Atomic oscillator, control method, controller, program

Abstract

To reduce the cost and size of magneto-optical trap-type atomic oscillators.SOLUTION: An atomic oscillator of the present disclosure comprises a first laser device 20 that irradiates a glass cell 1 containing alkali metal atoms with a first laser beam from a plurality of directions, and a second laser device 30 for irradiating a second laser beam, and the first laser beam La and the second laser beam L2 are configured to be incident into the glass cell 1 along the same optical path.SELECTED DRAWING: Figure 1

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 time accurately based on the natural frequency of an atom. Small atomic clocks 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. In CPT, when the difference in the frequencies of the two excitation light beams matches the transition frequency between the ground levels of the alkali metal, the amount of transmitted light increases without absorption of the excitation light. Therefore, atomic oscillators that use CPT as their operating principle sweep the difference in the frequencies of the two excitation light beams, and determine the resonant frequency, which is the difference in frequency at which the amount of transmitted light is maximized, 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 a CPT-type atomic oscillator, the linewidth of the CPT resonance contributes to frequency accuracy. For this reason, a magneto-optical trap type atomic oscillator that narrows the linewidth is known, as described in Patent Document 1. Specifically, in a magneto-optical trap type atomic oscillator, a quadrupole magnetic field is generated in a glass cell containing an alkali metal gas, and specific circularly polarized laser light is irradiated onto the center of the cell from six directions to spatially trap an atomic group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-141401 Summary of the Invention [Problem to be solved by the invention]

[0005] However, as mentioned above, in a magneto-optical trap type atomic oscillator, it is necessary to irradiate laser light from multiple optical axis directions, which increases the number of jigs and optical elements used, complicates the shape of the glass cell, and further requires anti-reflection film coating on both sides of the glass, which creates problems such as making it difficult to reduce cost and make the oscillator compact.

[0006] Therefore, an object of the present disclosure is to solve the above-mentioned problem that it is difficult to reduce the cost and size of a magneto-optical trap type atomic oscillator. [Means for solving the problem]

[0007] An atomic oscillator according to one embodiment of the present disclosure includes: a first laser device that irradiates a glass cell in which alkali metal atoms are sealed with a first laser beam from a plurality of directions, and a second laser device that irradiates a glass cell with a second laser beam, The first laser light and the second laser light in one direction are configured to be incident on the glass cell along the same optical path. The structure is as follows. [Effects of the Invention]

[0008] With the above-described configuration, the present disclosure can reduce the cost and size of a magneto-optical trap type atomic oscillator. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an atomic oscillator according to the present disclosure. [Figure 2] FIG. 1 is a diagram illustrating a configuration of an atomic oscillator according to the present disclosure. [Figure 3] FIG. 1 is a diagram illustrating a configuration of an atomic oscillator according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] FIG. 1 shows a schematic configuration of an atomic oscillator according to this embodiment. The atomic oscillator according to this embodiment is a CPT-type atomic oscillator including a magneto-optical trap unit 10. The atomic oscillator includes a glass cell 1 containing an alkali atomic gas, an ion pump 2, a magnetic field coil 3, and a photodetector 4 for detecting light transmitted through the glass cell 1. The atomic oscillator also includes a trapping laser unit 20 for magneto-optical trapping, a measurement laser unit 30 for measuring the CPT resonance frequency, and optical elements onto which laser light is irradiated, including a mirror 41, a λ / 4 wave plate 42, a λ / 2 wave plate 43, a bandpass optical element 44, and a polarizing beam splitter 45. The atomic oscillator also includes a magnetic field control unit 50 for controlling the magnetic field generated by the magnetic field coil 3, and a control unit (not shown) for controlling the operation of the atomic oscillator itself. Each component is described in detail below.

[0012] In this embodiment, the glass cell 1 is a cell formed into a substantially rectangular parallelepiped with predetermined surfaces formed flat, and an alkali metal gas is sealed inside. The alkali metal gas is, for example, cesium. Inside the glass cell 1, a magnetic field is controlled by a magnetic field coil 3 and a magnetic field control unit 50, and a quadrupole magnetic field, for example, is generated. As will be described later, a trapping laser beam L1 is irradiated onto the glass cell 1 to trap the alkali metal gas inside the glass cell 1, and a magneto-optical trap unit 10 is formed by optical elements including the glass cell 1. The shape of the glass cell 1 is not limited to the above-mentioned shape.

[0013] The trapping laser unit 20 (first laser device) emits trapping laser light L1 (first laser light) from multiple directions to capture the alkali metal gas in the glass cell 1. Specifically, the trapping laser unit 20 emits trapping laser light L1 consisting of at least two wavelengths, namely, trapping light and repumping light, each having a wavelength of around 852 nm, which corresponds to the D2 line of cesium.

[0014] 1, the trapping laser light L1 emitted from the trapping laser unit 20 is branched into a plurality of trapping laser lights La, Lb, and Lc by optical branching units 46, 47, and 48 (branching units). Here, the optical branching units 46, 47, and 48 are composed of a λ / 2 wave plate 43 and a polarizing beam splitter 45, and the power transmitted through and reflected by the beam splitter is controlled by the angle of the λ / 2 wave plate. In this embodiment, three optical branching units 46, 47, and 48 are provided, and the first optical branching unit 46 reflects one-third of the power of the trapping laser light L1 to be incident on the magneto-optical trapping unit 10 as first trapping laser light La, the second optical branching unit 47 reflects half the power of the light transmitted through the first optical branching unit 46 to be incident on the magneto-optical trapping unit 10 as second trapping laser light Lb, and the third optical branching unit 48 reflects the maximum power of the transmitted light through the second optical branching unit 47 to be incident on the magneto-optical trapping unit 10 as third trapping laser light Lc. The above-mentioned optical branching units 46, 47, and 48 may be composed of optical fiber couplers and lenses.

[0015] As shown in FIG. 1 , the three trapping laser beams La, Lb, and Lc pass through a 4 / λ waveplate 42, are reflected by a mirror 41, and are orthogonally incident on the magneto-optical trap unit 10. The second trapping laser beam Lb and the third trapping laser beam Lc enter the glass cell 1, pass through the glass cell 1, are reflected by the mirror 41, and are then incident on the glass cell 1 again from the opposite direction. The first trapping laser beam La enters the glass cell 1, passes through the glass cell 1, is reflected by a bandpass optical element 44, and is then incident on the glass cell 1 again from the opposite direction. The bandpass optical element 44 has a bandpass wavelength characteristic that reflects the trapping laser beam L1 (La) and transmits the measurement laser beam L2 (described later). In other words, the bandpass optical element 44 is a reflective bandpass filter that transmits only laser light with a wavelength of around 895 nm, i.e., the measurement laser beam L2 (described later).

[0016] In this way, the first trapping laser beam La, the second trapping laser beam Lb, and the third trapping laser beam Lc each enter the glass cell 1 once, pass through it, are reflected, and then enter the glass cell 1 again from the opposite direction, i.e., the transmission side. In other words, each of the trapping laser beams La, Lb, and Lc enters the glass cell 1 from two directions, for a total of six directions. In this way, atomic groups can be spatially trapped by irradiating the alkali metal gas in the glass cell 1 with the trapping laser beams La, Lb, and Lc from multiple directions.

[0017] The measurement laser unit 30 (second laser device) emits measurement laser light to measure the resonance frequency. Specifically, the trapping laser unit 20 emits measurement laser light L2 consisting of two laser lights with a wavelength of around 895 nm, which corresponds to the D1 line of cesium.

[0018] 1, measurement laser light L2 emitted from measurement laser unit 30 is incident on first optical branching unit 46 (combining unit) and multiplexed with first trapping laser light La branched by first optical branching unit 46. Specifically, first optical branching unit 46 transmits measurement laser light L2 in the branching direction of first trapping laser light La, which is branched by reflection of incident trapping laser light L1, thereby multiplexing first trapping laser light La and measurement laser light L2. As a result, first trapping laser light La and measurement laser light L2 are multiplexed along the same optical path.

[0019] 1, the first trapping laser beam La and the measurement laser beam L2, which have been combined onto the same optical path, are reflected by a mirror 41 and enter the glass cell 1 while maintaining the same optical path. At this time, the first trapping laser beam La and the measurement laser beam L2 are set to enter the glass cell 1 perpendicularly to the plane of the glass cell 1.

[0020] The first trapping laser beam La and the measurement laser beam L2, which have entered the glass cell 1 along the same optical path, pass through the glass cell 1 while maintaining the same optical path, and then enter the bandpass optical element 44, which is arranged in the optical path of the transmitted light. Then, the first trapping laser beam La is reflected by the bandpass optical element 44, as described above, while the measurement laser beam L2 passes through the bandpass optical element 44. This is because, as described above, the bandpass optical element 44 is a reflective bandpass filter that transmits only laser beams with wavelengths around 895 nm, which are the measurement laser beam L2.

[0021] In this way, the measurement laser beam L2 passes through the bandpass optical element 44 after passing through the glass cell 1, and can therefore be detected by the photodetector 4 arranged in the optical path of the transmitted light. Therefore, by detecting the transmitted light of the measurement laser beam L2 that has passed through the glass cell 1 with the photodetector 4, the resonant frequency required for the operation of the atomic oscillator can be identified, and the atomic oscillator can be operated. In actual operation, first, the trapping laser beam L1 (La, Lb, Lc) is irradiated to generate a magneto-optical trap, and immediately thereafter the intensity of the trapping laser beam L1 is weakened and the measurement laser beam L2 is irradiated to measure the resonant frequency.

[0022] As described above, according to the present disclosure, the optical path of one trapping laser beam La for magneto-optical trapping and the optical path of measurement laser beam L2 are made the same optical path, and these laser beams are incident on glass cell 1. This makes it possible to avoid providing optical paths beyond those necessary for magneto-optical trapping, thereby preventing an increase in the number of jigs and optical elements used, and further prevents the shape of the glass cell from becoming complicated. As a result, it is possible to reduce the cost and size of the magneto-optical trap type atomic oscillator.

[0023] <Embodiment 2> Next, a second embodiment of the present disclosure will be described with reference to the drawings, which may be relevant to any embodiment.

[0024] 2 shows an outline of the configuration of the atomic oscillator of this embodiment. As in embodiment 1, the atomic oscillator of this embodiment includes a trapping laser unit 20, a measurement laser unit 30, a mirror 41, a λ / 4 wavelength plate 42, a λ / 2 wavelength plate 43, and a polarizing beam splitter 45. Unlike embodiment 1, this embodiment does not include the above-mentioned bandpass optical element, and the arrangement of the mirror 41 and the like is different, so that the optical paths of the laser beams La, Lb, Lc, and L2 are formed differently. Below, the configuration that differs from the other embodiments described above will be mainly described in detail.

[0025] 2, the trapping laser beam L1 in this embodiment is branched into a plurality of trapping laser beams La, Lb, and Lc by optical branching units 46, 47, and 48. Then, as in the first embodiment, each of the trapping laser beams La, Lb, and Lc is reflected by a mirror 41 and travels back and forth to enter the glass cell 1. At this time, the second trapping laser beam Lb is reflected by the mirror 41 in a direction perpendicular to the plane of FIG. 2, enters the glass cell 1, passes through the glass cell 1, and then passes through a λ / 4 wave plate 42 (not shown) located on the opposite side of the glass cell 1. Then, it is reflected by the mirror 41 (not shown), passes through the λ / 4 wave plate 42 again, and enters the glass cell 1. In other words, in FIG. 2, the horizontal direction is the X direction, the vertical direction is the Y direction, and the direction perpendicular to the paper surface is the Z direction. Mirrors 41 are placed on both the front and back sides of the paper surface of FIG. 2, sandwiching the glass cell 1 between them, and the second trapping laser light Lb travels back and forth along the Z direction before being incident on the glass cell 1.

[0026] Furthermore, the measurement laser beam L2 is incident on the glass cell 1 along the Y direction in Fig. 2. As a result, just after the trapping laser beam L1 (La, Lb, Lc) is irradiated to generate a magneto-optical trap, the intensity of the trapping laser beam L1 can be weakened and the measurement laser beam L2 can be irradiated to measure the resonance frequency, as described above.

[0027] <Embodiment 3> Next, a third embodiment of the present disclosure will be described with reference to the drawings, which may be relevant to any embodiment.

[0028] 3 shows an outline of the configuration of the atomic oscillator of this embodiment. As with embodiment 1, the atomic oscillator of this embodiment includes a trapping laser unit 20, a measurement laser unit 30, a mirror 41, a λ / 4 wave plate 42, a λ / 2 wave plate 43, a bandpass optical element, and a polarizing beam splitter 45. In this embodiment, the arrangement of the mirror 41 and the like differs from that of the above-described embodiments 1 and 2. The following mainly describes in detail the configuration that differs from the above-described embodiments.

[0029] 3, the trapping laser light L1 in this embodiment is branched into a plurality of trapping laser lights La, Lb, and Lc by optical branching units 46, 47, and 48. Then, each of the trapping laser lights La, Lb, and Lc is reflected by mirror 41, as in the second embodiment, and enters the glass cell 1 after making a round trip. At this time, the measurement laser light L2 is configured to enter the glass cell 1 along the same optical path as the second trapping laser light Lb.

[0030] Furthermore, in this embodiment, a photodetector 4 is mounted inside the glass cell 1. In this case, by providing a bandpass optical element (not shown) having wavelength characteristics that transmit only the measurement laser light L2 on the surface of the photodetector 4, the photodetector 4 can measure only the measurement laser light L2 and can reflect the second trapping laser light Lb on the same optical path.

[0031] As a result, just after generating a magneto-optical trap by irradiating the trapping laser light L1 (La, Lb, Lc), the intensity of the trapping laser light L1 can be weakened and the measurement laser L2 can be irradiated to measure the resonance frequency, as described above.

[0032] Although the present invention has been described above with reference to the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0033] <Additional Notes> A part or all of the above-described embodiments can be described as follows: The configuration of the atomic oscillator according to the present invention will be outlined below. However, the present invention is not limited to the following configuration. (Appendix 1) a first laser device that irradiates a glass cell in which alkali metal atoms are sealed with a first laser beam from a plurality of directions, and a second laser device that irradiates a glass cell with a second laser beam, The first laser light and the second laser light in one direction are configured to be incident on the glass cell along the same optical path. Atomic oscillator. (Appendix 2) 2. The atomic oscillator according to claim 1, a photodetector for detecting transmitted light that has passed through the glass cell; an optical element that does not transmit the first laser beam but transmits the second laser beam to the photodetector is disposed in an optical path of the transmitted light; Atomic oscillator. (Appendix 3) 10. The atomic oscillator according to claim 2, the optical element disposed in the optical path of the transmitted light is configured to reflect the first laser light toward the glass cell and transmit the second laser light to the photodetector. Atomic oscillator. (Appendix 4) 2. The atomic oscillator according to claim 1, a multiplexing section that multiplexes the first laser light and the second laser light in the same direction on the same optical path by making the one first laser light and the second laser light incident on different optical paths, and reflecting the one first laser light and transmitting the second laser light; Atomic oscillator. (Appendix 5) 2. The atomic oscillator according to claim 1, a branching unit that branches the first laser light irradiated from the first laser device into a plurality of first laser light beams that are incident on the glass cell from a plurality of directions; a multiplexing section that multiplexes the first laser light and the second laser light in the same direction on the same optical path by making the one branched first laser light and the one branched second laser light incident on the same optical path from different optical paths and reflecting the one branched first laser light and transmitting the second laser light; Equipped with Atomic oscillator. (Appendix 6) 2. The atomic oscillator according to claim 1, a combining unit that splits the first laser light irradiated from the first laser device into a plurality of first laser light beams incident on the glass cell from a plurality of directions, and that makes the second laser light incident in the direction of one of the split first laser light beams and transmits the second laser light, thereby combining the first laser light and the second laser light in the one direction on the same optical path, Atomic oscillator. (Appendix 7) 2. The atomic oscillator according to claim 1, The first laser light and the second laser light in the one direction are configured to be incident perpendicularly to a plane of the glass cell along the same optical path. Atomic oscillator. (Appendix 8) 2. The atomic oscillator according to claim 1, a first laser device that irradiates the first laser light for capturing the alkali metal atoms from a plurality of directions; the second laser device irradiates the second laser light for measuring the resonance frequency; Atomic oscillator. [Explanation of symbols]

[0034] 1 glass cell 2. Ion pump 3 Magnetic field coils 4 Photodetector 10. Magneto-optical trap section 20 Trap laser unit 30 Measurement laser unit 41 Mirror 42 λ / 4 wave plate 43 λ / 2 wave plate 44 Polarizing Beam Splitter 45 Bandpass Optical Elements 46 First optical branching section 47 First optical branching section 48 First optical branching unit 50 Magnetic field control unit

Claims

1. a first laser device that irradiates a glass cell in which alkali metal atoms are sealed with a first laser beam from a plurality of directions, and a second laser device that irradiates a glass cell with a second laser beam, The first laser light and the second laser light in one direction are configured to be incident on the glass cell along the same optical path. Atomic oscillator.

2. 2. The atomic oscillator according to claim 1, a photodetector for detecting transmitted light that has passed through the glass cell; an optical element that does not transmit the first laser beam but transmits the second laser beam to the photodetector is disposed in an optical path of the transmitted light; Atomic oscillator.

3. 3. The atomic oscillator according to claim 2, the optical element disposed in the optical path of the transmitted light is configured to reflect the first laser light toward the glass cell and transmit the second laser light to the photodetector. Atomic oscillator.

4. 2. The atomic oscillator according to claim 1, a multiplexing section that multiplexes the first laser light and the second laser light in the same direction on the same optical path by making the first laser light and the second laser light incident on different optical paths, and reflecting the first laser light and transmitting the second laser light; Atomic oscillator.

5. 2. The atomic oscillator according to claim 1, a branching unit that branches the first laser light irradiated from the first laser device into a plurality of first laser light beams that are incident on the glass cell from a plurality of directions; a multiplexing section that multiplexes the first laser light and the second laser light in the same direction on the same optical path by making the one branched first laser light and the one branched second laser light incident on the same optical path from different optical paths and reflecting the one branched first laser light and transmitting the one branched second laser light; Equipped with Atomic oscillator.

6. 2. The atomic oscillator according to claim 1, a combining unit that branches the first laser light irradiated from the first laser device into a plurality of first laser light beams incident on the glass cell from a plurality of directions, and causes the second laser light beam to be incident in the direction of one of the branched first laser light beams and transmit the second laser light, thereby combining the first laser light and the second laser light in the one direction on the same optical path, Atomic oscillator.

7. 2. The atomic oscillator according to claim 1, The first laser light and the second laser light in the one direction are configured to be incident perpendicularly to a plane of the glass cell along the same optical path. Atomic oscillator.

8. 2. The atomic oscillator according to claim 1, a first laser device that irradiates the first laser light for capturing the alkali metal atoms from a plurality of directions; the second laser device irradiates the second laser light for measuring the resonance frequency; Atomic oscillator.

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