Gas cell and quantum sensor

Abstract

The present invention provides a gas cell having excellent thermal uniformity.　The gas cell contains alkali metal atoms sealed therein. The gas cell includes a body part having at least one opening and a transparent substrate provided at the opening. A thermal conductivity k of the body part is 30 W･m-1･K-1 or more. A product β･k of the thermal conductivity k and a value β, which is obtained by dividing the surface area of the body part by the surface area of the gas cell, is 20 W･m-1･K-1 or more.

Description

Gas cell and quantum sensor

[0001] The present invention relates to a gas cell and a quantum sensor including the gas cell.

[0002] When light acts on an alkali metal vapor, phenomena such as spin polarization or a quantum interference effect (e.g., CPT: Coherent Population Trapping) occur. In recent years, quantum sensors such as atomic oscillators and optical pumping magnetic sensors that utilize these phenomena have attracted attention. The optical pumping magnetic sensor is used as a brain function imaging device for measuring and imaging the physiological activities and functions of each part in the brain. Therefore, improving the optical pumping magnetic sensor leads to early detection and treatment of lesions and improvement of the quality of life (QOL), and thus can contribute to the achievement of Goal 3, "Ensure healthy lives and promote well-being for all," of the Sustainable Development Goals (SDGs) proposed by the United Nations.

[0003] Quantum sensors such as atomic oscillators and optical pumping magnetic sensors include, for example, a gas cell filled with an alkali metal vapor and buffer gases such as nitrogen, helium, and argon, a light source that emits excitation light for exciting the alkali metal in the gas cell, and a photodetector that detects the light passing through the gas cell. The alkali metal vapor is obtained by heating and vaporizing an alkali metal or an alkali metal compound enclosed in the gas cell. For this reason, the gas cell is operated in a high-temperature environment.

[0004] As an optical pumping magnetometer (optical pumping magnetic sensor) including the gas cell as described above, for example, in Patent Document 1, an optical pumping magnetometer including a glass cell, a temperature measuring body that measures the temperature of the cell, and a control unit that energizes and controls the temperature of a laser irradiation light transmission part has been proposed.

[0005] Japanese Unexamined Patent Application Publication No. 2009-010547

[0006] Here, from the perspective of improving measurement accuracy, it is important to uniformly fill the inside of the gas cell with alkali vapor. In order to uniformly fill the inside of the gas cell with alkali vapor, it is required that the temperature in the gas cell be uniform. Hereinafter, the degree of uniformity of the temperature in the gas cell is also referred to as "isothermal property", and a small variation in temperature in the gas cell is also referred to as "excellent isothermal property". When the present inventors examined the gas cell described in Patent Document 1, they found that there is room for improvement in the isothermal property of the gas cell.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a gas cell having excellent isothermal property. Another object of the present invention is to provide a quantum sensor including the above gas cell.

[0008] As a result of intensive studies on the above problems, the present inventors focused on the thermal conductivity of the main body portion constituting the gas cell and completed the present invention.

[0009] That is, the inventors have found that the above problems can be solved by the following configuration. [1] A gas cell in which an alkali metal atom is enclosed, the gas cell having a main body portion having at least one opening and a transparent substrate provided in the opening, wherein the thermal conductivity k of the main body portion is 30 W·m －１ ·K －１ or more, and β·k, which is the product of β, which is the value obtained by dividing the surface area of the main body portion by the surface area of the gas cell, and the thermal conductivity k, is 20 W·m －１ ·K －１ or more. [2] The gas cell according to [1], wherein the thermal conductivity k of the main body portion is 80 W·m －１ ·K －１ or more. [3] The gas cell according to [1], wherein the thermal conductivity of the main body portion is 180 W·m －１ ·K －１The gas cell according to [1] or [2], wherein the gas cell is substantially composed of SiSiC. [4] The gas cell according to any one of [1] to [3], wherein the main body portion comprises a fitting portion into which the transparent substrate is fitted. [5] The gas cell according to [4], wherein the transparent substrate has a first main surface that together with the main body portion constitutes a closed space for encapsulating the alkali metal atoms, a second main surface opposite to the first main surface, and a side surface that is incorporated into the outer edges of the first main surface and the second main surface, and the fitting portion of the main body portion is joined to at least two of the first main surface, the second main surface and the side surface of the transparent substrate. [6] The gas cell according to any one of [1] to [5], wherein the main body portion comprises a sealing portion for encapsulating alkali metals inside. [7] The gas cell according to any one of [1] to [6], wherein the main body has one opening and a reflective member provided inside the main body at a position facing the opening. [8] The gas cell according to any one of [1] to [7], wherein the main body has two or more openings. [9] A quantum sensor comprising the gas cell according to any one of [1] to [8], a light source that emits excitation light to excite electrons of alkali metal atoms contained in the gas cell, and a photodetector that detects light transmitted through the gas cell.

[10] The quantum sensor according to [9], which is an optical pumping magnetic sensor.

[11] The quantum sensor according to [9], which is an atomic oscillator.

[0010] According to the present invention, a gas cell with excellent heat uniformity can be provided. Furthermore, according to the present invention, a quantum sensor equipped with the above-mentioned gas cell can also be provided.

[0011] It is a perspective view showing an example of a gas cell according to the first embodiment of the present invention. It is a cross-sectional view showing an example of a gas cell according to the first embodiment of the present invention. It is a cross-sectional view showing a modified example of the gas cell according to the first embodiment of the present invention. It is a perspective view showing a modified example of the gas cell according to the first embodiment of the present invention. It is a cross-sectional view showing a modified example of the gas cell according to the first embodiment of the present invention. It is a cross-sectional view showing a modified example of the gas cell according to the first embodiment of the present invention. It is a perspective view showing an example of a gas cell according to the second embodiment of the present invention. It is a cross-sectional view showing an example of a gas cell according to the second embodiment of the present invention. It is a cross-sectional view showing a modified example of the gas cell according to the second embodiment of the present invention. It is a cross-sectional view showing a modified example of the gas cell according to the second embodiment of the present invention. It is a perspective view showing an example of a gas cell according to the third embodiment of the present invention. It is a cross-sectional view showing an example of a gas cell according to the third embodiment of the present invention. It is a perspective view showing a modified example of the gas cell according to the third embodiment of the present invention. It is a cross-sectional view showing a modified example of the gas cell according to the third embodiment of the present invention.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following embodiments and the drawings described in the embodiments are illustrative for explaining the present invention, and the present invention is not limited to the embodiments and drawings shown below. Various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention. In the drawings and the description of the drawings, the same reference numerals are assigned to common elements, and duplicate descriptions are omitted. In each drawing, the scale of the components may be appropriately different from the actual one in order to facilitate visual recognition and explanation.

[0013] In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions.

[0014] The gas cell according to the present invention is a gas cell in which an alkali metal atom is enclosed inside, and has a main body portion having at least one opening and a transparent substrate provided at the opening, and the thermal conductivity k of the main body portion is 30 W·m －１・K －１ The above is true, and the product of β, which is the value obtained by dividing the surface area of ​​the main body by the surface area of ​​the gas cell, and the thermal conductivity k, β·k is 20 W·m －１ ・K －１ This concludes the explanation. The gas cell according to the present invention has excellent uniform heating performance because the thermal conductivity k of the main body is greater than or equal to a predetermined value. Furthermore, in the gas cell according to the present invention, β·k, which is the product of β (the value obtained by dividing the surface area of ​​the main body by the surface area of ​​the gas cell) and the thermal conductivity k, is greater than or equal to a predetermined value. Therefore, the contribution of the thermal conductivity of the main body to the entire gas cell is large, and the uniform heating performance of the gas cell is considered to be further improved.

[0015] The thermal conductivity can be measured by the laser flash method in accordance with JIS R1611:2010. For measuring the thermal conductivity, for example, a sample of the heat dissipation member 10 processed to 5 × 5 × 1 mm is used. The thermal conductivity is the average value of two samples (n=2) measured. In this specification, the surface area of ​​the main body when calculating the above β refers to the surface area calculated from the geometry of the main body, and means the surface of the main body constituting the gas cell that is in contact with the external space. In other words, the surface area of ​​the main body does not include the area of ​​the surfaces that constitute the closed space described later. Also, in this specification, the surface area of ​​the gas cell when calculating the above β refers to the surface area calculated from the geometry of the gas cell, and means the surface of the gas cell that is in contact with the external space. In other words, the surface area of ​​the gas cell does not include the area of ​​the surfaces that constitute the closed space described later. The above β is preferably 0.4 or more, more preferably 0.5 or more, may be 0.6 or more, or may be 0.7 or more. The above β is often 0.9 or less.

[0016] Figures 1 to 14 are conceptual diagrams showing a gas cell according to the present invention. In the gas cell according to the present invention, as shown in Figures 1 to 14, it is preferable that the main body portion includes a fitting portion into which a transparent substrate is fitted. In the embodiments shown in Figures 1 to 14, the main body portion includes the fitting portion, but the gas cell according to the present invention does not necessarily have to include the fitting portion. Hereinafter, embodiments of the gas cell according to the present invention will be described with reference to the drawings.

[0017] [First Embodiment] An example of a gas cell according to the first embodiment of the present invention is shown in Figures 1 and 2. Figure 1 is a perspective view showing the gas cell 1 according to this embodiment. Figure 2 is a cross-sectional view of the gas cell 1 along the line I-I in Figure 1. Hereinafter, components common to the gas cell according to the first embodiment will be denoted by the same reference numerals, and their detailed descriptions will be omitted. The gas cell 1 of this embodiment has a main body 10, a transparent substrate 20, and a reflective member 30 (see Figure 2). In the gas cell 1, the main body 10 has one opening 11. The transparent substrate 20 is provided in the opening 11 of the main body 10, and light that excites alkali metal atoms as described later is transmitted through the transparent substrate 20. Inside the gas cell 1, a closed space 40 (see Figure 2) is formed, surrounded on all sides by the main body 10 and the transparent substrate 20, and alkali metal atoms and a sealed gas (buffer gas) are sealed in this closed space 40. The closed space 40 is the internal space of the main body 10.

[0018] The transparent substrate 20 has, for example, a first main surface 21 that, together with the main body 10, constitutes a closed space 40 for encapsulating alkali metal atoms, a second main surface 22 opposite to the first main surface 21, and a side surface 23 incorporated into the outer edges of the first main surface 21 and the second main surface 22. For example, the first main surface 21 and the second main surface 22 are parallel, and the side surface 23 is perpendicular to the first main surface 21 and the second main surface 22. However, the side surface 23 is not particularly limited to being perpendicular to the first main surface 21 and the second main surface 22.

[0019] In the gas cell 1 of this embodiment, the main body 10 is provided with a fitting portion 14 into which a transparent substrate 20 is fitted at the opening 11. By providing the fitting portion 14 into which the transparent substrate 20 is fitted in the main body 10, a gas cell 1 with superior airtightness between alkali metal atoms and enclosed gas can be obtained. This is thought to be because the area in which the main body 10 (side wall portion 13) and the transparent substrate 20 are joined has increased, thereby increasing the length of the fitting portion between the main body 10 and the transparent substrate 20, that is, the distance from the closed space 40 to the outside of the gas cell 1. In the gas cell 1 of this embodiment, since the transparent substrate 20 is fitted by the fitting portion 14 of the main body 10, displacement of the transparent substrate is less likely to occur during manufacturing or use, and the airtightness of the gas cell 1 is further improved. The gas cell of this embodiment will be described in more detail below.

[0020] The main body 10 has, for example, a plate-shaped base 12 with a rectangular outer shape in plan view, and a rectangular tubular side wall portion 13 having four side walls. The side wall portion 13 is provided so as to surround the entire circumference of the peripheral edge of the base portion 12. The main body 10 shown in Figures 1 and 2 has a configuration in which the base portion 12 and the side wall portion 13 are integrally molded. In the main body 10, the protruding end of the side wall portion 13 opposite to the base portion 12 is an opening 11, and a fitting portion 14 is provided on the inside (opening 11 side) of the protruding end of the side wall portion 13. As shown in Figure 2, the fitting portion 14 has, for example, two orthogonal first fitting surfaces 141 and a second fitting surface 142. The first main surface 21 of the transparent substrate 20 is joined to the first fitting surface 141, and the side surface 23 of the transparent substrate 20 is joined to the second fitting surface 142.

[0021] In this embodiment, the main body 10 has one opening 11. When the gas cell having one opening in this embodiment is used in a quantum sensor or the like, the light source that emits excitation light to excite alkali metal atoms and the photodetector that detects the light that has passed through the inside of the gas cell are arranged on the same side (transparent substrate 20 side) as the gas cell. This makes it possible to miniaturize the quantum sensor equipped with the gas cell 1.

[0022] In this embodiment, a reflective member 30 is provided on the surface of the base portion 12 of the main body portion 10 facing the transparent substrate 20, which has the function of reflecting light that excites alkali metal atoms. In this way, in a gas cell in which the main body portion has one opening, by providing a reflective member at a position facing the opening inside the main body portion, light that has passed through the transparent substrate provided in the opening and entered the closed space can excite alkali metal atoms, and then pass through the transparent substrate again to be detected by an external photodetector.

[0023] The thickness of the base portion 12 and side wall portion 13 of the main body portion 10 is preferably 0.3 mm or more and less than 10 mm, and more preferably 0.5 mm or more and less than 5.0 mm. By having the thickness of the base portion 12 and side wall portion 13 within the above range, shape stability and uniform heat distribution can be further improved while maintaining mechanical properties. Furthermore, by securing the bonding area with the transparent substrate, airtightness can be further improved. Mechanical properties refer to bending strength and impact resistance.

[0024] The main body 10 is constructed from materials with a thermal conductivity k of 30 W·m. －１ ・K －１ The above β·k is 20 W·m －１ ・K －１ The above are not particularly limited, but for example, metallic silicon (Si), silicon carbide (SiC), silicon carbide-silicon composite (hereinafter also referred to as "SiSiC," for example, silicon-impregnated reaction sintered silicon carbide), silicon nitride (Si ３ N ４ ), aluminum oxide (Al ２ O ３ Examples include ), and aluminum nitride (AlN). In particular, the constituent material of the main body 10 is Si, SiC, SiSiC, Si ３ N ４ Al ２ O ３ At least one selected from the group consisting of , and AlN is preferred, and SiSiC is more preferred from the viewpoint of moldability. In the case of SiSiC, it is preferable to contain 5 to 60 mass% Si (metallic silicon). Furthermore, the bulk density of the main body 10 made of SiSiC is 2.62 g / cm³. ３The above is preferable, and 2.85 g / cm³ ３ The above is more preferable. The porosity of the main body 10, which is made of SiSiC, is preferably less than 3 volume percent. Furthermore, it is also preferable that the SiSiC contains α-SiC (hexagonal crystal system), β-SiC (cubic crystal system), and metallic Si.

[0025] The thermal conductivity k of the main body 10 is 80 W・m －１ ・K －１ The above is preferable, 130 W·m －１ ・K －１ The above is more preferable, 180 W·m －１ ・K －１ The above is even more preferable. There is no particular upper limit to the thermal conductivity k, but 1000 W·m －１ ・K －１ The following is often the case: Thermal conductivity k is 80 W·m －１ ・K －１ The material that can form the main body portion 10 described above is Si ３ N ４ Examples include Si, SiC, AlN, and SiSiC. Furthermore, the thermal conductivity k is 180 W·m. －１ ・K －１ Materials that can form the main body portion 10 as described above include SiC, AlN, and SiSiC.

[0026] Furthermore, β·k, which is the product of β (the surface area of ​​the main body divided by the surface area of ​​the gas cell) and the thermal conductivity k, is 20 W·m －１ ・K －１ That is all. 50 W·m －１ ・K －１ The above is preferable, and 70 W·m －１ ・K －１ The above is more preferable, 100 W·m －１ ・K －１ The above is even more preferable. The upper limit of β·k is not particularly limited, but 500 W·m is preferable. －１ ・K －１ The following is often the case.

[0027] The transparent substrate 20 is provided in the opening 11 of the main body 10 and fitted in place by a fitting portion 14. The constituent material of the transparent substrate 20 is not particularly limited as long as it is a material that transmits to wavelengths used in quantum sensors, but examples include glass materials, inorganic crystals such as quartz and sapphire, and translucent ceramics, with glass materials being preferred. Examples of glass include alkali-free borosilicate glass, borosilicate glass, soda-lime glass, high-silica glass, and other oxide-based glasses mainly composed of silicon dioxide. In addition, an alkali barrier film may be formed on the first main surface 21 of the transparent substrate 20 as needed. In addition, an anti-reflective film may be formed on at least one of the first main surface 21 and the second main surface 22 of the transparent substrate 20.

[0028] The thickness t of the transparent substrate 20 in the thickness direction from the first main surface 21 to the second main surface 22 is preferably 0.2 to 4.0 mm, and more preferably 0.5 to 2.0 mm. When the thickness t of the transparent substrate 20 is greater than or equal to the lower limit, the rigidity of the transparent substrate 20 is increased, which suppresses warping of the substrate due to heating, etc., when the gas cell is used in a quantum sensor, and improves signal stability. Furthermore, when the thickness t of the transparent substrate 20 is less than or equal to the upper limit, the size of the gas cell 1 is suppressed, making it easier to miniaturize and lighten the quantum sensor equipped with the gas cell 1.

[0029] The external shape of the transparent substrate 20 is, for example, a rectangle in plan view. However, the shape of the transparent substrate in the gas cell of this embodiment is not limited to the shape into which the transparent substrate is fitted by the fitting portion of the main body, and may or may not be the same as the shape of the closed space inside the main body. It is preferable that the shape of the transparent substrate in plan view and the shape of the closed space in plan view are the same or similar in that a sufficient contact area with the main body is secured and the airtightness of the gas cell is improved.

[0030] The fitting portion into which the transparent substrate is fitted will be explained in more detail. In the gas cell 1 shown in Figure 2, the fitting portion 14 is joined to two of the transparent substrate 20's surfaces: the first main surface 21 and the side surface 23, out of the first main surface 21, the second main surface 22, and the side surface 23. In this specification, "joining" includes not only cases where two members are joined directly, but also cases where they are joined via other layers such as a bonding layer.

[0031] In the fitting portion 14, if the length in the thickness direction of the fitting portion that joins with the side surface 23 of the transparent substrate 20 is a, it is preferable that the length a of the fitting portion 14 and the thickness t of the transparent substrate are t > a. This makes it easier to generate uniform stress that presses the transparent substrate against the main body when joining the transparent substrate to the main body, and makes it easier to properly fit the transparent substrate into the fitting portion. This further improves the airtightness of the gas cell 1. In terms of further improving the airtightness of the gas cell 1, it is preferable that the difference between the thickness t of the transparent substrate and the length a is 0.1 mm or more and less than 1.0 mm.

[0032] The length a of the fitting portion 14 is preferably 0.1 mm or more, and more preferably 0.5 mm or more. When the length a is greater than or equal to the lower limit, the contact area between the transparent substrate 20 and the main body portion 10 increases, and the airtightness of the gas cell 1 is further improved. The length a of the fitting portion 14 may also be 3.9 mm or less, or 2.0 mm or less.

[0033] In the mating portion 14, if b is the length of the mating portion that joins the first main surface 21 of the transparent substrate 20 in a direction perpendicular to the thickness direction of the transparent substrate 20 (in Figure 2, the direction toward the central axis of the side wall portion 13 of the main body portion 10), then the length b is preferably 0.5 mm or more and less than 5.0 mm, and more preferably 0.7 to 3.0 mm. When the length b is greater than or equal to the lower limit, the joining area between the transparent substrate 20 and the main body portion 10 becomes larger, and the airtightness of the gas cell 1 is further improved. When the length b is less than the upper limit, the size of the main body portion is suppressed, and it becomes easier to miniaturize and lighten the quantum sensor equipped with the gas cell. In addition, the volume of the closed space becomes larger, and the signal sensitivity is further improved.

[0034] A bonding layer may be present between the main body and the transparent substrate of the gas cell in this embodiment. Examples of materials constituting the bonding layer include the bonding agent used to bond the main body and the transparent substrate, and components derived from the bonding agent. Examples of known bonding agents include glass frit, resin adhesives, and inorganic adhesives.

[0035] In this embodiment, alkali metal atoms are sealed in a closed space inside the gas cell. Examples of alkali metal atoms include lithium, potassium, cesium, rubidium, and sodium. The alkali metal atoms sealed in the closed space may be in the form of compounds of the above alkali metal atoms with zirconium, silicon, titanium, and aluminum, or compounds such as azides, halides, and nitrates. A buffer gas may be sealed in the closed space together with the alkali metal atoms. Examples of buffer gases include nitrogen gas, helium gas, neon gas, argon gas, and xenon gas. The alkali metal atoms and buffer gas sealed in the closed space are appropriately selected according to the application of the gas cell.

[0036] In this embodiment, it is preferable that a heater is provided in the gas cell to gasify the alkali metals in the internal space of the main body. The heater is not particularly limited, but it is preferable to use a ceramic heater with high power density when it is necessary to shorten the warm-up time of the atomic oscillator or quantum sensor such as an optical pumping magnetic sensor, or when high-temperature operation is required. On the other hand, it is also preferable to use a polyimide heater with low power density when it is necessary to make the temperature distribution of the main body more uniform, to miniaturize and lower the position of the atomic oscillator or optical pumping magnetic sensor, or to reduce the cost of the atomic oscillator or optical pumping magnetic sensor. The heater is provided at a position other than the opening of the main body. Since the main body satisfies the above requirements with respect to thermal conductivity k and β·k, heat from the heater is transferred to the entire gas cell, and the gas cell is heated uniformly.

[0037] Furthermore, the main body 10 may have a sealing portion for sealing alkali metals inside. The sealing portion is provided in the main body and has an open vent that connects the internal space of the main body to the outside, and a sealing agent that seals the open vent. The sealing portion seals alkali metal atoms and the enclosed gas into the internal space of the main body (inside the gas cell). Glass frit, for example, can be used as the sealing agent.

[0038] <Method for Manufacturing a Gas Cell of the First Embodiment> The method for manufacturing the gas cell 1 of this embodiment will be described below. The method for manufacturing the gas cell 1 of this embodiment includes, for example, a preparation step of preparing a main body 10 and a transparent substrate 20, and a fitting step of fitting the transparent substrate 20 into the fitting portion 14 to join the main body 10 and the transparent substrate 20, and fitting the transparent substrate 20 into the fitting portion 14.

[0039] In the preparation process, the main body 10 and the transparent substrate 20 are prepared. The main body 10, consisting of a base 12 and side wall 13, can be manufactured using known techniques such as etching, photolithography, casting, and 3D printing. A reflective member 30 is provided on the inner surface of the base 12 of the main body 10. It is also preferable that the main body 10 be molded as a single piece by 3D printing.

[0040] In the fitting process, the main body 10 and the transparent substrate 20 can be joined by known methods such as bonding with an adhesive, anodic bonding, heat bonding, and laser bonding, and the method is appropriately selected according to the respective constituent materials of the main body 10 and the transparent substrate 20. In the fitting process, it is preferable to join the main body 10 and the transparent substrate 20 using an adhesive, and then heat-treat the joint, in order to further improve airtightness.

[0041] When manufacturing a gas cell in which alkali metal atoms are sealed in a closed space 40, the sealing material containing alkali metal atoms should be placed inside the main body 10 before the fitting process. Examples of sealing materials containing alkali metal atoms include liquid or solid alkali metals, ampoules containing alkali metals, wax, etc. When liquid or solid alkali metals are placed, heating the gas cell during use creates a closed space 40 containing alkali metal atoms. When ampoules containing alkali metals are placed, after joining the main body 10 and the transparent substrate 20, the ampoules are destroyed by irradiation with an external laser beam, or the wax is melted, creating a closed space 40 containing alkali metal atoms. Alternatively, a stable alkali metal compound and an azide may be placed, and then heated to generate alkali metal vapor through a chemical reaction.

[0042] Another method for manufacturing a gas cell in which alkali metal atoms are sealed in a closed space 40 is to first provide open holes in either the base portion 12 or the side wall portion 13 of the main body portion 10, then join the main body portion 10 and the transparent substrate 20, introduce a sealing material containing alkali metal atoms, and then seal the open holes. The method for forming the closed space 40 in which alkali metal atoms are sealed by the sealing material is as described above. As a method for sealing the open holes, one method is to fill the open holes with the above-mentioned bonding agent and then perform heat treatment. The above procedure forms the sealed portion described above.

[0043] The gas cell of this embodiment has been described above based on the gas cell 1 shown in Figures 1 and 2, but other forms of gas cell besides the gas cell 1 are also included in this embodiment. The external shape of the gas cell 1 is a hexahedron with one face shaped like a square, but the external shape of the gas cell of this embodiment can be selected to suit the design of the quantum sensor. The external shape of the gas cell of this embodiment may be, for example, a polygonal prism, cylinder, elliptical prism, or polygon other than a rectangular parallelepiped (cube). The closed space 40 inside the main body 10 is a rectangular parallelepiped (cube), but the shape of the closed space may be a polygonal prism, cylinder, elliptical prism, or polygon other than a rectangular parallelepiped. The external shape of the gas cell and the shape of the closed space may be the same or different.

[0044] The following modifications are also possible for the gas cell of this embodiment. In each modification, elements common to the gas cell 1 shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0045] <Modification 1 of the First Embodiment> A modification 1 of the gas cell according to this embodiment is shown in Figure 3. The main body 10 of the gas cell 2 shown in Figure 3 is not a member in which the base 12 and the side wall 13 are integrally molded, but a member formed by joining a rectangular plate-shaped member corresponding to the base 12 and a rectangular tubular member corresponding to the side wall 13. The joining method is not particularly limited, but examples include joining using a bonding agent, anodic joining, heat compression bonding, and laser joining. In this modification, a reflective member 30 can be easily formed on the base 12. In this modification, the material constituting the base 12 and the material constituting the side wall 13 may be the same or different, but it is preferable that they be the same material in that the design regarding thermal expansion is easier.

[0046] <Modification 2 of the First Embodiment> A modification 2 of the gas cell according to this embodiment is shown in Figures 4 and 5. Figure 4 is a perspective view showing the gas cell 3 according to this modification. Figure 5 is a cross-sectional view of the gas cell 3 along the line I-I in Figure 4. As shown, the main body 10 of the gas cell 3 has, for example, a plate-shaped base 12 with a rectangular outer shape in plan view, and a rectangular tubular side wall portion 13 having four side walls. The side wall portion 13 is provided so as to surround the entire circumference of the peripheral edge of the base portion 12. On the inside of the protruding end of the side wall portion 13 opposite to the base portion 12 (on the opening 11 side), a fitting portion 14 having a frame-shaped lid portion 15 in plan view is provided. As shown, the fitting portion 14 has, for example, three orthogonal first fitting surfaces 141, a second fitting surface 142, and a third fitting surface 143. The first main surface 21 of the transparent substrate 20 is joined to the first mating surface 141, the side surface 23 of the transparent substrate 20 is joined to the second mating surface 142, and the second main surface 22 of the transparent substrate 20 is joined to the third mating surface 143. In this modified gas cell 3, the mating portion 14 of the main body 10 is joined to three surfaces of the transparent substrate 20: the first main surface 21, the second main surface 22, and the side surface 23. This configuration increases the bonding area between the main body 10 and the transparent substrate 20, further improving airtightness and resulting in a gas cell with superior robustness for use in harsher environments.

[0047] In this modified example, if c is the length in the thickness direction of the transparent substrate 20 of the fitting portion 14 that joins the first main surface 21, the second main surface 22, and the side surface 23 of the transparent substrate 20, then it is preferable that the length c and the thickness t of the transparent substrate are t ≤ c. This is because the airtightness of the gas cell 3 can be further improved, and a gas cell with superior robustness when used in more severe environments can be obtained. In terms of further improving the airtightness of the gas cell 3, the difference obtained by subtracting the thickness t of the transparent substrate from the length c of the fitting portion 14 is preferably 0 to 0.5 mm. It should be noted that the above length c can also be said to be the distance between the surface of the transparent substrate 20 facing the first main surface 21 at the fitting portion 14 and the surface of the transparent substrate 20 facing the second main surface 22 at the lid portion 15 of the fitting portion 14.

[0048] In this modified example, the length c of the fitting portion 14 is preferably 0.6 mm or more, and more preferably 1.0 mm or more. When the length c is greater than or equal to the lower limit, the contact area between the transparent substrate 20 and the main body portion 10 increases, and the airtightness of the gas cell 1 is further improved. The length c of the fitting portion 14 may also be 4.5 mm or less, or 2.1 mm or less.

[0049] In the lid portion 15 of the fitting portion 14, if the length of the fitting portion 14 that joins with the first main surface 22 of the transparent substrate 20 in a direction perpendicular to the thickness direction of the transparent substrate 20 (in Figure 5, the direction toward the central axis of the side wall portion 13 of the main body portion 10) is denoted as d, then the length d is preferably 0.5 to 6.0 mm, and more preferably 0.7 to 4.0 mm. When the length d is greater than or equal to the lower limit, the joining area between the transparent substrate 20 and the lid portion 15 becomes larger, and the airtightness of the gas cell 3 is further improved. When the length d is less than or equal to the upper limit, sufficient area can be secured for the excitation light that excites alkali metal atoms to enter the closed space 40 and for the excitation light to exit the closed space 40, making optical axis adjustment easier.

[0050] In this modified example, the main body portion 10 is a member formed by joining members corresponding to the base portion 12 and the side wall portion 13 with a frame-shaped member corresponding to the lid portion 15. The joining method is not particularly limited, but the joining method described in Modified Example 1 is an example. In this modified example, the materials constituting the base portion 12 and the side wall portion 13 and the material constituting the lid portion 15 may be the same or different, but it is preferable that they be the same material in that the design regarding thermal expansion is easier.

[0051] The base portion 12 and side wall portion 13 of the main body portion 10 may be members formed by joining a rectangular plate-shaped member corresponding to the base portion 12 and a rectangular tubular member corresponding to the side wall portion 13, similar to the first modification.

[0052] The manufacturing method for the gas cell 3 of this modified example includes, for example, a preparation step of preparing a member A that will become the base portion 12 and the side wall portion 13, a member B that will become the lid portion 15, and a transparent substrate 20; a first joining step of joining member A and the transparent substrate 20; and a second joining step of joining member B to member A and the transparent substrate 20.

[0053] The preparation of member A and the transparent substrate 20 in the preparation step is as described in the manufacturing method of the gas cell 1 above. Member B, which will become the frame-shaped lid portion 15, can be manufactured using known techniques such as etching, photolithography, casting, and 3D printing. The first joining step is the same as the fitting step in the manufacturing method of the gas cell 1 above, including the preferred form.

[0054] In the second joining step, member B is joined to member A and the transparent substrate 20 manufactured in the first joining step. The joining method in the second joining step may be the joining method described in the fitting step of the manufacturing method of the gas cell 1 described above, and is preferably the same as the joining method in the first joining step. In particular, the joining methods in the first and second joining steps are preferably joined using a bonding agent, and then the joined portion is heat-treated, in order to further improve airtightness.

[0055] The method for manufacturing a gas cell in which alkali metal atoms are sealed in the closed space 40 of the gas cell 3 (the method for sealing alkali metal atoms in the closed space 40) is as described in the manufacturing method of the gas cell 1 above.

[0056] <Modification 3 of the First Embodiment> A modification 3 of the gas cell according to this embodiment is shown in Figure 6. Figure 6 is a cross-sectional view showing the gas cell 4 according to this modification. The main body 10 of the gas cell 4 shown in Figure 6 has, for example, a plate-shaped base 12 with a rectangular outer shape in plan view, and a rectangular tubular side wall portion 13 having four side walls. The side wall portion 13 is provided so as to surround the entire circumference of the peripheral edge of the base portion 12. On the inner side (opening 11 side) of the protruding end side of one of the four side walls of the side wall portion 13, a fitting portion 14 into which a transparent substrate 20 is fitted is provided. As shown in Figure 6, the fitting portion 14 has, for example, three orthogonal first fitting surfaces 141, a second fitting surface 142, and a third fitting surface 143. The first main surface 21 of the transparent substrate 20 is joined to the first mating surface 141, the side surface 23 of the transparent substrate 20 is joined to the second mating surface 142, and the second main surface 22 of the transparent substrate 20 is joined to the third mating surface 143. In addition, on one side of the side wall portion 13 facing the mating portion 14, a through hole 16 is provided at the position where the mating portion 14 is located, with a shape corresponding to one of the side surfaces 23 of the transparent substrate 20. The main body portion 10 of the gas cell 4 has a structure in which the transparent substrate 20 is slid into the through hole 16 and fitted at the mating portion 14. The space outside the transparent substrate 20 within the internal space of the through hole 16 is sealed by the sealing portion 17. Thus, in this modified gas cell 4, the mating portion 14 of the main body portion 10 is joined to three surfaces of the transparent substrate 20: the first main surface 21, the second main surface 22, and the side surface 23. This configuration increases the contact area between the main body 10 and the transparent substrate 20, further improving airtightness and resulting in a gas cell with superior robustness for use in harsher environments.

[0057] In this modified example, if c is the length in the thickness direction of the transparent substrate 20 of the fitting portion 14 that joins the first main surface 21, the second main surface 22, and the side surface 23 of the transparent substrate 20, then the difference obtained by subtracting the thickness t of the transparent substrate 20 from the length c of the fitting portion 14 is preferably 0.1 to 0.5 mm. This is because it is possible to further improve the airtightness of the gas cell 4 and obtain a gas cell with superior robustness when used in more severe environments. Furthermore, if the above difference is 0.1 mm or more, the manufacturing of the gas cell 4, including insertion into the through hole 16 of the transparent substrate 20, becomes easier.

[0058] In the through-hole 16 of the main body 10, if e is the length of the fitting portion that joins the first main surface 21 (or second main surface 22) of the transparent substrate 20, in a direction perpendicular to the thickness direction of the transparent substrate 20 (in Figure 6, the direction toward the central axis of the side wall portion 13 of the main body 10), then e is preferably 0.7 to 10 mm, and more preferably 2 to 7 mm. When e is greater than or equal to the lower limit, the joining area between the transparent substrate 20 and the side wall portion 13 is increased, and the airtightness of the gas cell 4 is further improved. When e is less than or equal to the upper limit, the size of the main body is suppressed, making it easier to miniaturize and lighten the quantum sensor equipped with the gas cell.

[0059] In this modified example, the space outside the transparent substrate 20 within the through-hole 16 is sealed by the sealing portion 17. As the material constituting the sealing portion 17, the adhesive used to join the main body and the transparent substrate, or components derived from the adhesive, is preferred, as it further improves the airtightness of the gas cell 4.

[0060] In this modified example, the main body portion 10 is a member formed by integrally molding a base portion 12 and a side wall portion 13. In the gas cell 1 of this modified example, even though the main body portion 10 is integrally molded, the first main surface 21, second main surface 22, and side surface 23 of the transparent substrate 20 are joined to the main body portion 10, and the transparent substrate 20 can be fitted into the fitting portion 14 of the main body portion 10. The main body portion 10 may be a member formed by joining a rectangular plate-shaped member corresponding to the base portion 12 and a rectangular tubular member corresponding to the side wall portion 13, similar to the first modified example.

[0061] The manufacturing method for the gas cell 4 of this modified example includes, for example, a main body 10 having a base portion 12 and a side wall portion 13, with a through hole 16 provided in one of the four side walls of the side wall portion 13; a fitting step of inserting a transparent substrate 20 into the through hole 16 of the main body portion 10, joining the main body portion 10 and the transparent substrate 20, and fitting the transparent substrate 20 into the fitting portion 14; and a sealing step of sealing the through hole 16 with a sealing portion 17.

[0062] The preparation process is as described in the manufacturing method of the gas cell 1 above. The main body 10 having a through hole 16 on one surface of the side wall 13 may be manufactured by 3D printing, or a member consisting of a base 12 and a side wall 13 without a through hole 16 may be manufactured, and then a through hole may be formed on one surface of the side wall 13 using a technique such as etching.

[0063] In the fitting process, the transparent substrate 20 is inserted into the through hole 16 and slid to fit it into the fitting portion 14. The joining method for the main body 10 and the transparent substrate 20 can be the joining method described in the manufacturing method of the gas cell 1 above. In particular, in order to further improve the airtightness of the gas cell 4, it is preferable to apply an adhesive to the joining area of ​​the transparent substrate 20 in advance, insert it into the through hole 16 and fit it into the fitting portion 14, and then heat treat it.

[0064] The sealing process involves sealing the space outside the transparent substrate 20 within the through-hole 16 with a sealing agent to form a sealed portion 17. The sealing agent can be the bonding agent used to join the main body and the transparent substrate. It is preferable to further improve the airtightness of the gas cell 4 by heat-treating the sealing agent (preferably a bonding agent) after sealing.

[0065] The method for manufacturing a gas cell in which alkali metal atoms are sealed in the closed space 40 of the gas cell 4 (the method for sealing alkali metal atoms in the closed space 40) is as described in the manufacturing method of the gas cell 1 above.

[0066] The gas cells of the second and third embodiments are described below. As shown in the second and third embodiments, the gas cell of the present invention may have two or more openings in its main body. The gas cells of the second and third embodiments differ from those of the first embodiment in the number of transparent substrates and fitting parts, depending on the number of openings. The constituent materials, shape and size of the main body and transparent substrate, as well as the enclosed gas containing alkali metal atoms, are the same as those of the gas cell of the first embodiment in the gas cells of the second and third embodiments, unless otherwise specified.

[0067] [Second Embodiment] An example of a gas cell according to the second embodiment of the present invention is shown in Figures 7 and 8. Figure 7 is a perspective view showing a gas cell 5 according to this embodiment. Figure 8 is a cross-sectional view of the gas cell 5 along the line I-I in Figure 7. In the following description of the gas cell according to the second embodiment, components common to the gas cell of the first embodiment are denoted by the same reference numerals, and their detailed explanation is omitted. As shown in Figure 8, in the gas cell 5 according to this embodiment, the main body portion 10 consists of a rectangular tubular side wall portion 13, and the side wall portion 13 has two openings 11a and 11b on both ends of the central axis, facing each other with a closed space 40 in between. Also, fitting portions 14a and 14b are provided on the inside of the side wall portion 13 of the main body portion 10 (on the side of the opening 11a or 11b). The gas cell 5 has transparent substrates 20a and 20b, which are fitted into the fitting portions 14a and 14b, respectively. In this embodiment of the gas cell 5, as in the first embodiment, the transparent substrates 20a and 20b are fitted to the fitting portions 14a and 14b of the main body 10, respectively, thereby obtaining a gas cell 5 with excellent airtightness for the enclosed gas containing alkali metal atoms. Also, in this embodiment of the gas cell 5, as in the first embodiment, the thermal conductivity k of the main body 10 is 30 W·m －１ ・K －１ The above β·k is 20 W·m －１ ・K －１ That concludes the explanation. Therefore, the gas cell 5 according to this embodiment also exhibits excellent heat uniformity.

[0068] The transparent substrates 20a and 20b of the gas cell 5 according to this embodiment may differ in their constituent material, shape, and size, but it is preferable that they all be the same in terms of superior gas cell manufacturing and signal stability. The fitting portions 14a and 14b of the main body 10 are the same as the fitting portion 14 of the gas cell 1 of the first embodiment, including preferred forms. The gas cell 5 according to this embodiment can be manufactured in accordance with the manufacturing method of the gas cell 1 of the first embodiment.

[0069] In this embodiment, the main body 10 has two openings 11a and 11b that face each other across a closed space 40. When the gas cell 5 of this embodiment is used as a quantum sensor or the like, a light source that emits excitation light to excite alkali metal atoms is placed on one opening side (for example, opening 11a), and a photodetector that detects light that has passed through the closed space 40 is placed on the other opening side (for example, opening 11b).

[0070] The following modifications are also possible for the gas cell of this embodiment. In each modification, elements common to the gas cell 5 shown in Figure 8 are denoted by the same reference numerals, and their descriptions are omitted.

[0071] <Modification 1 of the Second Embodiment> A modification 1 of the gas cell according to this embodiment is shown in Figure 9. Figure 9 is a cross-sectional view showing the gas cell 6 according to this modification. In the gas cell 6 shown in Figure 9, the main body portion 10 has two openings 11a and 11b at positions facing each other across a closed space 40. The gas cell 6 has two transparent substrates 20a and 20b corresponding to these two openings 11a and 11b. The main body portion 10 also has a rectangular tubular side wall portion 13, and fitting portions 14a and 14b having frame-shaped lid portions 15a and 15b in a plan view are provided on the inside of both ends of the central axis of the side wall portion 13 (on the side of the opening 11a or 11b). The lid portions 15a and 15b are joined to the second main surface 22a of the transparent substrate 20a and the second main surface 22b of the transparent substrate 20b, respectively. As shown in the figure, the mating portion 14a has, for example, three orthogonal first mating surfaces 141a, a second mating surface 142a, and a third mating surface 143a. The first main surface 21a of the transparent substrate 20a is joined to the first mating surface 141a, the side surface 23a of the transparent substrate 20a is joined to the second mating surface 142a, and the second main surface 22a of the transparent substrate 20a is joined to the third mating surface 143a. Similarly, the mating portion 14b has, for example, three orthogonal first mating surfaces 141b, a second mating surface 142b, and a third mating surface 143b. The first main surface 21b of the transparent substrate 20b is joined to the first mating surface 141b, the side surface 23b of the transparent substrate 20b is joined to the second mating surface 142b, and the second main surface 22b of the transparent substrate 20b is joined to the third mating surface 143b. In this modified gas cell 6, the mating portion 14a is joined to the three surfaces of the transparent substrate 20a: the first main surface 21a, the second main surface 22a, and the side surface 23a, and the mating portion 14b is joined to the three surfaces of the transparent substrate 20b: the first main surface 21b, the second main surface 22b, and the side surface 23b. With this configuration, the bonding area between the main body 10 and the transparent substrates 20a and 20b is increased, which further improves airtightness and provides a gas cell with superior robustness when used in more severe environments.

[0072] The fitting portions 14a and 14b of the main body 10 in this modified example are the same as the fitting portion 14 of the main body 10 in Modification Example 2 of the first embodiment, including the preferred form. The gas cell 6 according to this modified example can be manufactured in accordance with the manufacturing method of the gas cell 3 according to Modification Example 2 of the first embodiment.

[0073] <Modification 2 of the Second Embodiment> A modification 2 of the gas cell according to this embodiment is shown in Figure 10. Figure 10 is a cross-sectional view showing the gas cell 7 according to this modification. In the gas cell 7 shown in Figure 10, the main body portion 10 has two openings 11a and 11b at positions facing each other across a closed space 40. The gas cell 7 has two transparent substrates 20a and 20b corresponding to these two openings 11a and 11b. The main body portion 10 has a rectangular tubular side wall portion 13, and fitting portions 14a and 14b are provided on the inside of both ends of the central axis of the side wall portion 13 (on the side of the opening 11a or 11b), into which the transparent substrates 20a and 20b are fitted, respectively. Furthermore, on one side of one of the four side walls of the side wall portion 13, a through hole 16a is provided at the position where the fitting portions 14a and 14b are provided, corresponding to one of the side surfaces 23a of the transparent substrate 20a and one of the side surfaces 23b of the transparent substrate 20b. The main body portion 10 of the gas cell 7 has a structure in which the transparent substrates 20a and 20b are slid into the through holes 16a and 16b and fitted together at the fitting portions 14a and 14b, respectively. In addition, the space outside the transparent substrate 20a within the through hole 16a is sealed by the sealing portion 17a, and the space outside the transparent substrate 20b within the through hole 16b is sealed by the sealing portion 17b. In this modified gas cell 7, the fitting portion 14a is joined to three surfaces of the transparent substrate 20a: the first main surface 21a, the second main surface 22a, and the side surface 23a, and the fitting portion 14b is joined to three surfaces of the transparent substrate 20b: the first main surface 21b, the second main surface 22b, and the side surface 23b. This configuration increases the bonding area between the main body 10 and the transparent substrates 20a and 20b, thereby further improving airtightness and providing a gas cell with superior robustness for use in harsher environments.

[0074] The fitting portions 14a and 14b of the main body portion 10 in this modified example are the same as the fitting portion 14 of the main body portion 10 in Modification 3 of the first embodiment, including preferred forms. The sealing portions 17a and 17b of this modified example are the same as the sealing portion 17 of the main body portion 10 in Modification 3 of the first embodiment, including preferred forms. In the gas cell 7 shown in Figure 10, the through holes 16a and 16b are provided on the same side wall of the side wall portion 13, but in this modified example, the two through holes may be provided on different side walls of the side wall portion. Whether or not to provide the two through holes on the same side wall portion is selected as appropriate depending on the structural design and manufacturing method. The gas cell 7 according to this modified example can be manufactured in accordance with the manufacturing method of the gas cell 4 according to Modification 3 of the first embodiment.

[0075] [Third Embodiment] An example of a gas cell according to the third embodiment of the present invention is shown in Figures 11 and 12. Figure 11 is a perspective view showing a gas cell 8 according to this embodiment. Figure 12 is a cross-sectional view of the gas cell 8 along the line I-I in Figure 11. In the following description of the gas cell according to the third embodiment, components common to the gas cells of the first and second embodiments are denoted by the same reference numerals, and their detailed descriptions are omitted. As shown in the figure, in the gas cell 8 according to this embodiment, the main body 10 has two base portions 12 and side wall portions 13. The two base portions 12 are plate-shaped with a rectangular outer shape in plan view and face each other across a closed space 40. The side wall portions 13 have four side walls provided so as to surround the entire circumference of each peripheral edge of the base portion 12. The main body 10 has openings 11a to 11d provided in each of the four side walls of the side wall portions 13. The gas cell 8 has four transparent substrates 20a to 20d corresponding to these four openings 11a to 11d. Each of the transparent substrates 20a to 20d has a first main surface 21a to 21d that, together with the main body 10, constitutes a closed space 40 for encapsulating alkali metal atoms, a second main surface 22a to 22d opposite to the first main surface 21a to 21d, and a side surface 23a to 23d incorporated into the outer edges of the first main surface 21a to 21d and the second main surface 22a to 22d. The base 12 and side wall 13 of the main body 10 are provided with fitting portions 14a to 14d into which the transparent substrates 20a to 20d are fitted. As shown in the figure, each of the fitting portions 14a to 14d has, for example, two orthogonal first fitting surfaces 141a to 141d and second fitting surfaces 142a to 142d. The first main surfaces 21a to 21d of the transparent substrates 20a to 20d are joined to the first mating surfaces 141a to 141d, respectively, and the side surfaces 23a to 23d of the transparent substrates 20a to 20d are joined to the second mating surfaces 142a to 142d, respectively. In the gas cell 8 according to this embodiment, as in the first embodiment, the transparent substrates 20a to 20d are fitted to the mating portions 14a to 14d of the main body 10, respectively, thereby obtaining a gas cell 8 with excellent airtightness for the enclosed gas containing alkali metal atoms. Also, in the gas cell 8 according to this embodiment, as in the first embodiment, the thermal conductivity k of the main body 10 is 30 W・m －１ ・K －１ The above β·k is 20 W·m－１ ・K －１ That concludes the explanation. Therefore, the gas cell 8 according to this embodiment also exhibits excellent heat uniformity.

[0076] In the gas cell 8 of this embodiment, the four openings 11a to 11d consist of two sets: a set of openings 11a and 11b facing each other across the closed space 40, and a set of openings 11c and 11d facing each other across the closed space 40. When the gas cell 8 of this embodiment is used in a quantum sensor or the like, two different alkali metal atoms are sealed in the closed space 40, and two sets of light sources and photodetectors suitable for each alkali metal are prepared, and the same sets of light sources and photodetectors are arranged to face each other across the gas cell 8. For example, a light source corresponding to alkali metal A is placed on the opening 11a side, a photodetector corresponding to alkali metal A is placed on the opening 11b side, a light source corresponding to alkali metal B is placed on the opening 11c side, and a photodetector corresponding to alkali metal B is placed on the opening 11d side. The positions of the same sets of light sources and photodetectors may be reversed from the above embodiment depending on the design of the quantum sensor.

[0077] The transparent substrates 20a to 20d of the gas cell 8 may differ in their constituent material, shape, and size, but it is preferable that they all be the same in terms of superior gas cell manufacturing and signal stability. The fitting portions 14a to 14d of the main body 10 are the same as the fitting portion 14 of the gas cell 1 of the first embodiment, including preferred forms. The external shape of the gas cell 8 shown in Figure 12 is a rectangular parallelepiped (cube), but the external shape of the gas cell in this embodiment can be selected to suit the design of the quantum sensor. The external shape of the gas cell in this embodiment may be, for example, a polygonal prism or polygonal shape other than a rectangular parallelepiped. The gas cell 8 according to this embodiment can be manufactured in accordance with the manufacturing method of the gas cell 1 of the first embodiment.

[0078] The following modifications are also possible for the gas cell of this embodiment. In these modifications, elements common to the gas cell 8 shown in Figure 12 are given the same reference numerals, and their descriptions are omitted.

[0079] <Modification of the Third Embodiment> Modifications of the gas cell according to this embodiment are shown in Figures 13 and 14. Figure 13 is a perspective view showing the gas cell 9 according to this embodiment. Figure 14 is a cross-sectional view of the gas cell 9 along the line I-I in Figure 13. In the gas cell 9 according to this embodiment, the main body portion 10 has two base portions 12 and side wall portions 13 provided so as to surround the entire circumference of each peripheral edge of the base portion 12. The main body portion 10 also has openings 11a to 11d provided in each of the four side walls of the side wall portion 13. The gas cell 9 has four transparent substrates 20a to 20d corresponding to these four openings 11a to 11d. The base portions 12 and side wall portions 13 of the main body portion 10 are provided with fitting portions 14a to 14d into which the transparent substrates 20a to 20d are fitted. Each of the fitting portions 14a to 14d has a frame-shaped lid portion 15a to 15d in plan view, and the lid portions 15a to 15d are joined to the second main surfaces 22a to 22d of the transparent substrates 20a to 20d, respectively. In this modified gas cell 9, each of the fitting portions 14a to 14d is joined to the first main surface, the second main surface, and the side surface of the transparent substrates 20a to 20d. This configuration increases the bonding area between the main body portion 10 and each of the transparent substrates 20a to 20d, thereby further improving airtightness and providing a gas cell with superior robustness for use in harsher environments.

[0080] The fitting portions 14a to 14d of the main body 10 in this modified example are the same as the fitting portion 14 of the main body 10 in Modification Example 2 of the First Embodiment, including the preferred form. The gas cell 9 according to this modified example can be manufactured in accordance with the manufacturing method of the gas cell 3 according to Modification Example 2 of the First Embodiment.

[0081] The gas cell according to the present invention, as described above, is suitably used in quantum sensors such as atomic oscillators and optical pumping magnetic sensors. An example of a quantum sensor is an embodiment comprising the gas cell according to the present invention, a light source emitting excitation light to excite electrons of alkali metal atoms contained in the gas cell, and a photodetector for detecting light transmitted through the gas cell. A known laser light source can be used as the light source emitting the excitation light. The excitation light may be linearly polarized or circularly polarized. The photodetector for detecting light transmitted through the gas cell may detect the excitation light transmitted through the gas cell, or it may detect probe light different from the excitation light transmitted through the gas cell. The quantum sensor may also include a coil for adjusting the magnetic field within the gas cell, a power supply for the coil, and a magnetic shield that covers the gas cell and attenuates or blocks external magnetic fields. Furthermore, the gas cell according to the present invention can also be applied to airtight containers in devices such as wavelength conversion members.

[0082] The present invention will be described in more detail below based on examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples. Examples 1 to 10 shown later are examples, and Examples 11 to 17 are comparative examples.

[0083] [Example 1] A heat conduction simulation was performed using the following method. First, a three-dimensional model of a gas cell with a shape that is a modified version of the embodiment (gas cell 5) shown in Figures 7 and 8 was created. Specifically, using Fujitsu iCAD SX, a three-dimensional model was generated with external dimensions of 15 mm in length, 15 mm in width, and 15 mm in height, and internal dimensions of 7 mm in length, 7 mm in width, and 12 mm in height. Here, the internal dimensions of 7 mm in length and 7 mm in width refer to the minimum distance between opposing side wall portions 13 that constitute the main body portion 10 being 7 mm. The internal height of 12 mm refers to the minimum distance between opposing transparent substrates 20 being 12 mm. The transparent substrate was set to be 12 mm in length, 12 mm in width, and 1.1 mm in thickness. In addition, in the above three-dimensional model, a sealing portion was provided on one surface constituting the side wall portion 13. The sealing portion was provided penetrating through the central part of the side wall portion 13 in the thickness direction. Furthermore, the shape of the sealing portion was a combination of a cylindrical shape with a diameter of 1 mm and a thickness of 3 mm in the thickness direction of the side wall portion 13, and a cylindrical shape with a diameter of 6 mm and a thickness of 1 mm in the thickness direction of the side wall portion 13, extending from the surface of the side wall portion 13 that constitutes the closed space 40. In addition, in the above three-dimensional model, a 5 mm x 5 mm heater was placed in the center of the two surfaces of the side wall portion 13 excluding the surface of the side wall portion 13 where the sealing portion is located and the surface of the side wall portion 13 opposite to that surface. That is, the 5 mm x 5 mm heater was placed on the two opposing surfaces of the side wall portion 13, on the surface opposite to the side that constitutes the closed space 40. The above 5 mm x 5 mm heater simulates the shape of a ceramic heater.

[0084] In Example 1, the main body material was SiSiC, and the transparent substrate material was glass. The sealing material was also glass. The thermal conductivity of each component is as shown in the <List of Thermal Properties> below. The above β・k (the product of β, which is the surface area of ​​the main body divided by the surface area of ​​the gas cell, and the above thermal conductivity k) was calculated and is shown in the table below. Using the above three-dimensional model, a thermal conduction simulation was performed using Fujitsu's CAE-linked software FJKSWAD. The heater output was as shown in Table 2 below. That is, the output of each of the two heaters was set to 2.5 W. The thermal conduction simulation was performed by setting the heater output to the output shown in Table 2 below, followed by a steady-state thermal conduction analysis. The heat generation amount of the heater was calculated assuming a uniform power density within the heater. The ambient temperature was 25°C, and the heat transfer coefficient of the outer surface was 14.5 W / m². ２ Natural convection was assumed. The table below shows ΔT (unit: °C), which is the maximum temperature difference on the outer surface of the entire gas cell, as an indicator of uniformity. In practical terms, ΔT is preferably 35°C or less, more preferably 30°C or less, and even more preferably 25°C or less.

[0085] [Examples 2 to 17] In Examples 2 to 17, the shape and material of the three-dimensional model were changed as shown in Table 2 below, and the above ΔT was calculated by performing a heat conduction simulation in the same manner as in Example 1. For example, in Example 2, a heat conduction simulation was performed using a three-dimensional model in which only one heater was installed. In Example 3, the shape of the heater was set to 13 mm x 12 mm. The shape of the heater described above simulates the shape of a polyimide heater. In Examples 4, 7, and 11, the number of transparent substrates in the gas cell was set to four. That is, in the gas cell 8 configuration shown in Figures 11 and 12, a heat conduction simulation was performed using a three-dimensional model in which a heater is installed on the base 12 where no transparent substrate 20 is placed. For three-dimensional models with four transparent substrates, such as in Example 4, the sealing portion was placed on the surface opposite to the surface where the heater is placed. In Examples 15 to 17, a three-dimensional model was created by hollowing out a rectangular prism with sides of 12 mm from the center of a rectangular prism with sides of 15 mm, and heat conduction simulations were performed using glass as the material. When creating the above three-dimensional model, the faces of the rectangular prism with sides of 15 mm and the faces of the rectangular prism with sides of 12 mm were made parallel to each other.

[0086] [List of Thermophysical Properties] Table 1 below shows the thermophysical properties of the materials used in each example. In Table 1, "d" represents density (unit: g / cm³). ３ ) and "k" is the thermal conductivity (unit: W・m －１ ・K －１ ) and "Cp" is the specific heat capacity (unit: J·g) －１ ・K －１ )

[0087]

[0088] [Results] Table 2 shows the shape of the three-dimensional model for each of the above examples, the material of each component, and the ΔT results calculated by performing heat conduction simulations. For convenience, in Examples 15 to 17, it is assumed that there are six transparent substrates.

[0089]

[0090] From the results shown in Table 2, the thermal conductivity k of the main body is 30 W·m －１ ・K －１ That is all, β·k is 20 W·m －１ ・K －１ In Examples 1 to 10 described above, the value of ΔT is 35°C or less, indicating excellent uniformity of heating. On the other hand, β·k is 20 W·m －１ ・K －１ In Example 11, where the value was less than 35°C, the ΔT value was greater than 35°C, indicating that the uniformity of the heat was inferior compared to Examples 1 to 10. Furthermore, the thermal conductivity k of the main body was 30 W·m. －１ ・K －１ In Examples 12 to 17, where the value of ΔT was less than 35°C, the uniformity of the heat distribution was inferior compared to Examples 1 to 10. From a comparison of Examples 1, 5, and 8, the thermal conductivity k of the main body was 80 W·m －１ ・K －１ (More preferably 180 W·m) －１ ・K －１ In the above cases, it was confirmed that the value of ΔT was smaller and the uniformity of heating was better. Furthermore, from a comparison of Example 2, Example 6, and Example 9, it was found that even when there is only one heater, the thermal conductivity k of the main body is 80 W·m －１ ・K －１ (More preferably 180 W·m) －１ ・K －１ In the above cases, it was confirmed that the value of ΔT was smaller and the uniformity of heating was better. If uniformity of heating can be ensured even when the number of heaters is reduced, the quantum sensor equipped with a gas cell can be made smaller. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-217392, filed on December 12, 2024, are incorporated herein by reference as disclosure of the present invention.

[0091] 1, 2, 3, 4, 5, 6, 7, 8, 9: Gascell 10: Body 11, 11a, 11b, 11c, 11d: Opening 12, 12a, 12b: Base 13: Sidewall 14, 14a, 14b, 14c, 14d: Fitting 15, 15a, 15b, 15c, 15d: Cover 16, 16a, 16b: Through Hole 17, 17a, 17b: Sealing 20, 20a, 20b, 20c, 20d: Transparent Substrate 21, 21a, 21b, 21c, 21d: First Main Surface 22, 22a, 22b, 22c, 22d: Second Main Surface 23, 23a, 23b, 23c, 23d Side surface 30; Reflective component 40; Closed space 141, 141a, 141b, 141c, 141d; First mating surface 142, 142a, 142b, 142c, 142d; Second mating surface 143, 143a, 143b; Third mating surface

Claims

1. A gas cell in which alkali metal atoms are sealed inside, wherein the gas cell comprises a main body having at least one opening and a transparent substrate provided in the opening, and the thermal conductivity k of the main body is 30 W·m －１ ・K －１ The above is true, and the product of β, which is the value obtained by dividing the surface area of ​​the main body by the surface area of ​​the gas cell, and the thermal conductivity k, β·k is 20 W·m －１ ・K －１ That's all, gas cell.

2. The thermal conductivity k of the main body is 80 W·m －１ ・K －１ The gas cell according to claim 1.

3. The thermal conductivity of the main body is 180 W·m －１ ・K －１ The gas cell according to claim 1, wherein the gas cell is substantially composed of SiSiC.

4. The gas cell according to claim 1, wherein the main body portion comprises a fitting portion into which the transparent substrate is fitted.

5. The gas cell according to claim 4, wherein the transparent substrate has a first main surface that together with the main body constitutes a closed space for encapsulating the alkali metal atoms, a second main surface opposite to the first main surface, and a side surface that is incorporated into the outer edges of the first and second main surfaces, and the fitting portion of the main body is joined to at least two of the first main surface, the second main surface, and the side surface of the transparent substrate.

6. The gas cell according to claim 1, wherein the main body portion has a sealing portion for sealing alkali metals inside.

7. The gas cell according to claim 1, wherein the main body portion has one opening, and a reflective member is provided inside the main body portion at a position facing the opening.

8. The gas cell according to claim 1, wherein the main body portion has two or more openings.

9. A quantum sensor comprising: a gas cell according to any one of claims 1 to 8; a light source that emits excitation light to excite electrons of alkali metal atoms contained in the gas cell; and a photodetector that detects light transmitted through the gas cell.

10. The quantum sensor according to claim 9, which is an optical pumping magnetic sensor.

11. The quantum sensor according to claim 9, which is an atomic oscillator.

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