram showing signals output from each component of the atomic oscillator according to the present disclosure. [Diagram 3] FIG. 1 is a diagram showing the processing state of an atomic oscillator in the present disclosure. [Figure 4] FIG. 1 is a diagram showing the processing state of an atomic oscillator in the present disclosure. [Diagram 5] 4 is a flowchart showing a processing operation of the atomic oscillator in the present disclosure. [Figure 6] FIG. 11 is a block diagram showing a configuration of a second atomic oscillator according to the present disclosure. [Figure 7] 11 is a flowchart showing the operation of a second atomic oscillator in the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Embodiment 1> A first embodiment of the present disclosure will be described with reference to the drawings, which may be relevant to any embodiment.

[0012] [composition] FIG. 1 is a block diagram showing the configuration of an atomic oscillator in this embodiment. The atomic oscillator in this embodiment includes a light generator 1, a gas cell 2, a photodetector 3, a controller 4, a VCXO (Voltage Controlled Crystal Oscillator) 51, a frequency converter 52, and a current modulator 53. The light generator 1 includes a laser 11 that emits excitation light, and the atomic oscillator includes a pulser 12 that pulses the excitation light from the laser 11. The controller 4 includes a resonance frequency and shift amount calculator 41, a current modulator control unit 42, a laser control unit 43, a frequency converter control unit 44, and a VCXO control unit 45. The controller 4 is composed of an information processing device (control device) that includes a calculation device and a storage device, and each unit 41 to 45 of the controller 4 is realized by executing a program in the calculation device. Each configuration will be described in detail below.

[0013] The light generator 1 cooperates with the controller 4, the VCXO 51, the frequency converter 52, and the current modulator 53 to generate two excitation lights (irradiation lights) having at least two different frequency components by performing frequency modulation from an excitation light of a single wavelength, and irradiates the gas cell 2 with the generated excitation lights. Here, FIG. 2 shows signals output from each component of the atomic oscillator. As shown in this figure, a preset current modulation frequency conversion coefficient and an output frequency conversion coefficient are output from the frequency converter control unit 44, and a VCXO oscillation voltage based on the output frequency conversion coefficient is output from the VCXO control unit 45, thereby controlling the oscillation frequency of the output frequency signal output from the VCXO 51 and output to the outside. In addition, the output frequency signal output from the VCXO 51 is frequency converted based on the current modulation frequency conversion coefficient by the frequency converter 52, and for example, a current modulation frequency signal of around 9.2 GHz, which corresponds to the transition frequency between the ground levels of cesium atoms, is output. Then, the laser drive current output from the laser control unit 43 is modulated by the current modulator 53 according to the setting value of the current modulator 53 output from the current modulator control unit 42, and the laser 11 is driven by the modulated laser drive current. As a result, two excitation lights of different frequencies are generated by the light generator 1, and the setting value of the current modulator 53 is changed, so that the frequency difference between the two excitation lights is swept around 9.2 GHz and irradiated onto the gas cell 2. Note that the configuration and method for generating excitation light by the light generator 1 of the atomic oscillator are known, and therefore a detailed description thereof will be omitted.

[0014] Here, the values ​​of the above-mentioned "current modulation frequency conversion coefficient" and "output frequency conversion coefficient" are preset and stored in the frequency converter control unit 44. However, in this embodiment, as will be described later, the amount of shift of the resonance frequency is calculated, and the "current modulation frequency conversion coefficient" and "output frequency conversion coefficient" are changed to values ​​corresponding to the amount of shift. This will be described later.

[0015] The gas cell 2 is filled with alkali metal atoms. The alkali metal atoms may be any alkali metal atoms such as cesium atoms, rubidium atoms, sodium atoms, potassium atoms, etc. As an example, the gas cell 2 is filled with cesium atoms as the alkali metal atoms, nitrogen is used as the buffer gas, and the gas pressure is 1 kPa.

[0016] The photodetector 3 detects the light transmitted through the gas cell 2 and measures the amount of the transmitted light. At this time, since the excitation light is irradiated while changing the setting value during frequency modulation, the photodetector 3 passes the measured amount of transmitted light to the controller 4 so that it is recorded in association with each changed setting value, i.e., the swept frequency difference.

[0017] Here, in this embodiment, the light generator 1 is configured to irradiate excitation light in two irradiation modes (irradiation methods) under the control of the controller 4. Specifically, the first mode is a CW (Continuous wave) mode in which excitation light E1 is irradiated as a continuous wave in which the excitation light intensity is constant on the time axis, as shown in FIG. 3 (3-1). The second mode is a CPT-Ramsey mode in which pulsed excitation light E2 in which the excitation light becomes a rectangular wave on the time axis, as shown in FIG. 3 (3-2). At this time, in the second mode, the CPT-Ramsey mode, the excitation light generated from the light generator 1 is pulsed by the pulser 12 under the control of the controller 4. The pulser 12 is, for example, composed of an acousto-optic modulator (AOM).

[0018] Then, in response to irradiation with excitation light in the two irradiation modes, the photodetector 3 measures the amount of transmitted light in each of the two irradiation modes. As a result, as shown in Fig. 3 (3-3), the photodetector 3 measures a graph of the amount of transmitted light when the excitation light E1, which is a continuous wave, is irradiated in the CW mode, and a graph of the amount of transmitted light when the excitation light E2, which is pulsed, is irradiated in the CPT-Ramsey mode, so that these are recorded by the controller 4. Note that, for the excitation light E2 pulsed in the CPT-Ramsey mode, the photodetector 3 can measure the amount of transmitted light by being controlled to turn on within the time that the excitation light is on and measure the amount of transmitted light.

[0019] In an atomic oscillator that uses CPT, it is known that the CPT-Ramsey method, in which pulsed excitation light E2 is irradiated onto the gas cell 2, reduces the amount of shift in the natural frequency of alkali metal atoms caused by changes in the intensity of the excitation light. Figure 4 shows the change in the resonance frequency F1 when irradiated with excitation light E1, which is a continuous wave in CW mode, and the change in the resonance frequency F2 when irradiated with pulsed excitation light E2 in CPT-Ramsey mode, relative to changes in excitation light intensity. In this figure, the slope of the resonance frequency with respect to excitation light intensity is 32 Hz / (μW·mm) when excitation light E1 is a continuous wave. -2 ) for pulsed excitation light E2, which is 4.2Hz / (μW mm -2 ) In this way, the characteristics of the change in the resonant frequency due to the change in the intensity of the excitation light are different between the CW mode in which the excitation light E1, which is a non-pulsed continuous wave, is irradiated and the CPT-Ramsey mode in which the excitation light E2 is irradiated.

[0020] In this embodiment, the excitation light is irradiated in two irradiation modes, the CW mode and the CPT-Ramsey mode, but the excitation light may be irradiated in both irradiation modes in the CPT-Ramsey mode. In this case, by setting the duty ratio of the pulsed excitation light in each CPT-Ramsey mode to a different value, the characteristics of the resonance frequency measured when the excitation light is irradiated in each CPT-Ramsey mode, in particular, the characteristics of the change in the resonance frequency due to the intensity change of the excitation light, are different from each other. However, the two irradiation modes are not necessarily limited to the above-mentioned irradiation methods, and it is sufficient that the characteristics of the change in the resonance frequency measured by the excitation light irradiated in each irradiation method, that is, the characteristics of the change in the resonance frequency due to the intensity change of the excitation light, are different from each other.

[0021] The resonance frequency and shift amount calculator 41 of the controller 4 determines the resonance frequency based on the amount of transmitted light measured by the photodetector 3 in each irradiation mode. That is, the resonance frequency and shift amount calculator 41 determines the resonance frequency F1 corresponding to the CW mode and the resonance frequency F2 corresponding to the CPT-Ramsey mode. For example, the resonance frequency and shift amount calculator 41 may determine the difference frequency at which the amount of transmitted light is maximized as the resonance frequency F1 or F2 in each graph shown in FIG. 3(3-3), or may determine the difference frequency at which the slope of the graph of the amount of transmitted light relative to the frequency difference is zero by measuring the differential waveform of the amount of transmitted light.

[0022] Then, the controller 4 controls the oscillation frequency based on at least one or both of the determined resonance frequencies F1, F2. For example, when irradiating excitation light in CW mode, the oscillation frequency is controlled using the resonance frequency F1 determined in CW mode, and when irradiating excitation light in CPT-Ramsey mode, the oscillation frequency is controlled using the resonance frequency F2 determined in CPT-Ramsey mode. Specifically, the controller 4 controls the oscillation frequency of the output frequency signal output by the VCXO 51 in the VCXO control unit 45 based on the determined resonance frequencies F1, F2 and an output frequency conversion coefficient (first parameter) pre-stored in the frequency converter control unit 44. Here, as an example, it is assumed that the atomic oscillator outputs an output frequency signal of 10 MHz from the VCXO 51, the determined resonance frequency F1 in the CW mode is "9.192631 GHz", and the preset output frequency conversion coefficient is "(10 MHz) / (9.192631 GHz)". In this case, the VCXO 51 outputs an output frequency signal of (9.192631 GHz)*(10 MHz) / (9.192631 GHz)=10 MHz. As a result, the atomic oscillator outputs an output frequency signal of 10 MHz to the outside and also inputs it to the frequency converter 52. In addition, if the preset current modulation frequency conversion coefficient (second parameter) is "(9.192631 GHz) / (10 MHz)", the frequency converter 52 generates a current modulation frequency signal of (10 MHz)*(9.192631 GHz) / (10 MHz)=9.192631 GHz, that is, a reference signal that is a reference for the irradiated light is generated and input to the current modulator 53. The values ​​of the output frequency conversion coefficient and the current modulation frequency conversion coefficient are preset and stored based on the oscillation frequency of the output frequency signal that is expected to be output by the VCXO 51 in the atomic oscillator and the characteristics of the resonance frequency and the excitation light intensity in each irradiation mode.

[0023] Here, the controller 4 in this embodiment is further configured to control the oscillation frequency based on the comparison result of the determined resonance frequencies F1, F2 in each irradiation mode, as described below, in order to respond to fluctuations in the resonance frequencies F1, F2 in each irradiation mode due to changes in the intensity of the excitation light.

[0024] Here, the resonance frequency and shift amount calculator 41 calculates the difference between the resonance frequencies F1 and F2 determined in the CW mode and the CPT-Ramsey mode, and calculates the light shift amount, which is the amount of change in the resonance frequency with respect to the change in the intensity of the excitation light, based on the difference between the resonance frequencies F1 and F2. Specifically, the resonance frequency and shift amount calculator 41 first stores a graph showing the relationship between the difference (F1-F2) between the resonance frequencies F1 and F2 in the CW mode and the CPT-Ramsey mode and the excitation light intensity, as shown in FIG. 4. The graph shown in FIG. 4 is created and stored in advance based on the characteristics of the resonance frequency and the excitation light intensity in each irradiation mode. In addition, the resonance frequency and shift amount calculator 41 stores data showing the relationship between the excitation light intensity and the light shift amount, which is the amount of change in the resonance frequency, in each irradiation mode. Specifically, the data of the light shift amount with respect to the excitation light intensity is represented by the correspondence data between the excitation light intensity and the output frequency conversion coefficient, and the correspondence data between the excitation light intensity and the current modulation frequency conversion coefficient, and the correspondence data consisting of a correspondence table and a correspondence graph is generated and stored in advance. Note that the correspondence data between the excitation light intensity and the output frequency conversion coefficient, and the correspondence data between the excitation light intensity and the current modulation frequency conversion coefficient are generated and stored in advance based on the oscillation frequency of the output frequency signal assumed to be output by the VCXO 51 in the atomic oscillator, and the shift amount of the resonance frequency in each irradiation mode and the characteristics of the excitation light intensity.

[0025] Then, the resonance frequency and shift amount calculator 41 specifies the excitation light intensity from the difference (F1-F2) in the resonance frequency between the measured CW mode and the CPT-Ramsey mode based on the graph and corresponding data stored as described above, and specifies the output frequency conversion coefficient and the current modulation frequency conversion coefficient from the excitation light intensity. The resonance frequency and shift amount calculator 41 performs light shift correction by changing and updating the output frequency conversion coefficient and the current modulation frequency conversion coefficient stored in the frequency converter control unit 44 to the newly specified output frequency conversion coefficient and the current modulation frequency conversion coefficient.

[0026] Then, the controller 4 uses the output frequency conversion coefficient and the current modulation frequency conversion coefficient updated by the light shift correction described above to control the oscillation frequency based on the resonance frequencies F1 and F2 determined in each irradiation mode, as described above. For example, when irradiating excitation light in CW mode, the oscillation frequency is controlled using the resonance frequency F1 determined in CW mode, and when irradiating excitation light in CPT-Ramsey mode, the oscillation frequency is controlled using the resonance frequency F2 determined in CPT-Ramsey mode. Here, as an example, a case where the resonance frequency F1 in CW mode changes from "9.192631 GHz" to "9.192632 GHz" due to the light shift and a case where the output frequency conversion coefficient and the current modulation frequency conversion coefficient are not corrected and are corrected will be described.

[0027] First, when no correction is made, the output frequency conversion coefficient remains "(10MHz) / (9.192631GHz)", and an output frequency signal of (9.192632GHz)*(10MHz) / (9.192631GHz)=10.0000011MHz is output from the VCXO 51 using the right-shifted resonant frequency (9.192632GHz) of the gas cell 2. Also, the current modulation frequency conversion coefficient remains "(9.192631GHz) / (10MHz)", and a current modulation frequency signal of (10.0000011MHz)*(9.192631GHz) / (10MHz)=9.192632GHz is output from the frequency converter 52. For this reason, although the atomic oscillator is intended to frequency-modulate the excitation light at "9.192631 GHz" and externally output an output frequency signal of "10 MHz", in reality it is frequency-modulating it at "9.192632 GHz" and externally outputting an output frequency signal of "10.0000011 MHz".

[0028] On the other hand, when the light shift correction is performed as described above, the output frequency conversion coefficient is updated to "(10MHz) / (9.192632GHz)", and an output frequency signal of (9.192632GHz)*(10MHz) / (9.192632GHz)=10MHz is output from the VCXO 51 using the resonance frequency (9.192632GHz) of the light-shifted gas cell 2. In addition, the current modulation frequency conversion coefficient is updated to "(9.192632GHz) / (10MHz)", and a current modulation frequency signal of (10MHz)*(9.192632GHz) / (10MHz)=9.192632GHz is output from the frequency converter 52. Therefore, the atomic oscillator frequency-modulates the excitation light with the resonance frequency "9.192632GHz" and outputs an output frequency signal of "10MHz" to the outside.

[0029] In this way, in the above-mentioned atomic oscillator, the influence of the change in the output frequency signal due to the right shift can be reduced by correcting the output frequency signal by changing the output frequency conversion coefficient by an amount corresponding to the change in the resonance frequency due to the right shift, while keeping the excitation light intensity the same, rather than restoring the excitation light intensity to its original state.

[0030] Instead of the above-mentioned correspondence data between the excitation light intensity and the output frequency conversion coefficient and the correspondence data between the excitation light intensity and the current modulation frequency conversion coefficient, the controller 4 may store correspondence data between the difference between the resonance frequencies F1 and F2 and the output frequency conversion coefficient or the current modulation frequency conversion coefficient, or may store correspondence data between the difference between the resonance frequencies F1 and F2 and the fluctuation amount of each resonance frequency F1 and F2, or a formula for calculating the fluctuation amount of each resonance frequency F1 and F2, the output frequency conversion coefficient or the current modulation frequency conversion coefficient from the difference between the resonance frequencies F1 and F2.The controller 4 may calculate the light shift amount of each resonance frequency from the above-mentioned difference between the resonance frequencies F1 and F2 based on the correspondence data and the calculation formula, and control the oscillation frequency based on the calculated value.

[0031] [Operation] Next, the operation of the above-mentioned atomic oscillator, particularly the operation when correcting the light shift of the resonance frequency, will be described.

[0032] First, the controller 4 switches the excitation light irradiation mode to CW mode or CPT-Ramsey mode (step S1 in FIG. 5). For example, the CW mode is set first, and non-pulsed continuous wave excitation light is irradiated. Then, the controller 4 sets various setting values, and the light generator 1 generates excitation light having at least two different frequency components. At this time, the current modulator control section 42 of the controller 4 changes and sweeps the modulation frequency, for example, around 9.2 GHz, which corresponds to the transition frequency between the ground levels of cesium atoms (step S2 in FIG. 5).

[0033] Then, the gas cell 2 is irradiated with non-pulsed excitation light in CW mode generated by the light generator 1, and the transmitted light is detected by the photodetector 3 (step S3 in FIG. 5). At this time, the controller 4 stores the measured amount of transmitted light in association with the modulation frequency (step S4 in FIG. 5). Then, the above process is repeated until the sweep of the modulation frequency and the measurement of the amount of transmitted light are completed (No in step S5 in FIG. 5, step S6).

[0034] When the measurement of the amount of transmitted light at the swept modulation frequency is completed (Yes in step S5 of FIG. 5), the controller 4 checks whether the measurement is completed in all irradiation modes (step S7 of FIG. 5). In this case, since the measurement in the CPT-Ramsey mode is not completed (No in step S7 of FIG. 5), the irradiation mode of the excitation light is switched to the CPT-Ramsey mode (step S1 of FIG. 5). Then, the controller 4 sets various setting values ​​in the same manner as described above, and generates excitation light having at least two different frequency components in the light generator 1. At this time, the current modulator control unit 42 of the controller 4 changes and sweeps the modulation frequency, for example, around 9.2 GHz, which corresponds to the transition frequency between the ground levels of cesium atoms (step S2 of FIG. 5).

[0035] Then, the gas cell 2 is irradiated with the excitation light generated by the light generator 1 and pulsed in the CPT-Ramsey mode, and the transmitted light is detected by the photodetector 3 (step S3 in FIG. 5). At this time, the controller 4 stores the measured amount of transmitted light in association with the modulation frequency (step S4 in FIG. 5). Then, the above process is repeated until the sweep of the modulation frequency and the measurement of the amount of transmitted light are completed (No in step S5 in FIG. 5, step S6).

[0036] The controller 4 performs light shift correction as follows at any timing after the measurement of the amount of transmitted light at the swept modulation frequency in all irradiation modes is completed (Yes in step S7 of FIG. 5). First, the controller 4 determines the resonance frequencies F1 and F2 in each irradiation mode based on the amount of transmitted light corresponding to each irradiation mode passed from the photodetector 3. Then, the controller 4 calculates the difference between the resonance frequencies F1 and F2 in each determined irradiation mode, and calculates the amount of light shift, which is the amount of fluctuation of the resonance frequency with respect to the excitation light intensity, based on the difference between the resonance frequencies F1 and F2 (step S8 of FIG. 5). For example, the controller 4 specifies the excitation light intensity based on a graph showing the relationship between the difference between the resonance frequencies F1 and F2 in each irradiation mode and the excitation light intensity as shown in FIG. 4. Furthermore, the controller 4 specifies the output frequency conversion coefficient and the current modulation frequency conversion coefficient corresponding to the specified excitation light intensity based on the correspondence data between the excitation light intensity and the output frequency conversion coefficient and the correspondence table between the excitation light intensity and the current modulation frequency conversion coefficient.

[0037] Then, the controller 4 changes and updates the stored output frequency conversion coefficient and current modulation frequency conversion coefficient to the newly specified output frequency conversion coefficient and current modulation frequency conversion coefficient (step S9 in FIG. 5). After that, the atomic oscillator can appropriately respond to the right shift by controlling the oscillation frequency from the VCXO 45 using the output frequency conversion coefficient and current modulation frequency conversion coefficient updated by the right shift correction.

[0038] As described above, the atomic oscillator of the present disclosure can appropriately deal with a light shift in which the resonant frequency varies due to a change in the intensity of the excitation light, thereby improving frequency stability.

[0039] <Embodiment 2> Next, a second embodiment of the present disclosure will be described. In this embodiment, an outline of the configuration of the atomic oscillator and the control method described in the above embodiments will be shown.

[0040] As shown in FIG. 6, the atomic oscillator 100 in this embodiment includes a gas cell 101 containing alkali metal atoms, a light generator 102 that irradiates the gas cell with irradiation light having at least two different frequency components, a photodetector 103 that detects the transmitted light that has passed through the gas cell, and a controller 104 that determines the resonant frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell and controls the oscillation frequency based on the determined resonant frequency.

[0041] 7, the controller 104 (control device) having the above configuration first irradiates the irradiation light by two irradiation methods each having different characteristics of change in resonance frequency due to change in intensity of the irradiation light (step S101). After that, the controller 104 controls the oscillation frequency based on a comparison result of the resonance frequency when the gas cell is irradiated with the irradiation light by each of the two irradiation methods (step S102).

[0042] As described above, the atomic oscillator according to the present disclosure can appropriately deal with a light shift in which the resonant frequency varies due to a change in the intensity of the excitation light, and can improve frequency stability.

[0043] Although the present invention has been described with reference to the above-mentioned embodiment, the present invention is not limited to the above-mentioned embodiment. Various modifications that can be understood by a person skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0044] <Additional Notes> A part or all of the above-described embodiments can be described as follows: The following describes an outline of the configuration of the atomic oscillator, control method, control device, and program according to the present invention. However, the present invention is not limited to the following configuration. (Appendix 1) a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a controller that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The irradiation light is irradiated by two irradiation methods each having different characteristics of a change in the resonance frequency due to a change in the intensity of the irradiation light, The controller controls the oscillation frequency based on a comparison result of the resonance frequency when the gas cell is irradiated with the irradiation light by each of the two irradiation methods. Atomic oscillator. (Appendix 2) 2. The atomic oscillator according to claim 1, A pulser for pulsing the irradiation light is further provided, At least one of the two irradiation methods is configured to irradiate the irradiation light pulsed by the pulser. Atomic oscillator. (Appendix 3) 3. The atomic oscillator according to claim 2, One of the two irradiation methods is to irradiate the irradiation light pulsed by the pulser, and the other is to irradiate the irradiation light not pulsed. Atomic oscillator. (Appendix 4) 3. The atomic oscillator according to claim 2, One of the two irradiation methods involves irradiating the first irradiation light pulsed by the pulser, and the other involves irradiating the second irradiation light pulsed by the pulser with a duty ratio different from that of the first irradiation light. Atomic oscillator. (Appendix 5) An atomic oscillator according to any one of claims 1 to 4, The controller controls the oscillation frequency based on a difference between the resonance frequencies when the gas cell is irradiated with the irradiation light in each of the two irradiation methods. Atomic oscillator. (Appendix 6) 6. The atomic oscillator according to claim 5, the controller calculates a fluctuation amount of the resonance frequency of the alkali metal atoms due to a change in intensity of the irradiation light based on a difference between the resonance frequencies when the irradiation light is irradiated to the gas cell by each of the two irradiation methods, and controls the oscillation frequency in accordance with the calculated fluctuation amount. Atomic oscillator. (Appendix 7) 7. The atomic oscillator according to claim 5 or 6, the controller controls the oscillation frequency based on the resonance frequency of the alkali metal atoms and a preset first parameter, changes the first parameter based on a difference between the resonance frequencies when the gas cell is irradiated with the irradiation light in each of the two irradiation methods, and controls the oscillation frequency based on the changed first parameter and the resonance frequency. Atomic oscillator. (Appendix 8) An atomic oscillator according to any one of Supplementary Notes 5 to 7, the controller controls to generate a reference signal serving as a reference for the irradiation light based on the oscillation frequency and a second parameter set in advance, and controls to change the second parameter based on a difference in the resonance frequency when the irradiation light is irradiated onto the gas cell using each of the two irradiation methods, and to generate the reference signal based on the changed second parameter and the oscillation frequency. Atomic oscillator. (Appendix 9) a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a controller that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; A method for controlling an atomic oscillator comprising: Irradiating the irradiation light using two irradiation methods each having different characteristics of change in the resonance frequency due to change in intensity of the irradiation light; The controller controls the oscillation frequency based on a comparison result of the resonance frequency when the gas cell is irradiated with the irradiation light by each of the two irradiation methods. Control methods. (Appendix 9.1) 10. The atomic oscillator according to claim 9, At least one of the two irradiation methods irradiates the irradiation light pulsed by a pulser. Control methods. (Appendix 9.2) 10. The atomic oscillator according to claim 9, One of the two irradiation methods is to irradiate the irradiation light pulsed by a pulser, and the other is to irradiate the irradiation light not pulsed. Control methods. (Appendix 10) a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a control device that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The control device for an atomic oscillator comprising: the control device irradiates the irradiation light by two irradiation methods having different characteristics of a change in the resonance frequency due to a change in intensity of the irradiation light, and controls the oscillation frequency based on a comparison result of the resonance frequency when the irradiation light is irradiated to the gas cell by each of the two irradiation methods. Control device. (Appendix 11) a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a control device that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The atomic oscillator is equipped with the control device irradiates the irradiation light by two irradiation methods each having a different characteristic of a change in the resonance frequency due to a change in intensity of the irradiation light, and controls the oscillation frequency based on a comparison result of the resonance frequency when the irradiation light is irradiated to the gas cell by each of the two irradiation methods. A program for executing a process. [Explanation of symbols]

[0045] 1 Light Generator 11. Laser 12 Pulse generator 2 Gas Cell 3. Photodetector 4. Controller 41 Resonant frequency and shift amount calculator 42 Current modulator control section 43 Laser control unit 44 Frequency converter control section 45 VCXO control section 51 VCXO 52 Frequency converter 53 Current Modulator 100 Atomic Oscillator 101 Gas Cell 102 Light Generator 103 Photodetector 104 Controller

Claims

1. a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a controller that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The irradiation light is irradiated by two irradiation methods each having different characteristics of a change in the resonance frequency due to a change in the intensity of the irradiation light, the controller controls the oscillation frequency based on a comparison result of the resonance frequency when the gas cell is irradiated with the irradiation light in each of the two irradiation methods. Atomic oscillator.

2. 2. The atomic oscillator according to claim 1, A pulser for pulsing the irradiation light is further provided, At least one of the two irradiation methods is configured to irradiate the irradiation light pulsed by the pulser. Atomic oscillator.

3. 3. The atomic oscillator according to claim 2, One of the two irradiation methods is to irradiate the irradiation light pulsed by the pulser, and the other is to irradiate the irradiation light not pulsed. Atomic oscillator.

4. 3. The atomic oscillator according to claim 2, One of the two irradiation methods involves irradiating the first irradiation light pulsed by the pulser, and the other involves irradiating the second irradiation light pulsed by the pulser with a duty ratio different from that of the first irradiation light. Atomic oscillator.

5. 2. The atomic oscillator according to claim 1, the controller controls the oscillation frequency based on a difference between the resonance frequencies when the gas cell is irradiated with the irradiation light in each of the two irradiation methods. Atomic oscillator.

6. 6. The atomic oscillator according to claim 5, the controller calculates a fluctuation amount of the resonance frequency of the alkali metal atoms due to a change in intensity of the irradiation light based on a difference between the resonance frequencies when the irradiation light is irradiated to the gas cell by each of the two irradiation methods, and controls the oscillation frequency in accordance with the calculated fluctuation amount. Atomic oscillator.

7. 6. The atomic oscillator according to claim 5, the controller controls the oscillation frequency based on the resonance frequency of the alkali metal atoms and a preset first parameter, changes the first parameter based on a difference between the resonance frequencies when the gas cell is irradiated with the irradiation light in each of the two irradiation methods, and controls the oscillation frequency based on the changed first parameter and the resonance frequency. Atomic oscillator.

8. 6. The atomic oscillator according to claim 5, the controller controls to generate a reference signal serving as a reference for the irradiation light based on the oscillation frequency and a second parameter set in advance, and controls to change the second parameter based on a difference in the resonance frequency when the irradiation light is irradiated onto the gas cell using each of the two irradiation methods, and to generate the reference signal based on the changed second parameter and the oscillation frequency. Atomic oscillator.

9. a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a controller that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; A method for controlling an atomic oscillator comprising: Irradiating the irradiation light using two irradiation methods each having different characteristics of change in the resonance frequency due to change in intensity of the irradiation light; the controller controls the oscillation frequency based on a comparison result of the resonance frequency when the gas cell is irradiated with the irradiation light in each of the two irradiation methods. Control methods.

10. a gas cell in which alkali metal atoms are sealed; a light generator for irradiating the gas cell with irradiation light having at least two different frequency components; a photodetector for detecting transmitted light that has passed through the gas cell; a control device that determines a resonance frequency of the alkali metal atoms based on the amount of light transmitted through the gas cell, and controls an oscillation frequency based on the determined resonance frequency; The control device for an atomic oscillator comprising: the control device irradiates the irradiation light by two irradiation methods each having a different characteristic of a change in the resonance frequency due to a change in intensity of the irradiation light, and controls the oscillation frequency based on a comparison result of the resonance frequency when the irradiation light is irradiated to the gas cell by each of the two irradiation methods. Control device.

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