JP2022552107A - Fabrication of a vapor cell having one or more optical windows bonded to a dielectric body - Google Patents

Abstract

In general aspect, a method of manufacturing a vapor cell is presented. The method includes obtaining a dielectric body having a surface defining an opening to a cavity in the dielectric body. The method further includes obtaining an optical window that includes the surface. A surface of the dielectric body and a surface of the optical window are each modified to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands. The method additionally includes disposing steam or a source of steam within the cavity. The altered surface of the dielectric body is brought into contact with the altered surface of the optical window to form a seal around the opening to the cavity. The seal comprises metal-oxygen bonds formed by reacting a first plurality of hydroxyl ligands with a second plurality of hydroxyl ligands during contact of the modified surface. [Selection drawing] Fig. 3

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. patent application Ser. incorporated into the specification.

The following description relates to vapor cells and methods of making them.

A vapor cell is manufactured by sealing a vapor or gas within an enclosed volume. To introduce steam or gas into the enclosed volume, the steam cell may include a glass-formed conduit, called a stem, that fuses when sufficient steam or gas enters the enclosed volume ( fuse-off). However, fused conduits protrude from the vapor cell, making the vapor cell fragile, difficult to package, and can disrupt the electric field measured in the vapor cell. Vapor cells are also typically manufactured using an anodic bond process. Anodic bonding processes require high temperatures and voltages and can outgas volatile species during bond formation. High temperatures prevent anti-mitigation coatings from being applied to the vapor cell, and volatile species can contaminate the vapor or gas within the vapor cell. A vapor cell and manufacturing method that avoids or mitigates these drawbacks is desired.

A method of manufacturing a vapor cell comprising obtaining a dielectric body including a surface defining an opening to a cavity of the dielectric body and obtaining an optical window including the surface. modifying the surface of the dielectric body and the surface of the optical window to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands, respectively; and vapor or a source of vapor. placing the (source) within the cavity and the modified surface of the dielectric body to the modified surface of the optical window to form a seal around the opening to the cavity; contacting, wherein the seal comprises metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contacting of the modified surface. and a method.

1 is a perspective exploded view of an exemplary vapor cell having a dielectric body and optical windows; FIG. 1B is a perspective view of the exemplary vapor cell of FIG. 1A, but with the optical window contact bonded to the dielectric body; FIG. 1 is a perspective exploded view of an exemplary vapor cell having two optical windows; FIG. 2B is a perspective view of the exemplary vapor cell 100 of FIG. 2A, but with both optical windows bonded to the dielectric body of the exemplary vapor cell; FIG. 1A-1D are diagrams of an exemplary vapor cell shown in perspective, top, and side views having a dielectric body formed of silicon and two optical windows formed of glass; 1A-1D are diagrams of an exemplary vapor cell shown in perspective, top, and side views having a dielectric body formed of glass and two optical windows formed of glass; 1 is a perspective view of an exemplary vapor cell including a circular dielectric body and a cavity defined by a square outer wall and a circular inner wall of the circular dielectric body; FIG. 1 is a perspective view of an exemplary vapor cell including a square dielectric body and a cavity defined by circular outer and inner walls of the square dielectric body; FIG. 1 is a perspective view of an exemplary vapor cell including a circular dielectric body and a cavity defined by circular outer and inner circular walls of the circular dielectric body; FIG.

Many applications in atom-based sensing require small stemless vapor cells with high-purity gas samples inside. These types of vapor cells are difficult to manufacture in large quantities, especially when the vapor cells require well-controlled, pure samples of atoms or molecules. Currently, the optimal vapor cells for such applications are fabricated using anodic junctions, which require high temperatures and voltages. However, during the anodic bonding process, outgassing often occurs within the vapor cell, introducing volatile contaminants into the internal vapor. Such contaminants can degrade vapor cell performance during atom-based sensing applications. Moreover, the high temperatures and voltages associated with anodic bonding also prevent anti-mitigation coatings from being applied to vapor cells.

Furthermore, stems in vapor cells are undesirable for many applications such as magnetometric, time sensing, and atom-based electric field sensing. The stem makes the vapor cell fragile, difficult to package, and disturbs the electromagnetic field to be measured. For atom-based sensing of electromagnetic fields, it is important that the size of the vapor cell is much smaller than the wavelength of the electromagnetic field to be detected. The presence of the stem prevents miniaturization of the vapor cell to dimensions smaller than the wavelength of the electromagnetic field to be detected. Additionally, the vapor cell is desirably manufactured to allow transmission of light into cavities containing atoms and/or molecules.

Small stemless vapor cells, which can hold pure samples of atoms or molecules, are important for atomic and molecular-based sensing. Applications such as vapor cell-based atomic clocks and sensors can enable room temperature operation of useful metrology devices that are self-calibrated and can outperform conventional devices. As the world becomes more standardized and connected, these types of equipment become increasingly important as the demands for precision and accuracy of electromagnetic field sensing and timing increase. For example, field calibration of radar systems by over-the-air testing requires standard measurements that are typically made in large test facilities. Clocks and accelerometers that can meet the demands of GPS applications in areas where GPS is not provided, as well as handle GPS dropouts, can benefit from such vapor cells. . Current coherent population trapping (CPT) atomic clocks operate with large amounts of buffer gas, which allows the use of anodic junctions to seal the vapor cells used in these applications. However, pure vapor samples of alkali atoms can enable other types of devices, including various types of clocks. For example, vapor cell magnetometers requiring spin-preserving anti-relaxation coatings are another application for this vapor cell preparation method.

In some aspects of what is described herein, a vapor cell for atom-based sensing is presented, including methods of fabrication thereof. In many variations, the vapor cells are small (eg, less than 1 mm ³ ) and stemless. However, larger vapor cells with adjustable geometry are also possible. The vapor cell can be made sufficiently small compared to the wavelength of the electromagnetic field measured in the vapor cell so that the scattering cross section of the vapor cell is reduced below the geometric cross section. Eliminating stems can further reduce the scattering cross section as well as reduce the distortion of the measured electromagnetic field. This manufacturing method makes it possible to fabricate such a vapor cell. This method can be based on creating an array of stemless vapor cells on a large substrate and then cutting the vapor cells using either a dicing saw or a laser. However, this method can also be based on individual chips corresponding to a single stemless vapor cell.

In this method, a frame is prepared that can be pumped out to low pressures (eg, less than 10 ^-9 Torr). The frame can be made by fabricating a cavity or hole in the substrate. Once the holes are fabricated, a strong high temperature bond such as anodic bonding or glass frit bonding can be used to bond an optical window or backing. Outgassing in such operation does not affect the vapor cell because the openings are not sealed, thereby allowing contaminant gases to escape. To seal the high purity gas within the vapor cell, the method performs a contact bond in a pure gas background environment. Contact bonding inserts a vaporizable source of alkali atoms (vaporizable alkali atom source) into the cavities or holes when a filling operation is performed, for example, when the cavities or holes of the frame are interspersed with an alkali metal. In some cases, it can also be formed in a pure vacuum.

Contact bonding for sealing the vapor cell works by using a plasma to chemically activate the surfaces of the frame and optical windows. Such activation may be supplemented with washing to create hydroxyl bonds (e.g., bonds to OH chemical groups) that ultimately form metal-oxygen bonds between the frame and window/cover. . For example, if the frame is made of silicon oxide (eg, quartz glass, single crystal quartz, etc.) and the optical window is glass containing silicon oxide, the metal-oxygen bond is a siloxane bond (ie, Si—O—Si). can include Siloxane contact bonding works well with frames and optical windows containing silicon oxide. However, other materials may be possible when coated with a layer of silicon oxide. For example, the front surface of the silicon frame can be coated with a layer of silicon oxide (eg, _SiO2 , _SiOx , etc.) to facilitate contact bonding between the optical window and the frame. After contact bonding, the vapor cell can be easily fiber bonded either by attaching the fiber directly to the window or by attaching a GRIN lens attached to the fiber to the vapor cell. Such coupling may allow the vapor cell to act as a sensor for sensing electromagnetic fields.

Referring now to FIG. 1A, a perspective exploded view of an exemplary vapor cell 100 having a dielectric body 102 and an optical window 104 is presented. FIG. 1B presents the exemplary vapor cell 100 of FIG. 1A, but with the optical window 104 contact bonded to the dielectric body 102 . The exemplary vapor cell 100 is stemless and, in many variations, less than 1 mm ³ in size. The dielectric body 102 can be a substrate defined by opposite planar surfaces, as shown in FIGS. 1A-1B. However, other configurations are possible for the dielectric body 102 . Moreover, although FIGS. 1A-1B show dielectric body 102 as being square, other shapes are possible. Optical window 104 can similarly be a substrate defined by an opposite planar surface. However, other configurations for optical window 104 are possible. Generally, optical window 104 includes one surface configured to mate (or bond) to a surface of dielectric body 102, thereby forming a seal (e.g., via contact bonding). ) becomes possible.

Dielectric body 102 may be formed of a material that is transparent to the electric field (or electromagnetic radiation) measured by vapor cell 100 . The material can be an insulating material with a high resistivity, eg, ρ>10 ⁸ Ω·cm, and can correspond to single crystals, polycrystalline ceramics, or amorphous glasses. For example, dielectric body 102 may be formed of silicon. In another example, dielectric body 102 can be formed of a glass containing silicon oxide (eg, SiO ₂ , SiO _x , etc.), such as fused silica, borosilicate glass, or aluminosilicate glass. In some examples, the material of dielectric body 102 is magnesium oxide (e.g., MgO), aluminum oxide (e.g., _Al2O3 ) _, silicon dioxide (e.g., _SiO2 ), titanium dioxide (e.g., _TiO2 ), dioxide Oxide materials such as zirconium (eg, ZrO ₂ ), yttrium oxide (eg, Y ₂ O ₃ ), lanthanum oxide (eg, La ₂ O ₃ ), and the like. The oxide material may be non-stoichiometric (eg, SiO _x ), or may be a combination of one or more binary oxides (eg, Y:ZrO ₂ , LaAlO ₃ , etc.). In other examples, the material of dielectric body 102 is a non-oxide material such as silicon (Si), diamond (C), gallium nitride (GaN), calcium fluoride (CaF), and the like. In these examples, an adhesion layer can be disposed on the dielectric body 102 to define the surface 106 of the dielectric body 102 . The adhesion layer can allow bonding of the dielectric body 102 to the non-oxide material, but can also allow formation of a contact bond with the optical window 104 . For example, dielectric body 102 may be formed of silicon, and exemplary vapor cell 100 may include an adhesion layer comprising silicon oxide (eg, SiO ₂ , SiO _x , etc.) on dielectric body 102 . . This adhesion layer defines the surface 106 of the dielectric body 102 and is capable of forming siloxane bonds when processed according to the fabrication methods described herein.

Dielectric body 102 includes a surface 106 that defines an opening 108 in dielectric body 102 to cavity 110 . Surface 106 can be a flat surface as shown in FIGS. 1A-1B, but other surfaces are possible (eg, curved). Aperture 108 can be any type of opening that allows access to the interior volume of cavity 110 and can have any shape (eg, circular, square, hexagonal, oval, etc.). . Such access may allow steam (or a source of steam (steam source)) to be placed within cavity 110 during manufacture of steam cell 100 . Cavity 110 extends from surface 106 into dielectric body 104 and stops before extending completely through dielectric body 104 . Cavity 110 can have a uniform cross-section along its extension through the dielectric body. However, in some variations, the cross-section of cavity 110 may vary along the extension.

Exemplary vapor cell 100 contains vapor (not shown) in cavity 110 of dielectric body 102 . The vapor can include components such as alkali metal atomic gases, noble gases, diatomic halogen molecular gases, or organic molecular gases. For example, the vapor can include gases of alkali metal atoms (eg, K, Rb, Cs, etc.), noble gases (eg, He, Ne, Ar, Kr, etc.), or both. In another example, the vapor can include _diatomic halogen molecules (eg, F2, _Cl2 , Br2, etc.) gases, noble gases, or _both . In yet another example, the vapor can include gases of organic molecules (eg, acetylene), noble gases, or both. Other combinations of vapors are possible, including other constituents.

Exemplary vapor cell 100 may further include a vapor source in cavity 110 of dielectric body 102 . The vapor source can generate vapor in response to an energy stimulus such as heat, exposure to ultraviolet light, and the like. For example, the vapor can correspond to a gas of alkali metal atoms, and the source of vapor corresponds to an alkali metal mass that has been cooled sufficiently to be in solid or liquid phase when placed in cavity 110. be able to. In some implementations, the source of vapor resides in the cavity of the dielectric body, and the source of vapor is a liquid or liquid of alkali metal atoms configured to produce a gas of alkali metal atoms when heated. Includes solid sources.

The exemplary vapor cell 100 additionally includes an optical window 104 . As shown in FIG. 1B, optical window 104 covers opening 108 of cavity 110 and has a surface 112 bonded to surface 106 of dielectric body 102 . This bond forms a seal around opening 108 . The seal comprises metal-oxygen bonds formed by reacting a first plurality of hydroxyl ligands on surface 106 of dielectric body 102 with a second plurality of hydroxyl ligands on surface 112 of optical window 104. can contain. If one or both of the dielectric body 102 (or an adhesion layer thereon) and the optical window 104 comprise silicon oxide, the metal-oxide bond can comprise siloxane bonds (i.e., Si--O--Si). . However, other types of metal-oxygen bonds are possible, including hybrid oxo-metal bonds. For example, if the dielectric body 102 and the optical window are both made of sapphire (eg, Al ₂ O ₃ ), the metal-oxygen bond is an oxo (oxygen)-aluminum bond (eg, Al-O-Al). can contain. When the dielectric body 102 is made of glass containing silicon oxide and the optical window 104 is made of sapphire, the metal-oxygen bond is a silicon-oxo-aluminum bond (eg, Si—O—Ai, Al—O -Si, etc.).

Optical window 104 may be formed of a material that is transparent to electromagnetic radiation (eg, laser light) used to interrogate vapor sealed within cavity 110 of dielectric body 102 . For example, the material of the optical window 104 is sensitive to infrared wavelengths of electromagnetic radiation (eg, 700-1000 nm), visible wavelengths of electromagnetic radiation (eg, 400-7000 nm), or ultraviolet wavelengths of electromagnetic radiation (eg, 10-400 nm). can be made transparent to Moreover, the material of the optical window 104 can be an insulating material with high resistivity, ^e.g. be able to. For example, the material of optical window 104 can include silicon oxide (eg, SiO ₂ , SiO _x , etc.) such as found in quartz, fused silica, or borosilicate glass. In another example, the material of optical window 104 can include aluminum oxide (eg, Al ₂ O ₃ , Al _x O _y , etc.) such as found in sapphire or aluminosilicate glass. In one example, the material of the optical window 104 is magnesium oxide (e.g. MgO), aluminum oxide (e.g. _Al2O3 ) _, silicon dioxide (e.g. _SiO2 ), titanium dioxide (e.g. _TiO2 ), zirconium dioxide. (eg ZrO ₂ ), yttrium oxide (eg Y ₂ O ₃ ), lanthanum oxide (eg La ₂ O ₃ ) and the like. The oxide material may be non-stoichiometric (eg, SiO _x ), or may be a combination of one or more binary oxides (eg, Y:ZrO ₂ , LaAlO ₃ , etc.). In other examples, the material of dielectric body 102 is a non-oxide material such as diamond (C), calcium fluoride (CaF), and the like.

In many implementations, the surface 106 of the dielectric body 102 and the surface 112 of the optical window 104 can have a surface roughness R _a less than or equal to the threshold surface roughness. A threshold surface roughness can ensure that no leak paths are formed through the seal during contact mating. Such pathways, if present, may allow contaminants to enter cavity 110 and vapor to exit vapor cell 100 . In some variations the threshold surface roughness is less than 50 nm. In some variations the threshold surface roughness is less than 30 nm. In some variations the threshold surface roughness is less than 10 nm. In some variations the threshold surface roughness is less than 1 nm.

Although FIGS. 1A and 1B show the exemplary vapor cell 100 as having a single optical window, more than one optical window is possible for the exemplary vapor cell 100. FIG. Moreover, in some variations, cavity 110 may extend completely through dielectric body 102 . FIG. 2A presents a perspective exploded view of an exemplary vapor cell 200 having two optical windows. Exemplary vapor cell 200 may be similar in many features to exemplary vapor cell 100 shown in FIGS. 1A-1B. FIG. 2B presents the example vapor cell 200 of FIG. 2A with both optical windows bonded to the dielectric body 202 of the example vapor cell 200 . At least one of the bonds is a contact bond as described in connection with the exemplary vapor cell 100 of FIGS. 1A-1B. The exemplary vapor cell 200 includes a dielectric body 202 and a cavity 204 within the dielectric body 202 . Cavity 204 extends completely through dielectric body 202 . A first surface 206 of dielectric body 202 defines a first opening 208 to cavity 204 and a second surface 210 of dielectric body 202 defines a second opening 212 to cavity 204 .

The exemplary vapor cell 200 further includes a first optical window 214 covering the first opening 208 of the cavity 204 . First optical window 214 has a surface 216 that is bonded to first surface 206 of dielectric body 202 to form a first seal around first opening 208 . The exemplary vapor cell 200 additionally includes a second optical window 218 covering the second opening 212 of the cavity 204 . A second optical window 218 has a surface 220 that is bonded to the second surface 210 of the dielectric body 202 to form a second seal around the second opening 212 . A second seal was formed by reacting a first plurality of hydroxyl ligands on the second surface 210 of the dielectric body 202 with a second plurality of hydroxyl ligands on the surface 220 of the second optical window 218 Contains metal-oxygen bonds. A vapor or source of vapor (not shown) resides in cavity 204 of dielectric body 202 .

Dielectric body 202 and optical windows 214, 218 may share features in common with dielectric body 102 and optical window 104, respectively, described in connection with exemplary vapor cell 100 of FIGS. 1A-1B. For example, dielectric body 202 can be formed of glass including silicon (Si), aluminum oxide (eg, Al ₂ O ₃ ), or silicon oxide (eg, SiO ₂ , SiO _x , etc.). In another example, one or both of the first and second optical windows 214, 218 are electromagnetic radiation (eg, laser light) used to interrogate the vapor sealed within the cavity 204 of the dielectric body 202. It can be made of a material that is transparent to the Other features and combinations thereof are possible. Similarly, the steam and steam source may share features in common with the steam and steam source, respectively, described in connection with the exemplary steam cell 100 of FIGS. 1A-1B. For example, the vapor can include a gas of alkali metal atoms, a noble gas, a gas of diatomic halogen molecules, a gas of organic molecules, or combinations thereof. In another example, a source of vapor can reside in cavity 204 of dielectric body 202, the source of vapor comprising alkali metal atoms configured to produce a gas of alkali metal atoms when heated. can include a liquid or solid source of Other features and combinations thereof are possible.

In embodiments in which dielectric body 202 is formed of a non-oxide material, an adhesion layer may be disposed on dielectric body 202 to define second surface 210 of dielectric body 202 . The adhesion layer can enable bonding of the dielectric body 202 to the non-oxide material, but can also enable formation of a contact bond with the surface 220 of the second optical window 218 . For example, dielectric body 202 may be formed of silicon, and exemplary vapor cell 200 may include an adhesion layer comprising silicon oxide (eg, SiO ₂ , SiO _x , etc.) on dielectric body 202 . . This adhesion layer defines the second surface 210 of the dielectric body 202 and is capable of forming siloxane bonds when processed according to the fabrication methods described herein. In some embodiments, the first seal connects the third plurality of hydroxyl ligands on the first surface 206 of the dielectric body 202 with the fourth plurality of hydroxyl ligands on the surface 216 of the first optical window 214. Contains metal-oxygen bonds formed by reacting. In these implementations, the exemplary vapor cell 200 is positioned over the dielectric body 202 to define a first surface 206 of the dielectric body 202 when the dielectric body is formed of a non-oxide material. An adhesive layer may be included.

In some implementations, such as those shown in FIGS. 2A-2B, the first and second surfaces 206, 210 of the dielectric body 202 are opposite planar surfaces and are the first optical window. Surface 216 of 214 and surface 220 of second optical window 218 are flat surfaces. In some implementations, the second surface 210 of the dielectric body 202 and the surface 220 of the second optical window 218 can have a surface roughness R _a less than or equal to the threshold surface roughness. In some variations the threshold surface roughness is less than 50 nm. In some variations the threshold surface roughness is less than 30 nm. In some variations the threshold surface roughness is less than 10 nm. In some variations the threshold surface roughness is less than 1 nm. In a further embodiment, the threshold surface roughness is a second threshold surface roughness, and the first surface 206 of the dielectric body 202 and the surface 216 of the first optical window 214 have the first threshold surface roughness It has the following surface roughness _Ra . The first threshold surface roughness need not be the same as the second threshold surface roughness.

In some implementations, the first seal includes an anodic bond between first surface 206 of dielectric body 202 and surface 216 of first optical window 214 . In some implementations, the dielectric body 202 is formed of glass including silicon oxide (eg, _SiO2 , _SiOx , etc.) and the first optical window 214 is formed of silicon oxide (eg, _SiO2 , _SiOx , etc.). etc.). In these implementations, exemplary vapor cell 200 includes a layer of silicon disposed between first surface 206 of dielectric body 202 and surface 216 of first optical window 214 . The first seal includes an anodic bond between a layer of silicon and one or both of first surface 206 of dielectric body 202 and surface 216 of first optical window 214 .

In some implementations, the dielectric body 202 is formed of glass including silicon oxide (eg, _SiO2 , _SiOx , etc.) and the first optical window 214 is formed of silicon oxide (eg, _SiO2 , _SiOx , etc.). etc.). In such cases, exemplary vapor cell 200 includes a fired layer of glass frit that bonds first surface 206 of dielectric body 202 to surface 216 of first optical window 214 . A fired layer of glass frit defines the first seal.

FIG. 3 shows an exemplary vapor cell 300 shown in perspective, top and side views having a dielectric body 302 made of silicon and two optical windows 304, 306 made of glass. Present. Exemplary vapor cell 300 may be a single vapor cell, or alternatively part of an array of such cells (eg, manufactured using a large substrate or wafer). good. The glass contains silicon oxide, but the composition of the glass may be the same or different for the two optical windows 304,306. Two optical windows 304 , 306 cover respective openings of the dielectric body 302 to the cavity 308 . In particular, a first optical window 304 is bonded to the dielectric body 302 to define a first seal and a second optical window 306 is bonded to the dielectric body 302 to define a second seal. be done. The first and second seals help contain vapor (or a source of vapor) within cavity 308 of dielectric body 302 . Adhesive layer 310 is disposed along interface 312 between second optical window 306 and dielectric body 302 . Adhesion layer 310 is formed of silicon dioxide (eg, single crystal quartz or fused silica) and enables contact bonding between dielectric body 302 and second optical window 306 . The contact bond helps define the second seal and includes a siloxane bond (ie, Si--O--Si) between the adhesive layer 310 and the second optical window 306. FIG. A first seal can include an anodic bond between the dielectric body 302 and the first optical window 304 . Alternatively, a fired layer of glass frit may bond the dielectric body 302 to the first optical window 304 to form the first seal.

FIG. 4 shows an exemplary vapor cell 400 shown in perspective, top and side views having a dielectric body 402 made of glass and two optical windows 404, 406 made of glass. Present. Similar to FIG. 3, exemplary vapor cell 400 may be a single vapor cell, or alternatively, an array of such cells (eg, fabricated using large substrates or wafers). It may be part. Although the glass includes silicon oxide, the composition of the glass may be the same or different for any combination of the dielectric body 402 and the two optical windows 404,406. Two optical windows 404 , 406 cover respective openings of dielectric body 402 to cavity 408 . In particular, a first optical window 404 is bonded to dielectric body 402 to define a first seal and a second optical window 406 is bonded to dielectric body 402 to define a second seal. be done. The first and second seals help contain vapor (or a source of vapor) within cavity 408 of dielectric body 402 . A layer of silicon 410 is disposed along the interface 412 between the first optical window 404 and the dielectric body 402 . A layer of silicon 410 enables anodic bonding between the first optical window 404 and the dielectric body 402, which helps define the first seal. The contact bond defines a second seal and includes a siloxane bond (ie, Si—O—Si) between dielectric body 402 and second optical window 406 .

Although FIGS. 1A-4 show square vapor cells with circular cavities, other shapes are possible for the vapor cells and their respective cavities. For example, FIGS. 5A-5C present alternative shapes of exemplary vapor cells 500, 520, 540 in perspective view. In FIG. 5A, an exemplary vapor cell 500 includes a circular dielectric body 502 and circular optical windows 504,506. Circular dielectric body 502 includes square walls 508 to define cavity 510 therein. In some variations, circular dielectric body 502 may be formed of silicon and may be approximately 0.5 mm thick. The circular dielectric body 502 may have a diameter of approximately 1.5 mm. In some variations, the circular optical windows 504, 506 can be approximately 0.05 mm to 0.30 mm thick. Circular optical windows 506 , 506 can share a common diameter with circular dielectric body 502 . In some variations, square wall 508 can have an edge length of about 0.9 mm.

In FIG. 5B, an exemplary vapor cell 520 includes a square dielectric body 522 and square optical windows 524,526. Square dielectric body 522 includes circular walls 528 to define cavity 530 therein. In some variations, square dielectric body 522 may be formed of silicon and may be approximately 0.5 mm thick. The edge length of the square dielectric body 522 may be about 1.5 mm. In some variations, the square optical windows 524, 526 can be approximately 0.05 mm to 0.30 mm thick. Square optical windows 524 , 526 may share a common edge length with square dielectric body 522 . In some variations, circular wall 528 can have a diameter of about 0.9 mm.

In FIG. 5C, an exemplary vapor cell 540 includes a circular dielectric body 542 and circular optical windows 544,546. Circular dielectric body 542 includes circular walls 548 to define cavity 550 therein. In some variations, circular dielectric body 542 may be formed of silicon and may be approximately 0.5 mm thick. The circular dielectric body 542 may have a diameter of approximately 1.5 mm. In some variations, the circular optical windows 544, 546 can be approximately 0.05 mm to 0.30 mm thick. Circular optical windows 544 , 546 may share a common diameter with circular dielectric body 542 . In some variations, circular wall 548 can have a diameter of about 0.9 mm.

The vapor cells described in connection with FIGS. 1A-5C can be manufactured using the methods described herein. This manufacturing method can result in vapor cell sizes that are much smaller than the wavelength of the electromagnetic radiation to be detected or measured. In atom-based magnetometry, the method can include cryogenic methods to seal the vapor cell, thereby coating the vapor cell with an anti-mitigation coating. This method uses laser machining or lithography techniques followed by etching methods such as deep reactive ion etching (DRIE) to fabricate individual or many structures on a chip, using vapor Involves building the frame or body of the cell. The material used for the frame (eg, silicon) is coated with a silicon oxide material (eg, SiO ₂ , SiO _x , etc.) or another adhesion layer or the like prior to chemical or laser machining. An optical window capable of transmitting the desired electromagnetic wave is then anodically bonded (or otherwise bonded, such as glass frit bonding) to the frame. This bonding operation provides a leak-free and strong bond to high vacuum. However, in some cases, the anodic bonding operation can also result in outgassing. For example, methods such as those used to construct chip-scale atomic clocks use anodic bonding to secure an optical window onto a frame or body. These methods require relatively high temperatures and voltages, which strongly drive ion diffusion and can result in large amounts of outgassing. Outgassing can cause the pressure of undesirable gases within the vapor cell to rise to unacceptably high levels, thereby degrading vapor cell performance.

To help avoid or reduce outgassing, the methods presented herein use a contact bonding operation to effect the seal. In contact bonding operations, adhesive layers and optical windows can be prepared using plasma activation. In some variations, the frame or body with the optical windows is placed in an atmosphere of gas, which allows the gas to fill the vapor cell to the desired pressure. A contact bond is then made by pressing the plasma-activated surfaces of the pieces together to form a seal. However, other filling techniques are possible. For example, alkali metal masses can be interspersed with windows that are anodically bonded and then sealed within the vapor cell by a contact bonding operation under high vacuum conditions. Alternatively, various laser-activated sources of gas vapor may be placed in a vapor cell and then sealed by a contact bonding operation under high vacuum conditions. The method presented herein is well suited for fabricating vapor cells coated with anti-relaxation coatings for magnetic force measurements, as the contact bonding operation is performed at low temperatures, which can accommodate the final operation. ing.

The fabrication methods described herein can create stemless vapor cells with high purity gas samples by combining powerful bonding methods (e.g., anodic bonding in air) with contact bonding in vacuum. This method lends itself to large scale manufacturing as many vapor cells can be fabricated simultaneously on a large substrate (e.g. wafer) and then cut using either a laser machining process or a dicing saw. . In some variations, the vapor cell has a dielectric body formed of silicon or glass including silicon oxide (eg, SiO ₂ , SiO _x , etc.). The dielectric body is chemically or laser machined to create cavities for the filling vapor. A first optical window is anodically bonded to one side of the dielectric body when the cavity created is through the dielectric body. If the holes do not pass through the frame, it is not necessary to anodically bond the first optical window. A glass frit bond or another type of bond may be used for the first optical window. Anodic bonding works well for glass-to-silicon bonding, and glass frit bonding works well for glass-to-glass bonding.

In certain of these methods, the dielectric body, if formed of silicon, is pretreated with a thin layer (e.g., about 500 nm) of silicon oxide (e.g., _SiO2 , _SiOx , etc.). , so that a contact bond can be made between the optical window (or the second optical window) and the dielectric body. The dielectric body may also be pretreated with a thin layer of silicon oxide if formed of another material similar to silicon (eg, a non-oxide material). This pretreatment is followed by contact bonding in a pure atmosphere of vapor or gas (eg, gas of alkali metal atoms including cesium or rubidium) filling the vapor cell. In many embodiments, contact bonding is performed at low temperatures (eg, less than 100° C.) and zero applied voltage to prevent unwanted outgassing of gases into the cavity of the vapor cell.

A contact bond is formed using a metal-oxygen bond between the surface of the dielectric body and the mating surface of the optical window. In variations in which the dielectric body is formed of silicon (or a glass containing silicon oxide) and the optical window is formed of a glass containing silicon oxide, the contact bonds are siloxane bonds (i.e., Si—O—Si). can be formed using The reaction of the contact bond formation process is

によって表すことができる。反応は可逆的であり、そこで、場合によっては、反応から生成された水分子を取り除くことが望ましい。そうでなければ、新しく形成されたシロキサン結合は、加水分解されてシラノール結合（すなわち、Ｓｉ－ＯＨ）に戻るリスクがある。

can be represented by The reaction is reversible, so it is sometimes desirable to remove water molecules produced from the reaction. Otherwise, newly formed siloxane bonds risk hydrolysis back to silanol bonds (ie, Si—OH).

Water molecules produced by contact bonding can be removed by a reaction in which the product becomes solid at room temperature. In some embodiments, water molecules are reacted with steam within the steam cell. For example, the vapor can be a gas of cesium atoms, and the water molecules react with some of the gas to form a solid, e.g., Cs ₂ O (T _{melt ≈340 °} C.) , CsOH (T _melt ≈272° C.) (T _melting ≈272° C.), or CsH (T _melt ≈170° C.) (T _melting ≈170° C.), etc. can be formed. In some embodiments, water molecules are reacted with desiccant material (eg, as a coating, interspersed clumps, etc.) present within the cavities of the dielectric body. The desiccant material may be inert to the vapor within the vapor cell. For example, the vapor can be a gas of diatomic halogen molecules (e.g., chlorine gas), and water molecules are reacted with an anhydrous chloride salt (e.g., _LaCl3 ) to form, for example, a hydrated salt or an oxyhydroxide. Products such as compounds (eg, LaCl ₃ .xH ₂ O, LaOCl, etc.) can be formed.

Although representative reactions are presented in the context of silicon as the metal atom involved, other metal atoms are possible. For example, if the dielectric body is formed of aluminum oxide (e.g., single crystal sapphire) and the optical window is also formed of aluminum oxide (e.g. _{, Al2O3} polycrystalline ceramic), the contact bond formation process may be performed by metal atoms Aluminum can be used as a to form oxo-aluminum bonds (eg, Al--O--Al). Mixtures of metals are also possible. For example, if the dielectric body is formed of zirconium oxide and the optical window is formed of magnesium oxide, the contact bond formation process can utilize zirconium and magnesium as the metal atoms to form a zirconium-oxomagnesium bond. can.

Generally, for a dielectric body formed of a material containing a _first metal M1 and an optical window formed of a material containing a _second metal M2, the reaction of the contact bond formation process is:

によって表すことができる。ここで、ヒドロキシルリガンド（すなわち、ＯＨ）は、金属原子Ｍ₁およびＭ₂の各々に配位結合され、ヒドロキシルリガンドは、金属－酸素結合（すなわち、Ｍ₁－Ｏ－Ｍ₂）の形成中にオキソリガンド（Ｏ）に縮合する。水分子は、この縮合プロセスの副産物として解放される。反応は、金属原子ごとに単一のヒドロキシルリガンドを示唆しているが、他の数のヒドロキシルリガンドが、金属原子Ｍ₁およびＭ₂の各々に配位結合される場合がある。

can be represented by Here, a hydroxyl ligand (ie, OH) is coordinated to each of the metal atoms M ₁ and M ₂ , and the hydroxyl ligand is coordinatively bonded during the formation of the metal-oxygen bond (ie, M ₁ -OM ₂ ). It condenses to an oxo ligand (O). Water molecules are released as a by-product of this condensation process. Although the reactions suggest a single hydroxyl ligand per metal atom, other numbers of hydroxyl ligands may be coordinated to _each of metal atoms M1 and _M2 .

In many variations condensation of the hydroxyl ligands occurs at room temperature when the surface of the dielectric body is brought into contact with the mating surface of the optical window. However, in some variations heat may be applied to initiate and/or complete the formation of the contact bond. Heat can further strengthen the contact bond. For example, heat can be applied to one or both of the dielectric body and the optical window to raise the temperature of each to the processing temperature. Processing temperatures can promote the formation of contact bonds. In some variations, the processing temperature is 250° C. or less. In some variations, the processing temperature is 120° C. or less. In some variations, the processing temperature is 75° C. or less.

After the contact bond is formed, the vapor cell can be abe coated with a material such as parylene or epoxy to protect the vapor cell. The vapor cell can also be fiber coupled by attaching the fiber to the window either directly or with a GRIN lens.

As mentioned above, the fabrication method allows the construction of small stemless vapor cells that can be used for atom-based sensing. Such sensors can be used for metrology purposes. A sub-wavelength vapor cell for sensing electromagnetic fields from MHz to THz reduces the physical cross-section of electromagnetic field scattering measured by the vapor cell. Cross-sectional area is measured as the ratio of the vapor cell dimension divided by lambda cubed. (Lambda corresponds to the wavelength of the electromagnetic radiation measured by the vapor cell.) Moreover, the stem of the vapor cell containing vapor (e.g. the gas of alkali metal atoms) can cause distortion of the measured electromagnetic field. There is Stemless vapor cells provide improved measurement performance compared to conventional vapor cells that include stems. Stemless vapor cells also contribute to chip-scale devices that utilize atom-based sensing.

This fabrication method also allows multiple vapor cells to be connected together or arranged in an array to make multiple simultaneous measurements over a region of space. For example, a large number of vapor cells can be arranged in a planar array so that the field properties can be determined at the sensor plane. Three-dimensional arrays are also possible. These functions are enabled by the insulating nature of the probe, since the vapor cells interact little with each other, ie the scattering cross section of the vapor cell is small. Light can be transported to the vapor cells in parallel or in series through optical waveguides such as fibers, but must be read out independently (signal light reflects absorption or dispersion signals associated with individual vapor cells). (must be isolated to each vapor cell to give an accurate measurement). Essentially, this is a multi-pixel array, but the transparent nature of the vapor cell allows three-dimensional imaging. Thick cells are made by stacking the unit cells together or creating a unique shape, e.g. using anodically bonded glass + frame (laser cut together), stacking them, and stacking some more together. can be manufactured by this method, such as by anodically bonding one by one with a contact bond and then capping the structure with a contact bond.

The manufacturing method can include a contact bonding operation to create the vapor cell. The contact bonding operation can include a process that chemically alters the surface of the dielectric body (or frame) and the mating surface of the optical window. The altered surfaces are then brought into contact together to form metal-oxygen bonds (eg, siloxane bonds), thereby creating a seal. In some embodiments, a method of manufacturing a vapor cell includes obtaining a dielectric body having a surface defining an opening to a cavity in the dielectric body. The method further includes obtaining an optical window having a surface (or mating surface). One or both of the surface of the dielectric body and the surface of the optical window can have a surface roughness Ra less than or equal to the threshold surface roughness, as described with respect to the vapor cell 100 of FIGS. 1A-1B. can. For example, the threshold surface roughness can be 1 nm. In some examples, the surface of the dielectric body and the surface of the optical window are flat surfaces.

In this method, the surface of the dielectric body and the surface of the optical window are each modified to contain a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands. The method additionally includes disposing steam or a source of steam within the cavity. The altered surface of the dielectric body is brought into contact with the altered surface of the optical window to form a seal around the opening to the cavity. The seal, which can define part or all of the contact bond, is a metal-oxygen bond formed by reacting a first plurality of hydroxyl ligands with a second plurality of hydroxyl ligands during contact of the modified surface. Including binding. In some variations, contacting the altered surface includes covering the opening of the cavity with an optical window to confine the vapor or vapor source within the cavity.

The dielectric body and optical window can be made of materials that are transparent to the electric field (or electromagnetic radiation) measured by the vapor cell. Examples of such materials are described in connection with dielectric body 102 and optical window 104 of FIGS. 1A-1B. For example, the dielectric body can be formed of silicon or glass containing silicon oxide (eg, SiO ₂ , SiO _x , etc.). The optical window can comprise silicon oxide (eg, _SiO2 , _SiOx , etc.). In these examples, the metal-oxygen bond can include a siloxane bond. In embodiments in which the dielectric body is formed of a non-oxide material, the method can include forming an adhesion layer on the dielectric body that defines a surface of the dielectric body. For example, if the dielectric body is formed of silicon, the adhesion layer may comprise silicon oxide (e.g., _SiO2 , _SiOx , etc.), as described with respect to vapor cell 300 of FIG. can.

As mentioned above, steam or a source of steam is placed in the cavity during the method. The vapor comprises a gas of alkali metal atoms, a gas of diatomic halogen molecules, a gas of organic molecules, a noble gas, or a combination thereof, as described in connection with the vapor cell 100 of FIGS. 1A-1B. be able to. In some embodiments, disposing the vapor or source of vapor includes exposing the cavity to a vacuum environment containing a gas of alkali metal atoms. In some embodiments, disposing a vapor or source of vapor includes disposing a solid or liquid source of alkali metal atoms within the cavity. In these embodiments, the method includes heating a solid or liquid source of alkali metal atoms after contacting to produce a gas of alkali metal atoms. However, solid or liquid sources of alkali metal atoms can be stimulated with other types of energy (eg, exposure to laser light, ultraviolet radiation, etc.).

In some embodiments, altering the surface includes activating one or both of the surface of the dielectric body and the surface of the optical window by exposing the respective surface to plasma. Such exposure increases the surface energy of one or both of the surface of the dielectric body and the surface of the optical window, and can chemically prepare the surfaces for subsequent contact bonding. A further chemical pretreatment can be performed by washing one or both of the activated surface of the dielectric body and the activated surface of the optical window with a basic aqueous solution. Upon contact with the basic aqueous solution, metal atoms on the surface of the dielectric body and the surface of the optical window can coordinate with hydroxyl ligands.

In some embodiments, contacting the denatured surfaces includes pressing the denatured surface of the dielectric body and the denatured surface of the optical window against each other. In some cases, a seal is formed when the denatured surfaces are brought into contact. In other cases, pressing can include contacting the modified surface with a pressure of up to 2 MPa. In some embodiments, the method includes heating one or both of the dielectric body and the optical window after contacting the altered surface. For example, one or both of the dielectric body and the optical window can be heated to temperatures ranging from 100° C. to 250° C. after contacting the altered surfaces. During heating, the dielectric body and optical window can be clamped together to keep the modified surfaces in contact.

In some implementations, obtaining the dielectric body includes removing material from the dielectric body to form the cavity. Removing material can include machining material from the surface of the dielectric body with a laser. Removing material may further include etching material from the surface of the dielectric body. Such etching can include one or both of a dry etching process or a wet etching process. Other types of subtractive processes are possible for material removal operations (eg, ablation, grinding, polishing, etc.).

Vapor cells with more than one optical window can be made using the fabrication methods described herein. In some embodiments, a method of manufacturing a vapor cell having at least two optical windows includes obtaining a dielectric body. The dielectric body has a cavity therein and includes a first surface defining a first opening to the cavity and a second surface defining a second opening to the cavity. The method further includes obtaining a first optical window having a surface. A surface of the first optical window is bonded to the first surface of the dielectric body to form a first seal around the first opening to the cavity. In some implementations, bonding the surfaces includes covering a first opening of the cavity with a first optical window.

The method additionally includes obtaining a second optical window that includes the surface. A second surface of the dielectric body and a surface of the second optical window are modified to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands, respectively. The method further includes placing steam or a source of steam into the cavity through the second opening. The modified second surface of the dielectric body is brought into contact with the modified surface of the second optical window to form a second seal around the second opening to the cavity. The second seal comprises metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contact of the modified surface. In some embodiments, contacting the altered surface includes covering a second opening of the cavity with a second optical window to confine the vapor or source of vapor within the cavity.

One or both of the second surface of the dielectric body and the surface of the second optical window have a surface roughness less than or equal to the threshold surface roughness, as described with respect to the vapor cell 200 of FIGS. 2A-2B. can have a height Ra. For example, the threshold surface roughness can be 1 nm. In some implementations, the threshold surface roughness is a second threshold surface roughness, and one or both of the first surface of the dielectric body and the surface of the first optical window is the first threshold surface It can have a surface roughness Ra equal to or less than the roughness. The first threshold surface roughness need not be the same as the second threshold surface roughness. In some variations, the first and second surfaces of the dielectric body are opposite planar surfaces, and the surface of the first optical window and the surface of the second optical window are planar surfaces. be.

In this method, the surface of the dielectric body and the surface of the optical window are each modified to contain a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands. The method additionally includes disposing steam or a source of steam within the cavity. The altered surface of the dielectric body is brought into contact with the altered surface of the optical window to form a seal around the opening to the cavity. The seal, which can define part or all of the contact bond, is a metal-oxygen bond formed by reacting a first plurality of hydroxyl ligands with a second plurality of hydroxyl ligands during contact of the modified surface. Including binding. In some variations, contacting the altered surface includes covering the opening of the cavity with an optical window to confine the vapor or vapor source within the cavity.

The dielectric body, first optical window, and second optical window can be formed of materials that are highly transparent to the electric field (or electromagnetic radiation) measured by the vapor cell. Examples of such materials are described in connection with dielectric bodies 102, 202 and optical windows 104, 214, 218 of FIGS. 1A-2B. For example, the dielectric body can be formed of silicon or a glass comprising silicon oxide (e.g., _SiO2 , _SiOx , etc.), and one or both of the first and second optical windows can comprise silicon oxide (e.g., , SiO ₂ , SiO _x , etc.). In these examples, the metal-oxygen bond can include a siloxane bond. In embodiments in which the dielectric body is formed of a non-oxide material, the method can include forming an adhesion layer on the dielectric body that defines the second surface of the dielectric body. For example, if the dielectric body is formed of silicon, the adhesion layer may comprise silicon oxide (e.g., _SiO2 , _SiOx , etc.), as described with respect to vapor cell 300 of FIG. can.

As mentioned above, steam or a source of steam is placed in the cavity during the method. The vapor may be a gas of alkali metal atoms, a gas of diatomic halogen molecules, a gas of organic molecules, a noble gas, or a combination thereof, as described in connection with the vapor cells 100, 200 of FIGS. 1A-2B. can include In some embodiments, disposing the vapor or source of vapor includes exposing the cavity to a vacuum environment containing a gas of alkali metal atoms. In some embodiments, disposing the vapor or source of vapor includes disposing a solid or liquid source of alkali metal atoms through the second opening and into the cavity. In these embodiments, the method includes heating a solid or liquid source of alkali metal atoms after contacting to produce a gas of alkali metal atoms. However, solid or liquid sources of alkali metal atoms can be stimulated with other types of energy (eg, exposure to laser light, ultraviolet radiation, etc.).

In some embodiments, modifying the surface comprises activating one or both of the second surface of the dielectric body and the surface of the second optical window by exposing the respective surface to plasma. include. Such exposure may increase the surface energy of one or both of the second surface of the dielectric body and the surface of the second optical window, chemically pretreating the surfaces for subsequent contact bonding. can. A further chemical pretreatment can be performed by washing one or both of the activated surface of the dielectric body and the activated surface of the second optical window with a basic aqueous solution. Upon contact with the basic aqueous solution, metal atoms on the surface of the dielectric body and the surface of the optical window can coordinate with hydroxyl ligands.

In some embodiments, contacting the altered surfaces includes pressing the altered second surface of the dielectric body and the altered surface of the second optical window against each other. In some cases, a second seal is formed when the altered surfaces are brought into contact. In other cases, pressing can include contacting the modified surface with a pressure of up to 2 MPa. In some embodiments, the method includes heating one or both of the dielectric body and the second optical window after contacting the altered surface. For example, one or both of the dielectric body and the second optical window can be heated to temperatures ranging from 100° C. to 250° C. after contacting the altered surfaces. During heating, the dielectric body and the second optical window can be clamped together to keep the altered surfaces in contact.

In this method, the first optical window can be contact bonded to the dielectric body in addition to the second optical window. In some embodiments, bonding the surface of the first optical window comprises the first surface of the dielectric body to each include a third plurality of hydroxyl ligands and a fourth plurality of hydroxyl ligands. and altering the surface of the first optical window. The modified first surface of the dielectric body is brought into contact with the modified surface of the first optical window to form a first seal around the first opening to the cavity. The first seal comprises metal-oxygen bonds formed by reacting a third plurality of hydroxyl ligands with a fourth plurality of hydroxyl ligands during contact of the modified surface. In these embodiments, contacting the modified first surface of the dielectric body with the modified surface of the first optical window can include pressing the modified surfaces together. In some cases, a first seal is formed when the altered surfaces are brought into contact. In other cases, pressing can include contacting the modified surface with a pressure of up to 2 MPa. In some variations, one or both of the dielectric body and the first optical window are heated after contacting the altered surface. For example, one or both of the dielectric body and the first optical window can be heated to temperatures ranging from 100° C. to 250° C. after contacting the altered surfaces. During heating, the dielectric body and the first optical window can be clamped together to keep the altered surfaces in contact.

The method further allows the first optical window to be contact bonded to the dielectric body by bonding other than contact bonding. For example, the dielectric body can be formed of silicon and the first optical window can include silicon oxide (eg, _SiO2 , _SiOx , etc.). In this example, bonding the surface of the first optical window includes anodically bonding the surface of the first optical window to the first surface of the dielectric body to form the first seal. Exemplary vapor cell 300 of FIG. 3 may correspond to a vapor cell manufactured by this variation of the method. In another example, the dielectric body can be formed of glass including silicon oxide, and the first optical window can include silicon oxide (eg, _SiO2 , _SiOx , etc.). In this second example, the method includes depositing a layer of silicon on the first surface of the dielectric body and bonding the surfaces of the first optical window to form the first seal. anodically bonding a layer of silicon to the surface of the first optical window. Exemplary vapor cell 400 of FIG. 4 may correspond to a vapor cell manufactured by this variation of the method. In yet another example, the dielectric body can be formed of glass including silicon oxide, and the first optical window can include silicon oxide (eg, _SiO2 , _SiOx , etc.). In this third example, bonding the surfaces of the first optical window includes applying a glass frit to one or both of the first surface of the dielectric body and the surface of the first optical window. A first surface of the dielectric body is contacted with a surface of the first optical window, and at least one of the glass frit, the dielectric body, or the first optical window to form a first seal It is heated to the firing temperature. Although the previous examples were presented in the context of silicon and silicon oxide, other materials are possible for this method.

In some implementations, obtaining the dielectric body includes removing material from the dielectric body to form the cavity. Removing material can include machining material from the surface of the dielectric body with a laser. Removing material may further include etching material from the surface of the dielectric body. Such etching can include one or both of a dry etching process or a wet etching process. Other types of subtractive processes are possible for operations that remove material (eg, ablation, grinding, polishing, etc.).

A method of manufacturing a vapor cell can be illustrated by the following example. However, the examples are for illustrative purposes only. It will be apparent to those skilled in the art that many variations, both of materials and methods, can be practiced without departing from the scope of this disclosure.

(Example 1)
Double side polished and <100> oriented p-type silicon wafers were obtained. The silicon wafer had a diameter of 4 inches, was 500 μm thick, and had a surface roughness R _a of 1 nm or less on each side. Electrical properties of the silicon wafers included resistances ranging from 0.1 Ω-cm to 0.3 Ω-cm. Glass wafers formed of borosilicate glass were also obtained from Schott. The glass wafer was a MEMpax wafer with a diameter of 4 inches and a thickness of 300 μm. The surface roughness was less than 0.5 nm.

Silicon and glass wafers were tested for anodic bonding and contact bonding. Specifically, the wafers were visually inspected for chips, microcracks, and scratches. Wafers were also verified to have a surface roughness of less than 1 nm. A layer of 500 nm _SiO2 was grown on both sides of the silicon wafer using a wet growth process in an oxidation furnace. The temperature of the oxidation furnace was set at about 1100° C. and the silicon wafer processing time was about 40 minutes. The thickness uniformity of the silicon wafer (with the SiO ₂ layer) was verified to within 500±(plus or minus) 6 nm over a 4 inch diameter area. It was also verified that the surface roughness was less than 1 nm.

A number of silicon chips were cut from the silicon wafer using either a Protolaser U3 microlaser tool, a Protolaser R microlaser tool, or a DISCO DAD 3240 dicing saw. Each silicon chip had dimensions of 10 mm x 20 mm. Nine holes were subsequently machined into each of the silicon chips using a Protolaser U3 microlaser tool or a Protolaser R microlaser tool. The holes were each circular with a diameter of 1 mm or square with an edge length of 1 mm. In some cases, a combination of circles and holes were machined into the silicon chip. The silicon chips were visually inspected using 5x and 10x magnifying loupes for any cracks or chips that may have occurred during cutting. Silicon chips with zero or minimal surface defects were selected for subsequent vapor cell fabrication.

Selected silicon chips were then cleaned with methanol and isopropanol using cotton swabs and optical tissue. The silicon chip was then immersed in a buffered oxide etch (BOE) solution with a 10:1 volume ratio and an etch rate of 55 nm/min at room temperature. The buffered oxide etch solution contained hydrofluoric acid buffered with ammonium fluoride. The silicon chip was soaked for at least 11 minutes to remove a 500 nm layer of _SiO2 from the surface on each side of the silicon chip. After being removed by a buffered oxide etch, the silicon chips were visually inspected. If embedded material from the cutting process was found on the silicon chip, the silicon chip was discarded. If areas of _SiO2 remained on the silicon chip, the silicon chip was re-immersed in a buffered oxide etchant, removed, and then re-inspected. A silicon chip without a 500 nm _SiO2 layer on both sides was selected for final cleaning and growth of a 100 nm _SiO2 layer.

Selected silicon chips were then cleaned with acetone and isopropanol using cotton swabs and optical tissue. An ultrasonic cleaner was optionally used to assist the cleaning process by agitating a bath of acetone or isopropanol in which the selected silicon chips were immersed. A layer of 100 nm SiO ₂ was then grown on one side of the silicon chip. The temperature of the oxidation furnace was set at a minimum of 600° C. to obtain a surface roughness of 1 nm or less for a 100 nm SiO ₂ layer. The thickness uniformity of the 100 nm SiO ₂ layer was verified to within 100±6 nm over the area of the silicon chip. Silicon chips that failed to achieve uniformity criteria were discarded.

Silicon chips with a 100 nm _SiO2 layer were then cleaned with methanol and isopropanol using cotton swabs and optical tissue paper to eliminate unbound residues on the surface (such as those due to handling). became. Subsequently, silicon chips were thoroughly cleaned with acetone and isopropanol using cotton swabs and optical tissue. A low power loupe (eg, 10x) is used for the first visual inspection during the deep cleaning process, followed by a high power microscope (eg, 50x-200x) for a second visual inspection. was done. Silicon chips that passed the second visual inspection were placed in a bath of acetone (eg, in a Branson ultrasonic cleaner CPX-952-117R) for ultrasonic cleaning at 40 kHz. For example, a silicon chip could be placed in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the silicon chips were dried with particle-free compressed air and stored in an airtight container until needed for bonding.

Separately, a dicing saw was used to cut the glass wafers to the appropriate size for bonding to the (stored) silicon chips. Two glass chips were prepared for each silicon chip. If the glass chip was intended for anodic bonding, the glass chip was cut to the same dimensions as the silicon chip. However, if the glass chip was intended for contact bonding, the glass chip was cut to have a longer dimension than the silicon chip. For example, the glass chips for anodic bonding had dimensions of 10 mm x 20 mm and those for contact bonding had dimensions of 10 mm x 35 mm. After cutting, each glass chip was inspected to ensure that the optical clarity had not deteriorated (eg, clouded) or that no scratches or cracks were present. Glass chips found to be acceptable were then cleaned with acetone using a cotton swab and optical tissue. If necessary, the glass chips were placed in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the glass chips were dried with particle-free compressed air and then stored in an airtight container until needed for bonding.

One silicon chip and one glass chip were then put into the assembly for anodic bonding. In the silicon chip, the flat surface opposite the flat surface defined by the 100 nm _SiO2 layer was involved in the anodic bonding process. In assembly, the flat surfaces of the silicon and glass chips were brought into contact to define an interface, which was visually inspected to confirm the presence of optical interference fringes. The silicon chip was then heated to a temperature of approximately 400°C. After reaching this temperature, 600 V was applied across the silicon and glass chips for about 15 minutes, which drove the formation of the anodic junction. The interface was inspected again to confirm the disappearance of the optical interference fringes indicating that the anodic bonding was complete. The anodic bond was then inspected for defects (eg, bubbles, microcracks, unbonded areas, etc.). If more than 80% of the area around the hole was free of defects, the anodic junction was further inspected for open channels (eg, hole to environment, hole to another hole, etc.). If an open channel was found, the anodically bonded chip was discarded as the anodic bonding was not found to be leak-free.

Silicon and glass chips bonded by leak-free anodic bonding were cleaned with acetone and methanol. During this cleaning process, the unbonded surface of the silicon chip was cleaned with a cotton swab and an optical cleaner to eliminate residue (e.g. residue from the graphite plates of the assembly used to form the anodic bond). Cleaned with acetone and methanol using tissue paper. The unbonded surface of the silicon chip is then visually inspected to ensure that it is free of defects (e.g., scratches, pitting, etc.) that could impair the contact bond that is about to form. inspected. The anodically bonded chips were then individually cleaned. Specifically, the anodically bonded chips were placed individually (ie, without other chips) in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the anodically bonded chips were dried with particle-free compressed air. A low power loupe (eg, 10x) is used for a first visual inspection of the anodically bonded chip, followed by a high power microscope (eg, 50x-200x) for a second visual inspection. Used. A first and second visual inspection was used to ensure that no visible residue or deposits remained on the anodically bonded chips.

The anodically bonded chip was then brought (together with the glass chip) into a clean room environment (eg class 1000 or better) for contact bonding. A single instance of anodically bonded chips was paired with a single instance of glass chips to define a pair of chips for contact bonding. For each pair, the flat surface defined by a layer of 100 nm _SiO2 on the silicon chip and the flat surface of the glass chip were subjected to optical cleaning to clean them of macroscopic deposits or contaminants. Wiped with paper and acetone. Each pair was then immersed in an acetone bath (eg, acetone in a beaker) and cleaned via ultrasonic cleaning for 15 minutes. Each chip pair was then removed from the acetone bath, rinsed with isopropanol (eg, immersed in an isopropanol bath), and blown dry with dry nitrogen gas.

A pair of chips was placed in a YES-CV200RFS plasma cleaner and cleaned using nitrogen plasma for 45 seconds. (In some cases, multiple pairs of chips were placed in the plasma cleaner.) In particular, the flat surface defined by a layer of 100 nm _SiO2 on the silicon chip and the flat surface of the glass chip. was activated by plasma cleaning. The plasma purifier RF power was set to about 75 W and the internal pressure was maintained at about 150 mTorr. Nitrogen gas was introduced into the plasma purifier at a volumetric flow rate of about 20 sccm. After activation by plasma cleaning, the chip pair was removed from the YES-CV200RFS plasma cleaner and rinsed with deionized water for 5 minutes. The rinse process served to hydroxylate the activated surface. In some variations, the rinse process was performed with a basic aqueous solution (eg, an aqueous solution of ammonium hydroxide). Care was taken not to let the two hydroxylated and activated surfaces touch together.

The chip pair was then transferred to a vacuum chamber and mounted in a fixture with "press fingers". A fixture held the glass chip adjacent to the silicon chip of the anodically bonded chip to define a gap. The activated and hydroxylated surface of the glass chip faced the activated and hydroxylated _SiO2 surface of the silicon chip. The vacuum chamber is then sealed and evacuated (e.g., , less than 10 ⁻³ Torr). The fixture was then cooled with a thermoelectric cooler, which cooled the anodically bonded chip to a temperature of at least between -20°C and 0°C.

After the temperature of the chip pair stabilized, cesium atomic vapor was introduced into the vacuum chamber by opening the valve connecting the source of cesium vapor to the vacuum chamber. The source of cesium vapor was an oven containing a large amount of cesium heated to the process temperature. The target pressure of the cesium vapor in the vacuum chamber could be controlled by changing the valve opening, by changing the process temperature induced by the oven, or both. After the pressure in the vacuum chamber stabilized at the target pressure of cesium vapor, the pair of chips was exposed to vapor of cesium atoms for a period of time.

The pressure of the cesium vapor in the vacuum chamber affects the time required to fill the anodically bonded chip. One or both of the pressure and duration of the cesium vapor in the vacuum chamber can be varied to control the amount of cesium vapor that condenses within the cavity of the anodically bonded chip. After the period had elapsed, the value to the source of cesium vapor was closed. The vacuum chamber was pumped down to reduced pressure (eg, less than 10 ⁻³ Torr) and power to the thermoelectric cooler was turned off.

After the pair of chips reached ambient temperature, the fixture was activated to bring the activated and hydroxylated surface of the glass chip into contact with the activated and hydroxylated _SiO2 surface of the silicon chip. A "press finger" was used to hold the contacted surfaces together for 20 minutes, thereby driving the formation of the contact bond. In some variations, a "press finger" was used to apply a target pressure (eg, about 2 MPa) for a period of 20 minutes.

(Example 2)
Thick glass wafers with a thickness of 1 mm and a diameter of 4 inches are available from Howard Glass Co. , Inc. obtained from The thick glass wafer had a surface roughness R _a of less than 1 nm on each side. Electrical properties of the silicon wafers included resistances ranging from 0.1 Ω-cm to 0.3 Ω-cm. Thin glass wafers formed of borosilicate glass were also obtained from Schott. The thin glass wafers were MEMpax wafers with a diameter of 4 inches and a thickness of 300 μm. The surface roughness was less than 0.5 nm. Thick and thin glass wafers were tested for anodic bonding and contact bonding. Specifically, the glass wafers were visually inspected for chips, microcracks, and scratches. Wafers were also verified to have a surface roughness of less than 1 nm.

A number of thick glass chips were then cut from the thick glass wafer using either a Protolaser R microlaser tool or a DISCO DAD 3240 dicing saw. Each thick glass chip had dimensions of 10 mm x 20 mm. Nine holes were subsequently machined into each of the thick glass chips using a Protolaser R microlaser tool. The holes were each circular with a diameter of 1 mm or square with an edge length of 1 mm. In some cases, combinations of circles and holes were machined into thick glass chips. Thick glass chips were visually inspected using 5x and 10x magnifying loupes for cracks or chips that may have occurred during cutting. Thick glass chips with zero or minimal surface defects were selected for subsequent vapor cell fabrication.

Selected thick glass chips were then cleaned with acetone and isopropanol using cotton swabs and optical tissue. An ultrasonic cleaner was optionally used to assist the cleaning process by agitating a bath of acetone or isopropanol in which the selected thick glass silicon chips were immersed. A layer of <1 μm Si was then grown on one side of the thick glass chip using plasma-enhanced chemical vapor deposition (PECVD). The thickness uniformity of the Si layer was verified to be within ±(plus or minus) 3 nm over the area of the thick glass chip. Thick glass chips that failed to achieve uniformity criteria were discarded.

The thick glass chips were then cleaned with methanol and isopropanol using cotton swabs and optical tissue paper to eliminate unbound residue on the surface (such as from handling). Thick glass chips were then thoroughly cleaned with acetone and isopropanol using cotton swabs and optical tissue. A low power loupe (eg, 10x) is used for the first visual inspection during the deep cleaning process, followed by a high power microscope (eg, 50x-200x) for a second visual inspection. was done. Thick glass chips that passed the second visual inspection were placed in a bath of acetone (eg, in a Branson ultrasonic cleaner CPX-952-117R) for ultrasonic cleaning at 40 kHz. For example, a thick glass chip could be placed in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the thick glass chips were dried with particle-free compressed air and then stored in an airtight container until needed for bonding.

Separately, a dicing saw was used to cut the thin glass wafers to the appropriate size for bonding to the (stored) thick glass chips. Two thin glass chips were prepared for each thick glass chip. If the thin glass chip was intended for anodic bonding, the thin glass chip was cut to the same dimensions as the thick glass chip. However, when the thin glass chips were intended for contact bonding, the thin glass chips were cut to have a longer dimension than the thick glass chips. For example, the thin glass chips for anodic bonding had dimensions of 10 mm x 20 mm and the thin glass chips for contact bonding had dimensions of 10 mm x 35 mm. After cutting, each thin glass chip was inspected to ensure that the optical clarity had not deteriorated (eg, clouded) or that no scratches or cracks were present. Glass chips found to be acceptable were then cleaned with acetone using a cotton swab and optical tissue. If necessary, thin glass chips were placed in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the glass chips were dried with particle-free compressed air and then stored in an airtight container until needed for bonding.

One thick glass chip (with a layer of Si up to 1 μm thick) and one thin glass chip were then put into the assembly for anodic bonding. For thick glass chips, a flat surface defined by a layer of Si up to 1 μm was involved in the anodic bonding process. In assembly, the flat surfaces of the thick and thin glass chips were brought into contact to define an interface, which was visually inspected to confirm the presence of optical interference fringes. The thick glass chip was then heated to a temperature of approximately 400°C. After reaching this temperature, 600 V was applied across the thick and thin glass chips for about 15 minutes, which drove the formation of an anodic junction. The interface was inspected again to confirm the disappearance of the optical interference fringes indicating that the anodic bonding was complete. The anodic bond was then inspected for defects (eg, bubbles, microcracks, unbonded areas, etc.). If more than 80% of the area around the hole was free of defects, the anodic junction was further inspected for open channels (eg, hole to environment, hole to another hole, etc.). If an open channel was found, the anodically bonded chip was discarded as the anodic bonding was not found to be leak-free.

Thick and thin glass chips bonded by leak-free anodic bonding were cleaned with acetone and methanol. During this cleaning process, the unbonded surface of the thick glass chip is cleaned with a cotton swab and a cloth to remove any residue (e.g. residue from the graphite plates of the assembly used to form the anodic bond). Cleaned with acetone and methanol using optical tissue paper. The unbonded surface of the thick glass chip is then visually inspected to ensure that there are no defects (e.g., scratches, pitting, etc.) that could impair the contact bond that is about to form. was inspected. The anodically bonded chips were then individually cleaned. Specifically, the anodically bonded chips were placed individually (ie, without other chips) in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the anodically bonded chips were dried with particle-free compressed air. A low power loupe (eg, 10x) is used for a first visual inspection of the anodically bonded chip, followed by a high power microscope (eg, 50x-200x) for a second visual inspection. Used. A first and second visual inspection was used to ensure that no visible residue or deposits remained on the anodically bonded chips.

The anodically bonded chip (together with the unbonded thin glass chip) was then brought into a clean room environment (eg, class 1000 or better) for contact bonding. A single instance of the anodically bonded chip was paired with a single instance of the thin glass chip to define the pair for contact bonding. Pairwise, the unbonded flat surface of the thick glass chip (i.e. no layer of Si up to 1 μm) and the flat surface of the thin glass chip clean them of macroscopic deposits or contaminants. To clean, it was wiped with optical paper and acetone. Each pair was then immersed in an acetone bath (eg, acetone in a beaker) and cleaned via ultrasonic cleaning for 15 minutes. Each chip pair was then removed from the acetone bath, rinsed with isopropanol (eg, immersed in an isopropanol bath), and blown dry with dry nitrogen gas.

A pair of chips was placed in a YES-CV200RFS plasma cleaner and cleaned using nitrogen plasma for 45 seconds. (In some cases, multiple chip pairs were placed in the plasma cleaner.) In particular, the unbonded flat surface of the thick glass chip and the flat surface of the glass chip were significantly reduced by plasma cleaning. Activated. The plasma purifier RF power was set to about 75 W and the internal pressure was maintained at about 150 mTorr. Nitrogen gas was introduced into the plasma purifier at a volumetric flow rate of about 20 sccm. After activation by plasma cleaning, the chip pair was removed from the YES-CV200RFS plasma cleaner and rinsed with deionized water for 5 minutes. The rinse process served to hydroxylate the activated surface. In some variations, the rinse process was performed with a basic aqueous solution (eg, an aqueous solution of ammonium hydroxide). Care was taken not to let the two hydroxylated and activated surfaces touch together.

The chip pair was then transferred to a vacuum chamber and mounted in a fixture with "press fingers". A fixture held the thin glass chip adjacent to the thick glass chip of the anodically bonded chip to define a gap. The activated and hydroxylated surface of the thin glass chip faced the activated and hydroxylated unbonded surface of the thick glass chip. The vacuum chamber is then sealed and evacuated (e.g., , less than 10 ⁻³ Torr). The fixture was then cooled with a thermoelectric cooler, which cooled the anodically bonded chip to a temperature of at least between -20°C and 0°C.

After the temperature of the chip pair stabilized, cesium atomic vapor was introduced into the vacuum chamber by opening the valve connecting the source of cesium vapor to the vacuum chamber. The source of cesium vapor was an oven containing a large amount of cesium heated to the process temperature. The target pressure of the cesium vapor in the vacuum chamber could be controlled by changing the valve opening, by changing the process temperature induced by the oven, or both. After the pressure in the vacuum chamber stabilized at the target pressure of cesium vapor, the pair of chips was exposed to vapor of cesium atoms for a period of time.

The pressure of the cesium vapor in the vacuum chamber affects the time required to fill the anodically bonded chip. One or both of the pressure and duration of the cesium vapor in the vacuum chamber can be varied to control the amount of cesium vapor that condenses within the cavity of the anodically bonded chip. After that period had elapsed, the valve to the source of cesium vapor was closed. The vacuum chamber was pumped down to reduced pressure (eg, less than 10 ⁻³ Torr) and power to the thermoelectric cooler was turned off.

After the pair of chips reached ambient temperature, the fixture was activated to bring the activated and hydroxylated surface of the glass chip into contact with the activated and hydroxylated unbonded surface of the thick glass chip. . A "press finger" was used to hold the contacted surfaces together for 20 minutes, thereby driving the formation of the contact bond. In some variations, a "press finger" was used to apply a target pressure (eg, about 2 MPa) for a period of 20 minutes.

In some aspects of what is described, the method of manufacturing a vapor cell can be further illustrated by the following examples.
Example 1
A method of manufacturing a vapor cell, comprising:
obtaining a dielectric body including a surface defining an opening to a cavity in the dielectric body;
obtaining an optical window comprising a surface;
modifying the surface of the dielectric body and the surface of the optical window to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands, respectively;
disposing steam or a source of steam within the cavity;
contacting the altered surface of the dielectric body with the altered surface of the optical window to form a seal around the opening to the cavity, the seal first contacting the altered surface during contact of the altered surface; contacting a metal-oxygen bond formed by reacting a plurality of hydroxyl ligands with a second plurality of hydroxyl ligands.
Example 2
2. The method of Example 1, wherein contacting the altered surface comprises covering the opening of the cavity with an optical window to confine the vapor or source of vapor within the cavity.
Example 3
The method of example 1 or example 2, wherein the dielectric body is formed of silicon.
Example 4
4. The method of Example 3, comprising forming an adhesion layer on the dielectric body that defines a surface of the dielectric body, the adhesion layer comprising silicon oxide.
Example 5
The method of Example 1 or Example 2, wherein the dielectric body is formed of glass comprising silicon oxide.
Example 6
The method of Example 1 or any one of Examples 2-5, wherein the metal-oxygen bond comprises a siloxane bond.
Example 7
The method of Example 1 or any one of Examples 2-6, wherein the optical window comprises silicon oxide.
Example 8
The method of Example 1 or any one of Examples 2-7, wherein the vapor comprises a gas of alkali metal atoms.
Example 9
The method of Example 1 or any one of Examples 2-7, wherein the vapor comprises a gas of diatomic halogen molecules.
Example 10
The method of Example 1 or any one of Examples 2-7, wherein the vapor comprises a gas of organic molecules.
Example 11
The method of Example 1 or any one of Examples 2-8, wherein disposing the vapor or source of vapor comprises exposing the cavity to a vacuum environment containing a gas of alkali metal atoms.
Example 12
disposing a vapor or source of vapor comprises disposing a solid or liquid source of alkali metal atoms within the cavity;
This method
The method of Example 1, or any one of Examples 2-8, comprising, after contacting, heating the solid or liquid source of alkali metal atoms to produce a gas of alkali metal atoms.
Example 13
The method of Example 1 or any one of Examples 2-12, wherein the vapor comprises a noble gas.
Example 14
The method of Example 1, or Examples 2-13, wherein altering the surface comprises activating one or both of the surface of the dielectric body and the surface of the optical window by exposing the respective surface to plasma. A method according to any one of the preceding claims.
Example 15
15. The method of Example 14, wherein altering the surface further comprises washing one or both of the activated surface of the dielectric body and the activated surface of the optical window with a basic aqueous solution.
Example 16
The method of Example 1, or any one of Examples 2-15, wherein the surface of the dielectric body and the surface of the optical window are planar surfaces.
Example 17
The method of Example 1 or any one of Examples 2-16, wherein the surface of the dielectric body and the surface of the optical window have a surface roughness Ra of 1 nm or less.
Example 18
The method of Example 1, or any one of Examples 2-17, wherein contacting the altered surfaces comprises pressing together the altered surface of the dielectric body and the altered surface of the optical window. the method of.
Example 19
heating one or both of the dielectric body and the optical window after contacting the altered surface;
The method of Example 1 or any one of Examples 2-18, comprising clamping the dielectric body and the optical window together to keep the altered surfaces in contact during heating. .
Example 20
The method of Example 1 or any one of Examples 2-19, wherein obtaining the dielectric body comprises removing material from the dielectric body to form the cavity.
Example 21
21. The method of example 20, wherein removing material comprises machining material from the surface of the dielectric body with a laser.
Example 22
22. The method of example 20 or example 21, wherein removing material comprises etching material from a surface of the dielectric body.

In some aspects of what is described, the vapor cell can be further illustrated by the following examples.
Example 23
a dielectric body including a surface defining an opening to the cavity of the dielectric body;
a vapor or source of vapor within the cavity of the dielectric body;
An optical window covering an opening of the cavity and having a surface bonded to a surface of the dielectric body to form a seal around the opening, the seal binding a first plurality of hydroxyl ligands on the surface of the dielectric body. an optical window comprising metal-oxygen bonds formed by reacting with a second plurality of hydroxyl ligands on the surface of the optical window.
Example 24
24. The vapor cell of example 23, wherein the dielectric body is formed of silicon.
Example 25
25. The vapor cell of example 24, wherein the vapor cell includes an adhesion layer on the dielectric body defining a surface of the dielectric body, the adhesion layer comprising silicon oxide.
Example 26
24. The vapor cell of example 23, wherein the dielectric body is formed of glass comprising silicon oxide.
Example 27
The vapor cell of Example 23, or any one of Examples 24-26, wherein the metal-oxygen bond comprises a siloxane bond.
Example 28
The vapor cell of Example 23 or any one of Examples 24-27, wherein the optical windows comprise silicon oxide.
Example 29
The vapor cell of Example 23 or any one of Examples 24-28, wherein the vapor comprises a gas of alkali metal atoms.
Example 30
The vapor cell of Example 23 or any one of Examples 24-28, wherein the vapor comprises a gas of diatomic halogen molecules.
Example 31
The vapor cell of Example 23 or any one of Examples 24-28, wherein the vapor comprises a gas of organic molecules.
Example 32
a source of vapor is present in the cavity of the dielectric body;
Example 23, or any one of Examples 24-29, wherein the vapor source comprises a liquid or solid source of alkali metal atoms configured to produce a gas of alkali metal atoms when heated. Vapor cell as described.
Example 33
The vapor cell of Example 23 or any one of Examples 24-32, wherein the vapor comprises a noble gas.
Example 34
The vapor cell of Example 23, or any one of Examples 24-33, wherein the surface of the dielectric body and the surface of the optical window have a surface roughness Ra of 1 nm or less.

In some aspects of what is described, the method of manufacturing a vapor cell having at least two optical windows can be further illustrated by the following examples.
Example 35
A method of manufacturing a vapor cell having at least two optical windows, comprising:
obtaining a dielectric body, the dielectric body comprising:
a cavity in the dielectric body;
a first surface defining a first opening to the cavity; and a second surface defining a second opening to the cavity;
obtaining a first optical window comprising a surface;
bonding the surface of the first optical window to the first surface of the dielectric body to form a first seal around the first opening to the cavity;
obtaining a second optical window comprising a surface;
modifying the second surface of the dielectric body and the surface of the second optical window to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands, respectively;
disposing steam or a source of steam into the cavity through the second opening;
contacting the modified second surface of the dielectric body with the modified surface of the second optical window to form a second seal around the second opening to the cavity; wherein the seal of comprises a metal-oxygen bond formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contact of the altered surface. .
Example 36
36. The method of example 35, wherein bonding the surface of the first optical window to the first surface of the dielectric body comprises covering the first opening of the cavity with the first optical window.
Example 37
37. The method of Example 35 or Example 36, wherein contacting the altered surface comprises covering the second opening of the cavity with a second optical window to confine the vapor or source of vapor within the cavity. Method.
Example 38
The method of Example 35 or any one of Examples 36-37, wherein the dielectric body is formed of silicon.
Example 39
39. The method of Example 38, comprising forming an adhesion layer on the dielectric body that defines the second surface of the dielectric body, the adhesion layer comprising silicon oxide.
Example 40
The method of Example 35 or any one of Examples 36-37, wherein the dielectric body is formed of a glass comprising silicon oxide.
Example 41
The method of Example 35 or any one of Examples 36-40, wherein the metal-oxygen bond of the second seal comprises a siloxane bond.
Example 42
The method of Example 35 or any one of Examples 36-41, wherein the first and second optical windows comprise silicon oxide.
Example 43
The method of Example 35 or any one of Examples 36-42, wherein the vapor comprises a gas of alkali metal atoms.
Example 44
The method of Example 35, or any one of Examples 36-42, wherein the vapor comprises a gas of diatomic halogen molecules.
Example 45
The method of Example 35 or any one of Examples 36-42, wherein the vapor comprises a gas of organic molecules.
Example 46
The method of Example 35, or any one of Examples 36-43, wherein disposing the vapor or source of vapor comprises exposing the cavity to a vacuum environment comprising a gas of alkali metal atoms.
Example 47
disposing a vapor or source of vapor includes disposing a solid or liquid source of alkali metal atoms through the second opening and into the cavity;
This method
The method of Example 35, or any one of Examples 36-43, after contacting, comprising heating the solid or liquid source of alkali metal atoms to produce a gas of alkali metal atoms.
Example 48
The method of Example 35 or any one of Examples 36-47, wherein the vapor comprises a noble gas.
Example 49
Example 35, wherein altering the surface comprises activating one or both of the second surface of the dielectric body and the surface of the second optical window by exposing the respective surface to plasma; or The method of any one of Examples 36-48.
Example 50
50. According to Example 49, wherein altering the surface further comprises washing one or both of the activated surface of the dielectric body and the activated surface of the second optical window with a basic aqueous solution. Method.
Example 51
The method of Example 35 or any one of Examples 36-50, wherein the second surface of the dielectric body and the surface of the second optical window have a surface roughness Ra of 1 nm or less.
Example 52
The method of Example 35, or Examples 36-51, wherein contacting the altered surfaces comprises pressing the altered second surface of the dielectric body and the altered surface of the second optical window against each other. A method according to any one of the preceding claims.
Example 53
heating one or both of the dielectric body and the second optical window after contacting the altered surface;
Clamping the dielectric body and the second optical window together to keep the altered surfaces in contact during heating. described method.
Example 54
bonding the surface of the first optical window,
modifying the first surface of the dielectric body and the surface of the first optical window to include a third plurality of hydroxyl ligands and a fourth plurality of hydroxyl ligands, respectively;
contacting the modified first surface of the dielectric body with the modified surface of the first optical window to form a first seal around the first opening to the cavity; wherein the seal of comprises a metal-oxygen bond formed by reacting a third plurality of hydroxyl ligands with a fourth plurality of hydroxyl ligands during contact of the altered surface; The method of Example 35, or any one of Examples 36-53.
Example 55
the dielectric body is formed of silicon and the first optical window comprises silicon oxide;
Example 35, wherein bonding the surface of the first optical window comprises anodically bonding the surface of the first optical window to the first surface of the dielectric body to form a first seal; or the method according to any one of Examples 36-39 (excluding the subject matter of Example 40 in any combination of Examples, including Example 55).
Example 56
a dielectric body formed of a glass containing silicon oxide, a first optical window containing silicon oxide,
The method comprises depositing a layer of silicon on the first surface of the dielectric body;
Example 35, or Example 36-, wherein bonding the surface of the first optical window comprises anodically bonding a layer of silicon to the surface of the first optical window to form a first seal 37 and any one of 40-53 (excluding the subject matter of Examples 38-39 in any combination of Examples, including Example 56).
Example 57
a dielectric body formed of a glass containing silicon oxide, a first optical window containing silicon oxide,
bonding the surface of the first optical window,
applying a glass frit to one or both of the first surface of the dielectric body and the surface of the first optical window;
contacting the first surface of the dielectric body with the surface of the first optical window;
heating at least one of the glass frit, the dielectric body, or the first optical window to a firing temperature to form the first seal. and the method of any one of 40-53 (excluding the subject matter of Examples 38-39 in any combination of Examples, including Example 57).
Example 58
the first and second surfaces of the dielectric body are opposite planar surfaces;
The method of Example 35, or any one of Examples 36-57, wherein the surface of the first optical window and the surface of the second optical window are flat surfaces.
Example 59
The method of Example 35 or any one of Examples 36-58, wherein obtaining the dielectric body comprises removing material from the dielectric body to form the cavity.
Example 60
60. The method of Example 59, wherein removing material comprises machining material from the surface of the dielectric body with a laser.
Example 61
61. The method of example 59 or example 60, wherein removing material comprises etching material from a surface of the dielectric body.

In some aspects of what is described, a vapor cell having at least two optical windows can be further illustrated by the following examples.
Example 62
A vapor cell having at least two optical windows,
is a dielectric body,
a cavity in the dielectric body;
a dielectric body comprising: a first surface defining a first opening to the cavity; and a second surface defining a second opening to the cavity;
a vapor or source of vapor within the cavity of the dielectric body;
a first optical window covering the first opening of the cavity and having a surface bonded to the first surface of the dielectric body to form a first seal around the first opening; and a second of the cavity. a second optical window having a surface that covers the opening of and is bonded to the second surface of the dielectric body to form a second seal around the second opening, the second seal comprising: a second plurality of hydroxyl ligands on the second surface of the dielectric body comprising metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands on the second surface of the dielectric body with a second plurality of hydroxyl ligands on the surface of the second optical window; A vapor cell including an optical window.
Example 63
63. The vapor cell of embodiment 62, wherein the dielectric body is formed of silicon.
Example 64
64. The vapor cell of example 63, wherein the vapor cell includes an adhesion layer on the dielectric body defining a second surface of the dielectric body, the adhesion layer comprising silicon oxide.
Example 65
63. The vapor cell of example 62, wherein the dielectric body is formed of glass comprising silicon oxide.
Example 66
The vapor cell of Example 62 or any one of Examples 63-65, wherein the metal-oxygen bond of the second seal comprises a siloxane bond.
Example 67
The vapor cell of Example 62 or any one of Examples 63-66, wherein the first and second optical windows comprise silicon oxide.
Example 68
The vapor cell of Example 62 or any one of Examples 63-67, wherein the vapor comprises a gas of alkali metal atoms.
Example 69
The vapor cell of Example 62, or any one of Examples 63-67, wherein the vapor comprises a gas of diatomic halogen molecules.
Example 70
The vapor cell of Example 62 or any one of Examples 63-67, wherein the vapor comprises a gas of organic molecules.
Example 71
a source of vapor is present in the cavity of the dielectric body;
Example 62, or any one of Examples 63-68, wherein the vapor source comprises a liquid or solid source of alkali metal atoms configured to produce a gas of alkali metal atoms when heated. Vapor cell as described.
Example 72
The vapor cell of Example 62, or any one of Examples 63-71, wherein the vapor comprises a noble gas.
Example 73
The vapor cell of Example 62, or any one of Examples 63-72, wherein the second surface of the dielectric body and the surface of the second optical window have a surface roughness Ra of 1 nm or less.
Example 74
the first and second surfaces of the dielectric body are opposite planar surfaces;
The vapor cell of Example 62, or any one of Examples 63-73, wherein the surface of the first optical window and the surface of the second optical window are flat surfaces.
Example 75
The first seal is a metal-oxygen bond formed by reacting a third plurality of hydroxyl ligands on the first surface of the dielectric body with a fourth plurality of hydroxyl ligands on the surface of the first optical window. The vapor cell of Example 62, or any one of Examples 63-74, comprising:
Example 76
The vapor cell of Example 62 or any one of Examples 63-74, wherein the dielectric body is formed of silicon and the first optical window comprises silicon oxide.
Example 77
77. The vapor cell of example 76, wherein the first seal comprises an anodic bond between the first surface of the dielectric body and the surface of the first optical window.
Example 78
a dielectric body formed of a glass containing silicon oxide, a first optical window containing silicon oxide,
the vapor cell comprising a layer of silicon disposed between the first surface of the dielectric body and the surface of the first optical window;
Example 62, or Examples 63-74, wherein the first seal comprises an anodic bond between the layer of silicon and one or both of the first surface of the dielectric body and the surface of the first optical window A vapor cell according to any one of the preceding claims.
Example 79
a dielectric body formed of a glass containing silicon oxide, a first optical window containing silicon oxide,
Example 62, wherein the vapor cell comprises a fired layer of glass frit bonding the first surface of the dielectric body to the surface of the first optical window, the fired layer of glass frit defining the first seal, or The vapor cell of any one of Examples 63-74.

While this specification contains many details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features described in the specification or illustrated in the drawings in the context of separate embodiments can also be combined. Conversely, various features that are described or illustrated in the context of a single embodiment can also be combined in multiple embodiments separately or in any suitable subcombination.

Similarly, although acts may be shown or described in the drawings in a particular order, it is understood that such acts may be performed in the specific order presented or in a sequential order to achieve desirable results. It should not be understood that it is performed or requires that all illustrated acts be performed. Multitasking and parallel processing may be advantageous in certain situations. Moreover, the separation of various system components in the above-described implementations should not be understood to require such separation in all implementations, and the described program components and systems are generally implemented in a single unit. products, or may be packaged in multiple products.

A number of embodiments have been described. It will nevertheless be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims.

Dielectric body 102 includes a surface 106 that defines an opening 108 in dielectric body 102 to cavity 110 . Surface 106 can be a flat surface as shown in FIGS. 1A-1B, but other surfaces are possible (eg, curved). Aperture 108 can be any type of opening that allows access to the interior volume of cavity 110 and can have any shape (eg, circular, square, hexagonal, oval, etc.). . Such access may allow steam (or a source of steam (steam source)) to be placed within cavity 110 during manufacture of steam cell 100 . Cavity 110 extends from surface 106 into dielectric body 102 and stops before extending completely through dielectric body 102 . Cavity 110 can have a uniform cross-section along its extension through the dielectric body. However, in some variations, the cross-section of cavity 110 may vary along the extension.

Optical window 104 may be formed of a material that is transparent to electromagnetic radiation (eg, laser light) used to interrogate vapor sealed within cavity 110 of dielectric body 102 . For example, the material of the optical window 104 is sensitive to infrared wavelengths of electromagnetic radiation (eg, 700-1000 nm), visible wavelengths of electromagnetic radiation (eg, 400-7000 nm), or ultraviolet wavelengths of electromagnetic radiation (eg, 10-400 nm). can be made transparent to Moreover, the material of the optical window 104 can be an insulating material with high resistivity, ^e.g. be able to. For example, the material of optical window 104 can include silicon oxide (eg, SiO ₂ , SiO _x , etc.) such as found in quartz, fused silica, or borosilicate glass. In another example, the material of optical window 104 can include aluminum oxide (eg, Al ₂ O ₃ , Al _x O _y , etc.) such as found in sapphire or aluminosilicate glass. In one example, the material of the optical window 104 is magnesium oxide (e.g. MgO), aluminum oxide (e.g. _Al2O3 ) _, silicon dioxide (e.g. _SiO2 ), titanium dioxide (e.g. _TiO2 ), zirconium dioxide. (eg ZrO ₂ ), yttrium oxide (eg Y ₂ O ₃ ), lanthanum oxide (eg La ₂ O ₃ ) and the like. The oxide material may be non-stoichiometric (eg, SiO _x ), or may be a combination of one or more binary oxides (eg, Y:ZrO ₂ , LaAlO ₃ , etc.). In another example, the material of optical window 104 is a non-oxide material such as diamond (C), calcium fluoride (CaF), and the like.

Although FIGS. 1A-4 show square vapor cells with circular cavities, other shapes are possible for the vapor cells and their respective cavities. For example, FIGS. 5A-5C present alternative shapes of exemplary vapor cells 500, 520, 540 in perspective view. In FIG. 5A, an exemplary vapor cell 500 includes a circular dielectric body 502 and circular optical windows 504,506. Circular dielectric body 502 includes square walls 508 to define cavity 510 therein. In some variations, circular dielectric body 502 may be formed of silicon and may be approximately 0.5 mm thick. The circular dielectric body 502 may have a diameter of approximately 1.5 mm. In some variations, the circular optical windows 504, 506 can be approximately 0.05 mm to 0.30 mm thick. Circular optical windows 504 , 506 can share a common diameter with circular dielectric body 502 . In some variations, square wall 508 can have an edge length of about 0.9 mm.

After the contact bond is formed, the vapor cell can be coated with a material such as parylene or epoxy to protect the vapor cell. The vapor cell can also be fiber coupled by attaching the fiber to the window either directly or with a GRIN lens.

Claims (60)

A method of manufacturing a vapor cell, comprising:
obtaining a dielectric body including a surface defining an opening to a cavity of the dielectric body;
obtaining an optical window comprising a surface;
modifying the surface of the dielectric body and the surface of the optical window to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands, respectively;
disposing steam or a source of said steam within said cavity;
contacting the altered surface of the dielectric body with the altered surface of the optical window to form a seal around the opening to the cavity, the seal being in contact with the altered surface of the optical window; contacting comprising a metal-oxygen bond formed by reacting said first plurality of hydroxyl ligands with said second plurality of hydroxyl ligands during surface contacting. 2. The method of claim 1, wherein contacting the altered surface comprises covering the opening of the cavity with the optical window to confine the vapor or the source of the vapor within the cavity. 3. The method of claim 1 or claim 2, wherein the dielectric body is formed of silicon. 4. The method of claim 3, comprising forming an adhesion layer on the dielectric body defining the surface of the dielectric body, the adhesion layer comprising silicon oxide. 3. The method of claim 1 or claim 2, wherein the dielectric body is formed of glass containing silicon oxide. 3. The method of claim 1 or claim 2, wherein the metal-oxygen bond comprises a siloxane bond. 3. The method of claim 1 or claim 2, wherein the optical window comprises silicon oxide. 3. A method according to claim 1 or claim 2, wherein the vapor comprises a gas of alkali metal atoms. 3. The method of claim 1 or claim 2, wherein disposing the vapor or the source of the vapor comprises exposing the cavity to a vacuum environment containing a gas of alkali metal atoms. disposing the vapor or the source of the vapor comprises disposing a solid or liquid source of alkali metal atoms within the cavity;
the method comprising:
3. The method of claim 1 or claim 2, comprising heating said solid or liquid source of said alkali metal atoms after contacting to produce a gas of said alkali metal atoms. Claim 1 or claim, wherein altering the surface comprises activating one or both of the surface of the dielectric body and the surface of the optical window by exposing the respective surface to a plasma. Item 2. The method according to item 2. 12. The method of claim 11, wherein altering the surface further comprises washing one or both of the activated surface of the dielectric body and the activated surface of the optical window with a basic aqueous solution. described method. 3. The method of claim 1 or claim 2, wherein the surface of the dielectric body and the surface of the optical window have a surface roughness Ra of 1 nm or less. 3. The method of claim 1 or claim 2, wherein obtaining the dielectric body comprises removing material from the dielectric body to form the cavity. A method of manufacturing a vapor cell having at least two optical windows, comprising:
obtaining a dielectric body, said dielectric body comprising:
a cavity in the dielectric body;
a first surface defining a first opening to the cavity and a second surface defining a second opening to the cavity;
obtaining a first optical window comprising a surface;
bonding the surface of the first optical window to the first surface of the dielectric body to form a first seal around the first opening to the cavity;
obtaining a second optical window comprising a surface;
modifying the second surface of the dielectric body and the surface of the second optical window to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands, respectively;
disposing steam or a source of said steam into said cavity through said second opening;
contacting the altered second surface of the dielectric body with the altered surface of the second optical window to form a second seal around the second opening to the cavity; wherein said second seal binds metal-oxygen bonds formed by reacting said first plurality of hydroxyl ligands with said second plurality of hydroxyl ligands during contact of said modified surface; A method comprising contacting. 4. The contacting of the altered surface comprises covering the second opening of the cavity with the second optical window to confine the vapor or the source of the vapor within the cavity. 15. The method according to 15. 17. A method according to claim 15 or 16, wherein said dielectric body is formed of silicon. 18. The method of claim 17, comprising forming an adhesion layer on the dielectric body defining the second surface of the dielectric body, the adhesion layer comprising silicon oxide. . 17. The method of claim 15 or 16, wherein the dielectric body is formed of glass containing silicon oxide. 17. The method of claim 15 or claim 16, wherein said metal-oxygen bond of said second seal comprises a siloxane bond. 17. The method of claim 15 or claim 16, wherein the first and second optical windows comprise silicon oxide. 17. A method according to claim 15 or claim 16, wherein the vapor comprises a gas of alkali metal atoms. 17. The method of claim 15 or claim 16, wherein disposing the vapor or the source of the vapor comprises exposing the cavity to a vacuum environment containing a gas of alkali metal atoms. disposing the vapor or the source of the vapor comprises disposing a solid or liquid source of alkali metal atoms through the second opening and into the cavity;
said method comprising:
17. The method of claim 15 or claim 16, comprising heating said solid or liquid source of said alkali metal atoms after contacting to produce a gas of said alkali metal atoms. Altering the surface includes activating one or both of the second surface of the dielectric body and the surface of the second optical window by exposing the respective surfaces to plasma. 17. A method according to claim 15 or 16. 26. The method of claim 25, wherein altering the surface further comprises washing one or both of the activated surface of the dielectric body and the activated surface of the optical window with a basic aqueous solution. described method. wherein the dielectric body is formed of silicon and the first optical window comprises silicon oxide;
bonding the surface of the first optical window anodically bonding the surface of the first optical window to the first surface of the dielectric body to form the first seal; 17. A method according to claim 15 or claim 16, comprising wherein the dielectric body is formed of glass containing silicon oxide, the first optical window contains silicon oxide,
the method comprising depositing a layer of silicon on the first surface of the dielectric body;
16. Bonding the surface of the first optical window comprises anodically bonding the layer of silicon to the surface of the first optical window to form the first seal. Or the method of claim 16. wherein the dielectric body is formed of glass containing silicon oxide, the first optical window contains silicon oxide,
bonding the surface of the first optical window,
applying a glass frit to one or both of the first surface of the dielectric body and the surface of the first optical window;
contacting the first surface of the dielectric body with the surface of the first optical window;
heating at least one of the glass frit, the dielectric body, or the first optical window to a firing temperature to form the first seal. 16. The method according to 16. 17. A method according to claim 15 or 16, wherein obtaining the dielectric body comprises removing material from the dielectric body to form the cavity. said dielectric body including a surface defining an opening to a cavity of said dielectric body;
vapor in the cavity of the dielectric body or a source of the vapor;
an optical window covering the opening of the cavity and having a surface bonded to the surface of the dielectric body to form a seal around the opening, the seal being attached to the surface of the dielectric body; an optical window comprising metal-oxygen bonds formed by reacting a first plurality of hydroxyl ligands with a second plurality of hydroxyl ligands on the surface of the optical window. 32. The vapor cell of claim 31, wherein said dielectric body is formed of silicon. 33. The vapor cell of claim 32, wherein the vapor cell includes an adhesion layer on the dielectric body defining the surface of the dielectric body, the adhesion layer comprising silicon oxide. 32. The vapor cell of claim 31, wherein said dielectric body is formed of glass comprising silicon oxide. 31. The vapor cell of claim 31 or any one of claims 32-34, wherein the metal-oxygen bond comprises a siloxane bond. The vapor cell of claim 31 or any one of claims 32-34, wherein the optical windows comprise silicon oxide. The vapor cell of claim 31 or any one of claims 32-34, wherein the vapor comprises a gas of alkali metal atoms. The vapor cell of claim 31 or any one of claims 32-34, wherein the vapor comprises a noble gas. The vapor cell of claim 31 or any one of claims 32-34, wherein the vapor comprises a gas of diatomic halogen molecules. The vapor cell of claim 31 or any one of claims 32-34, wherein the vapor comprises a gas of organic molecules. said source of said vapor is present in said cavity of said dielectric body;
Claim 31, or any of claims 32-34, wherein said source of said vapor comprises a liquid or solid source of said alkali metal atoms configured to produce a gas of alkali metal atoms when heated. 2. The vapor cell of claim 1. 31. The vapor cell of claim 31 or any one of claims 32-34, wherein the surface of the dielectric body and the surface of the optical window have a surface roughness Ra of 1 nm or less. A vapor cell having at least two optical windows,
is a dielectric body,
a cavity in the dielectric body;
a dielectric body comprising a first surface defining a first opening to said cavity and a second surface defining a second opening to said cavity;
vapor in the cavity of the dielectric body or a source of the vapor;
A first optical window covering the first opening of the cavity and having a surface bonded to the first surface of the dielectric body to form a first seal around the first opening. and a second optic covering said second opening of said cavity and having a surface bonded to said second surface of said dielectric body to form a second seal around said second opening. a window, wherein the second seal reacts a first plurality of hydroxyl ligands on the second surface of the dielectric body with a second plurality of hydroxyl ligands on the surface of the second optical window; a second optical window comprising a metal-oxygen bond formed by 44. The vapor cell of claim 43, wherein said dielectric body is formed of silicon. 45. The vapor cell of claim 44, wherein the vapor cell includes an adhesion layer on the dielectric body defining the second surface of the dielectric body, the adhesion layer comprising silicon oxide. 44. The vapor cell of claim 43, wherein said dielectric body is formed of glass comprising silicon oxide. 47. The vapor cell of claim 43 or any one of claims 44-46, wherein said metal-oxygen bond of said second seal comprises a siloxane bond. 47. The vapor cell of claim 43 or any one of claims 44-46, wherein the first and second optical windows comprise silicon oxide. 47. The vapor cell of claim 43 or any one of claims 44-46, wherein the vapor comprises a gas of alkali metal atoms. The vapor cell of claim 43 or any one of claims 44-46, wherein the vapor comprises a noble gas. 47. The vapor cell of claim 43 or any one of claims 44-46, wherein the vapor comprises a gas of diatomic halogen molecules. The vapor cell of claim 43 or any one of claims 44-46, wherein the vapor comprises a gas of organic molecules. said source of said vapor is present in said cavity of said dielectric body;
Claim 43, or any of claims 44-46, wherein the source of the vapor comprises a liquid or solid source of alkali metal atoms configured to produce a gas of the alkali metal atoms when heated. 2. The vapor cell of claim 1. Claim 43 or any one of claims 44 to 46, wherein the second surface of the dielectric body and the surface of the second optical window have a surface roughness Ra of 1 nm or less. steam cell. said first and second surfaces of said dielectric body being opposite planar surfaces;
47. The vapor cell of claim 43 or any one of claims 44-46, wherein the surface of the first optical window and the surface of the second optical window are flat surfaces. The first seal is formed by reacting a third plurality of hydroxyl ligands on the first surface of the dielectric body with a fourth plurality of hydroxyl ligands on the surface of the first optical window. 47. The vapor cell of claim 43 or any one of claims 44-46, comprising a metal-oxygen bond. 47. The vapor cell of claim 43 or any one of claims 44-46, wherein the dielectric body is formed of silicon and the first optical window comprises silicon oxide. 58. The vapor cell of claim 57, wherein said first seal comprises an anodic bond between said first surface of said dielectric body and said surface of said first optical window. wherein the dielectric body is formed of glass containing silicon oxide, the first optical window contains silicon oxide,
said vapor cell comprising a layer of silicon disposed between said first surface of said dielectric body and said surface of said first optical window;
44, wherein said first seal comprises an anodic bond between said layer of silicon and one or both of said first surface of said dielectric body and said surface of said first optical window; Or the vapor cell of any one of claims 44-46. wherein the dielectric body is formed of glass containing silicon oxide, the first optical window contains silicon oxide,
The vapor cell includes a first layer of glass frit bonding the first surface of the dielectric body to the surface of the first optical window, the first layer of glass frit bonding to the first surface of the first optical window. 43 or any one of claims 44 to 46, wherein the vapor cell defines a seal of .

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