JP2017135529A - Atomic oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atomic oscillator capable of stabilizing a frequency of a high frequency signal input to a light source of the atomic oscillator in a short time.SOLUTION: An atomic oscillator includes: a quantum interference device including at least a gas cell encapsulating a metal atom, a coil arranged around the gas cell, and a laser light source which emits excitation light to the gas cell; and a circuit board including an excitation light control unit which generates a high frequency signal for modulation of the laser light source. In the circuit board, a high-frequency transmission wiring is disposed between an end part on the circuit board side of a high-frequency signal transmission path for connecting the excitation light control unit and the laser light source, and the excitation light control unit. A protective layer is formed on a board surface on which the high-frequency transmission wiring of the circuit board is arranged. The protective layer is formed with an opening through which a part of an upper surface of the high-frequency transmission wiring is exposed.SELECTED DRAWING: Figure 1

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 to incorporate an atomic oscillator into various electronic devices. For incorporation into electronic equipment, it is expected that the atomic oscillator will be further reduced in size and height and provided with stable oscillation performance. Further, in electronic devices, it is also demanded to improve workability by reducing the time from when the power is turned on until stable performance is obtained, so-called waiting time.

JP 2009-231688 A

  However, an electronic device including an atomic oscillator using CPT has a problem that a high-frequency signal input to excitation light of the atomic oscillator at startup is not stable in a short time and requires a standby time. Therefore, an object is to obtain an atomic oscillator that can stabilize the frequency of a high-frequency signal input to the light source of the atomic oscillator in a short time.

  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 a quantum cell including at least a gas cell in which metal atoms are sealed, a coil disposed around the gas cell, and a laser light source that emits excitation light to the gas cell. An atomic oscillator including an interference device and a circuit board including a pumping light control unit that generates a modulation high-frequency signal of the laser light source, the circuit board including the pumping light control unit and the laser light source, A substrate surface on which the high frequency transmission wiring is disposed between an end of the circuit board side of the high frequency signal transmission path for connecting the circuit board and the excitation light control unit, and the high frequency transmission wiring of the circuit board is disposed A protective layer is formed on the protective layer, and the protective layer has an opening that exposes a part of the upper surface of the high-frequency transmission wiring.

  Volatile components such as moisture contained in the protective layer formed on the circuit board included in the atomic oscillator of this application example may be used when the atomic oscillator operates, such as a heater that heats a gas cell, a heater that heats a laser light source, or an IC. It gradually evaporates and evaporates as the temperature rises due to heat generated from a heat source such as electronic components. The change in the content of the volatile component due to the evaporation of the volatile component in the protective layer causes a change in the dielectric constant of the protective layer.

  Therefore, the atomic oscillator of this application example is protected by not forming a protective layer in the high-frequency transmission wiring region where the modulation high-frequency signal is transmitted from the excitation light control unit that generates the modulation high-frequency signal that operates the laser light source. The influence of the change in the dielectric constant of the layer is eliminated, and a stable output frequency can be obtained in a short time.

  Application Example 2 In the application example described above, the protective layer is continuous with the opening and continuous with the opening in the plan view of the high-frequency transmission wiring, and the substrate surface extends along the high-frequency transmission wiring. An exposed spacing portion is formed.

  According to the application example described above, the protective layer is formed so as to be separated from the high-frequency transmission wiring, and can be made less susceptible to changes in the dielectric constant of the protective layer. Therefore, the influence of the change in the dielectric constant of the protective layer can be eliminated, and a stable output frequency can be obtained in a short time.

  In addition, the planar view in this application example means a state in which an arrow is seen in a direction orthogonal to the circuit board surface on which the high-frequency transmission wiring is disposed.

  Application Example 3 In the application example described above, an electrical insulating layer is provided on the upper surface of the high-frequency transmission wiring, and the electrical insulating layer has a moisture absorption rate lower than that of the protective layer.

  According to the application example described above, it is possible to protect the surface of the high-frequency transmission wiring and prevent circuit deterioration, electrical short-circuiting, and the like.

  Application Example 4 In the application example described above, the high-frequency transmission wiring is formed by stacking a plurality of conductive films, and the uppermost layer of the plurality of conductive films is gold.

  According to the application example described above, corrosion of the lower layer, for example, copper wiring is prevented by laminating gold having excellent corrosion resistance on the uppermost layer. Furthermore, a protective layer that does not change the dielectric constant due to water absorption can be formed. Moreover, the high frequency transmission loss in a high frequency transmission wiring can be suppressed.

FIG. 2 is a plan external view showing the atomic oscillator according to the first embodiment. Sectional drawing of the AA 'part shown in FIG. Sectional drawing of the BB 'part shown in FIG. 1 is a schematic configuration diagram of an atomic oscillator according to a first embodiment. 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 of CC 'part shown in FIG. Sectional drawing of the DD 'part shown in FIG. The graph which shows typically the time-dependent change of the output frequency of the atomic oscillator shown in 1st Embodiment. Sectional drawing which shows the other form of the resist film of the atomic oscillator which concerns on 1st Embodiment. Sectional drawing which shows the other form of the resist film of the atomic oscillator which concerns on 1st Embodiment. Sectional drawing which shows the other form of the resist film of the atomic oscillator which concerns on 1st Embodiment. 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)
FIG. 1 is a plan external view showing an atomic oscillator using the quantum interference effect according to the first embodiment. An atomic oscillator 1000 shown in FIG. 1 includes a cell unit 100 as a quantum interference device including a gas cell in which metal atoms described later are accommodated on a mounting surface 300a (hereinafter referred to as a base surface 300a) of a base 300, and a cell unit. A circuit unit 200 as a circuit board constituting a control unit that controls 100 is disposed.

  2 and 3 schematically show the cell unit 100 included in the atomic oscillator 1000 using the quantum interference effect according to the first embodiment. FIG. 2 is a cross-sectional view taken along line AA ′ shown in FIG. FIG. 3 is a cross-sectional view taken along the line BB ′ shown in FIG.

  The cell unit 100 shown in FIGS. 1 and 2 accommodates the gas cell unit 10, the light emitting unit 20, and the gas cell unit 10, and the atomic oscillator 1000 according to the present embodiment serves as a first container having magnetic shielding properties. A first magnetic shield 40. 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.

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

  The light emitting portion 20 includes a base portion 21a, a main body frame portion 21b that accommodates and fixes the base portion 21a therein, and high-quality glass (for example, “ABC glass: Japan” used for a cover glass of an image sensor that transmits excitation light. A light source housing 21 formed of a metal lid portion 21c having a light transmission portion 21d formed by an electric glass, etc., a light source 22 housed in the light source housing 21, and heating the light source 22 And a Peltier element 23 as a heating element. The light source 22 has a function of emitting excitation light that excites alkali metal atoms in the gas cell 11, and for example, a semiconductor laser is used. The light source 22 is disposed inside the light source housing 21 so as to face the gas cell 11 along the emission direction of the excitation light (the optical axis direction R indicated by the arrow in the drawing). The excitation light is emitted through the gas cell 11 after passing through.

  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 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 1000 can be improved. 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 first magnetic shield 40. The first magnetic shield 40 includes a base 42 placed on the gas cell substrate 50 and a box-shaped first lid 41, and the gas cell unit 10 including the light detection unit 30 placed on the base 42. The first magnetic shield 40 is configured by covering the first cover body 41 so as to cover the base portion 42. The first magnetic shield 40 has a function of shielding magnetism from the outside with respect to the inside of the first magnetic shield 40, and shields magnetism from the outside to the gas cell unit 10 accommodated in the first magnetic shield 40. To do.

  A through hole 41 a is provided at a position facing the through hole 12 a formed in the gas cell holding member 12 of the first lid 41, 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 first magnetic shield 40 can be made an airtight space. Although not shown in FIGS. 1 and 2, the first magnetic shield 40 may contain components other than the components described above.

  As a constituent material of the first lid 41 and the base portion 42, it is more preferable 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 more preferable. By using such a material for the first lid 41 and the base portion 42, magnetism from the outside (change in magnetic field) can be shielded by the first magnetic shield 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 stabilize the oscillation characteristics of the atomic oscillator 1000.

  The first lid 41 is joined to the base 42, and the opening of the first lid 41 is sealed by the base 42. The joining method of the base 42 and the first lid 41 is not particularly limited, and 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 1st cover body 41, the joining member for joining these may intervene.

  Moreover, it is preferable that the base part 42 and the 1st cover body 41 are airtightly joined. That is, it is preferable that the inside of the first magnetic shield 40 is an airtight space. Thereby, the inside of the 1st magnetic shielding body 40 can be made into a pressure reduction state or an inert gas enclosure state, As a result, the characteristic of the atomic oscillator 1000 can be improved. In particular, the inside of the first magnetic shield 40 is preferably in a reduced pressure state. Thereby, heat transfer through the space in the first magnetic shield 40 can be suppressed. 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 heat transfer of the heater is suppressed in the space between the gas cell holding member 12 and the first magnetic shield 40. By doing so, the temperature difference between the two window portions 11b and 11c can be suppressed. In addition, heat transfer between the gas cell unit 10 and the outside of the first magnetic shield 40 can be more effectively suppressed.

  As shown in FIG. 3, the atomic oscillator 1000 according to this embodiment includes a heater 60 as a heating element that heats the gas cell unit 10. The heater 60 is a heating resistor (heat generating portion) that generates heat when energized. The heater 60 is disposed outside the first magnetic shield 40, and the heat generated by the heater 60 is transmitted to the gas cell 11 via the first magnetic shield 40. In the atomic oscillator 1000 according to the present embodiment, the heater 60 is illustrated as being bonded and fixed to the outside of the first lid 41 of the first magnetic shield 40 with a high thermal conductivity adhesive. However, the present invention is not limited to this, and the arrangement means of the heater 60 is not limited as long as the heat transmission loss generated by the heater 60 is reduced. For example, it may be a metal brazing or a physical fixing means using screws.

  The heat generated by the heater 60 is transmitted to the gas cell 11 so that the gas cell 11 can be maintained at a predetermined temperature and the alkali metal in the gas cell 11 can be maintained in a gaseous state. Note that a Peltier element may be used instead of the heater 60 or in combination with the heater 60. In this case, the portion on the heat generating side of the Peltier element constitutes a heat generating portion.

  As shown in FIGS. 2 and 3, the atomic oscillator 1000 includes a first magnetic shield 40 in which the gas cell unit 10 is housed, a light detection unit 30, a heater 60, a light emission unit 20, and the like. The second magnetic shielding body 70 is provided as a second housing body having magnetic shielding properties. The second magnetic shield 70 includes a bottom 72 and a second lid 71, and the opening of the second lid 71 is sealed by the gas cell substrate 50. Thereby, a space for accommodating the first magnetic shield 40 is formed. And the bottom part 72 is arrange | positioned in the surface opposite to the surface of the gas cell substrate 50 in which the 2nd cover body 71 is arrange | positioned, and the 2nd magnetic shielding body 70 which shields an inside from external magnetism is comprised.

  More preferably, the constituent material of the second lid 71 and the bottom 72 has a magnetic shielding effect, such as 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 second lid 71 and the bottom portion 72, magnetism from outside (change in the magnetic field) can be shielded by the second magnetic shield 70. In addition, since the first magnetic shield 40 is provided between the second magnetic shield 70 and the low permeability layer of the air layer or the gas cell substrate 50, a double magnetic shield is provided. The influence on the metal atoms in the gas cell 11 due to magnetism (change in the magnetic field) can be further suppressed.

  As described above, the gas cell substrate 50 has a second surface that covers the first magnetic shield 40 containing the gas cell unit 10 and the light emitting unit 20 having the light source 22 that emits excitation light on one surface of the gas cell substrate 50. A second lid 71 of the magnetic shield 70 is connected. Further, a bottom portion 72 constituting the second magnetic shield 70 is connected to the back surface of the one surface of the gas cell substrate 50. In addition, although it does not specifically limit as a constituent material of the gas cell board | substrate 50, For example, a resin material, a ceramic material, etc. can be used. Although not shown, the gas cell substrate 50 is provided with a plurality of wirings and a plurality of terminals for energizing the gas cell unit 10 or the light emitting unit 20 from the outside.

  FIG. 4 is a schematic configuration diagram showing the configuration of the atomic oscillator 1000 shown in FIG. 5 is a diagram for explaining the energy state of the alkali metal in the gas cell 11 of the cell unit 100 shown in FIGS. 1 and 2, and FIG. 6 is a light emitting part 20 of the cell unit 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 1000 will be briefly described. In the atomic oscillator 1000, gaseous metal (metal atoms) such as rubidium, cesium, and sodium is sealed in the gas cell 11 provided in the cell unit 100. 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 1000 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 1000 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 LL 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 211 provided in the control unit 210 (not shown in FIGS. 2 and 3) included in the circuit unit 200 shown in FIG. The frequencies of the resonance light 1 and the resonance light 2 emitted from the light are controlled based on the detection result of the light detection unit 30. More specifically, the excitation light control unit 211 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 211 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 210 outputs a crystal oscillator signal (not shown) in synchronization with the EIT signal.

  The control unit 210 includes a temperature control unit 212 and a magnetic field control unit 213. The temperature control unit 212 controls the energization to the heater 60 based on the measurement detection result from the temperature sensor 61 that detects the temperature of the gas cell 11 not shown in FIGS. Keep in. The magnetic field control unit 213 controls energization of the coil 13 so that the magnetic field generated by the coil 13 is constant.

  A high frequency signal that causes the light source 22 of the light emitting unit 20 to emit the excitation light LL is transmitted through the high frequency signal transmission path 214 from the excitation light control unit 211 included in the control unit 210 illustrated in FIG. The high-frequency signal transmission path 214 includes a coaxial cable 80 in a part of the path, and is disposed between one end of the coaxial cable 80 formed on the substrate of the circuit unit 200 described later and the excitation light control unit 211. The high frequency transmission wiring 220 and the light source wiring 80a and 80b between the light source 22 of the light emission part 20, and the other edge part of the coaxial cable 80 are included.

  The circuit unit 200 constituting the control unit 210 will be described. In this example, the excitation light control unit 211, the temperature control unit 212, and the magnetic field control unit 213 included in the control unit 210 are configured by, for example, a semiconductor device for convenience of explanation, and are arranged on the substrate to configure the control unit 210. It will be described as being done.

  As shown in FIG. 1, the circuit unit 200 is provided with an excitation light control unit 211, a temperature control unit 212, and a magnetic field control unit 213 of the semiconductor device. Further, a coaxial cable connector portion 230 (hereinafter referred to as a connector portion 230) to which a coaxial cable 80 for transmitting a high frequency signal is connected to the light source 22 provided in the cell unit 100 is disposed. A high-frequency transmission wiring 220 that transmits a high-frequency signal is formed between the excitation light control unit 211 and the connector unit 230.

  7 is a cross-sectional view taken along the line CC ′ shown in FIG. 1, and FIG. 8 is a cross-sectional view taken along the line DD ′ shown in FIG. As shown in FIG. 7, the circuit unit 200 includes a control unit 211, 212, and 213 that configure a substrate 240, a resist film 250 as a protective layer, and a control unit 210 from a base surface 300 a of the base 300 to be placed. Are stacked.

  The resist film 250 is formed so as to expose a connection pad 260a that is electrically connected to a connection electrode (not shown) included in each of the control units 211, 212, and 213 formed on the surface 240a of the substrate 240. A pad opening 250a is formed. In the pad opening 250a, the connection electrodes of the control units 211, 212, and 213 and the connection pads 260a are electrically connected by the solder 270, and the control units 212, 213, and 214 are fixed to the substrate 240, Is done.

  As shown in FIG. 8, a connection wiring 260 b for connecting a connection pad 260 a or an external connection electrode (not shown) is formed on the surface 240 a of the substrate 240. The connection wiring 260 b is covered with the resist film 250 to prevent wiring protection or electrical short circuit.

  However, as shown in FIG. 1 and FIG. 8, in the arrangement region of the high-frequency transmission wiring 220 (hereinafter referred to as transmission line 220) that transmits a high-frequency signal from the excitation light control unit 211 to the connector unit 230 to which the coaxial cable 80 is connected. Is provided with a high-frequency transmission wiring opening 250b (hereinafter referred to as a transmission line opening 250b) as an opening of the resist film 250.

  As described above, the high-frequency signal generated by the excitation light control unit 211 is transmitted to the transmission line 220 and input to the light source 22 provided in the cell unit 100 via the coaxial cable 80 connected to the connector unit 230. Here, when the transmission line 220 is formed so as to be covered with the resist film 250 in the same manner as the other connection wiring 260 b, the control units 211, 212, and 213 are prepared by starting the atomic oscillator 1000, that is, by turning on the power. The atomic oscillator 1000 starts to rise in temperature due to heat generated by the electronic element, the connection wiring 260b, and further the heater 60 that heats the gas cell unit 10. The resist film 250 contains a small amount of volatile components such as moisture. As the temperature of the atomic oscillator 1000 rises, the contained volatile components are evaporated to the outside of the resist film 250, and the resist film 250. The content of volatile components in the gradual decrease.

  As a result, the dielectric constant of the resist film 250 changes, and impedance matching of the high-frequency signal transmitted through the transmission line 220 and input to the light source 22 changes with time. For this reason, the input level of the high-frequency signal changes, leading to a change in the amount of excitation light emitted from the light source 22. That is, the change in the amount of excitation light causes a change in the resonance frequency, which leads to a change with time in the output frequency.

  FIG. 9 is a graph schematically showing the change over time of the output frequency described above, and a curve E shows a shift in output frequency with respect to the target frequency (f0) in the case where the transmission line 220 according to the prior art is covered with the resist film 250. The curve F indicates the elapsed time of the output frequency deviation with respect to the target frequency (f0) when the transmission line 220 according to the present embodiment is exposed by the transmission line opening 250b provided in the resist film 250. Showing change.

  As shown in FIG. 9, in the curve E showing the conventional atomic oscillator, a time passage of day (24 hours) is required from starting (power-on) to the target output frequency f0. Such an atomic oscillator 1000 can reach the target main frequency f0 in several hours.

  As described above, in the atomic oscillator 1000 according to the present embodiment, the transmission line opening of the resist film 250 is formed in the region of the transmission line 220 that transmits the high-frequency signal that controls the excitation light output from the excitation light control unit 211. By forming the portion 250b, the target output frequency f0 of the atomic oscillator 1000 can be reached in a short time. Therefore, it is possible to shorten the rise time of a device including the atomic oscillator 1000 according to this embodiment, and workability can be improved.

  FIG. 10 is a cross-sectional view showing another form of the resist film 250 in the above-described transmission line 220 region. As shown in FIG. 10, in the region where the transmission line 220 is provided in the resist film 251, the transmission line opening 251b and the separation parts 251c and 251d are formed. That is, the transmission line opening 251b has the same opening width W as the width of the transmission line 220. The transmission line opening 251b is spaced from one side end of the transmission line 220 continuously to the transmission line opening 251b. The opening 251f of the resist film 251 is formed by separating the portion 251e from the other side end of the transmission line 220.

  By exposing the transmission line 220 from the resist film 251 in this way, it is possible to further reduce the influence of the change over time due to the evaporation of the volatile components of the resist film 251 on the high-frequency signal transmitted through the transmission line 220. In this example, either or both of d1 and d2 may be 0. That is, it is only necessary to have at least the transmission line opening 251 b having the same opening width W as the transmission line 220.

  11 and 12 are cross-sectional views showing other forms of the transmission line 220, in which the resist film 251 shown in FIG. 10, that is, the transmission line opening 251b and the separation parts 251c and 251d are formed. Show.

As shown in FIG. 11, the transmission line 221 formed on the substrate 241 is formed by a conductive wiring 221a and an insulating layer 221b as an electric insulating layer covering the conductive wiring 221a. The insulating layer 221b is formed from a metal oxide such as silicon oxide (SiO ₂ ). With this configuration, it is possible to protect the conductive wiring 221a of the transmission line 221 exposed from the resist film 251 and to prevent an electrical short circuit. Note that the insulating layer 221b may be formed on the surface of the connection wiring 260b.

  Since the insulating layer 221b formed of a metal oxide or the like has a very low water absorption rate, the dielectric constant does not change and the output frequency does not easily change with time. Therefore, a stable output frequency can be obtained in a short time.

  The transmission line 222 formed on the substrate 242 shown in FIG. 12 is a surface 222c opposite to the substrate surface 242a side of the substrate transmission line 222a formed on the substrate surface 242a, such as copper or aluminum (hereinafter referred to as the substrate). Gold (Au) is laminated as a transmission line upper layer 222b on the transmission line upper surface 222c).

  By laminating the upper layer 222b of the gold transmission line on the upper surface 222c of the substrate transmission line, corrosion of the lower layer, for example, copper wiring is prevented. Furthermore, a protective layer that does not change the dielectric constant due to water absorption can be formed. Moreover, the high frequency transmission loss in a high frequency transmission wiring can be suppressed. Note that an upper layer of gold may also be stacked on the connection wiring 260b. Further, the substrate transmission line 222a may have a form in which a plurality of wiring layers are laminated. When the transmission line upper layer 222b is gold, a nickel layer is disposed below the transmission line upper layer 222b. The adhesion of the transmission line 222 can be improved.

(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 1000 according to the first embodiment. FIG. 13 is a diagram showing a schematic configuration when the atomic oscillator 1000 according to the first embodiment is used in a positioning system using a GPS satellite.

  The positioning system 2000 shown in FIG. 13 includes a GPS satellite 2100, a base station device 2200, and a GPS receiver 2300. The GPS satellite 2100 transmits positioning information (GPS signal). The base station device 2200 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 device 2202 receives the positioning information. And a transmission device 2204 that transmits positioning information via the antenna 2203.

  Here, the receiving device 2202 is an electronic device including the atomic oscillator 1000 according to the first embodiment of the present invention described above as the reference frequency oscillation source. Such a receiving apparatus 2202 has excellent reliability. In addition, the positioning information received by the receiving device 2202 is transmitted by the transmitting device 2204 in real time. The GPS receiver 2300 includes a satellite receiver 2302 that receives positioning information from the GPS satellite 2100 via the antenna 2301, and a base station receiver 2304 that receives positioning information from the base station device 2200 via the antenna 2303. 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 1000 according to the first embodiment. FIG. 14 is a diagram showing a schematic configuration when the atomic oscillator 1000 according to the first embodiment is used in the clock transmission system.

  A clock transmission system 3000 shown in FIG. 14 is a system that matches clocks of respective devices in a time division multiplexing network, and has a redundant configuration of N (normal) system and E (emergency) system.

  This clock transmission system 3000 includes a clock supply device (CSM: Clock Supply Module) 3001 and an SDH (Synchronous Digital Hierarchy) device 3002 of station A (upper (N system)), and a clock of station B (upper (E system)). A supply device 3003 and an SDH device 3004, and a clock supply device 3005 and SDH devices 3006 and 3007 of station C (lower level) are provided. The clock supply device 3001 has an atomic oscillator 1000 and generates an N-system clock signal. The atomic oscillator 1000 in the clock supply device 3001 generates a clock signal in synchronization with a clock signal with higher accuracy from master clocks 3008 and 3009 including an atomic oscillator using cesium.

  The SDH device 3002 transmits and receives the main signal based on the clock signal from the clock supply device 3001, and superimposes the N-system clock signal on the main signal and transmits it to the lower clock supply device 3005. The clock supply device 3003 has an atomic oscillator 1000 and generates an E-system clock signal. The atomic oscillator 1000 in the clock supply device 3003 generates a clock signal in synchronization with a higher-accuracy clock signal from master clocks 3008 and 3009 including an atomic oscillator using cesium.

  The SDH device 3004 transmits and receives the main signal based on the clock signal from the clock supply device 3003, superimposes the E-system clock signal on the main signal, and transmits it to the lower clock supply device 3005. The clock supply device 3005 receives the clock signal from the clock supply devices 3001 and 3003 and generates a clock signal in synchronization with the received clock signal.

  Here, the clock supply device 3005 normally generates a clock signal in synchronization with the N-system clock signal from the clock supply device 3001. When an abnormality occurs in the N system, the clock supply device 3005 generates a clock signal in synchronization with the E system clock signal from the clock supply device 3003. 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 3006 transmits and receives the main signal based on the clock signal from the clock supply device 3005. Similarly, the SDH device 3007 transmits and receives the main signal based on the clock signal from the clock supply device 3005. 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 1000 according to the first embodiment. FIG. 15 is a perspective view showing a schematic configuration when the atomic oscillator 1000 according to the first embodiment is used in an automobile as a moving body.

  An automobile 4000 as a moving body shown in FIG. 15 includes a vehicle body 4001 and four wheels 4002, and is configured to rotate the wheels 4002 by a power source (not shown) provided in the vehicle body 4001. Such an automobile 4000 has an atomic oscillator 1000 built therein. Based on the oscillation signal from the atomic oscillator 1000, 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 100 ... Cell unit, 200 ... Circuit board, 210 ... Control part, 300 ... Base, 1000 ... Atomic oscillator.

Claims (4)

A quantum interference device including at least a gas cell in which metal atoms are sealed, a coil disposed around the gas cell, and a laser light source that emits excitation light to the gas cell;
An atomic oscillator including a circuit board including a pumping light control unit that generates a high-frequency signal for modulation of the laser light source,
On the circuit board, a high frequency transmission wiring is arranged between an end of the circuit board side of a high frequency signal transmission path connecting the excitation light control unit and the laser light source and the excitation light control unit. Established,
A protective layer is formed on the substrate surface on which the high-frequency transmission wiring of the circuit board is disposed,
In the protective layer, an opening that exposes a part of the upper surface of the high-frequency transmission wiring is formed,
An atomic oscillator characterized by that. The protective layer is formed continuously with the opening in a plan view of the high-frequency transmission wiring, and is formed with a spacing portion that is continuous with the opening and exposes the substrate surface along the high-frequency transmission wiring.
The atomic oscillator according to claim 1. An electrical insulating layer is provided on the upper surface of the high-frequency transmission wiring, and the electrical insulating layer has a moisture absorption rate lower than that of the protective layer.
The atomic oscillator according to claim 1 or 2, wherein The high-frequency transmission wiring is formed by laminating a plurality of conductive films, and the uppermost layer of the plurality of conductive films is gold.
The atomic oscillator according to claim 1, wherein:

Images