JP2017050665A - Atomic oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atomic oscillator capable of maintaining stable oscillation characteristics by preventing instability in oscillation characteristics due to influences of magnetism due to fluctuation of external magnetic field and deviation of optical axis due to temperature interference while achieving miniaturization and low profile.SOLUTION: An atomic oscillator includes: at least a gas cell in which metal atoms are sealed; a coil disposed around the gas cell; a first magnetic shield housing the gas cell and the coil; and a heating element for heating the gas cell. The atomic oscillator comprises a second magnetic shield housing the heating element.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an atomic oscillator.

  2. Description of the Related Art Atomic oscillators that oscillate based on energy transitions of alkali metal atoms such as rubidium and cesium are known. In general, the operating principle of an atomic oscillator is broadly divided into a method using a double resonance phenomenon by light and microwave and a method using a quantum interference effect (CPT: Coherent Population Trapping) by two types of light having different wavelengths. Is done.

  In any type of atomic oscillator, an alkali metal is sealed in a gas cell together with a buffer gas, and how much light incident on the gas cell is absorbed by the alkali metal is detected by a detector provided on the opposite side. Thus, the atomic resonance is detected, and the detected atomic resonance is output as a reference signal by the control system. As such an atomic oscillator, a configuration is disclosed in which a gas cell is provided on a substrate, and a light (excitation light) light source and a detector are disposed on both sides of the gas cell (see, for example, Patent Document 1). ).

  In addition, since an atomic oscillator using CPT is smaller than an atomic oscillator using a double resonance phenomenon, it is expected that the atomic oscillator will be incorporated into various electronic devices. Is desired.

JP 2009-231688 A

  However, downsizing and low profile have caused problems such as optical axis shift due to temperature interference and unstable oscillation characteristics because metal atoms in the gas cell are easily affected by external magnetism. The risk of occurrence increases.

  The object of the present invention is to reduce the size and height of the device, and to suppress the influence of magnetism due to fluctuations in the external magnetic field and the instability of the oscillation characteristics due to the optical axis shift due to temperature interference, thereby maintaining stable oscillation characteristics. It is to provide a possible atomic oscillator.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 An atomic oscillator according to this application example includes at least a gas cell in which metal atoms are sealed, a coil disposed around the gas cell, and a first magnetic shield that houses the gas cell and the coil. And a heating element that heats the gas cell, and a second magnetic shield that houses the heating element.

  Although the magnetism generated by the heating element, which is an electronic component, is weak, the influence of the magnetism cannot be ignored because the heating element is arranged in the vicinity of the gas cell that is susceptible to magnetism. Therefore, according to the atomic oscillator of this application example, the magnetism (change in the magnetic field) generated by the heating element can be shielded by the second magnetic shield. That is, by enclosing the heating element with a second magnetic shield formed of a material having a magnetic shielding effect, magnetic leakage from the heating element is prevented, and the influence on metal atoms in the gas cell is suppressed. It becomes possible to stabilize the oscillation characteristics as an oscillator.

  Application Example 2 In the application example described above, an intermediate member sandwiched between the first magnetic shield and the second magnetic shield is provided, and the intermediate member includes the first magnetic shield and the second magnetic shield. It has a magnetic permeability lower than the magnetic permeability of the shield.

  According to the above application example, the magnetic field generated by the heating element accommodated in the second magnetic shield is prevented from flowing (leaking) into the adjacent first magnetic shield, and the influence on the metal atoms in the gas cell is prevented. Thus, it is possible to stabilize the oscillation characteristics as an atomic oscillator.

  Application Example 3 In the application example described above, the intermediate member has a thermal conductivity higher than that of the first magnetic shield.

  The heat generated by the heating element is transferred to the gas cell through the second magnetic shield and the first magnetic shield. At this time, the heat transfer loss in the intermediate member sandwiched between the first magnetic shield and the second magnetic shield must be suppressed. Therefore, according to the application example described above, the transmission loss of heat transmitted from the second magnetic shield can be reduced by using an intermediate member having a higher thermal conductivity than the first magnetic shield.

  Application Example 4 In the application example described above, the second magnetic shield includes a pressing portion that presses the heating element toward the first magnetic shield.

  According to the application example described above, the heating element is pressed to the side (region) facing the first magnetic shield in the second magnetic shield, so that the first magnetic shield of the heating element and the second magnetic shield Adhering to the facing side (region), the heat generated by the heating element is reliably transmitted to the side (region) facing the first magnetic shield of the second magnetic shield, and further, the intermediate member and the first magnetic shield By supplying predetermined heat to the gas cell through the body, stable oscillation performance of the atomic oscillator can be obtained.

  Application Example 5 In the application example described above, a buffer member sandwiched between the pressing portion and the heating element is provided.

  According to the application example described above, the buffer member can be prevented from directly contacting the pressing portion with the heating element, and damage to the heating element can be prevented.

  Application Example 6 In the application example described above, the buffer member is a substrate on which a power supply wiring to the heating element is formed.

  According to the application example described above, it is possible to reduce the cost by downsizing the atomic oscillator and reducing the number of parts.

1 is a front sectional view showing an outline of an atomic oscillator according to a first embodiment. Sectional drawing of the AA 'part shown in FIG. 1 which shows the outline of the atomic oscillator which concerns on 1st Embodiment. The elements on larger scale in the B section shown in FIG. The schematic block diagram of the atomic oscillator shown in FIG. 1 and FIG. The figure for demonstrating the energy state of the alkali metal in the gas cell of the atomic oscillator which concerns on 1st Embodiment. The graph which shows the relationship between the frequency difference of the two lights from a light emission part (light source), and the detection intensity in a light detection part about the light emission part (light source) and light detection part of the atomic oscillator which concerns on 1st Embodiment. . Sectional drawing which shows the other form of an atomic oscillator. The elements on larger scale of the C section shown in FIG. The figure which shows schematic structure of the positioning system using a GPS satellite as an example of the electronic device which concerns on 2nd Embodiment. The schematic block diagram which shows the clock transmission system as an example of the electronic device which concerns on 3rd Embodiment. The perspective view which shows the structure of the motor vehicle as an example of the mobile body which concerns on 4th Embodiment.

  Embodiments according to the present invention will be described below with reference to the drawings.

(First embodiment)
1 and 2 schematically show the atomic oscillator according to the first embodiment. FIG. 1 is a front sectional view, and FIG. 2 is a sectional view taken along the line AA ′ shown in FIG.

  An atomic oscillator 100 shown in FIGS. 1 and 2 is an atomic oscillator using a quantum interference effect. The atomic oscillator 100 includes a gas cell unit 10, a light emitting unit 20, and a gas cell side magnetic shield 40 (hereinafter referred to as a cell side shield 40) as a first magnetic shield that houses the gas cell unit 10. Yes.

  The gas cell unit 10 is wound around the gas cell 11, the gas cell holding member 12 that holds the gas cell 11, and conducts heat generated in a heater, which will be described later, to the gas cell 11, and the outer peripheral surface along the X-axis direction of the gas cell holding member 12. A coil 13.

  In the gas cell 11, an internal space S is formed by sealing a main body portion 11a having a columnar through-hole and openings on both sides of the through-hole by a pair of windows 11b and 11c. The gas cell inner space S is filled with gaseous alkali metal such as rubidium, cesium, sodium.

  The light emission part 20 includes a light source container 21 including a main body part 21a having a columnar through hole, and a pair of lid parts 21b and 21c for sealing openings on both sides of the through hole, and a light source container. 21 and a light source 22 housed and fixed in 21. The light source 22 has a function of emitting excitation light that excites alkali metal atoms in the gas cell 11. The light source 22 is disposed inside the light source housing 21 so as to face the gas cell 11 along the excitation light emission direction (the optical axis direction R indicated by the arrow in the figure), and intersects the excitation light emission direction of the main body 21a. A through hole 21d is provided in the region, and excitation light is emitted from the light source 22 toward the gas cell 11 through the through hole 21d.

  The emitted excitation light is an optical component arranged in the through hole 12a on the light emitting part 20 side among the through holes 12a and 12b formed in the portion where the gas cell holding member 12 and the optical axis direction R intersect. 14 and 15 are transmitted. In the present embodiment, the optical components 14 and 15 are arranged in this order from the light source 22 side to the gas cell 11 side. The optical component 14 is a λ / 4 wavelength plate. Thereby, the excitation light LL from the light source 22 can be converted from linearly polarized light into circularly polarized light (right circularly polarized light or left circularly polarized light). The optical component 15 is a neutral density filter (ND filter). Thereby, the intensity | strength of the excitation light which injects into the gas cell 11 can be adjusted (decrease). Therefore, even when the output of the light source 22 is large, the excitation light incident on the gas cell 11 can be set to a desired light amount.

  A coil 13 is wound around the outer peripheral portion 12 c parallel to the optical axis direction R of the gas cell holding member 12 along the outer peripheral portion 12 c. The coil 13 has a function of generating a magnetic field when energized. Thereby, by applying a magnetic field to the alkali metal in the gas cell 11, the gap between different energy levels in which the alkali metal is degenerated can be expanded by Zeeman splitting, and the resolution can be improved. As a result, the accuracy of the oscillation frequency of the atomic oscillator 100 can be increased. The magnetic field generated by the coil 13 may be either a DC magnetic field or an AC magnetic field, or may be a magnetic field in which a DC magnetic field and an AC magnetic field are superimposed. The coil 13 may be a solenoid coil provided so as to surround the gas cell 11 or a Helmholtz coil provided so as to sandwich the gas cell 11.

  A light detection unit 30 is provided at a position facing the light emitting unit 20 along the optical axis direction R with the gas cell 11 interposed therebetween. The light detection unit 30 has a function of detecting the intensity of excitation light LL (resonance light 1 and resonance light 2), which will be described later, transmitted through the gas cell 11. In the present embodiment, the light detection unit 30 is joined to the gas cell holding member 12 via an adhesive 31. Here, as the adhesive 31, a known adhesive can be used. The light detector 30 is not particularly limited as long as it can detect the excitation light as described above. For example, a photodetector (light receiving element) such as a solar cell or a photodiode is used. it can.

  The gas cell unit 10 and the light detection unit 30 described above are accommodated inside the cell-side shield 40. The cell-side shield 40 includes a base portion 42 placed on the substrate 50 and a box-shaped lid body 41 so as to cover the gas cell unit 10 including the light detection unit 30 placed on the base portion 42. The cell side shield 40 is configured by covering the lid 41 and matching the lid 42. The cell side shield 40 has a function of shielding magnetism from the outside with respect to the inside of the cell side shield 40, and shields magnetism from the outside to the gas cell unit 10 accommodated in the cell side shield 40.

  A through hole 41 a is provided at a position of the lid 41 facing the through hole 12 a formed in the gas cell holding member 12, that is, at a position where excitation light passes. The through hole 41a is not particularly limited as long as it is a material that can transmit excitation light. For example, transparent glass, transparent quartz glass, transparent crystal, or the like may be airtightly joined. Thus, the through-hole 41a is airtightly joined, so that the inside of the cell side shield 40 can be made an airtight space. Although not shown in FIGS. 1 and 2, the cell-side shield 40 may contain components other than the components described above. Although not shown, the substrate 50 is provided with a plurality of wirings for energizing the gas cell unit 10 from the outside of the cell-side shield 40.

  As a constituent material of the lid body 41 and the base portion 42, it is only necessary to have a magnetic shielding effect. For example, iron (Fe), various Fe alloys (silicon iron, permalloy, supermalloy, amorphous, sendust), copper (Cu ), And soft magnetic materials such as copper alloys are preferred. By using such a material for the lid body 41 and the base portion 42, magnetism from the outside (change in the magnetic field) can be shielded by the cell side shield body 40. As a result, it is possible to suppress the influence on the metal atoms in the gas cell 11 due to external magnetism (change in the magnetic field), and to stabilize the oscillation characteristics of the atomic oscillator 100.

  A lid 41 is joined to the base 42, and the opening of the lid 41 is sealed by the base 42. A method for joining the base portion 42 and the lid body 41 is not particularly limited. For example, brazing, seam welding, energy beam welding (laser welding, electron beam welding, etc.), or the like can be used. In addition, between the base part 42 and the cover body 41, the joining member for joining these may intervene.

  Moreover, it is preferable that the base part 42 and the cover body 41 are airtightly joined. That is, the inside of the cell side shield 40 is preferably an airtight space. Thereby, the inside of the cell side shield 40 can be made into a pressure reduction state or an inert gas enclosure state, and as a result, the characteristics of the atomic oscillator 100 can be improved. In particular, the inside of the cell-side shield 40 is preferably in a reduced pressure state. Thereby, heat transfer through the space in the cell-side shield 40 can be suppressed. Therefore, it is possible to suppress thermal interference between the gas cell holding member 12 and the outside of the cell side shield 40 or between the heater and the gas cell 11 described later via the space in the cell side shield 40. Therefore, the heat of the heater is efficiently transmitted to the two windows 11b and 11c via the gas cell holding member 12, and the temperature difference between the two windows 11b and 11c can be suppressed. In addition, heat transfer between the gas cell unit 10 and the outside of the cell-side shield 40 can be more effectively suppressed.

  As shown in FIG. 2, the atomic oscillator 100 according to this embodiment includes a heater 70 as a heating element that heats the gas cell unit 10. The heater 70 is a heating resistor (heat generating part) that generates heat when energized. The heat generated by the heater 70 is transmitted to the gas cell 11, the gas cell 11 (more specifically, the alkali metal in the gas cell 11) is heated, and the alkali metal in the gas cell 11 can be maintained in a gaseous state. A Peltier element may be used in place of the heater 70 or in combination with the heater 70. In this case, the portion on the heat generating side of the Peltier element constitutes a heat generating portion.

  The heater 70 is accommodated in a heater accommodating body 60 as a second magnetic shield. FIG. 3 is a partially enlarged view of a portion B shown in FIG. As shown in FIG. 3, the heater housing 60 includes a heater housing 61 including a box-shaped heater housing 61a in which the heater 70 is housed, and a flange 61b extending from the heater housing 61a, and at least A heater storage lid 62 that covers the heater storage 61a. And the space | gap 61b of the heater accommodating body 61 and the heater accommodating cover body 62 are match | combined, and the space of the heater accommodating part 61a is comprised as heater accommodating space Sh.

  The constituent material of the heater housing 61 and the heater housing lid 62 only needs to have a magnetic shielding effect. For example, iron (Fe), various Fe alloys (silicon iron, permalloy, supermalloy, amorphous, sendust) Soft magnetic materials such as copper (Cu) and copper alloys are preferred. By using such a material for the heater housing 61 and the heater housing lid 62, the magnetism (change in magnetic field) generated by the heater 70 can be shielded by the heater housing 60. Although the magnetism generated by the heater 70 is weak, since the heater 70 is disposed in the vicinity of the gas cell 11 that is easily affected by magnetism, the influence of magnetism cannot be ignored. Therefore, the heater 70 is encased by the heater housing 60 formed of a material having a magnetic shielding effect, thereby preventing magnetic leakage from the heater 70 and suppressing the influence on the metal atoms in the gas cell 11. It is possible to stabilize the oscillation characteristics of the oscillator 100.

  The heater storage lid 62 is formed with a protrusion 62 a corresponding to the heater 70 as a pressing portion that protrudes toward the heater 70 in a state where the heater storage body 60 is configured. Then, a flexible substrate 71 (hereinafter referred to as a flexible substrate 71) in which wiring for supplying electric power to the heater 70 is formed between the tip portion 62b of the protrusion 62a and the heater 70 is sandwiched. Furthermore, the heater 62 is pressed and fixed to the inner bottom surface 61c of the heater housing 61a by the tip 62b of the protrusion 62a via the flexible substrate 71.

  By pressing the heater 70 toward the inner bottom surface 61c of the heater accommodating portion 61a, the heater 70 and the inner bottom surface 61c are brought into close contact with each other, and the heat generated by the heater 70 is reliably transmitted to the heater accommodating portion 61a. Then, predetermined heat is supplied to the gas cell 11 through the outer shell magnetic shield 90 (hereinafter referred to as the outer shell shield 90), and stable oscillation performance of the atomic oscillator 100 can be obtained.

  The heater housing 60 is provided on the outside of the outer shell lid 91 that constitutes the outer shell shielding body 90 as the third magnetic shielding body provided outside the cell side shielding body 40 shown in FIG. 1 or FIG. The flange 61b of the 61 and the heater storage lid 62 are fixed by screws 60a. At this time, the outer shell lid 91 is formed with an insertion hole 91 b into which the heater accommodating portion 61 a of the heater accommodating body 61 can be inserted, and the heater accommodating body 60 in which the heater 70 is accommodated is formed in the outer shell lid 91. By being fixed, the external connection surface 61d that faces the inner bottom surface 61c of the heater housing 61a through the insertion hole 91b is disposed so as to protrude to the inside of the outer shell lid body 91.

  Then, the intermediate member 80 is sandwiched between the external connection surface 61d and the lid body 41 of the cell-side shield 40. The intermediate member 80 is preferably made of a material having a high thermal conductivity and a low magnetic permeability, such as aluminum. As described above, the heater housing 60 is formed using a material having high magnetic permeability. This intermediate member 80 blocks the flow (leakage) of magnetism from the heater 70 generated by the direct contact between the heater housing 60 and the cell-side shield 40, and the heater 70 is generated. Heat to be transmitted to the gas cell 11 through the cell-side shield 40.

  Therefore, the magnetic permeability of the intermediate member 80 is preferably lower than the magnetic permeability of the cell-side shield 40 and the outer shell shield 90. Moreover, the heat conductivity of the intermediate member 80 can be reduced by setting the heat conductivity of the intermediate member 80 to be at least higher than that of the cell-side shield 40, that is, the lid 41. The intermediate member 80 may be joined to the external connection surface 61d of the heater accommodating portion 61a by an adhesive having a high thermal conductivity, brazing using metal brazing, or welding means such as spot welding.

  As described above, in order to ensure that the heat generated by the heater 70 can be transmitted to the intermediate member 80 via the heater accommodating portion 61a, the heater accommodating portion is formed by the tip 62b of the protrusion 62a of the heater accommodating lid 62. The heater 70 is urged toward the inner bottom surface 61c of 61a. However, there is a possibility that the heater 70 may be damaged when the protrusion 62a directly contacts the heater 70.

  Therefore, the heater 70 is configured such that a part of the resin-made flexible substrate 71 having a power supply wiring for supplying electric power to the heater 70 from the outside is interposed and sandwiched between the heater 70 and the tip 62b of the protrusion 62a. Can prevent damage. In other words, the flexible substrate 71 can be used as a buffer member between the protrusion 62 a and the heater 70. In addition, since the flexible substrate 71 is made of resin, that is, has elasticity, the pressing force to the heater 70 by the tip 62b of the protrusion 62a can be maintained.

  In addition, although the flexible substrate 71 was used as a buffer member, it is not limited to this. For example, a resin sheet may be sandwiched between the protrusion 62a and the heater 70, or a resin coat may be applied to the protrusion 62a. However, it is preferable to use the flexible substrate 71 as a cushioning member because of cost reduction due to downsizing and reduction in the number of components.

  As shown in FIGS. 1 and 2, the above-described outer shell shield 90 houses the cell side shield 40, and together with the cell side shield 40, the gas cell unit 10 and the light detection unit 30 are externally magnetized. Has a function of shielding. The outer shell shield 90 includes a bottom 92 and an outer shell lid body 91, and the opening of the outer shell lid body 91 is sealed by the substrate 50. Thereby, the space which accommodates the cell side shield 40 is formed.

  In the outer lid 91, a through hole 91 a is provided at a position facing the through hole 41 a provided in the cell side shield 40, that is, at a position where excitation light passes. The through hole 91a may be a through hole, or a material that can transmit excitation light, such as transparent glass, transparent quartz glass, or transparent crystal, may be bonded thereto. The outer shell lid body 91 is joined to the substrate 50, and the opening of the outer shell lid body 91 is sealed. As a method for joining the substrate 50 and the outer shell lid body 91, for example, a resin adhesive, brazing, seam welding, energy beam welding (laser welding, electron beam welding, etc.) or the like can be used. Note that a bonding member for bonding these may be interposed between the substrate 50 and the outer shell lid 91.

  The bottom portion 92 is connected to the back surface of the substrate 50 opposite to the surface to which the outer shell lid body 91 is connected. That is, the bottom portion 92 is disposed so as to face the base portion 42 of the cell-side shield 40 with the substrate 50 interposed therebetween and further to a position facing a light emitting portion 20 described later. As shown in FIG. 2, the bottom 92 has a rectangular shape. The bottom 92 has a function as a reinforcing plate for the substrate 50 in addition to a function as a magnetic shielding plate. Further, since the outer shell shield 90 is configured such that the bottom portion 92 is connected to the base portion 42 of the cell side shield 40 with the substrate 50 interposed therebetween, the following advantages are obtained. In this configuration, the optical axes of the gas cell 11 and the light source 22 arranged on the substrate 50 with the cell-side shield 40 interposed therebetween are aligned, and after the optical axes are aligned, the bottom 92 is connected with the substrate 50 interposed therebetween. can do. As described above, even in the so-called horizontal arrangement in which the gas cell 11 and the light source 22 are arranged side by side on the one surface of the substrate 50, the cell-side shield 40 and the outer shell shield 90 are double. It becomes possible to easily align the optical axes of the gas cell 11 and the light source 22 while having a magnetic shield.

  As a constituent material of the outer shell lid body 91 and the bottom portion 92, it is only necessary to have a magnetic shielding effect. For example, iron (Fe), various Fe alloys (silicon iron, permalloy, supermalloy, amorphous, sendust), copper Soft magnetic materials such as (Cu) and copper alloys are preferred. By using such a material for the outer shell lid body 91 and the bottom portion 92, it is possible to shield the external magnetism (change in the magnetic field) by the outer shell shield body 90. In addition, since the outer shield 90 is a double magnetic shield provided with the cell-side shield 40 sandwiching the air layer and the low-permeability layer of the substrate 50, the external magnetic (magnetic field) The influence on the metal atoms in the gas cell 11 due to the change of the

  As described above, the substrate 50 includes the cell-side shield 40 containing the gas cell unit 10 (gas cell 11) and the outer shell cover 91 of the outer shell shield 90 covering the cell-side shield 40 on one surface of the substrate 50. And a light emitting unit 20 having a light source 22 that emits excitation light. In other words, between the gas cell 11 and the light emitting part 20 having the light source 22 arranged side by side with the gas cell 11, the cell side shield 40 and the outer shell lid 91 of the outer shell shield 90 are provided. Two magnetic shields are provided. That is, the gas cell 11, the cell-side shield 40, the outer shell lid 91 of the outer shell shield 90, and the light emitting unit 20 are arranged along the optical axis direction R of the excitation light. Further, a bottom 92 constituting the outer shell shield 90 is connected to the back surface of one surface of the substrate 50.

  Thus, by providing the double magnetic shield of the cell side shield 40 and the outer shell shield 90 between the gas cell 11 and the light source 22 arranged side by side on the one surface of the substrate 50, It is possible to suppress the influence of the magnetism on the metal atoms in the gas cell 11 and stabilize the oscillation characteristics. In addition, although it does not specifically limit as a constituent material of the board | substrate 50, For example, a resin material, a ceramic material, etc. can be used. Although not shown, the substrate 50 is provided with a plurality of wirings and a plurality of terminals for energizing the gas cell unit 10 (gas cell 11) or the light emitting unit 20 from the outside.

  FIG. 4 is a schematic configuration diagram showing the operation of the atomic oscillator 100 shown in FIGS. 5 is a diagram for explaining the energy state of the alkali metal in the gas cell 11 of the atomic oscillator 100 shown in FIGS. 1 and 2, and FIG. 6 is a light emitting unit 20 of the atomic oscillator 100 shown in FIGS. 5 is a graph showing the relationship between the frequency difference between two lights from the light emitting unit 20 (light source 22) and the detection intensity at the light detecting unit for the (light source 22) and the light detecting unit 30.

  First, the principle of the atomic oscillator 100 will be briefly described. In the atomic oscillator 100, gaseous alkali metals (metal atoms) such as rubidium, cesium, and sodium are sealed in the gas cell 11. As shown in FIG. 5, the alkali metal has a three-level energy level, and has three states of two ground states (ground states 1 and 2) having different energy levels and an excited state. Can take. Here, the ground state 1 is a lower energy state than the ground state 2.

  When two types of resonant light 1 and resonant light 2 having different frequencies are irradiated onto such a gaseous alkali metal, the difference (ω1-ω2) between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 Accordingly, the light absorptance (light transmittance) of the resonance light 1 and the resonance light 2 in the alkali metal changes. When the difference (ω1−ω2) between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 matches the frequency corresponding to the energy difference between the ground state 1 and the ground state 2, the ground state 1 and The excitation from the ground state 2 to the excited state stops. At this time, both the resonance light 1 and the resonance light 2 are transmitted without being absorbed by the alkali metal. Such a phenomenon is referred to as a CPT (Coherent Population Trapping) phenomenon, or an electromagnetically induced transparency (EIT: Electromagnetically Induced Transparency).

  The light source 22 emits two types of light (resonant light 1 and resonant light 2) having different frequencies as described above toward the gas cell 11. For example, when the light source 22 fixes the frequency ω1 of the resonant light 1 and changes the frequency ω2 of the resonant light 2, the difference (ω1-ω2) between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 is obtained. When the frequency ω 0 corresponding to the energy difference between the ground state 1 and the ground state 2 coincides with the frequency ω 0, the detection intensity of the light detection unit 30 increases sharply as shown in FIG. Such a steep signal is detected as an EIT signal. This EIT signal has an eigenvalue determined by the type of alkali metal. Therefore, an oscillator can be configured by using such an EIT signal.

  As shown in FIG. 4, the atomic oscillator 100 according to the present embodiment emits excitation light LL as incident light to the gas cell 11 from the light source 22 provided in the light emitting unit 20 toward the gas cell 11. As described above, two types of light having different frequencies (resonant light 1 and resonant light 2) are emitted as the excitation light LL. The frequency ω1 of the resonant light 1 can excite the alkali metal in the gas cell 11 from the ground state 1 to the excited state. Further, the frequency ω2 of the resonant light 2 can excite the alkali metal in the gas cell 11 from the ground state 2 to the excited state.

  The light source 22 is not particularly limited as long as it can emit the excitation light as described above. For example, a semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) can be used.

  The excitation light LL emitted from the light emitting unit 20 passes through the optical components 14 and 15 provided in the through holes 12a formed in the gas cell holding member 12 in the optical axis direction R of the excitation light LL. The optical component 14 is a λ / 4 wavelength plate as described above, and can convert the linearly polarized excitation light LL emitted from the light source 22 into circularly polarized light (right polarized light or left polarized light). Next, the optical component 15 is a neutral density filter (ND filter), which can adjust (decrease) the intensity of the excitation light LL incident on the gas cell 11, and even if the output of the light source 22 is large, The incident excitation light LL can be set to a desired light amount.

  When the excitation light LL is converted into circularly polarized light by the optical component 14, the circularly polarized excitation light LL is irradiated to the alkali metal atoms in a state where the alkali metal atoms in the gas cell 11 are Zeeman split by the magnetic field of the coil 13. And the interaction between the excitation light LL and the alkali metal atom, the number of alkali metal atoms having a desired energy level among the plurality of levels in which the alkali metal atom is Zeeman-splitted is determined as the alkali metal atom having another energy level. Relative to the number of Therefore, the number of atoms that express the desired EIT phenomenon increases, and the intensity of the desired EIT signal increases, and as a result, the oscillation characteristics of the atomic oscillator 100 can be improved.

  In addition to the wave plate and the neutral density filter, other optical components such as a lens and a polarizing plate may be disposed between the light source 22 and the gas cell 11. Further, depending on the intensity of the excitation light from the light source 22, the optical component 15 can be omitted.

  The intensity of the excitation light LL (resonance light 1, resonance light 2) transmitted through the gas cell 11 is detected by the light detection unit 30. The detection result of the excitation light LL by the light detection unit 30 is input to the excitation light control unit 111 provided in the control unit 110 (not shown in FIGS. 1 and 2), and the resonance light 1 and the resonance light 2 emitted from the light source 22. Is controlled based on the detection result of the light detection unit 30. More specifically, the excitation light control unit 111 uses the resonance light emitted from the light source 22 so that (ω1−ω2) detected by the light detection unit 30 described above becomes the frequency ω0 specific to the alkali metal described above. 1. Control the frequency of the resonant light 2. The excitation light control unit 111 controls the center frequencies of the resonance light 1 and the resonance light 2 emitted from the light source 22. Thereby, the EIT signal as described above can be detected. Then, the control unit 110 outputs a crystal oscillator signal (not shown) in synchronization with the EIT signal.

  The control unit 110 includes a temperature control unit 112 and a magnetic field control unit 113. The temperature control unit 112 controls energization to the heater 70 based on the measurement detection result from the temperature sensor 72 that detects the temperature of the gas cell 11 (not shown in FIGS. 1 and 2). Thereby, the gas cell 11 can be maintained within a desired temperature range. The magnetic field control unit 113 controls energization of the coil 13 so that the magnetic field generated by the coil 13 is constant.

  Such a control unit 110 is provided, for example, in an electronic circuit device (for example, a semiconductor device) mounted on a mounting substrate on which the atomic oscillator 100 is mounted. The control unit 110 may be provided inside the outer shell shield 90 or the cell side shield 40.

(Other forms)
FIG. 7 is a cross-sectional view taken along the line AA ′ in FIG. 1 showing an atomic oscillator 200 as another form of the atomic oscillator 100 according to the first embodiment. FIG. 8 is a partially enlarged view of a portion C in FIG. In addition, the same code | symbol is attached | subjected to the same component as the atomic oscillator 100 shown to FIG.1, 2,3, and description is abbreviate | omitted.

  The atomic oscillator 200 shown in FIG. 7 is different in the configuration of the heater container 60 provided in the atomic oscillator 100 shown in FIG.

  As shown in FIG. 8, the heater housing 260 differs from the heater housing 60 provided in the atomic oscillator 100 described with reference to FIG. 3 in the form of the heater housing lid 62. In the atomic oscillator 200 according to the present embodiment, the heater housing 260 is configured by combining the heater housing 61 and the heater housing lid 262.

  A screw 261 as a pressing portion is screwed into the heater storage lid 262. By rotating the screw 261, so-called screwing, the heater 70 can be biased toward the gas cell 11 via the flexible substrate 71 by the tip 261 a of the screw 261.

  Thus, by providing the screw 261 as the pressing portion of the heater housing lid 262, it becomes possible to properly adjust the biasing pressure of the heater 70, and the biasing pressure to the heater 70 due to the variation of each part is so-called. Increase / decrease can be optimized.

(Second Embodiment)
As a second embodiment, a positioning system using a GPS satellite will be described as an example of an electronic device including the atomic oscillator 100 according to the first embodiment. FIG. 9 is a diagram showing a schematic configuration when the atomic oscillator according to the present invention is used in a positioning system using a GPS satellite.

  A positioning system 1000 shown in FIG. 9 includes a GPS satellite 1100, a base station device 1200, and a GPS receiver 1300. The GPS satellite 1100 transmits positioning information (GPS signal). The base station apparatus 1200 receives the positioning information from the GPS satellite 1100 with high accuracy via the antenna 1201 installed at the electronic reference point (GPS continuous observation station), for example, and the reception apparatus 1202 receives the positioning information. A transmission device 1204 that transmits positioning information via an antenna 1203.

  Here, the receiving device 1202 is an electronic device including the atomic oscillator 100 according to the first embodiment of the present invention described above as the reference frequency oscillation source. Such a receiving apparatus 1202 has excellent reliability. In addition, the positioning information received by the receiving device 1202 is transmitted by the transmitting device 1204 in real time. The GPS receiver 1300 includes a satellite receiver 1302 that receives positioning information from the GPS satellite 1100 via the antenna 1301 and a base station receiver 1304 that receives positioning information from the base station apparatus 1200 via the antenna 1303. With.

(Third embodiment)
As a third embodiment, a clock transmission system will be described as an example of an electronic apparatus including the atomic oscillator 100 according to the first embodiment. FIG. 10 is a diagram showing a schematic configuration when the atomic oscillator according to the present invention is used in a clock transmission system.

  A clock transmission system 2000 shown in FIG. 10 is a system that matches clocks of devices in a time division multiplexing network, and has N (Normal) and E (Emergency) redundant configurations.

  This clock transmission system 2000 includes a clock supply device (CSM: Clock Supply Module) 2001 and an SDH (Synchronous Digital Hierarchy) device 2002 of station A (upper (N system)), and a clock of station B (upper (E system)). A supply device 2003 and an SDH device 2004, and a clock supply device 2005 and SDH devices 2006 and 2007 of station C (lower level) are provided. The clock supply apparatus 2001 includes the atomic oscillator 100 and generates an N-system clock signal. The atomic oscillator 100 in the clock supply device 2001 generates a clock signal in synchronization with a clock signal with higher accuracy from master clocks 2008 and 2009 including an atomic oscillator using cesium.

  The SDH apparatus 2002 transmits / receives a main signal based on the clock signal from the clock supply apparatus 2001, superimposes an N-system clock signal on the main signal, and transmits it to the lower clock supply apparatus 2005. The clock supply device 2003 includes the atomic oscillator 100 and generates an E-system clock signal. The atomic oscillator 100 in the clock supply device 2003 generates a clock signal in synchronization with a clock signal with higher accuracy from master clocks 2008 and 2009 including an atomic oscillator using cesium.

  The SDH device 2004 transmits / receives the main signal based on the clock signal from the clock supply device 2003, superimposes the E-system clock signal on the main signal, and transmits it to the lower clock supply device 2005. The clock supply device 2005 receives the clock signal from the clock supply devices 2001 and 2003, and generates a clock signal in synchronization with the received clock signal.

  Here, the clock supply device 2005 normally generates a clock signal in synchronization with the N-system clock signal from the clock supply device 2001. When an abnormality occurs in the N system, the clock supply device 2005 generates a clock signal in synchronization with the E system clock signal from the clock supply device 2003. By switching from the N system to the E system in this way, stable clock supply can be ensured and the reliability of the clock path network can be improved. The SDH device 2006 transmits and receives the main signal based on the clock signal from the clock supply device 2005. Similarly, the SDH apparatus 2007 performs transmission / reception of the main signal based on the clock signal from the clock supply apparatus 2005. As a result, the C station apparatus can be synchronized with the A station or B station apparatus.

(Fourth embodiment)
As a fourth embodiment, an automobile will be described as an example of a moving object including the atomic oscillator 100 according to the first embodiment. FIG. 11 is a perspective view showing a schematic configuration when the atomic oscillator according to the present invention is used in an automobile as a moving body.

  An automobile 3000 as a moving body shown in FIG. 11 has a vehicle body 3001 and four wheels 3002, and is configured to rotate the wheels 3002 by a power source (not shown) provided in the vehicle body 3001. Such an automobile 3000 has a built-in atomic oscillator 100. Based on the oscillation signal from the atomic oscillator 100, for example, a control unit (not shown) controls driving of the power source.

  Note that the electronic device or the moving body in which the atomic oscillator of the present invention is incorporated is not limited to the above-described one, and for example, a mobile phone, a digital still camera, an ink jet type ejection device (for example, an ink jet printer), a personal computer (a mobile personal computer) , Laptop personal computer), TV, video camera, video tape recorder, car navigation device, pager, electronic organizer (including communication function), electronic dictionary, calculator, electronic game device, word processor, workstation, video phone, TV monitor for crime prevention, electronic binoculars, POS terminal, medical equipment (for example, electronic thermometer, blood pressure monitor, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments ( For example, Two, aircraft, gauges of a ship), can be applied to a flight simulator or the like.

  The atomic oscillator of the present invention has been described based on the illustrated embodiments. However, the present invention is not limited to these, and for example, the configuration of each part of the above-described embodiments exhibits the same function. It is possible to replace with any configuration, and any configuration can be added. Moreover, you may make it this invention combine arbitrary structures of each embodiment mentioned above.

  DESCRIPTION OF SYMBOLS 10 ... Gas cell unit, 20 ... Light emission part, 30 ... Light detection part, 40 ... Gas cell side magnetic shielding body, 50 ... Board | substrate, 60 ... Heater container, 70 ... Heater, 80 ... Intermediate member, 90 ... Outer shell magnetic shielding Body, 100 ... atomic oscillator.

Claims (6)

At least a gas cell in which metal atoms are enclosed, a coil disposed around the gas cell, a first magnetic shield that houses the gas cell and the coil, and a heating element that heats the gas cell. An atomic oscillator,
A second magnetic shield containing the heating element;
An atomic oscillator characterized by that. An intermediate member sandwiched between the first magnetic shield and the second magnetic shield;
The intermediate member has a magnetic permeability lower than that of the first magnetic shield and the second magnetic shield,
The atomic oscillator according to claim 1. The intermediate member has a thermal conductivity higher than that of the first magnetic shield,
The atomic oscillator according to claim 1 or 2, wherein The second magnetic shield includes a pressing portion that presses the heating element toward the first magnetic shield.
The atomic oscillator according to any one of claims 1 to 3, wherein A buffer member sandwiched between the pressing portion and the heating element;
The atomic oscillator according to claim 4. The buffer member is a substrate on which a power supply wiring to the heating element is formed.
The atomic oscillator according to claim 5.

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