WO2024096158A1

WO2024096158A1 - Vapor cell structure for preventing metal condensation

Info

Publication number: WO2024096158A1
Application number: PCT/KR2022/017009
Authority: WO
Inventors: 홍현규; 홍영표; 배인호; 유재근; 강노원
Original assignee: 한국표준과학연구원
Priority date: 2022-11-02
Filing date: 2022-11-02
Publication date: 2024-05-10
Also published as: KR20240062536A

Abstract

The present invention relates to a vapor cell structure manufactured by a micro-electro mechanical systems (MEMS) process. Disclosed is a vapor cell structure comprising: a frame having at least one hollow formed through one portion thereof; substrates sealing the respective sides of the hollow; and metal nanoparticles which are disposed on one side of a substrate, overlap the hollow in the direction in which the hollow extends, and when light waves are incident within a preset wavelength range, induce surface plasmon resonance by light waves of the same wavelength in order to detect the atomic energy level. Accordingly, a temperature deviation depending on the location of the vapor cell structure is further alleviated, the phenomenon of metal condensation on the path of the light waves can be prevented, and the transmittance of light waves incident on the vapor cell structure can be further improved.

Description

Vapor cell structure to prevent metal condensation

The present invention relates to a vapor cell structure manufactured through a MEMS (Micro-Electro Mechanical Systems) process, and more specifically, to a vapor cell structure in which the transmittance of incident light can be further improved without a separate additional heating means.

The present invention was derived from research conducted as part of the Radio Industry Core Technology Development Project of the Korea IT Planning and Evaluation Institute below.

[Project management (professional) organization name] Information and Communications Planning and Evaluation Institute

[Research Project Name] Radio Industry Core Technology Development Project (162554313013125002531305)

[Research project name] Development of non-metal-based ultra-sensitive electric field detection technology

[Name of project carrying out organization] Korea Research Institute of Standards and Science

[Contribution rate] 1/1

[Research period] 2021.04.01 ~ 2022.12.31

MEMS (Micro-Electro Mechanical Systems) refers to ultra-small precision mechanical systems ranging in size from a few millimeters to several nanometers. In general, MEMS refers to the manufacturing process and technology of ultra-fine mechanical structures such as ultra-high-density integrated circuits manufactured by processing silicon, crystal, glass, etc.

The MEMS process can also be used to miniaturize and mass produce atomic vapor cells. The vapor cell is provided in a device that detects the energy level of the atoms so that light waves can be irradiated to the atomic vapors. In particular, miniaturized vapor cells can be used in various types of chip-scale devices, including atomic clocks and atomic magnetometers.

The above-mentioned vapor cell refers to a cell in which vaporized atoms are mounted in an internal space, and both sides are sealed by transparent glass. When a specific light wave is incident on a vapor cell, the energy state of the atom changes depending on the energy level of the gas atom mounted inside, and absorption or emission of photons may occur. This change in energy state can be used in various fields such as atomic clocks, atomic magnetometers, and gyroscopes. However, in order to detect changes in energy state more precisely and ensure long-term operational reliability, it is necessary to maintain a high transmittance of light waves incident on atoms by preventing the metal condensed within the vapor cell from interfering with the progress of light waves. .

However, the vapor cell manufactured through the MEMS process has a small area through which light waves pass, and the light waves can only approach two of the six sides (the entrance surface and the exit surface). Accordingly, when a temperature difference occurs between the outside and the center of the frame, gas atoms condense at the center, which is a relatively low temperature point, and inhibit the transmission of light waves to the vapor cell.

Therefore, the development of a vapor cell structure that can prevent metal condensation and improve the transmittance of incident light by mitigating the temperature difference depending on the position of the opening through which light waves pass may be considered. In particular, the development of a vapor cell structure that can alleviate temperature deviation by utilizing light waves irradiated for energy level detection without any additional heating means may be considered.

Korean Patent Publication No. 10-2018893 discloses a vapor cell and a method of manufacturing the same. Specifically, a vapor cell that seals an internal space by irradiating a laser pulse to a bonding layer of a sealing paste and a method of manufacturing the same are disclosed.

However, this type of vapor cell does not disclose a structure for resolving temperature differences depending on the vapor cell location.

Korean Patent Publication No. 10-1709557 discloses a vapor cell equipped with electro-optical functions for a chip-scale atomic clock. Specifically, a vapor cell is disclosed that maintains a constant temperature by applying voltage to a silicon body.

However, this type of vapor cell requires a separate power source and connection configuration to alleviate temperature differences depending on location.

(Patent Document 1) Korean Patent Publication No. 10-2018893 (2019.09.05.)

(Patent Document 2) Korean Patent Publication No. 10-1709557 (2017.02.23.)

One object of the present invention is to provide a vapor cell structure manufactured through a MEMS (Micro-Electro Mechanical Systems) process in which the transmittance of incident light can be further improved without a separate additional heating means.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below. will be.

In order to achieve the above object, the vapor cell structure according to an embodiment of the present invention is a vapor cell structure manufactured through a MEMS (Micro-Electro Mechanical Systems) process, and at least one hollow is formed through a portion. frame; a first substrate coupled to one side of the frame to seal one side of the hollow; a second substrate coupled to the other side of the frame to seal the other side of the hollow; and disposed on a side of one of the first substrate and the second substrate opposite to the frame, overlapping the hollow in the extending direction of the hollow, and generating surface plasmon when a light wave within a preset wavelength range is incident. It contains nanoparticles formed from a metal material in which resonance is induced.

Additionally, the preset wavelength range may be 775 nm or more and 900 nm or less.

In addition, the nanoparticles include an interior angle formed in a spherical shape with a constant radius; And it may include an outer shell disposed radially outside the inner angle and formed to surround the outer peripheral surface of the inner angle to a certain thickness.

In addition, the preset wavelength range may be 775 nm or more and 900 nm or less, the radius of the inner angle may be 27 nm or more and 28 nm or less, and the thickness of the outer angle may be 3 nm or more and 4 nm or less.

Additionally, the inner shell may be formed of a silicon dioxide (SiO2) material, and the outer shell may be formed of a gold (Au) material.

Additionally, the hollow may contain alkaline vapor therein.

Additionally, the alkaline vapor may be rubidium (Rb) or cesium (Cs).

Additionally, the frame may be formed of a silicon (Si) material, and the first and second substrates may be formed of a glass material.

Among the various effects of the present invention, the effects that can be obtained through the above-described solution are as follows.

The vapor cell structure according to an embodiment of the present invention includes a frame, a first substrate, a second substrate, and nanoparticles. The first substrate and the second substrate seal the hollow formed through the frame on both sides. At this time, nanoparticles that overlap the hollow in the extending direction of the hollow are disposed on one side of either the first or second substrate. Nanoparticles are heated by inducing surface plasmon resonance when light waves within a preset wavelength range are incident to detect the atomic energy level.

Therefore, as incident light is irradiated, the hollow is heated and the temperature difference between the outside of the frame and the vapor cell area can be further reduced. In other words, temperature differences depending on location can be more alleviated. Accordingly, gas atoms can be prevented from condensing intensively in a specific area. As a result, the transmittance of light waves incident on the vapor cell is further increased and a constant transmittance can be maintained over time.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a schematic diagram showing the relationship between a vapor cell structure, a light source, and a detector according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the vapor cell structure of FIG. 1.

FIG. 3 is an exploded perspective view showing the vapor cell structure of FIG. 1.

FIG. 4 is a front cross-sectional view showing the vapor cell structure of FIG. 1.

FIG. 5 is a conceptual diagram showing nanoparticles provided in the vapor cell structure of FIG. 1.

Figure 6 is a graph showing changes in absorption cross-section and scattering cross-section according to the wavelength of light waves incident on the vapor cell structure.

Figure 7 is a conceptual diagram showing temperature distribution according to each position of (a) a vapor cell structure according to the prior art and (b) a vapor cell structure according to an embodiment of the present invention.

Hereinafter, the vapor cell structure 10 according to an embodiment of the present invention will be described in more detail with reference to the drawings.

In the following description, in order to clarify the characteristics of the present invention, descriptions of some components may be omitted.

In this specification, the same reference numbers are assigned to the same components even in different embodiments, and duplicate descriptions thereof are omitted.

The attached drawings are only intended to facilitate understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the attached drawings.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

Hereinafter, the vapor cell structure 10 according to an embodiment of the present invention will be described with reference to FIG. 1.

The vapor cell structure 10 according to an embodiment of the present invention refers to a cell structure in which vaporized atoms are mounted in an internal space and both sides are sealed by transparent glass.

The vapor cell structure 10 can be used to detect a change in the energy level of gas atoms mounted therein. Specifically, when a specific light wave is incident on the vapor cell structure 10, the state of the atom may change depending on the energy level of the gas atom mounted therein, and photon absorption or emission may occur.

The vapor cell structure 10 receives incident light from the light source 20. In one embodiment, incident light generated from the light source 20 may be laser light.

A portion of the incident light irradiated to the vapor cell structure 10 is absorbed by atoms inside the vapor cell structure 10, and the remaining portion is emitted toward the detector 30. The detector 30 receives the emitted light that passes through the vapor cell structure 10 and detects changes in the energy level of atoms through it.

Hereinafter, the components of the vapor cell structure 10 will be described in more detail with reference to FIGS. 2 to 5.

In the illustrated embodiment, vapor cell structure 10 includes a frame 110, a substrate 120, and nanoparticles 130.

Frame 110 forms the exterior of vapor cell structure 10.

In the illustrated embodiment, the frame 110 is formed in the shape of a square pillar. However, the frame 110 is not limited to the shape shown and may be formed in various structures in which the hollow 111 can be formed. For example, the frame 110 may be formed in a disk or cylinder shape.

In one embodiment, the frame 110 may be formed of silicon (Si) material.

At least one hollow 111 is formed through a portion of the frame 110. At this time, the side of the hollow 111 is surrounded by the side wall 112. That is, the inner peripheral surface of the hollow 111 is formed by the side wall 112.

The hollow 111 forms an optical path for light waves incident on the vapor cell structure 10 and provides a space for accommodating gas atoms.

The hollow 111 is formed in a pillar shape that is open on both sides and extends in one direction. In the illustrated embodiment, the hollow 111 is formed in the shape of a square pillar that is open on the upper and lower sides and extends in the vertical direction. However, the hollow 111 is not limited to the shape shown and may be formed in various structures that do not interfere with the optical path of light waves incident on the vapor cell structure 10. For example, the hollow 111 may be formed in a cylindrical shape.

Gas atoms are accommodated inside the hollow 111. In one embodiment, alkaline vapor may be accommodated inside the hollow 111. In another embodiment, rubidium (Rb) vapor or cesium (Cs) vapor may be accommodated inside the hollow 111.

Additionally, a buffer gas may be injected into the hollow 111 in addition to the metal gas that is the object of measurement for changes by energy level.

In one embodiment, a plurality of hollows 111 may be provided in one frame 110.

The openings of the hollows 111 are each sealed by a substrate 120, which will be described later.

The substrate 120 serves to seal the hollow 111 and maintain high airtightness of the hollow 111.

The substrate 120 is bonded to both sides of the frame 110. At this time, the substrate 120 is coupled to the frame 110 so that the hollow 111 formed in the frame 110 can be completely blocked. That is, the substrate 120 overlaps the hollow 111 in the direction in which the hollow 111 extends.

In the illustrated embodiment, the substrate 120 includes a first substrate 121 and a second substrate 122.

The first substrate 121 and the second substrate 122 are coupled to the upper and lower surfaces of the frame 110, respectively, to seal the upper and lower openings of the hollow 111. The sides of the hollow 111 are surrounded by the side walls 112, so all sides of the hollow 111 can be completely sealed.

The substrate 120 is made of a material with high transparency. In one embodiment, the substrate 120 may be formed of a glass material.

Nanoparticles 130 are disposed on one side of the substrate 120.

Nanoparticles 130 generate heat when surface plasma resonance is induced by incident light.

Nanoparticles 130 are disposed on a side opposite to the frame 110 of either the first substrate 121 or the second substrate 122. Preferably, it is placed on the incident surface of either the first substrate 121 or the second substrate 122. In the illustrated embodiment, nanoparticles 130 are disposed on the upper surface of the first substrate 121.

Nanoparticles 130 overlap with the hollow 111 of the frame 110 in the extension direction of the hollow 111.

The nanoparticles 130 are formed of a metal material that is heated by inducing surface plasma resonance when a light wave within a preset wavelength range is incident to detect the energy level of the atom. In one embodiment, the preset wavelength range may be 775 nm or more and 900 nm or less. In another embodiment, the preset wavelength range may be 780 nm.

The nanoparticles 130 are arranged to face the hollow 111 of the frame 110 with the substrate 120 interposed therebetween. Accordingly, when the nanoparticles 130 are heated, the heat may be transferred to the hollow 111.

Therefore, as the incident light is irradiated, the hollow 111 is heated by resonance, and the temperature difference between the outside and the center of the frame 110 can be further reduced. That is, the temperature difference depending on the position of the vapor cell structure 10 can be more alleviated. This can prevent gas atoms from condensing intensively in specific areas. As a result, the transmittance of light waves incident on the vapor cell structure 10 can be further increased.

In the embodiment shown in Figure 5, the nanoparticle 130 consists of an inner shell 131 and an outer shell 132.

The inner angle 131 is formed in a spherical shape with a constant radius (Rc). In one embodiment, the interior cabinet 131 may be formed of silicon dioxide (SiO2).

An outer shell 132 is disposed radially outside the inner shell 131.

The outer shell 132 is formed to surround the outer peripheral surface of the inner shell 131 with a certain thickness ts. That is, the outer shell 132 is formed in a spherical shape with a certain thickness ts. In one embodiment, the outer shell 132 may be formed of gold (Au) material.

In one embodiment, the radius (Rc) of the inner angle 131 may be 27 nm or more and 28 nm or less, and the thickness (ts) of the outer angle 132 may be 3 nm or more and 4 nm or less.

Hereinafter, the conditions of the nanoparticles 130 required to heat the vapor cell structure 10 will be described with reference to FIG. 6.

FIG. 6 shows changes in the absorption cross-section and scattering cross-section depending on the wavelength of the light wave incident on the vapor cell structure 10.

The wavelength incident on the vapor cell structure 10 has a large absorption cross-section and a small scattering cross-section. Therefore, most of the light energy loss is used for heating the vapor cell structure 10 through absorption of the nanoparticles 130.

According to the graph shown in FIG. 6, when the wavelength of incident light is about 780 nm, the absorption cross-sectional area is about 2.3 x 10-14 m2, which is a relatively large value compared to other wavelengths.

Assuming that the inner angle 131 radius (Rc) of the nanoparticle 130 is 27.8 nm and the outer angle 132 thickness (ts) is 3.7 nm, the general heating intensity per unit area is 1 mW/mm2 or less, so per unit particle The absorption power will be less than 10-11W. That is, in order to satisfy a heating rate of 1 μW, approximately 105 unit nanoparticles 130 will need to be provided.

However, the above-mentioned results are only examples, and the size and number of nanoparticles 130 may be derived differently depending on changes in other conditions, such as the material of the nanoparticles 130 and the light wave incident on the vapor cell structure 10. there is.

Hereinafter, the change in temperature distribution of the vapor cell structure 10 depending on whether the nanoparticles 130 are disposed will be described with reference to FIG. 7.

FIG. 7 shows temperature distribution depending on the position of the vapor cell structure 10.

Figure 7(a) shows the temperature distribution of the vapor cell structure 10 according to the prior art. That is, it shows the temperature distribution of the vapor cell structure 10 in a state in which the nanoparticles 130 are not disposed.

When heat is transferred to the frame 110 of the vapor cell structure 10 of FIG. 7(a), the frame 110 is heated from the outside, generating a temperature difference between the outside and the center. In the embodiment shown in Figure 7(a), while the outside of the frame 110 is heated to 100°C, the central hollow 111 is only 94°C, showing a temperature difference of 6°C between the outside and the center. can confirm.

Figure 7(b) shows the temperature distribution of the vapor cell structure 10 according to an embodiment of the present invention. That is, it shows the temperature distribution of the vapor cell structure 10 with the nanoparticles 130 disposed on one side of the substrate 120.

When light waves within a preset wavelength range for detecting the energy level of atoms are irradiated to the vapor cell structure 10 of FIG. 7(b), surface plasma resonance is induced in the nanoparticles 130, thereby increasing the temperature around the nanoparticles 130. rises. The nanoparticles 130 overlap the hollow 111 in the direction in which the hollow 111 extends. When the nanoparticles 130 are heated, the temperature of the hollow 111 also increases. Accordingly, the temperature difference between the outside and the center of the frame 110 can be reduced.

In the embodiment shown in FIG. 7(b), while the outside of the frame 110 is heated to 100°C, the central hollow 111 shows a temperature distribution of about 97 to 98°C. In other words, it can be seen that there is a temperature difference of about 2 to 3 degrees Celsius between the outside and the center. Through this, it can be confirmed that the temperature difference depending on the position of the vapor cell structure 10 is more relaxed compared to the embodiment shown in FIG. 7(a). In addition, it can be confirmed that the lowest temperature point, which is a point where metal is likely to condense, is not located on the path of light waves.

As a result, it can be expected that as the nanoparticles 130 are arranged to face the hollow 111 with the substrate 120 in between, intensive condensation of gas atoms in a specific area is prevented and the transmittance of incident light is increased. will be.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to the configuration of the above-described embodiments.

In addition, the present invention can be modified and changed in various ways by those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below.

Furthermore, the above embodiments may be configured by selectively combining all or part of each embodiment so that various modifications can be made.

(Explanation of symbols)

10: Vapor cell structure

110: frame

111: hollow

112: side wall

120: substrate

121: first substrate

122: second substrate

130: Nanoparticles

131: Cabinet

132: outer shell

20: light source

30: detector

Claims

A vapor cell structure manufactured through a MEMS (Micro-Electro Mechanical Systems) process,

A frame having at least one hollow formed through one portion;

a first substrate coupled to one side of the frame to seal one side of the hollow;

a second substrate coupled to the other side of the frame to seal the other side of the hollow; and

It is disposed on a side of either the first substrate or the second substrate opposite to the frame, and overlaps the hollow in the extending direction of the hollow, and when a light wave within a preset wavelength range is incident, surface plasmon resonance occurs. Containing nanoparticles formed from this derived metal material,

Vapor cell structure.
According to paragraph 1,

The preset wavelength range is,

775 nm or more and 900 nm or less,

Vapor cell structure.
According to paragraph 1,

The nanoparticles are,

An interior angle formed in the shape of a sphere of constant radius; and

An outer shell disposed radially outside the inner angle and formed to surround the outer peripheral surface of the inner angle to a certain thickness,

Vapor cell structure.
According to clause 3,

The preset wavelength range is,

775 nm or more and 900 nm or less,

The radius of the interior angle is,

27nm or more and 28nm or less,

The thickness of the outer shell is,

3 nm or more and 4 nm or less,

Vapor cell structure.
According to clause 3,

The above cabinet is:

It is made of silicon dioxide (SiO2) material,

The outer shell is,

Formed from gold (Au) material,

Vapor cell structure.
According to paragraph 1,

The hollow is,

Alkaline vapor is accommodated therein,

Vapor cell structure.
According to clause 6,

The alkaline vapor is rubidium (Rb) or cesium (Cs),

Vapor cell structure.
According to paragraph 1,

The frame is,

Made of silicon (Si) material,

The first and second substrates are:

Formed from glass material,

Vapor cell structure.