JP2015185984A - Atomic cell, method for manufacturing atomic cell, quantum interference device, atomic oscillator, electronic equipment, and mobile body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atomic cell and a method for manufacturing the atomic cell that can be reduced in size and achieve power saving, and to provide a quantum interference device, an atomic oscillator, electronic equipment, and a mobile body including the atomic cell.SOLUTION: A gas cell 2 of the present invention includes: an alkali metal; a body part 21 and windows 22, 23 constituting an inner space S where the alkali metal is encapsulated; and block layers 221, 231 constituting at least a part of the inner wall of the inner space S and containing a metal. A portion having a higher density of the metal than that of the surface on an inner space S side of the block layers 221, 231 is disposed in the block layers 221, 231.

Description

The present invention relates to an atomic cell, an atomic cell manufacturing method, a quantum interference device, an atomic oscillator, an electronic device, and a moving object.

As an oscillator having long-term highly accurate oscillation characteristics, an atomic oscillator that oscillates based on energy transition of an alkali metal atom such as rubidium or cesium is known.

In general, the operating principle of an atomic oscillator is based on a method using a double resonance phenomenon by light and microwave and a quantum interference effect (CPT: Coherent Population Tr) by two types of light having different wavelengths.
It is roughly divided into methods using apping).

In any type of atomic oscillator, an alkali metal is usually enclosed in a gas cell (atomic cell), and the gas cell is heated to a predetermined temperature by a heater in order to keep the alkali metal in a certain gas state.

In general, the gas cell is made of glass, and the alkali metal sealed in the gas cell has the property of being absorbed by the glass. Therefore, the amount of alkali metal in the gas cell is expected to decrease over time due to the absorption. Enclosed more than necessary. Such excess alkali metal is present as a liquid by precipitating (condensation) in the low temperature part of the gas cell, but if it is present in the excitation light passage region, it blocks the excitation light, resulting in atoms. The oscillation characteristics of the oscillator are degraded.

Therefore, in the gas cell according to Patent Document 1, an infrared absorbing member is provided in the excitation light passage region, and the infrared absorption member is irradiated with infrared rays to increase the temperature of the excitation light passage region.

However, the gas cell according to Patent Document 1 requires a separate light source for irradiating infrared rays, and thus there is a problem that it is difficult to reduce the size and power consumption.

JP 2010-109411 A

An object of the present invention is to provide an atomic cell that can be reduced in size and save power and a method for manufacturing the same, and to provide a quantum interference device, an atomic oscillator, an electronic device, and a moving body including the atomic cell. There is.

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]
The atomic cell of the present invention comprises a metal,
An internal space in which the metal is enclosed, and a wall portion containing the metal inside;
Have
The wall is provided with a block layer having a metal concentration higher than that of the internal space.

According to such an atomic cell, since at least a part of the wall portion is composed of a block layer containing a metal, it blocks the movement (absorption or permeation) of the metal from the internal space to the inside of the wall portion. Can be blocked by layer. Therefore, it is possible to reduce the metal encapsulated in the internal space from being absorbed or penetrated into the wall portion. As a result, the amount of surplus metal enclosed in the internal space can be reduced, and accordingly, the amount of heat (heating amount) for preventing condensation (precipitation) of surplus metal as in the prior art can be reduced. In addition, since the heating means itself can be dispensed with, it is possible to reduce the size and power consumption.

[Application Example 2]
In the atomic cell of the present invention, the wall has a portion containing glass,
It is preferable that the block layer is disposed in the portion.

Glass has a large crystal structure gap, and metal is easily absorbed or penetrated. Therefore,
The effect is remarkably exhibited by providing a block layer in the part comprised by the glass of a wall part.

[Application Example 3]
In the atomic cell of the present invention, it is preferable that the peak position of the metal concentration in the block layer is closer to the inner wall surface than the center in the thickness direction of the wall portion.
Thereby, the block function of a block layer can be improved effectively.

[Application Example 4]
In the atomic cell of the present invention, the wall portion is
A pair of windows,
A body part disposed between the pair of window parts and constituting the internal space together with the pair of window parts;
Have
It is preferable that the block layer is disposed on at least one of the window portion and the body portion.

Thereby, even if the main material of at least one of a window part and a trunk | drum part has the property to absorb a metal, absorption or osmosis | permeation of a metal can be reduced.

[Application Example 5]
In the atomic cell of the present invention, it is preferable that the block layer surrounds the internal space.

Thereby, even if the main material of the whole wall part has a property which absorbs a metal, absorption or osmosis | permeation of a metal can be reduced.

[Application Example 6]
In the atomic cell of the present invention, it is preferable that the metal contained in the block layer is an element belonging to the same group as the metal enclosed in the internal space.
Thereby, the block function of a block layer can be improved effectively.

[Application Example 7]
The method for producing an atomic cell of the present invention includes a step of preparing a window part forming substrate having light transmittance and a body part forming substrate having a recess or a through hole,
Forming a metal film on at least one surface of the window portion forming substrate and the body portion forming substrate;
Diffusing metal from the metal film to the window portion forming substrate or the body portion forming substrate by heat treatment;
Removing at least a part of the metal film after the heat treatment;
Encapsulating metal in an internal space formed by the window portion forming substrate and the body portion forming substrate;
It is characterized by including.

According to such an atomic cell manufacturing method, it is possible to obtain an atomic cell in which at least a part of the inner wall surface of the wall portion is constituted by a block layer containing a metal. Therefore, it is possible to reduce the size and power consumption of the obtained atomic cell.

[Application Example 8]
In the method for manufacturing an atomic cell according to the present invention, the body part forming substrate preferably contains glass.

Glass has a large crystal structure gap, and metal is easily absorbed or penetrated. Therefore,
The effect is remarkably exhibited by providing a block layer in the part comprised by the glass of a wall part. Further, the body portion forming substrate made of glass can be relatively easily and hermetically bonded to the window portion forming substrate made of silicon or glass by heat bonding or the like.

[Application Example 9]
In the method for producing an atomic cell according to the present invention, the temperature of the heat treatment is preferably 60 ° C. or higher and 800 ° C. or lower.
Thereby, the block function of a block layer can be improved effectively.

[Application Example 10]
In the method for manufacturing an atomic cell according to the present invention, the step of removing the metal film is preferably performed by acid cleaning.

This makes it possible to easily and effectively remove excess metal remaining on the surface of the window forming substrate and the body forming substrate.

[Application Example 11]
The method for manufacturing an atomic cell according to the present invention includes a step of forming the internal space by thermally bonding the window portion forming substrate and the body portion forming substrate after the step of removing the metal film. It is preferable.

Thereby, it is possible to relatively easily form the metal film, diffuse the metal, and remove the metal film on the window forming substrate and the body forming substrate.

[Application Example 12]
In the method for manufacturing an atomic cell according to the present invention, it is preferable to include a step of pushing and diffusing the metal of the window portion forming substrate or the body portion forming substrate by heat treatment after the step of removing the metal film.

As a result, a portion having a higher metal concentration than the surface of the block layer on the inner space side can be provided inside the block layer.

[Application Example 13]
The quantum interference device of the present invention includes the atomic cell of the present invention.
Accordingly, it is possible to provide a quantum interference device including an atomic cell that is reduced in size and power consumption.

[Application Example 14]
The atomic oscillator of the present invention includes the atomic cell of the present invention.

Thereby, it is possible to provide an atomic oscillator including an atomic cell that is reduced in size and power consumption.

[Application Example 15]
The electronic device of the present invention includes the atomic cell of the present invention.

Thereby, an electronic device provided with the atomic cell in which size reduction and power saving were achieved can be provided.

[Application Example 16]
The moving body of the present invention includes the atomic cell of the present invention.

Thereby, a mobile object provided with the atomic cell in which size reduction and power saving were achieved can be provided.

1 is a schematic diagram showing an atomic oscillator (quantum interference device) according to a first embodiment of the present invention. It is a figure for demonstrating the energy state of an alkali metal. It is a graph which shows the relationship between the frequency difference of two light radiate | emitted from a light-projection part, and the intensity | strength of the light detected by a photon detection part. It is a perspective view of the atomic cell with which the atomic oscillator shown in FIG. 1 is provided. (A) is a cross-sectional view of the atomic cell shown in FIG. 4, and (b) is a vertical cross-sectional view of the atomic cell shown in FIG. It is a graph which shows the relationship between the depth from the surface (inner wall surface) by the side of the internal space of a block layer shown in FIG. 5, and a metal concentration. It is a figure which shows the manufacturing method (block layer formation process) of the atomic cell shown in FIG. It is a graph which shows the relationship between the depth from the surface of the board | substrate for window part formation in the formation process of the block layer shown in FIG. 7, and a metal concentration. It is a figure which shows the manufacturing method (joining process of the board | substrate for window part formation, and the body part formation substrate) of the atomic cell shown in FIG. (A) is a cross-sectional view of the atomic cell according to the second embodiment of the present invention, and (b) is a vertical cross-sectional view of the atomic cell shown in (a). It is a figure which shows the manufacturing method (joining process of the board | substrate for window part formation, and the board | substrate for trunk | drum part formation) shown in FIG. It is a figure which shows schematic structure at the time of using the atomic oscillator of this invention for the positioning system using a GPS satellite. It is a figure which shows an example of the moving body of this invention.

Hereinafter, an atomic cell, a manufacturing method of an atomic cell, a quantum interference device, an atomic oscillator, an electronic apparatus, and a moving body of the present invention will be described in detail based on embodiments shown in the accompanying drawings.

1. Atomic oscillator (quantum interference device)
First, the atomic oscillator of the present invention (the atomic oscillator including the quantum interference device of the present invention) will be described. In the following, an example in which the quantum interference device of the present invention is applied to an atomic oscillator will be described.
The quantum interference device of the present invention is not limited to this, in addition to an atomic oscillator, for example, a magnetic sensor,
It can also be applied to quantum memories.

<First Embodiment>
FIG. 1 is a schematic diagram showing an atomic oscillator (quantum interference device) according to a first embodiment of the present invention. 2 is a diagram for explaining the energy state of the alkali metal, and FIG. 3 is a relationship between the frequency difference between the two lights emitted from the light emitting part and the intensity of the light detected by the light detecting part. It is a graph which shows.

An atomic oscillator 1 shown in FIG. 1 is an atomic oscillator using a quantum interference effect. As shown in FIG. 1, the atomic oscillator 1 includes a gas cell 2 (atomic cell), a light emitting portion 3, an optical component 41,
42, 43, 44, a light detection unit 5, a heater 6, a temperature sensor 7, a magnetic field generation unit 8, and a control unit 10.
First, the principle of the atomic oscillator 1 will be briefly described.

As shown in FIG. 1, in the atomic oscillator 1, the light emitting unit 3 emits the excitation light LL toward the gas cell 2, and the light detection unit 5 detects the excitation light LL transmitted through the gas cell 2.

The gas cell 2 is filled with gaseous alkali metal (metal atom), and the alkali metal has energy levels of a three-level system and has different energy levels as shown in FIG.
Three ground states (ground states 1 and 2) and an excited state can be taken. Here, the ground state 1 is a lower energy state than the ground state 2.

The excitation light LL emitted from the light emitting unit 3 includes two types of resonance lights 1 and 2 having different frequencies. The two types of resonance lights 1 and 2 are irradiated onto the gaseous alkali metal as described above. When
Depending on the difference (ω1-ω2) between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2, the resonant light 1
The light absorptivity (light transmittance) of the alkali metal 2 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 states 1 and 2 Each excitation to the excited state stops. At this time, both the resonant lights 1 and 2 are transmitted without being absorbed by the alkali metal. Such a phenomenon is called a CPT phenomenon or an electromagnetically induced transparency (EIT) phenomenon.

For example, when the light emitting unit 3 fixes the frequency ω1 of the resonant light 1 and changes the frequency ω2 of the resonant light 2, the difference between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 (ω1-ω2). ) Matches the frequency ω 0 corresponding to the energy difference between the ground state 1 and the ground state 2, the light detection unit 5
As shown in FIG. 3, the detected intensity rises sharply. 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.

Hereinafter, each part of the atomic oscillator 1 will be described in detail sequentially.
[Gas cell]
The gas cell 2 is filled with gaseous alkali metals such as rubidium, cesium and sodium. In addition, in the gas cell 2, a rare gas such as argon or neon, if necessary,
An inert gas such as nitrogen may be enclosed with the alkali metal gas as a buffer gas.

As will be described in detail later, the gas cell 2 has a body portion having a through hole and a pair of windows that close the opening of the through hole of the body portion, thereby enclosing a gaseous alkali metal. An internal space is formed.

[Light emitting part]
The light emitting unit 3 (light source) has a function of emitting excitation light LL that excites alkali metal atoms in the gas cell 2.

More specifically, the light emitting unit 3 is a pumping light LL having a different frequency 2 as described above.
It emits seed light (resonant light 1 and resonant light 2). The resonant light 1 can excite (resonate) the alkali metal in the gas cell 2 from the ground state 1 to the excited state. On the other hand, the resonant light 2 excites the alkali metal in the gas cell 2 from the ground state 2 to the excited state (
Resonance).

The light emitting unit 3 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 light emitting unit 3 is temperature adjusted to a predetermined temperature by a temperature adjusting element (a heating resistor, a Peltier element, etc.) (not shown).

[Optical parts]
The plurality of optical components 41, 42, 43, and 44 are respectively provided on the optical path of the excitation light LL between the light emitting unit 3 and the gas cell 2 described above. Here, the optical component 41, the optical component 42, the optical component 43, and the optical component 44 are arranged in this order from the light emitting portion 3 side to the gas cell 2 side.

The optical component 41 is a lens. Thereby, the excitation light LL can be irradiated to the gas cell 2 without waste.

The optical component 41 has a function of making the excitation light LL a parallel light. Thereby, it is possible to easily and reliably prevent the excitation light LL from being reflected by the inner wall of the gas cell 2. For this reason, resonance of excitation light in the gas cell 2 is preferably generated, and as a result, the oscillation characteristics of the atomic oscillator 1 can be enhanced.

The optical component 42 is a polarizing plate. Thereby, the polarization of the excitation light LL from the light emitting part 3 can be adjusted in a predetermined direction.

The optical component 43 is a neutral density filter (ND filter). Thereby, the gas cell 2
It is possible to adjust (decrease) the intensity of the excitation light LL incident on. Therefore, the light emitting part 3
Even if the output of is high, the excitation light incident on the gas cell 2 can be set to a desired light amount. In the present embodiment, the excitation light LL having polarized light in a predetermined direction that has passed through the optical component 42 described above.
Is adjusted by the optical component 43.

The optical component 44 is a λ / 4 wavelength plate. Thereby, the excitation light LL from the light emitting unit 3 can be converted from linearly polarized light into circularly polarized light (right circularly polarized light or left circularly polarized light).

As will be described later, in the state where the alkali metal atoms in the gas cell 2 are Zeeman split by the magnetic field of the magnetic field generation unit 8, if the alkali metal atoms are irradiated with linearly polarized excitation light, the interaction between the excitation light and the alkali metal atoms is caused. In other words, the alkali metal atoms are present evenly dispersed in a plurality of Zeeman split levels. As a result, the number of alkali metal atoms at a desired energy level is relatively small with respect to the number of alkali metal atoms at other energy levels, so that the number of atoms that develop a desired EIT phenomenon is reduced and desired. As a result, the oscillation characteristics of the atomic oscillator 1 are deteriorated.

On the other hand, when the alkali metal atom is irradiated with circularly polarized excitation light in a state where the alkali metal atom in the gas cell 2 is Zeeman split by the magnetic field of the magnetic field generator 8 as described later,
Among the multiple levels in which the alkali metal atom is Zeeman split due to the interaction between the excitation light and the alkali metal atom, the number of alkali metal atoms at the desired energy level is changed to the number of alkali metal atoms at other energy levels. On the other hand, it can be relatively increased. Therefore, desired EIT
The number of atoms that develop the phenomenon increases, and the intensity of the desired EIT signal increases. As a result, the oscillation characteristics of the atomic oscillator 1 can be improved.

[Photodetection section]
The light detection unit 5 has a function of detecting the intensity of the excitation light LL (resonance light 1 and 2) transmitted through the gas cell 2.

The photodetector 5 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 can be used.

[heater]
The heater 6 (heating unit) has a function of heating the above-described gas cell 2 (more specifically, an alkali metal in the gas cell 2). Thereby, the alkali metal in the gas cell 2 can be maintained in a gaseous state with an appropriate concentration.

The heater 6 includes, for example, a heating resistor that generates heat when energized.
The heating resistor may be provided in contact with the gas cell 2 or may be provided in non-contact with the gas cell 2.

For example, when the heating resistor is provided in contact with the gas cell 2, the heating resistor is provided in each of the pair of windows of the gas cell 2. Thereby, it is possible to prevent alkali metal atoms from condensing on the window portion of the gas cell 2. As a result, the characteristics (oscillation characteristics) of the atomic oscillator 1 can be made excellent over a long period of time. Such a heating resistor is a material having transparency to excitation light, specifically, for example, ITO (Indium Tin Oxide),
IZO (Indium Zinc Oxide), In ₃ O ₃ , SnO ₂ , Sb-containing Sn
O _2, formed of a transparent electrode material of the oxide such as Al-containing ZnO. The heating resistor is
For example, it can be formed using a chemical vapor deposition method (CVD) such as plasma CVD or thermal CVD, a dry plating method such as vacuum deposition, a sol-gel method, or the like.

Further, when the heating resistor is provided in a non-contact manner with respect to the gas cell 2, heat may be transferred from the heating resistor to the gas cell 2 through a member such as a metal having excellent thermal conductivity, such as ceramic.

The heater 6 is not limited to the above-described form as long as the gas cell 2 can be heated, and various heaters can be used. Further, the gas cell 2 may be heated using a Peltier element instead of the heater 6 or in combination with the heater 6.

[Temperature sensor]
The temperature sensor 7 detects the temperature of the heater 6 or the gas cell 2. Based on the detection result of the temperature sensor 7, the amount of heat generated by the heater 6 is controlled. Thereby, the alkali metal atom in the gas cell 2 can be maintained at a desired temperature.

The installation position of the temperature sensor 7 is not particularly limited, and may be on the heater 6 or on the outer surface of the gas cell 2, for example.

The temperature sensor 7 is not particularly limited, and various known temperature sensors such as a thermistor and a thermocouple can be used.

[Magnetic field generator]
The magnetic field generation unit 8 has a function of generating a magnetic field that causes Zeeman splitting of a plurality of energy levels in which the alkali metal in the gas cell 2 is degenerated. Thereby, by Zeeman splitting, the gap between different energy levels in which the alkali metal is degenerated can be widened to improve the resolution. As a result, the accuracy of the oscillation frequency of the atomic oscillator 1 can be increased.

The magnetic field generator 8 is configured by, for example, a Helmholtz coil arranged so as to sandwich the gas cell 2 or a solenoid coil arranged so as to cover the gas cell 2. Thereby, a uniform magnetic field in one direction can be generated in the gas cell 2.

The magnetic field generated by the magnetic field generator 8 is a constant magnetic field (DC magnetic field), but an AC magnetic field may be superimposed.

[Control unit]
The control unit 10 has a function of controlling the light emitting unit 3, the heater 6, and the magnetic field generation unit 8.

The control unit 10 includes an excitation light control unit 12 that controls the frequencies of the resonance lights 1 and 2 of the light emitting unit 3, a temperature control unit 11 that controls the temperature of the alkali metal in the gas cell 2, and a magnetic field generation unit 8. And a magnetic field control unit 13 for controlling the magnetic field.

The excitation light control unit 12 controls the frequencies of the resonant lights 1 and 2 emitted from the light emitting unit 3 based on the detection result of the light detecting unit 5 described above. More specifically, the excitation light control unit 12 determines the resonance lights 1 and 2 emitted from the light emitting unit 3 so that the frequency difference (ω1−ω2) described above becomes the frequency ω0 specific to the alkali metal described above. Control the frequency.

Here, although not shown, the excitation light control unit 12 includes a voltage-controlled crystal oscillator (oscillation circuit), and the oscillation frequency of the voltage-controlled crystal oscillator is synchronized with the detection result of the light detection unit 5. While adjusting, the output signal of the voltage controlled crystal oscillator is output as the output signal of the atomic oscillator 1.

For example, although not shown, the pumping light control unit 12 includes a multiplier that multiplies the output signal from the voltage controlled crystal oscillator, and a signal (high frequency signal) multiplied by the multiplier is converted into a DC bias current. Is input to the light emitting unit 3 as a drive signal. Thus, by controlling the voltage controlled crystal oscillator so that the light detection unit 5 detects the EIT signal, a signal having a desired frequency is output from the voltage controlled crystal oscillator. For example, when the desired frequency of the output signal from the atomic oscillator 1 is f, the multiplication factor of this multiplier is ω0 / (2 ×
f). As a result, when the oscillation frequency of the voltage controlled crystal oscillator is f, a signal from the multiplier is used to modulate a light emitting element such as a semiconductor laser included in the light emitting unit 3, and a frequency difference (ω1-ω2). ) Can be emitted as ω0.

Further, the temperature control unit 11 controls energization to the heater 6 based on the detection result of the temperature sensor 7. Thereby, the gas cell 2 can be maintained within a desired temperature range. For example, the temperature of the gas cell 2 is adjusted to, for example, about 70 ° C. by the heater 6.

The magnetic field control unit 13 controls energization to the magnetic field generation unit 8 so that the magnetic field generated by the magnetic field generation unit 8 is constant.

Such a control unit 10 is provided, for example, on an IC chip mounted on a substrate.
The configuration of the atomic oscillator 1 has been briefly described above.

(Detailed description of gas cell)
4 is a perspective view of the atomic cell included in the atomic oscillator shown in FIG. 1, FIG. 5A is a cross-sectional view of the atomic cell shown in FIG. 4, and FIG. 5B is a cross-sectional view of the atomic cell shown in FIG. It is a longitudinal cross-sectional view. In addition, FIG.
These are the graphs which show the relationship between the depth from the surface (inner wall surface) by the side of the internal space of a block layer shown in FIG. 5, and a metal concentration.

In FIG. 4, for convenience of explanation, the three axes orthogonal to each other are the X axis, the Y axis, and the Z axis.
The axis is illustrated, and the leading end side of each illustrated arrow is “+ (plus)” and the base end side is “− (
Minus) ”. In the following, for convenience of explanation, the direction parallel to the X axis is referred to as “X axis direction”.
A direction parallel to the Y axis is referred to as a “Y axis direction”, and a direction parallel to the Z axis is referred to as a “Z axis direction”. +
The Z-axis direction side is also referred to as “upper”, and the −Z-axis direction side is also referred to as “lower”.

As shown in FIGS. 4 and 5, the gas cell 2 includes a body portion 21 and a pair of window portions 22 and 23 provided with the body portion 21 interposed therebetween.

The body portion 21 is formed with a columnar through hole 211 penetrating in the Z-axis direction. The constituent material of the body portion 21 is not particularly limited, and examples thereof include a glass material, a crystal, a metal material, a resin material, a silicon material, and the like. Among these, it is preferable to use any one of a glass material, a crystal, and a silicon material. It is more preferable to use a silicon material. Thereby, even if it is a case where the small gas cell 2 whose width and height are 10 mm or less is formed, the highly accurate body part 21 can be easily formed by using a fine processing technique such as etching. .

The window portion 22 is joined to the end surface (lower end surface) on the −Z axis direction side of the body portion 21, while the window portion 23 is connected to the end surface (upper end surface) on the + Z axis direction side of the body portion 21. It is joined. Thereby, both ends opening of the through-hole 211 is sealed, and the internal space S in which gaseous alkali metal is accommodated is formed. Here, it can be said that the body portion 21 and the pair of window portions 22 and 23 are “wall portions” constituting the internal space S in which the alkali metal is enclosed.

The joining method of the body part 21 and the window parts 22 and 23 is determined according to these constituent materials and is not particularly limited as long as it can be hermetically joined. For example, joining by an adhesive A method, a direct bonding method, an anodic bonding method, or the like can be used.

The internal space S mainly stores gaseous alkali metal, and the gaseous alkali metal stored in the internal space S is excited by the excitation light LL. That is, the internal space S constitutes a “light passage space” through which the excitation light LL passes. In the present embodiment, the cross section of the internal space S has a circular shape, while the cross section of the light passage space has a similar shape to the cross section of the internal space S and is more than the cross section of the internal space S. Is also set slightly smaller. The cross-sectional shape of the internal space S is not limited to a circle, and may be, for example, a polygon such as a quadrangle or a pentagon, an ellipse, or the like.

Each window part 22 and 23 joined to the trunk | drum 21 has the permeability | transmittance with respect to the excitation light from the light-projection part 3 mentioned above. One window portion 22 is an incident-side window portion through which the excitation light LL enters the internal space S of the gas cell 2, and the other window portion 23 emits the excitation light LL from the internal space S of the gas cell 2. It is an emission side window part.
Each of the window portions 22 and 23 has a plate shape.

Although it will not specifically limit as a constituent material of the window parts 22 and 23, if it has the transmittance | permeability with respect to excitation light as mentioned above, For example, a glass material, a crystal | crystallization, etc. are mentioned. Windows 22, 23
Is made of a glass material, the body portion 21 and the window portions 22 and 23 made of a silicon material can be easily and airtightly joined by an anodic bonding method. Depending on the thickness of the windows 22 and 23 and the intensity of the excitation light, the windows 22 and 23 can be made of silicon.

A block layer 221 constituting a part of the inner wall surface of the internal space S is provided at a portion of the window portion 22 facing the internal space S. Similarly, a block layer 231 constituting a part of the inner wall surface of the internal space S is provided at a portion of the window portion 23 facing the internal space S.

The block layers 221 and 231 are obtained by diffusing metal into the material (base material) constituting the window portions 22 and 23. The block layers 221 and 231 are each provided with a portion having a higher metal concentration than the surface of the block layers 221 and 231 on the inner space S side. More specifically, for example, each of the block layers 221 and 231 is diffused with a metal having a concentration distribution as shown in FIG. FIG. 6 is an example of a concentration distribution when cesium (Cs) is used as the metal contained in the block layers 221 and 231.

In such block layers 221 and 231, the gap in the crystal structure of the base material of the window portions 22 and 23 is filled with metal, so that the alkali metal moves from the internal space S to the inside of the window portions 22 and 23 ( A function of reducing or preventing (absorption or permeation) (hereinafter, also referred to as “block function” or “block property”). Therefore, it is possible to reduce the absorption or penetration of the alkali metal sealed in the internal space S into the window portions 22 and 23. As a result, the amount of excess alkali metal sealed in the internal space S can be reduced, and accordingly, a heating means for preventing condensation (precipitation) of excess alkali metal as in the prior art becomes unnecessary. Therefore, size reduction and power saving can be achieved.

Here, by setting the portion where the metal concentration is higher than the surface of the block layers 221 and 231 on the side of the internal space S to a position close to the inner wall surface of the internal space S, it is possible to ensure the block property as described above. . That is, the peak position of the metal concentration in the block layers 221 and 231 is on the inner wall surface side of the window portions 22 and 23 (on the inner space S side than the center of the window portions 22 and 23). The block function can be effectively enhanced.

Further, by reducing the metal concentration on the surface of the block layers 221 and 231 on the inner space S side, it is possible to improve the bondability at the time of heat bonding between the body portion 21 and the window portions 22 and 23. In the present embodiment, the block layers 221 and 231 are the body portions 2 of the window portions 22 and 23.
1 is disposed in a portion excluding the joint surface with 1. Thereby, the joining property at the time of the heat joining of the trunk | drum 21 and the window parts 22 and 23 can be made favorable.

Moreover, when the base material of the window parts 22 and 23 is comprised with glass, the clearance gap between crystal structures is large, and an alkali metal is easy to be absorbed or osmose | permeated. Therefore, by providing the block layers 221 and 223 in the window portions 22 and 23, the effect is remarkably exhibited. That is, even if the main material of the windows 22 and 23 has the property of absorbing alkali metal, the absorption or penetration of the alkali metal can be reduced.

Further, the metal contained in the block layers 221 and 231 is not particularly limited as long as the metal enclosed in the internal space S can be blocked from being absorbed or penetrated into the window portions 22 and 23, and the inside is not limited. It may be different from the metal enclosed in the space S, but is preferably an element of the same family as the metal enclosed in the internal space S, that is, an alkali metal such as rubidium, cesium, sodium, etc. More preferably, it is the same metal as the encapsulated metal. Thereby, the block function of the block layers 221 and 231 can be effectively enhanced.

The metal concentrations of the block layers 221 and 231 are preferably 1% or more and 10% or less with respect to the solid solution limit of the metal of the base material (for example, glass) constituting the window portions 22 and 231.
It is more preferable that it is 8% or more. Thereby, coexistence with the block property as mentioned above and the joining property at the time of heat joining can be aimed at effectively.

Further, the metal concentration on the inner space S side surface of the block layers 221 and 231 is set to A [Atoms / c.
m ³ ] and B / A is preferably 10 or more and 10 ⁵ or less, and B 2 / A is preferably 10 ² or more and 10 ⁴ or less, where B is the metal concentration at the aforementioned peak positions of the block layers 221 and 231. Is more preferable. Thereby, coexistence with the block property as mentioned above and the joining property at the time of heat joining can be aimed at.

In addition, the specific metal concentration on the surface of the block layers 221 and 231 on the inner space S side is preferably 10 ² atoms / cm ³ or more and 10 ¹⁵ atoms / cm ³ or less, although it depends on the peak position described above. More preferably, it is 10 ⁵ atoms / cm ³ or more and 10 ¹¹ atoms / cm ³ or less. Thereby, coexistence with the block property as mentioned above and the joining property at the time of heat joining can be aimed at effectively.

The metal concentration at the peak position of the specific block layer 221 and 231, depending on the peak ^position, it is preferably 10 8 Atoms / cm ³ or more ¹⁰ 18 Atoms / cm ³ or ^less, 10 10 Atoms It is more preferable that it is not less than / cm ^{3 and not} more than 10 ¹⁵ atoms / cm ³ . Thereby, coexistence with the block property as mentioned above and the joining property at the time of heat joining can be aimed at effectively.

In addition, the specific peak positions of the metal concentrations of the block layers 221 and 231 are preferably in the range of 0.05 μm or more and 1 μm or less from the inner wall surface of the internal space S (inner surfaces of the block layers 221 and 231). More preferably, it is in the range of 0.1 μm to 0.5 μm. Thereby, coexistence with the block property as mentioned above and the joining property at the time of heat joining can be aimed at effectively.

The thicknesses of the block layers 221 and 231 are preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 5 μm or less. Thereby, the block layers 221 and 231 can be formed relatively easily, and the block properties of the block layers 221 and 231 can be made excellent. On the other hand, if the block layers 221 and 231 are too thin, the block property tends to be insufficient depending on the metal concentration of the block layers 221 and 231. On the other hand, if the block layers 221 and 231 are too thick, the block layers 221 and 23
1 may be difficult to form, or depending on the metal concentration of the block layers 221 and 231, the transparency of the excitation light tends to be insufficient. Here, the thicknesses of the block layers 221 and 231 are:
The thickness of the portion where the metal concentration is 10 atoms / cm ³ or more.

The gas cell 2 having the block layers 221 and 231 as described above can be manufactured as follows.

(Atom cell manufacturing method)
Hereinafter, the case of manufacturing the above-described gas cell 2 will be described as an example of the method for manufacturing an atomic cell of the present invention. In the following, a case where the body portion 21 is made of silicon and the window portions 22 and 23 are made of glass will be described as an example.

FIG. 7 is a diagram showing a manufacturing method (block layer forming step) of the atomic cell shown in FIG. 5, and FIG.
It is a graph which shows the relationship between the depth from the surface of the board | substrate for window part formation in the formation process of the block layer shown in FIG. 7, and a metal concentration.

The manufacturing method of the gas cell 2 includes [1] a step of preparing a window portion forming substrate and a body portion forming substrate, [2] a step of forming block layers 221 and 231 on the window portion forming substrate, and [3]. And encapsulating an alkali metal in the internal space S constituted by the window portion forming substrate and the body portion forming substrate. Hereinafter, each process is demonstrated one by one.

[1]
First, as shown in FIG. 7A, a window forming substrate 22X is prepared. The window forming substrate 22X is a glass substrate having optical transparency, and the block layer 2 is formed in the step [2] described later.
21 is a substrate that becomes the window portion 22 by being diced as necessary.

On the other hand, although not shown, a window forming substrate similar to the window forming substrate 22X is prepared as a substrate for forming the window 23, and a through hole 211 is used as a substrate for forming the body portion 21. A body part forming substrate (silicon substrate) having the above is prepared.

[2]
2-1
Next, as shown in FIG. 7B, a metal film 20 is formed on one surface of the window forming substrate 22X. The metal film 20 is disposed corresponding to the formation region of the block layer 221.

As the constituent material of the metal film 20, the metal in the block layer 221 described above is used. Moreover, as a formation method of the metal film 20, a vacuum evaporation method etc. can be used, for example. Further, the thickness of the metal film 20 is not particularly limited as long as it is equal to or more than the amount of metal necessary for forming the block layer 221. Before forming the metal film 20, the window forming substrate 22X may be subjected to acid cleaning or the like.

2-2
Next, as shown in FIG. 7C, the metal film 20 and the window forming substrate 22X are heat-treated. As a result, the metal is diffused (thermally diffused) from the metal film 20 to the window forming substrate 22X to form the diffusion layer 221X.

The temperature of the heat treatment can diffuse the metal of the metal film 20 into the window forming substrate 22X, and
Although it should just be below the softening point of the board | substrate 22X for window part formation, it is preferable that it is 60 to 800 degreeC, It is more preferable that it is 300 to 800 degreeC, 400 to 700 degreeC
More preferably, it is not higher than ° C. Thereby, the block function of the block layer 221 can be improved effectively.

Further, this heat treatment is preferably performed in a reducing atmosphere or an inert gas atmosphere.
Thereby, the block function of the block layer 221 can be improved effectively.

The heat treatment time is determined according to the thickness of the block layer 221 and is not particularly limited, but is about 10 minutes to 10 hours.

Here, the profile of thermal diffusion follows Fick's law. The heat treatment time t is t ₁ ,
The metal concentration distribution of the diffusion layer 221X when a t ₂ shown in FIG. Note that t ₁ <t ₂ .

2-3
Next, the metal film 20 remaining after the heat treatment is removed. As a result, as shown in FIG. 7D, the diffusion layer 221X is exposed.

The step of removing the metal film 20 is preferably performed by acid cleaning. Thereby, the excess metal remaining on the surface of the window forming substrate 22X can be easily and effectively removed.

2-4
Next, indentation diffusion is performed by further heat treatment in the absence of the metal film 20. Thereby, as shown in FIG.7 (e), the window part 22 which has the block layer 221 is obtained.

This indentation diffusion can be performed at the same temperature as the heat treatment in Step 2-2 described above. Further, the processing time of this step is determined according to the thickness of the block layer 221 because the thermal diffusion profile follows Fick's law as described above. The metal concentration distribution of the block layer 221 obtained after the heat treatment in this step is as shown in FIG. FIG. 8 shows a case where the heat treatment time t in the above-described step 2-2 is t2, and the heat treatment in this step is performed after performing the above-described step 2-3 (t = t ₃ ). Yes. By such indentation diffusion, a portion having a higher metal concentration than the surface of the block layer 221 on the inner space S side can be provided inside the block layer 221.

By the process [2] described above, the window portion 22 having the block layer 221 is obtained. Although not shown, the window portion 23 having the block layer 231 can be obtained in the same manner.
Thereby, as shown to Fig.9 (a), the trunk | drum 21 and the window parts 22 and 23 are obtained. The block layer 231 is formed after the window portion forming substrate for forming the window portion 23 is bonded to the body portion forming substrate, and then the bonded body (the body portion forming substrate having a recess). May be.

[3]
Next, the window parts 22 and 23 are joined to the body part 21 as shown in FIG. Thereby, the internal space S is formed and the alkali metal is sealed in the internal space S.

In this step, it is preferable that the body portion 21 and the window portions 22 and 23 are joined by anodic joining, which is a kind of heat joining. Thus, after the step of removing the metal film 20, the window portions 22, 2
3 and the body portion 21 are heated and joined to form the internal space S, so that the metal film 20 can be formed, the metal can be diffused, and the metal film 20 can be removed relatively easily. . In addition, highly reliable airtight joining is possible.

According to the manufacturing method of the gas cell 2 as described above, it is possible to obtain the gas cell 2 in which the inner wall surfaces of the window portions 22 and 23 are configured by the block layers 221 and 231 containing metal.
Therefore, it is possible to reduce the size and power consumption of the obtained gas cell 2.

Second Embodiment
Next, a second embodiment of the present invention will be described.

FIG. 10A is a cross-sectional view of an atomic cell according to the second embodiment of the present invention, and FIG.
It is a longitudinal cross-sectional view of the atomic cell shown to Fig.10 (a).

This embodiment is the same as the first embodiment described above except that the body layer is also provided with a block layer.

In the following description, the second embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.

A gas cell 2A (atomic cell) shown in FIG. 10 includes a body part 21A instead of the body part 21 of the first embodiment.

A block layer 212 constituting a part of the inner wall surface of the internal space S is provided at a portion facing the internal space S of the trunk portion 21A. The block layer 212 is obtained by diffusing metal into the material (base material) constituting the body portion 21A. And like the block layers 221 and 231 of the first embodiment described above, the block layer 212 is provided with a portion having a higher metal concentration than the surface of the block layer 212 on the inner space S side. .

By providing such a block layer 212, when the base material of the trunk | drum 21 is comprised with glass, for example, it can reduce that an alkali metal is absorbed or osmose | permeated by the trunk | drum 21A.

In the present embodiment, the internal space S is surrounded by the block layers 212, 221, and 231. Thereby, even if the main material of the whole wall part which divides and forms internal space S has a property which absorbs a metal, absorption or osmosis | permeation of a metal can be reduced.

The gas cell 2A having the block layers 212, 221, and 231 as described above can be manufactured as follows. In the following, the body portion 21A and the window portions 22, 2
The case where 3 is each comprised with glass is demonstrated to an example. Further, the description of matters similar to those of the first embodiment described above is omitted.

FIG. 11 is a diagram showing a method for manufacturing the atomic cell shown in FIG. 10 (joining step of the window portion forming substrate and the body portion forming substrate).

The manufacturing method of the gas cell 2A includes [1A] a step of preparing a window portion forming substrate and a body portion forming substrate, [2A] a step of forming block layers 212, 221, and 231 on the window portion forming substrate, [ 3A] a step of encapsulating an alkali metal in the internal space S constituted by the window portion forming substrate and the body portion forming substrate. Hereinafter, each process is demonstrated one by one.

[1A]
First, similarly to the first embodiment described above, a window part forming substrate and a body part forming substrate are prepared.

[2A]
Next, the block layers 221 and 231 are formed as in the first embodiment described above. Also,
The block layer 212 can also be formed in the same manner as the block layers 221 and 231. Thereby, as shown to Fig.11 (a), the trunk | drum 21 and the window parts 22 and 23 are obtained. Here, before the block layer 231 is formed, the window portion forming substrate and the body portion forming substrate for forming the window portion 23 are bonded together, and a metal film is formed on the bonded body. By performing diffusion and washing by heat treatment, the block layer 212 can be formed together with the block layer 231.

[3A]
Next, as shown in FIG. 11B, the window portions 22 and 23 are joined to the trunk portion 21A in an alkali metal atmosphere. As a result, the internal space S is formed and the internal space S
Alkaline metal is sealed in

2. Electronic equipment The atomic oscillator described above can be incorporated into various electronic equipment. Such an electronic device has excellent reliability.

Hereinafter, the electronic apparatus of the present invention will be described.
FIG. 12 is a diagram showing a schematic configuration when the atomic oscillator of the present invention is used in a positioning system using a GPS satellite.

The positioning system 100 shown in FIG. 12 includes a GPS satellite 200, a base station device 300, a GP
S receiver 400 is comprised.

The GPS satellite 200 transmits positioning information (GPS signal).
The base station device 300 includes, for example, an antenna 3 installed at an electronic reference point (GPS continuous observation station).
A receiving device 302 that receives positioning information from the GPS satellite 200 with high accuracy via 01, and a transmitting device 304 that transmits positioning information received by the receiving device 302 via the antenna 303.
With.

Here, the receiving device 302 is an electronic device provided with the above-described atomic oscillator 1 of the present invention as its reference frequency oscillation source. Such a receiving apparatus 302 has excellent reliability. In addition, the positioning information received by the receiving device 302 is transmitted by the transmitting device 304 in real time.

The GPS receiver 400 includes a satellite receiver 402 that receives positioning information from the GPS satellite 200 via the antenna 401, and a base station receiver 404 that receives positioning information from the base station device 300 via the antenna 403. Prepare.

3. Mobile Object FIG. 13 is a diagram showing an example of a mobile object of the present invention.

In this figure, a moving body 1500 has a vehicle body 1501 and four wheels 1502, and is configured to rotate the wheels 1502 by a power source (engine) (not shown) provided in the vehicle body 1501. In such a moving body 1500, the atomic oscillator 1 is built.
According to such a moving body, excellent reliability can be exhibited.

Note that the electronic apparatus of the present invention is not limited to the above-described ones. For example, a mobile phone, a digital still camera, an ink jet discharge device (for example, an ink jet printer), a personal computer (a mobile personal computer, a laptop personal computer). , TV, camcorder, video tape recorder, car navigation device, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game device, word processor, workstation, video phone, TV monitor for security,
Electronic binoculars, POS terminal, medical equipment (eg electronic thermometer, blood pressure meter, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments (eg, vehicle, aircraft) , Ship instruments), flight simulators, digital terrestrial broadcasting, mobile phone base stations, and the like.

As described above, the atomic cell, the atomic cell manufacturing method, the quantum interference device, the atomic oscillator, the electronic apparatus, and the moving body of the present invention have been described based on the illustrated embodiments. However, the present invention is not limited to these. Absent.

Moreover, the structure of each part of this invention can be substituted by the thing of the arbitrary structures which exhibit the same function of embodiment mentioned above, and arbitrary structures can also be added.

Moreover, you may make it this invention combine arbitrary structures of each embodiment mentioned above.

In the above-described embodiment, the case where the atomic cell of the present invention is used in a quantum interference device that resonantly transitions cesium or the like using the quantum interference effect of two types of light having different wavelengths has been described as an example. The atomic cell of the invention is not limited to this, and can also be used for a double resonance apparatus that makes a resonance transition of rubidium or the like by utilizing a double resonance phenomenon caused by light and microwaves.

In the embodiment described above, the case where the window portion forming substrate and the body portion forming substrate are joined after the block layer is formed has been described as an example. A body portion forming substrate is joined to form an internal space, and a window portion forming substrate or a body portion forming substrate is formed with a hole that communicates the internal space with the outside, and a metal film is formed through the hole. After forming, diffusing, washing and introducing an alkali metal, the hole may be sealed.

DESCRIPTION OF SYMBOLS 1 ... Atomic oscillator 2 ... Gas cell 2A ... Gas cell 3 ... Light emission part 5 ... Light detection part 6 ... Heater 7 ... Temperature sensor 8 ... Magnetic field generation part 10 ... Control part 11 ... Temperature control Section 12 Excitation light control section 13 Magnetic field control section 20 Metal film 21 Body section 21A Body section 22 Window section 22X Window section forming substrate 23 Window section 41 Optical part 42 ... Optical part 43 ... Optical part 44 ... Optical part 100 ... Positioning system 200 ... GPS satellite 211 ... Through hole 212 ... Block layer 221 ... Block layer 221X ... Diffusion layer 231 ... Block layer 300 ... base station device 301 ... antenna 302 ... reception device 303 ... antenna 304 ... transmission device 400 ... GPS reception device 401 ... antenna 402 ... satellite reception unit 403 ... antenna 404 ... Chikyoku receiver 1500 ‥‥ mobile 1501 ‥‥ body 1502 ‥‥ wheel LL ‥‥ excitation light S ‥‥ interior space

Claims (16)

Metal,
An internal space in which the metal is enclosed, and a wall portion containing the metal inside;
Have
The atomic cell, wherein the wall portion is provided with a block layer having a higher metal concentration than the inner space side. The wall has a portion containing glass,
The atomic cell according to claim 1, wherein the block layer is disposed in the portion. 3. The atomic cell according to claim 1, wherein a peak position of the metal concentration in the block layer is closer to an inner wall surface than a center in a thickness direction of the wall portion. The wall is
A pair of windows,
A body part disposed between the pair of window parts and constituting the internal space together with the pair of window parts;
Have
4. The atomic cell according to claim 1, wherein the block layer is disposed on at least one of the window portion and the body portion. 5. The atomic cell according to claim 1, wherein the block layer surrounds the internal space. The atomic cell according to any one of claims 1 to 5, wherein the metal contained in the block layer is an element of the same group as the metal sealed in the internal space. A window forming substrate having optical transparency, a body forming substrate having a recess or a through hole, and
The process of preparing
Forming a metal film on at least one surface of the window portion forming substrate and the body portion forming substrate;
Diffusing metal from the metal film to the window portion forming substrate or the body portion forming substrate by heat treatment;
Removing at least a part of the metal film after the heat treatment;
Encapsulating metal in an internal space formed by the window portion forming substrate and the body portion forming substrate;
A method for producing an atomic cell, comprising:   The method for manufacturing an atomic cell according to claim 7, wherein the body part forming substrate includes glass. The method for producing an atomic cell according to claim 7 or 8, wherein the temperature of the heat treatment is 60 ° C or higher and 800 ° C or lower. The method for manufacturing an atomic cell according to claim 7, wherein the step of removing the metal film is performed by acid cleaning. 11. The method according to claim 7, further comprising a step of forming the internal space by thermally bonding the window portion forming substrate and the body portion forming substrate after the step of removing the metal film. A method for producing an atomic cell according to claim 1. The atom according to any one of claims 7 to 11, further comprising a step of pushing and diffusing the metal of the window portion forming substrate or the body portion forming substrate by heat treatment after the step of removing the metal film. Cell manufacturing method. A quantum interference device comprising the atomic cell according to claim 1. An atomic oscillator comprising the atomic cell according to claim 1. An electronic apparatus comprising the atomic cell according to claim 1.   A moving body comprising the atomic cell according to claim 1.

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