Connectable Vapor Cells

Abstract

In a general aspect, the vapor cell includes a body defined by a stack of layers bonded together. The stack of layers includes a first end layer disposed at a first end of the body and a second end layer disposed at an opposite second end of the body. An intermediate layer extends between the first end layer and the second end layer and defines an interior cavity extending through the body between the first end layer and the second end layer. The stack of layers also includes first and second sets of tabs. The first set of tabs extend outwardly from the intermediate layer at a first exterior portion of the body and the second set of tabs extend outwardly from the intermediate layer at a second exterior portion of the body. The vapor cell also includes a vapor or vapor source disposed in the interior cavity.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Application No. 17 / 480,443, filed September 21, 2021, entitled "Interlockable Vapor Cells," and U.S. Provisional Application No. 63 / 174,289, filed April 13, 2021, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] (Technical field) The following description refers to vapor cells, which can be coupled in several configurations. [Background technology]

[0003] A vapor cell is produced by sealing a vapor or gas in a closed volume. The vapor or gas can be used as a medium to interact with electromagnetic radiation generated by an external source. A laser can be directed through the vapor cell and the response to the laser can be used to determine a characteristic of the electromagnetic radiation and act as a sensor of the electromagnetic radiation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Application Serial No. 17 / 480,448 [Patent Document 2] U.S. Provisional Application No. 63 / 174,289 [Patent Document 3] U.S. Patent No. 10,509,065 [Patent Document 4] U.S. Patent No. 10,859,981 [Brief description of the drawings]

[0005] [Figure 1A] FIG. 1 is a schematic perspective view of an exemplary vapor cell 100. [Figure 1B] FIG. 1B is a schematic bottom perspective view of the exemplary vapor cell depicted in FIG. 1A. [Figure 1C] FIG. 1B is a schematic perspective view of the exemplary vapor cell depicted in FIG. 1A having a spherical shape and an internal cavity of the spherical shape. [Figure 1D] FIG. 1D is a schematic perspective view of one half of the exemplary vapor cell of FIG. 1C. [Figure 1E] FIG. 1B is a schematic diagram of an exemplary vapor cell as depicted in FIG. 1A but having an octagonal shape and no mechanical joints. [Figure 1F] FIG. 1B is a schematic diagram of an exemplary vapor cell 100 as depicted in FIG. 1A, but having a square shape and no mechanical joints. [Figure 1G] FIG. 1B is a schematic perspective view of three illustrations of the exemplary vapor cell shown in FIG. 1A, two of which are bonded together. [Figure 2A] FIG. 1B is a schematic perspective view of five illustrations of the exemplary vapor cell shown in FIG. 1A coupled together to form a “T-shaped” subassembly. [Figure 2B] FIG. 1B is a schematic perspective view of eight instances of the exemplary vapor cell shown in FIG. 1A coupled together to form an octagonal subassembly. [Figure 3A] 2B is a schematic perspective view of five examples of the "T-shaped" subassemblies shown in FIG. 2A that are connected together to form an arc-shaped assembly. FIG. [Figure 3B] FIG. 2C is a schematic top view of five illustrative octagonal subassemblies shown in FIG. 2B interlocked together to form a tile array pattern. [Figure 4A] 1 is a graph illustrating an electromagnetic simulation of an exemplary configuration of a vapor cell with multiple holes present in each intermediate layer. [Figure 4B] 4B is a graph showing an electromagnetic simulation of an exemplary configuration of a vapor cell as described in FIG. 4A but without the multiple holes. [Diagram 5] 11 is a graph showing electromagnetic simulations of the electric field distribution inside various exemplary configurations of a vapor cell having perforated walls. [Figure 6A]FIG. 2 is a schematic diagram of an exemplary vapor cell having an array of cavities therein. [Figure 6B] FIG. 6B is a schematic diagram of the exemplary vapor cell depicted in FIG. 6A, but with its intermediate layer lacking tabs extending outwardly therefrom. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] In a general aspect, the vapor cell can include a body defined by a stack of layers bonded together, such as a stack of layers stacked or bonded. This configuration can allow the vapor cell to be manufactured to tight tolerances in large quantities. This configuration can also allow structuring in three dimensions and tiling multiple instantiations of the vapor cell to build an array. In operation, the vapor cell has a fairly uniform RF field at its center, which allows measurements to be fairly accurate and precise. In some examples, the average RF field amplitude within the interaction region of the vapor cell can be within 1% of the incident RF amplitude with less than 1% variation over the intended interaction region. The background gas within the vapor cell can also be lower than the vapor pressure (e.g., alkali vapor pressure) so that collision spread is reduced or minimized. In some cases, the vapor cell has a radar cross section that is smaller than its geometric cross section, and in some configurations significantly smaller. Transparency criteria can be met using a cell geometry that can be scaled for frequencies above 40 GHz. The vapor cell interaction area can also be scaled to account for frequency to reduce or minimize transit time spread. In some cases, the vapor cell can be fiber coupled and configured to function in counterpropagating, copropagating, or both light propagation geometries. In some configurations, multiple instantiations of the vapor cell can be coupled together by mechanical joints. However, non-coupled configurations are possible.

[0007] 1A-6B present schematic diagrams of exemplary configurations for a vapor cell along with exemplary arrangements of some possible tiled patterns or assemblies. The exemplary vapor cells shown in FIGS. 1A-6B include a stack of layers, such as those made of glass and highly resistive (floating) silicon. Although the schematic diagrams illustrate alternating layers of dielectric materials (e.g., alternating layers of silicon and glass), other arrangements of dielectric materials are possible. The stacked configuration allows the vapor cell to be structured in three dimensions and eases manufacturing requirements, since the individual layers can be cut in two dimensions from a large high-quality wafer or substrate. In some variations, the layers are anodically bonded to each other to form the stacked configuration. The top and bottom windows (or end layers) can be made of optically transparent dielectric materials, such as borosilicate glass or aluminosilicate glass. Each unit can be fiber-bonded, and the windows can have optical mirrors and filters disposed thereon. The vapor cell configuration is flexible, allowing for three-dimensional structuring and efficient manufacturing. In some variations, the vapor cells have mechanical joints (eg, interlocking tabs) that can be used to tile multiple vapor cells together.

[0008] Referring now to FIG. 1A, a schematic diagram of an exemplary vapor cell 100 is provided. FIG. 1B shows a schematic diagram of the exemplary vapor cell 100 depicted in FIG. 1A. The exemplary vapor cell 100 includes a body 102 defined by a stack 104 of layers (e.g., a laminate defined by the stack 104 of layers) bonded together. The stack 104 of layers can include one or more outer surfaces that define the profile of the body 102 (e.g., a rectangular profile, a spherical profile, a rectangular profile, an ellipsoid profile, etc.). For example, each layer of the stack 104 can include a perimeter surface that defines a cross-section of the profile at that location of the layer (e.g., a square cross-section, a circular cross-section, a rectangular cross-section, etc.). The cross-section can remain constant along the stack 104 of layers, vary along the stack 104 of layers, or some combination thereof. To vary the cross-section, at least two adjacent layers can have respective perimeter surfaces that differ from each other in one or both of shape and size. 1A and 1B depict an exemplary vapor cell 100 having an outer rectangular shape with a constant cross-section along the stack of layers, however, other shapes are possible (see, e.g., FIGS. 1C and 1E).

[0009] In many implementations, the layer stack 104 is formed of a dielectric material that is transparent to the target electromagnetic radiation measured by the exemplary vapor cell 100. The dielectric material can enable the layer stack 104 to absorb no more than 1% of the target electromagnetic radiation as it passes through the body 102. The dielectric material can also be transparent to the target electromagnetic radiation, e.g., ρ>10 8 The insulating material may have a high resistivity of Ω·cm and may correspond to a single crystal dielectric material, a polycrystalline dielectric material, or an amorphous dielectric material.

[0010] In some implementations, the "transparent" dielectric material is one that minimizes absorption and scattering of the target electromagnetic radiation by the body 102. In these implementations, the layer stack 104 can transmit the target electromagnetic radiation to the rear or into the body 102 without significant distortion. In some variations, the layer stack 104 has a radar scattering cross section that is smaller than its geometric cross-sectional area. The layer stack 104 can also have an absorption rate of less than 1% for the target electromagnetic radiation. For example, the layer stack 104 can be formed in whole or in part of floating silicon. The loss target of floating silicon is about 10% for frequencies up to 400 GHz. -3 In certain applications, such as antenna testing, high transparency is required to minimize reflections in the test environment and to accurately measure power across more than one spatial plane or surface. In some cases, the dielectric materials forming the stack of layers 104 allow the target electromagnetic field inside the exemplary vapor cell 100 to be within 1% of the target electromagnetic field at the incident on the vapor cell 100.

[0011] For example, one or more layers of stack 104 may be formed of silicon, such as single crystal silicon. In another example, one or more layers of stack 104 may be formed of silicon oxide (SiO, SiO 2 ), such as vitreous silica, borosilicate glass, or aluminosilicate glass. x In yet another example, one or more layers of stack 104 can be formed of an oxide material, such as magnesium oxide (e.g., MgO), aluminum oxide (e.g., Al2O3), silicon dioxide (e.g., SiO2), titanium dioxide (e.g., TiO2), zirconium dioxide (e.g., ZrO2), yttrium oxide (e.g., Y2O3), lanthanum oxide (e.g., La2O3), and the like. Oxide materials can be non-stoichiometric (e.g., SiO x ), and further comprising one or more binary oxides (e.g., Y: ZrO2, LaAlO3, BaLa2Ti4O 12The oxide material may be a combination of oxides, such as silicon (Si), diamond (C), gallium nitride (GaN), calcium fluoride (CaF), and the like. The oxide material may be a single crystal material, a polycrystalline material, or an amorphous material. In yet another example, one or more layers of the stack 104 may be formed of a non-oxide material, such as silicon (Si), diamond (C), gallium nitride (GaN), calcium fluoride (CaF), and the like. Other dielectric materials are possible.

[0012] The stack of layers 104 includes a first terminal layer 106 disposed at a first end 108 of the body 102. The first terminal layer 106 is formed of a first type of dielectric material that is optically transparent. The first type of dielectric material can be optically transparent to electromagnetic radiation in the infrared wavelengths (e.g., 700-1000 nm), electromagnetic radiation in the visible wavelengths (e.g., 400-7000 nm), electromagnetic radiation in the ultraviolet wavelengths (e.g., 10-400 nm), or any combination thereof. The stack of layers 104 further includes a second terminal layer 110 disposed at an opposite second end 112 of the body 102. The second terminal layer 110 is formed of a dielectric material, for example, as described above with respect to the stack of layers 104. The dielectric material can be different from the first type of dielectric material forming the first terminal layer 106. However, in some variations, the second terminal layer 110 is formed of the first type of dielectric material.

[0013] In some variations, the first type of dielectric material is a silicon oxide (e.g., SiO, SiO 2 ), such as those found in quartz, vitreous silica, or borosilicate glass. x In some variations, the first type of dielectric material includes aluminum oxides (e.g., Al2O3, Al, etc.), such as those found in sapphire or aluminosilicate glasses. x O yIn some variations, the first type of dielectric material is an oxide material, such as magnesium oxide (e.g., MgO), aluminum oxide (e.g., Al2O3), silicon dioxide (e.g., SiO2), titanium dioxide (e.g., TiO2), zirconium dioxide (e.g., ZrO2), yttrium oxide (e.g., Y2O3), lanthanum oxide (e.g., La2O3), and the like. The oxide materials may be non-stoichiometric (e.g., SiO x ), and further comprising one or more binary oxides (e.g., Y: ZrO2, LaAlO3, BaLa2Ti4O 12 The oxide material may be a combination of a single crystal oxide material, a polycrystalline oxide material, or an amorphous oxide material. In other variations, the first type of dielectric material is a non-oxide material, such as diamond (C), calcium fluoride (CaF), and the like. Other dielectric materials are possible.

[0014] The stack of layers 104 further includes an intermediate layer 114 between the first end layer 106 and the second end layer 110. The intermediate layer 114 can be formed of a dielectric material, such as those described above with respect to the stack of layers 104. The intermediate layer 114 defines an internal cavity 116 that extends through the body 102 between the first end layer 106 and the second end layer 110. The internal cavity 116 can extend along an axis perpendicular to the stack of layers 104, although other orientations (e.g., tilted axes) are possible. Additionally, although FIGS. 1A and 1B depict the internal cavity 116 as having a cylindrical shape, other shapes (e.g., rectangular, hexagonal, ellipsoidal, spherical, etc.) are possible. For example, FIG. 1C presents a schematic perspective view of an exemplary vapor cell 100, but having a spherical shape, and further having a spherical-shaped internal cavity 116. FIG. 1D provides a schematic perspective view of one half of the exemplary vapor cell 100 depicted in FIG. 1C.

[0015] In some implementations, each intermediate layer 114 includes a through hole that defines a portion of the internal cavity 116 therethrough. In these implementations, the through holes can be selectively configured to define a target three-dimensional volume (e.g., a sphere, a frustum, a tilted parallelepiped, etc.) for the internal cavity 116 when the intermediate layers 114 are stacked. The through holes can be configured in any combination of shape, size, and location. Other characteristics are possible. In some variations, each through hole is equal in shape and size. In these variations, the internal cavity 116 can have a constant cross-section through the multiple intermediate layers 114. FIGS. 1A and 1B show examples where the through holes are circular, share a common size, and are aligned in a direction perpendicular to the stack of layers 104. Thus, the through holes define a cylindrical volume for the internal cavity 116. In some variations, at least two adjacent intermediate layers 114 have respective through holes that differ from each other in one or both of shape and size. In these variations, the internal cavity 116 can have a cross-section that varies at least partially through the multiple intermediate layers 114. Figures 1C and 1D show variations in which the through-holes are circular but of different sizes. The through-holes are aligned in a direction perpendicular to the stack of layers 104 to define a spherical volume for the internal cavity 116.

[0016] Other features of the intermediate layer 114 can be used to define the target three-dimensional volume. For example, two or more intermediate layers 114 (e.g., adjacent intermediate layers) have different thicknesses. As another example, a through hole in an intermediate layer can define an inner periphery of the intermediate layer that includes an inner periphery. The inner periphery can be angled, chamfered, or rounded to help define the target three-dimensional volume.

[0017] The target three-dimensional volume can be selected to shape the profile of electromagnetic radiation formed within the internal cavity 116 when electromagnetic radiation is incident on the exemplary vapor cell 100. For example, the target three-dimensional volume can be selected to focus the incident electromagnetic radiation at the center of the internal cavity 116. Such shaping can increase the amplitude of the incident electromagnetic radiation (e.g., the amplitude of the electric or magnetic field) within the internal cavity 116, making the exemplary vapor cell 100 more sensitive to the incident electromagnetic radiation. The target three-dimensional volume can also be selected to make the profile of the incident electromagnetic radiation more uniform, such as across a desired region within the internal cavity 116. Increasing uniformity can increase the amount of vapor that interacts with the incident electromagnetic radiation, thereby expanding the sensing area within the internal cavity 116. Additionally, the target three-dimensional volume can be selected to reduce the thickness of the walls surrounding the internal cavity 116, thereby allowing the body 102 of the exemplary vapor cell 100 to be more transparent to the incident electromagnetic radiation. Other advantages are possible.

[0018] The target three-dimensional volume may also be selected in conjunction with the geometry of the body 102. Certain volume and geometry combinations may improve the performance of the example vapor cell 100 for the target application. For example, the interior cavity 116 may have a spherical volume and the body 102 may have a spherical geometry (e.g., as shown in FIGS. 1C-1D). This combination may allow for easier modeling of the electromagnetic field profiles inside and outside the example vapor cell 100. Such ease of modeling may be used to improve the performance of the example vapor cell 100 in metrology or other applications.

[0019] In some implementations, such as those that reduce or prevent helium transmission, the stack of layers 104 includes layers formed of aluminosilicate glass or borosilicate glass (e.g., Pyrex®). The stack of layers 104 can be coated with materials that exhibit low helium transmission. Various optical coatings (e.g., Bragg mirrors) can be deposited on the first and second end layers 106, 110 to act as high reflectors and filters for optical signals used for laser preparation and signaling. Wave plates can be used to control polarization in conjunction with polarization-maintaining fibers. For example, the exemplary vapor cell 100 can be optically coupled fiber with a GRIN (gradient index) lens centered on its end layer (e.g., the first end layer 106 or the second end layer 110).

[0020] The exemplary vapor cell 100 further includes a vapor (not shown) disposed within the interior cavity 116 defined by the intermediate layer 114. The vapor can include components such as a gas of alkali metal atoms, a noble gas, a gas of diatomic halogen molecules, a gas of organic molecules, or any combination thereof. For example, the vapor can include a gas of alkali metal atoms (e.g., K, Rb, Cs, etc.), a noble gas (e.g., He, Ne, Ar, Kr, etc.), or both. In another example, the vapor can include a gas of diatomic halogen molecules (e.g., F2, Cl2, Br2, etc.), a noble gas, or both. In yet another example, the vapor can include a gas of organic molecules (e.g., acetylene), a noble gas, or both. Other combinations including other components for the vapor are possible.

[0021] Additionally or alternatively, the exemplary vapor cell 100 can include a vapor generation source disposed within the internal cavity 116 defined by the intermediate layer 114. The vapor generation source can generate vapor in response to an energy stimulus such as heat, irradiation, and the like. For example, the vapor can correspond to a gas of alkali metal atoms, and the vapor generation source can correspond to a mass of alkali metal that is cooled sufficiently to be a solid or liquid when disposed within the cavity 116. In some variations, the vapor generation source includes a liquid or solid alkali metal atom source present within the internal cavity 116 and configured to generate a gas of alkali metal atoms when heated. In some variations, the vapor generation source can function in part as a getter.

[0022] In some implementations, all of the intermediate layers 114 are formed of the same type of dielectric material (e.g., the first type of dielectric material discussed above). In some implementations, the vapor cell can include multiple different types of intermediate layers 114 (e.g., layers of different materials, different thicknesses, different structural features, etc.). In some cases, the intermediate layers 114 can include one or more layer subsets that define the arrangement. In these cases, the layers within each subset can share common characteristics. For example, the intermediate layers 114 can include a first subset of layers 114a and a second subset of layers 114b, such as those shown in Figures 1A and 1B. The first subset of layers 114a can be formed of a first type of dielectric material (e.g., including silicon oxide), and the second subset of layers 114b can be formed of a second, different type of dielectric material (e.g., silicon). In another example, the intermediate layers 114 can include a first subset of layers having a different thickness than the second subset of layers. Other common characteristics shared for the layer subsets are possible (eg, through-hole shape, through-hole size, presence of additional cavities, tabs for mechanical joints, etc.).

[0023] In some implementations, such as those shown in Figures 1A and 1B, the second end layer 110 is formed of a first type of dielectric material, and the layers 104 are ordered to alternate between the first type of dielectric material and the second type of dielectric material within the stack. For example, the first and second end layers 106, 110 can be formed of a first type of dielectric material, and the first and second subsets of layers 114a, 114b can alternate in sequence within the intermediate layers 114. In this configuration, the first subset of layers 114a can be formed of a first type of dielectric material, and the second subset of layers 114b can be formed of a second type of dielectric material. Furthermore, the first subset of layers 114a can include outer intermediate layers (e.g., the first and last intermediate layers in the sequence). Such an alternating configuration can allow the stack of layers 104 to be more easily interconnected. The alternating configuration can also reduce the effective dielectric constant of the body 102. Other advantages are possible.

[0024] In some implementations, the stack of layers 104 includes a set of tabs 118 extending outwardly from one or more outer portions 120 of the body 102. Each tab set 118 can define a mechanical joint that allows the exemplary vapor cell 100 to mate (e.g., couple) with another vapor cell. In some variations, the tab set 118 includes one or more tabs that are an integral part of the layer. For example, the intermediate layer 114 can have an inner periphery disposed within the outer periphery. The inner periphery can define a through hole in the intermediate layer 114, and the outer periphery can define a tab extending outwardly from an outer portion of the intermediate layer 114. In another example, the first end layer 106 can have an outer periphery defining a tab extending outwardly from its outer portion.

[0025] In some implementations, the exemplary vapor cell 100 is free of mechanical joints (e.g., free of tabs). FIG. 1E provides a schematic diagram of the exemplary vapor cell 100 of FIG. 1A, but with an octagonal shape and free of mechanical joints. Similarly, FIG. 1F provides a schematic diagram of the exemplary vapor cell 100 of FIG. 1A, but with a square shape and free of mechanical joints. The exemplary vapor cell 100 of FIGS. 1E and 1F includes a plurality of holes 128 between the interior cavity 116 and the exterior surface of the body 102. The plurality of holes 128 can be selected in shape, size, and number to configure the exemplary vapor cell 100 to detect (or improve such detection of) target radiation. The plurality of holes 128 can also reduce the radar cross section of the exemplary vapor cell 100. Features of the plurality of holes 128 are described in more detail in conjunction with FIGS. 4A-5.

[0026] 1A and 1B illustrate the stack of layers 104 as having a tab set 118 extending outwardly from each outer portion 120 of the body 102. Further, the tab set 118 is illustrated as defining a single centrally positioned row on each outer portion 120. However, other configurations are possible. For example, it is contemplated that the stack of layers 104 could include a tab set 118 extending outwardly from only a single outer portion 120 of the body 102. As another example, it is contemplated that the stack of layers 104 could have a tab set 118 defined by a single tab extending outwardly from the single outer portion 120. The single tab could be non-centrally positioned on the single outer portion 120. In yet another example, it is contemplated that the stack of layers 104 could include a tab set 118 aligned with one another along a first dimension on the outer portion 120. Adjacent tab pairs along the first dimension could be separated by a gap. In some cases, the gap may correspond to the thickness of a single intermediate layer 114 (e.g., tabs 118 extend outward from every other intermediate layer 114). However, the gap may correspond to other thicknesses (e.g., two intermediate layers 114). Additionally, the gap need not be the same for each adjacent pair of tabs.

[0027] In implementations in which the intermediate layer 114 includes a first subset of layers 114a and a second subset of layers 114b, the stack of layers 104 can include a first set of tabs 118a and a second set of tabs 118b. The first set of tabs 118a extend outwardly from the first subset of layers 114a on the first outer side 120a of the body 102. The second set of tabs 118b extend outwardly from the second subset of layers 114b on the second outer side 120b of the body 102. In some implementations, the first set of tabs 118a extends from a center of the first outer side 120a of the body 102 and the second set of tabs 118b extends from a center of the second outer side 120b of the body 102. In this case, the tabs in each subset 118a, 118b are aligned with one another along a first dimension (e.g., from the first end layer 106 to the second end layer 110) on their respective outer sides and each is centered along a second dimension perpendicular to the first dimension on their respective outer sides. In some implementations, each tab in the first set 118a is an integral part of a respective layer in the first subset of layers 114a, and each tab in the second set 118b is an integral part of a respective layer in the second subset of layers 114b.

[0028] In some implementations, such as those shown in Figures 1A and 1B, the body 102 has four outer portions 120 that define its square cross section. The four outer portions 120 include first and second outer portions 120a, 120b. The first and second outer portions 120a, 120b can be adjacent to one another or alternatively opposite one another. In some variations, the four outer portions 120 include third and fourth outer portions 120c, 120d. In these variations, the stack of layers 104 includes a third set 118c of tabs extending outwardly from the first subset of layers 114a on the third outer portion 120c of the body 102. The body 102 further includes a fourth set 118d of tabs extending outwardly from the second subset of layers 114b on its fourth outer portion 120d. The first, second, third, and fourth sets of tabs 118a, 118b, 118c, 118d may be aligned with the centers of the first, second, third, and fourth outer portions 120a, 120b, 120c, 120d, respectively.

[0029] During operation of the exemplary vapor cell 100, one or more optical signals (e.g., laser light) can interact with the vapor within the internal cavity 116. For example, the optical signal can enter the internal cavity 116 through the first end layer 106 and then exit the internal cavity 116 through the second end layer 110. In another example, the optical signal can enter the internal cavity 116 through the first end layer 106, reflect off the inner surface of the second end layer 110, and then exit the internal cavity 116 through the second end layer 110. When two or more optical signals are used, co-propagating or counter-propagating modes of operation can be established. In a co-propagating mode, each optical signal passes through the internal cavity 116 along the same direction. In a counter-propagating mode, each optical signal passes through the internal cavity 116 along opposite directions. An example of a propagation mode for a vapor cell is described in US Pat. No. 10,509,065, entitled "Imaging of Electromagnetic Fields."

[0030] To aid in the optical signal propagating through the internal cavity 116, the first and second end layers 106, 110 may include one or more optical coatings. Examples of such optical coatings include reflective coatings, anti-reflective coatings, filter coatings, polarizing coatings, and the like. In some implementations, the first end layer 106 includes an inner surface that covers the first opening 122 of the internal cavity 116 adjacent thereto. The first end layer 106 further includes an outer surface opposite the inner surface. In these implementations, either or both of the inner surface and the outer surface may have an optical coating disposed thereon. A combination of multiple optical coatings for each of the inner surface and the outer surface is possible. In some implementations, the second end layer 110 includes an inner surface that covers the second opening 124 of the internal cavity 116 adjacent thereto. The second end layer 110 further includes an outer surface opposite the inner surface. In these implementations, either or both of the inner surface and the outer surface may have an optical coating disposed thereon. Multiple optical coating combinations are possible for each of the interior and exterior surfaces.

[0031] The stack of layers 104 may include joints 126 between adjacent layers of the stack. In some implementations, the joints 126 between at least one pair of adjacent layers in the stack 104 include a direct bond between the pair. In some implementations, the joints 126 between at least one pair of adjacent layers in the stack of layers 104 include an adhesion layer. The adhesion layer may assist in bonding the adjacent layers to one another. In some variations, the adhesion layer includes a silicon oxide. For example, the stack of layers 104 may alternate between layers formed of silicon and layers formed of borosilicate glass. Silicon oxide (e.g., SiO2, SiO x An adhesion layer, such as a tungsten carbide (e.g., tungsten carbide), may be present at one or more of the joints 126. An adhesion layer may be formed on one or both sides of each silicon layer to define a bonding surface upon which a siloxane bond may be formed with the borosilicate glass layer, such as by an anodic or contact bonding process.

[0032] The stack of layers 104 can be bonded together using, for example, an anodic bonding process, a contact bonding process, a glass frit bonding process, or any other type of bonding process. A combination of bonding processes is also possible. In some variations, a contact bonding process is the final bonding process used to bond the layers together. For example, the first end layer 106 and the intermediate layer 114 can be bonded together using an anodic bonding process. The second end layer 110 can then be bonded to the intermediate layer 114 using a contact bonding process, thereby hermetically sealing the vapor or vapor source within the internal cavity 116. As part of the contact bonding process, the second end layer 110 can be positioned to cover the opening of the cavity 116 after the internal cavity 116 is filled with vapor or contains a vapor source. In many cases, the internal cavity 116 is evacuated before receiving the vapor or vapor source.

[0033] The contact bonding process can include chemically modifying a first bonding surface of a first layer (e.g., a rearmost intermediate layer) and a second bonding surface of a second layer (e.g., the second end layer 110). Prior to modification, one or both of the first and second bonding surfaces have a surface roughness R that does not exceed a threshold surface roughness. a For example, the threshold surface roughness can be 1 nm. In some cases, the first and second bonding surfaces are planar surfaces. The contact bonding process includes modifying the first and second bonding surfaces to include a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands, respectively. The modified surfaces are then contacted together to form metal-oxygen bonds (e.g., siloxane bonds) that create a bond (e.g., a seal) between the first layer and the second layer. The metal-oxygen bonds can be formed when the first plurality of hydroxyl ligands react with the second plurality of hydroxyl ligands during contact.

[0034] In some implementations, altering the first and second bonding surfaces includes activating one or both of the first and second bonding surfaces by exposing the respective surfaces to a plasma. Such exposure can increase the surface energy of the first and second bonding surfaces and chemically pretreat the first and second surfaces for subsequent contact bonding. After activation, one or both of the first and second bonding surfaces can be further chemically pretreated by washing in water (e.g., deionized water) or in an aqueous base solution. Contact with water or an aqueous base solution can coordinate hydroxyl ligands to metal atoms on the first and second bonding surfaces.

[0035] In some implementations, the contact bond may be formed using metal-oxygen bonds between adjacent layers in the stack of layers 104. For example, the interlayers 114 may extend in sequence from a leading interlayer to a trailing interlayer. The leading interlayer may be bonded to the first terminal layer 106, and the second terminal layer 110 may be positioned adjacent to the trailing interlayer. In some variations, the contact bond may be formed using siloxane bonds (i.e., Si-O-Si) between the second terminal layer 110 and the trailing interlayer. The reaction of the contact bond formation process may be represented by equation (1): This reaction may be possible, for example, if the second terminal layer 110 is formed of silicon oxide and the last intermediate layer is formed of silicon. However, other silicon-containing materials are possible. This reaction is reversible, and therefore in some cases it may be desirable to remove the water molecules generated from this reaction. Otherwise, the newly formed siloxane bonds are at risk of being hydrolyzed back to silanol bonds (i.e., Si-OH).

[0036] The water molecules generated by the contact bonding can be removed by a reaction in which the product is a solid at room temperature. In some implementations, the water molecules are reacted with steam in the exemplary steam cell 100. For example, the steam can be a gas of cesium atoms, and the water molecules are reacted with a portion of this gas to produce CsO(T 融解 ≒340℃), CsOH(T 融解 ≒272℃), or CsH(T 融解 ≈170° C. In some implementations, the water molecules are reacted with a desiccant material present in the interior cavity 116 (e.g., as a coating, scattered chunks, etc.). The desiccant material can be inert to the vapor in the vapor cell. For example, the vapor can be a gas of diatomic halogen molecules (e.g., chlorine gas) and the water molecules react with an anhydrous chloride salt (e.g., LaCl3) to form a hydrated salt or oxyhydroxide compound (e.g., LaCl3· x HO, LaOCl, etc.) can be formed.

[0037] Although the above formation reactions are presented in the context of silicon as the metal atom involved, other metal atoms are possible. For example, if a first layer is formed of aluminum oxide (e.g., single crystal sapphire) and a second adjacent layer is also formed of aluminum oxide (e.g., Al2O3 polycrystalline ceramic), the contact bond formation process can utilize aluminum as the metal atom to form an oxo-aluminum bond (e.g., Al-O-Al). Metal mixtures are also possible. For example, if a first layer is formed of zirconium oxide and a second adjacent layer is formed of magnesium oxide, the contact bond process can utilize zirconium and magnesium as the metal atoms to form a zirconium-oxo-magnesium bond.

[0038] In general, for a first layer comprising a first metal M1 and a second adjacent layer comprising a second metal M2, the reaction of the contact bond formation process can be represented by equation (2). TIFF0007603174000002.tif6150In this case, a hydroxyl ligand (i.e., OH) is coordinated to each of the metals M1 and M2 and condenses into an oxo ligand (O) during the formation of a metal-oxygen bond (i.e., M1-O-M2). A water molecule is liberated as a by-product of the condensation process. Although this reaction suggests one hydroxyl ligand per metal atom, other numbers of hydroxyl ligands can be coordinated to each of the metal atoms M1 and M2.

[0039] In many variations, condensation of the hydroxyl ligands occurs upon contact of the first and second adjacent layers (or their mating surfaces) at room temperature. However, in some variations, heat can be applied to initiate and / or complete the formation of the contact bond. Heat can also strengthen the contact bond. For example, heat can be applied to one or both of the first and second adjacent layers to raise the temperature of each of the layers to a processing temperature. The processing temperature can facilitate the formation of the contact bond. In some variations, the processing temperature does not exceed 250° C. In some variations, the processing temperature does not exceed 120° C. In some variations, the processing temperature does not exceed 75° C. The contact bonding process is described in more detail in U.S. Pat. No. 10,859,981, entitled “Vapor Cells Having One or More Optical Windows Bonded to a Dielectric Body.”

[0040] In some implementations, the contact bonding process may provide certain advantages over the anodic bonding process, for example, in applications that depend on the purity of the vapor in the internal cavity 116. The process of forming an anodic bond may introduce undesirable gases into the internal cavity 116, such as by generating one or more volatile species in some cases. These gases may create a background vapor pressure that may have deleterious effects on the vapor (e.g., broadening the Rydberg transition of atoms or molecules in the vapor). The process of forming a contact bond does not rely on the large electric fields and high temperatures common in anodic bonding, thereby mitigating (or eliminating entirely) the introduction of undesirable gases into the internal cavity 116. If no background vapor pressure results from the contact bonding process, this background vapor pressure may be significantly lower than the pressure of the desired vapor in the internal cavity 116, allowing for a still high purity vapor.

[0041] In some implementations, the exemplary vapor cell 100 is a first vapor cell that can be mechanically connected (e.g., coupled) to other vapor cells. The mechanical connection between the vapor cells can be formed by mating complementary mechanical joints of the respective vapor cells. For example, the first set of tabs 118a can define a first mechanical joint configured to couple with a mechanical joint of a second vapor cell. Similarly, the second set of tabs 118b can define a second mechanical joint configured to couple with a mechanical joint of a third vapor cell. In some implementations, the exemplary vapor cell 100 is part of a plurality of such cells. In these implementations, the first and second tab subsets 118a, 118b of each vapor cell are coupled with the second tab subset 118b of the first vapor cell and the first tab subset 118a of a second different vapor cell, respectively.

[0042] FIG. 1G is a schematic perspective view of three illustrative examples 100a, 100b, 100c of the exemplary vapor cell 100 depicted in FIG. 1A, showing two illustrative examples 100a, 100b bonded together. The first illustrative example 100a includes a set of tabs 150 extending outwardly from the second subset of layers 114b but not from the first subset of layers 114a. The first and second subsets of layers 114a, 114b alternate in sequence, thus creating gaps (e.g., gaps between adjacent tabs) in the tab set 150 that can receive tabs from another illustrative example, such as the third illustrative example 100c. These gaps can be dimensioned to allow a sliding fit, such as a slip fit, with these tabs. The third illustrative example 100c includes a set of tabs 152 extending outwardly from the first subset of layers 114a but not from the second subset of layers 114b, contrary to the first illustrative example 100a. This inverted arrangement allows tab set 152 to interlock with tab set 150 during engagement. Tab sets 150, 152 thus define respective interlockable mechanical joints for first and third examples 100a, 100c. Arrow 154 indicates movement of third example 100c to engage or disengage tab set 152 with tab set 150 from first example 100a, thereby joining or separating the two examples 100a, 100c. In some variations, tab sets 150, 152 can be bonded together after interlocking, for example, by using an anodic bonding process, a contact bonding process, a glass frit bonding process, or any other type of bonding process (e.g., mechanical bonds such as screws or pins formed of a dielectric material).

[0043] Multiple instances of the exemplary vapor cell 100 can be connected together to form a multi-dimensional array or tiled pattern. In some variations, multiple instances of the exemplary vapor cell 100 are connected together to form a patterned subassembly. For example, FIG. 2A presents a schematic perspective view of five instances of the exemplary vapor cell 100 as depicted in FIG. 1A connected together to form a "T-shaped" subassembly. As another example, FIG. 2B presents a schematic perspective view of eight instances of the exemplary vapor cell 100 as depicted in FIG. 1A connected together to form an octagonal subassembly. Other arrangements of the patterned subassemblies are possible. In further variations, the patterned subassemblies define a repeatable pattern suitable for a larger assembly or tiled pattern (e.g., a mosaic). For example, FIG. 3A presents a schematic perspective view of five instances of the "T-shaped" subassembly as depicted in FIG. 2A connected together to form an arc-shaped assembly. As another example, Figure 3B presents a schematic top view of five illustrative octagonal subassemblies as shown in Figure 2B that are interconnected to form a tiled pattern. Other larger assemblies or tiled patterns are possible. For example, the linked vapor cells of the assemblies can be connected to form various spatial arrangements (e.g., ordered or random arrays) in two or three spatial dimensions.

[0044] A tiled pattern or array of coupled vapor cells can have several advantages, especially for imaging applications. During operation, the coupled vapor cells can measure a target electromagnetic field passing through a volume occupied by the coupled vapor cells. As part of this measurement, a laser can generate an optical signal that interacts with vapor within the internal cavity of one or more coupled vapor cells. Such interaction allows the target electromagnetic field to be read out by one or more coupled vapor cells. On the other hand, when arranged in a tiled pattern or array, the power used by the laser to read out the target electromagnetic field can be efficiently distributed (e.g., through a fiber optic cable or a group of such cables) to each individual vapor cell. This distribution allows only the required sampling of the target electromagnetic field during readout. Furthermore, after interacting with the vapor, the optical signal can be detected using individual optical detectors (e.g., photodiodes). These optical detectors can then generate respective detector signals (e.g., electrical signals) that can be processed using a SoC or FPGA. In some cases, modulation techniques can be implemented to achieve a high signal-to-noise ratio for each coupled vapor cell (or channel).

[0045] The coupled vapor cells, when arranged in a tiled pattern or array, also present less material to the target electromagnetic field, thereby maximizing the transparency of the coupled group of vapor cells. Furthermore, unlike implementations that rely on large single vapor cells, the tiled pattern or array can be repaired at a granular level, for example, by replacing one or more individual coupled vapor cells. This capability avoids the need to replace the entire tiled pattern or array if its operational performance becomes compromised due to a malfunctioning part. Furthermore, detector signals generated during operation of the tiled pattern or array can be equalized to completely eliminate interference from certain directions. By equalizing these signals, more reliable detection of the desired signal can be obtained. Furthermore, the signal equalization step can enable the tiled pattern or array to select a direction in which to measure the target electromagnetic field. Such selection or "steering" is similar to the steering of a multi-element beam-forming metallic antenna. It will be appreciated that the tiled pattern or array can also compensate for dysfunctional or dead cells in the tiled pattern or array due to its fine-grained configuration. For example, the array or tiled arrangement can oversample signals arriving from different directions and thus remain robust against degradation over time. Other advantages are possible.

[0046] In some implementations, at least one of the intermediate layers 114 includes a plurality of holes 128 between the internal cavity 116 and the periphery of the intermediate layer 114 (e.g., as shown in FIGS. 1E and 1F). The plurality of holes 128 can extend partially or completely through the intermediate layer. In these implementations, the exemplary vapor cell 100 can be configured to detect target radiation, and each of the plurality of holes 128 can have a maximum dimension that does not exceed the wavelength of the target radiation. For example, the target radiation can have a wavelength of at least 0.3 mm, and each of the plurality of holes 128 can have a maximum dimension that does not exceed 0.3 mm. In some implementations, one or more of the plurality of holes 128 can include a vapor source therein. In these embodiments, the intermediate layer 114 can define a channel (or a portion thereof) that fluidly couples the one or more holes 128 to the internal cavity 116.

[0047] 4A and 4B present electromagnetic simulations, including absorption effects, of two exemplary configurations of a vapor cell. The exemplary vapor cell depicted in FIG. 4A and 4B can include similar features to the exemplary vapor cell 100 described in FIG. 1A. In the exemplary simulation depicted in FIG. 4A and 4B, -14A corresponds to a vapor cell with holes present in each intermediate layer (e.g., between the internal cavity and the periphery of the intermediate layer). In comparison, the exemplary configurations depicted in FIG. 4B correspond to a vapor cell without holes (e.g., the body has a solid wall). In these exemplary configurations, the outer geometric configuration has a square cross section. However, other shapes (e.g., circular cross section) are possible. The outer dimensions are a square with sides of 1 cm. The diameter of the cylindrical internal cavity is 7 mm. In FIG. 4A, material has been removed from the intermediate layer to create perforations (e.g., holes, cavities, etc.) in the intermediate layer. Such perforations can allow the vapor cell to be engineered to suit the RF electric field inside the internal cavity. The layer thicknesses and the hole patterns used for each layer can be modified as needed, such as to match the target radiation for sensing. The electric field distribution in the perforated configuration is more uniform and unperturbed than in the non-perforated configuration. Additionally, in the perforated configuration, the first dipole resonance of the structure peaks at a higher frequency than in the non-perforated configuration.

[0048] Each of the vapor cells of FIG. 4A and FIG. 4B can be configured to detect target radiation having a wavelength λ. Although each vapor cell has a dimension of about λ / 15 at 2 GHz, differences in the electric field distribution inside the vapor cell volume, e.g., electric field uniformity, can be found. These differences can be amplified at higher frequencies. For example, the first dipole resonance of the vapor cell will start to become significant in configurations with non-perforated walls unless the λ / 15 dimension is maintained, which weakens the vapor cell and at the same time reduces the sensing volume. In some cases, perforated walls can enable higher performance in larger vapor cells, which increases the signal-to-noise ratio (e.g., due to smaller vapors) and makes it easier to build vapor cell arrays. The larger size of the vapor cells can also be useful for mass manufacturing of vapor cells to a certain specification. At higher frequencies (e.g., higher than 40 Hz), vapor cells can also be fabricated from a single wafer of glass and silicon using the same principles. In some examples, the radar cross section for a square cell is 8×10 at 2 GHz. -7 m 2 (approximately 0.008 times the geometric cross section), whereas the radar cross section for the perforated configuration is 4 × 10 at 2 GHz. -7 m 2 (approximately 0.004 times the geometric cross section).

[0049] FIG. 5 presents electromagnetic simulations of the electric field distribution inside various exemplary configurations of vapor cells with perforated walls. Various configurations of hole patterns, for example in sections (2)-(4), are compared to that of a cubic cell with no perforations in the walls, for example in section (1). In the exemplary simulations depicted in FIG. 5, the incident electric field has unity amplitude. As shown, the vapor cells with perforated walls have a narrower electric field amplitude distribution than the non-perforated control vapor cell. The average electric field illustrated in sections (2) and (4) has less than 1% variation across the vapor cell within the illustrated interaction region (hatched area in the center of each cross section). These vapor cells are configured to detect target radiation having a wavelength λ and are simulated for frequencies with dimensions (e.g., side lengths) of approximately λ / 3 to λ / 4.

[0050] In some implementations, fabricating the exemplary vapor cell 100 includes obtaining a stack 104 of layers bonded together, such as by anodic bonding, contact bonding, glass frit bonding, or any other type of bonding. A combination of bonding processes is also possible. The stack 104 of layers includes a first end layer 106 and intermediate layers 114 extending in sequence from a leading intermediate layer to a trailing intermediate layer. The first end layer 106 is formed of a first type of optically transparent dielectric material, and the leading intermediate layer is bonded to the first end layer 106. The intermediate layers 114 include a first subset 114a of layers and a second subset 114b of layers. The first subset 114a of layers is formed of a first type of dielectric material, and the second subset 114b of layers is formed of a second, different type of dielectric material. An interior cavity 116 extends through the intermediate layers 114 and includes an opening 122 defined by a surface of the rearmost intermediate layer.

[0051] The manufacturing process may also include disposing a vapor or a vapor source in the internal cavity 116 and bonding a second terminal layer 110 of the stack of layers 104 to a rearmost intermediate layer to seal the vapor or vapor source within the internal cavity 116. The second terminal layer 110 is formed of a dielectric material, which in some variations is a first type of dielectric material. The stack of layers 104, when including the bonded second terminal layer 110, defines the body 102 of the exemplary vapor cell 100. Additionally, the first terminal layer 106 is at a first end of the body 102 and the second terminal layer 110 is at an opposite second end of the body 102.

[0052] In some implementations, obtaining the stack of layers 104 includes alternating layers of the first and second subsets of layers 114a, 114b bonded together to form the intermediate layer 114. Obtaining the stack of layers 104 may also include bonding the leading intermediate layer to the first end layer 106, such as by anodic bonding, contact bonding, glass frit bonding, or any other type of bonding. In further implementations, obtaining the stack of layers 104 includes removing material from a first wafer formed of a first type of dielectric material to produce the first end layer, one or more of the first subset of layers, or both. Obtaining the stack of layers 104 may also include removing material from a second wafer formed of a second type of dielectric material to produce one or more of the second subset of layers. Removing material may include machining material from the wafer using a laser, etching material from the wafer, or both. The etching process may include one or both of a dry or wet etching process. Other types of subtractive processes for removing material are possible (eg, ablation, grinding, polishing, etc.).

[0053] In some implementations, bonding the second terminal layer 110 includes modifying a surface of the last intermediate layer to include a first plurality of hydroxyl ligands. Bonding the second terminal layer 110 further includes modifying a surface of the second terminal layer to include a second plurality of hydroxyl ligands. In these implementations, the modified surfaces can be contacted to form a seal around the opening of the internal cavity. The seal is defined by metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands as described above in connection with formulas (1) and (2) during contact of the two modified surfaces.

[0054] 1A-5 illustrate the exemplary vapor cell 100 in the context of a single internal cavity 116. However, other numbers and types of cavities are possible. In some implementations, the stack of layers 104 defines a plurality of internal cavities 116, each corresponding to a vapor partial cell (or unit cell). In some implementations, the stack of layers 104 can define one or more holes (e.g., through holes) therethrough. The one or more holes can extend between a pair of openings defined by the outer surfaces of the first and second end layers 106, 110. In some implementations, the stack of layers 104 defines both a plurality of internal cavities 116 and one or more holes. The plurality of internal cavities 116 and the one or more holes can be arranged according to a pattern or array, such as those shown in FIGS. 2A-2B and 3A-3B. In implementations having multiple cavities and / or one or more holes, the stack of layers 104 can be configured without the first and second sets of tabs 118a, 118b.

[0055] In some implementations, the plurality of cavities 116 and the one or more holes can be arranged according to a two-dimensional lattice (e.g., a square lattice, a rectangular lattice, a hexagonal lattice, a rhombic lattice, a centroid lattice, an oblique lattice, etc.). In these implementations, the two-dimensional lattice can include first lattice sites for the plurality of cavities 116. The first lattice sites can each be occupied by an internal cavity 116. However, in some variations, only a portion of the first lattice sites are occupied. The two-dimensional lattice can further include second lattice sites for one or more holes. The second lattice sites can each be occupied by a hole. However, in some variations, only a portion of the second lattice sites are occupied. It will be appreciated that the occupation (or lack) of the first and second lattice sites can be selected to allow the internal cavities 116 and holes to be arranged in a desired pattern or array. Such a selection can also allow the stack of layers 104 to define a desired shape for the body 102.

[0056] 6A presents a schematic diagram of an exemplary vapor cell 600 having an array of cavities 612. The schematic diagram illustrates the exemplary vapor cell 600 in the context of a unit cell 602 as part of a vapor cell tiling pattern 604. The schematic diagram also illustrates a cross-section 606 of the exemplary vapor cell 600. The exemplary vapor cell 600 includes a body 608 defined by a stack of layers 610 bonded together. The stack of layers 610 defines an array of cavities 612 including a first subset of cavities 612a and a second subset of cavities 612b. The first subset of cavities 612a extends through a plurality of intermediate layers 614 of the stack of layers 610, and the second subset of cavities 612b extends completely through the stack of layers 610. The first subset of cavities 612a may be similar to the internal cavities 116 described in connection with Figures 1A-5, and the second subset of cavities 612b may each correspond to a through hole. A vapor or a vapor source is disposed within each of the first subset of cavities 612a.

[0057] The first and second subsets of cavities 612a, 612b can each share a common shape as shown in FIG. 6A. However, in some cases, one or more of the first subsets of cavities 612a can have different shapes. In some cases, one or more of the second subsets of cavities 612b can also have different shapes. In many variations, the first and second subsets of cavities 612a, 612b extend along respective axes perpendicular to the stack of layers 610, although other orientations (e.g., tilted axes) are possible. Furthermore, while FIG. 6A depicts the first subset of cavities 612a as having a cylindrical shape and the second subset of cavities 612b as having a square tube shape, other shapes (e.g., hexagonal, ellipsoidal, spherical, etc.) are possible. For example, each intermediate layer 614 can include a through hole that defines a portion of a cavity therethrough. In this case, one or more interlayers 614 can be selectively configured to define a target three-dimensional volume for the cavity when stacked (e.g., a sphere, a frustum, a tilted parallelepiped, etc.). In some variations, at least two adjacent interlayers 614 have respective through-holes that differ in one or both of shape and size from one another. In some variations, two or more interlayers 614 (e.g., adjacent interlayers) have different thicknesses. Other configurable features (e.g., angles relative to inner peripheries surrounding the through-holes of an interlayer) are possible.

[0058] The stack of layers 610 includes a first end layer 616 at a first end 618 of the body 608. The first end layer 616 is formed of a first type of dielectric material that is optically transparent. The stack of layers 610 further includes a second end layer 620 at an opposite second end 622 of the body 608. The second end layer 620 is formed of a dielectric material. An intermediate layer 614 of the stack of layers 610 is positioned between the first end layer 616 and the second end layer 620 and includes a first subset 614a of layers formed of the first type of dielectric material and a second subset 614b of layers formed of a second, different type of dielectric material. FIG. 6A depicts the first and second subsets of layers 614a, 614b as being only one layer each. However, other numbers of layers for either or both of the first and second subsets of layers 614a, 614b are possible.

[0059] In some variations, such as that shown in FIG. 6A , the stack of layers 610 includes a first set of tabs 624a extending outward from a first subset of layers 614a at a first location 626a of the periphery 628 of the body 608. The stack of layers 610 can further include a second set of tabs 624b extending outward from a second subset of layers 614b at a second location 626b of the periphery 628 of the body 608. The first and second sets of tabs 624a, 624b can function as first and second mechanical joints, respectively, for coupling with another similarly configured vapor cell (e.g., the second instantiation of the exemplary vapor cell 600). However, in some variations, the first and second sets of layers 614a, 614b do not have tabs extending therefrom. FIG. 6B presents a schematic diagram of the example vapor cell of FIG. 6A, but with its middle layers (first and second layer sets 614a, 614b) lacking tabs extending outward therefrom.

[0060] In one particular case, each of the first subset of cavities 612a is surrounded by a sidewall 630 formed by the stack of layers 610. The sidewall 630 includes a corner that defines a portion of the perimeter 628. In such a case, the first location 626a is a first corner of the perimeter 628 and the second location 626b is a second, different corner of the perimeter 628. However, the first and second locations 626a, 626b can be other locations on the perimeter 628. For example, the sidewall 630 can include a flat surface that defines a portion of the perimeter 628 (e.g., a center of the outer portion). In this case, the first location 626a can be a first flat surface of the perimeter 628 and the second location 626b is a second, different flat surface of the perimeter 628.

[0061] The array of cavities 612 can be arranged according to a two-dimensional lattice. In some cases, the two-dimensional lattice includes first and second lattice sites for the first and second subsets of cavities 612a, 612b, respectively. For example, the two-dimensional lattice can be a square lattice with the first and second lattice sites alternating in the row and column directions. In this arrangement, the cavities 612 of the array are arranged at respective locations of a square lattice, with the first subset of cavities 612a and the second subset of cavities 612b alternating in the rows and columns of the square lattice. In some cases, the first and second lattice sites are partially occupied by the first and second subsets of cavities 612a, 612b. For example, as shown in FIG. 6, four of the first lattice sites can be occupied by each cavity of the first subset 612a, and one second lattice site can be occupied by each cavity of the second subset 612b. This configuration can allow the body 608 of the example vapor cell 600 to assume a plus (+) shape. However, other arrangements are possible. For example, the array 612 of cavities in the example vapor cell 600 of FIG. 6B is arranged to define a butterfly shape relative to the body 608.

[0062] In some variations, the sidewall 630 has four exterior surfaces that define its square cross section. In these variations, each of the second subset 612b of cavities has a square cross section. In some variations, the sidewall 630 has one or more exterior surfaces that define a unit cell perimeter 632 of the cavity. For purposes of clarity, only one unit cell perimeter 632 is depicted in dashed lines in FIGS. 6A and 6B. For one or more of the cavities of the first subset 612a, the at least one intermediate layer 614 includes a plurality of holes between the one or more cavities and the respective unit cell perimeter 632 of the cavity. The plurality of holes can be similar to those described in connection with FIGS. 1A-1B and 4A-5. For example, the plurality of holes can extend through the at least one intermediate layer 614. As another example, the exemplary vapor cell 600 can be configured to detect target radiation, and each of the plurality of holes has a maximum dimension that does not exceed a wavelength of the target radiation (e.g., a wavelength of at least 0.3 mm). In certain cases, one or more of the plurality of holes adjacent one or more cavities can include a vapor source therein. In these embodiments, the at least one intermediate layer 614 can define a channel (or a portion thereof) that fluidly couples the one or more holes to the one or more cavities.

[0063] Some aspects of the described subject matter may be illustrated by the examples that follow for vapor cells. Example 1. 1. A vapor cell comprising: a body defined by a stack of layers bonded together, the stack of layers including: a first terminal layer at a first end of the body and formed of a first type of optically transparent dielectric material; a second terminal layer at an opposite second end of the body and formed of a dielectric material; and an intermediate layer between the first and second terminal layers and formed of a dielectric material, the intermediate layer defining an interior cavity extending through the body between the first and second terminal layers; a steam or steam source disposed in the internal cavity; A vapor cell comprising: Example 2. 2. The vapor cell of example 1, wherein the second terminal layer is formed of the first type of dielectric material. Example 3. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second, different type of dielectric material; and 3. The vapor cell of example 1 or example 2, comprising: Example 4. 4. The vapor cell of example 3, wherein the layers are ordered to alternate between the first type of dielectric material and the second type of dielectric material within the stack. Example 5. The vapor cell of example 3 or example 4, wherein the second type of dielectric material is silicon. Example 6. The vapor cell of any one of Example 1 or Example 2 to Example 5, wherein the first type of dielectric material comprises silicon oxide. Example 7. The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at a first exterior portion (or location) of the body; a second set of tabs extending outwardly from the intermediate layer at a second outer portion (or location) of the body; Including, The vapor cell according to any one of the preceding claims. Example 8. the vapor cell is a first vapor cell; the first set of tabs defines a first mechanical joint configured to couple with a second vapor cell (e.g., a second instantiation of the first vapor cell); the second set of tabs defines a second mechanical joint configured to couple with a third vapor cell (e.g., a third instantiation of the first vapor cell); Vapor cell as described in Example 7. Example 9. each tab of the first set is an integral part of the intermediate layer from which it extends; each tab of the second set is an integral part of the intermediate layer from which it extends; The vapor cell described in Example 7 or Example 8. Example 10. The vapor cell of any one of Example 7 or Examples 8 to 9, wherein the first and second sets of tabs are aligned with centers of the first and second outer portions, respectively. Example 11. the intermediate layer includes a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab in the first set extends outwardly from a respective layer in the first subset of layers; each tab in the second set extends outwardly from a respective layer in the second subset of layers; The vapor cell according to any one of Example 7 or Examples 8 to 10. Example 12. A plurality of vapor cells, each corresponding to the vapor cell of any one of Example 7 or Examples 8 to 11, wherein a first and second set of tabs of each vapor cell are respectively connected to a second set of tabs of a first vapor cell and a first set of tabs of a second, different vapor cell. Example 13. the body defining a square cross-section of the body and having four outer portions including a first and a second outer portion; The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at the first outer portion of the body; a second set of tabs extending outwardly from the intermediate layer at the second outer portion of the body; and Including, The vapor cell according to any one of the preceding claims, wherein the vapor cell is a gas. Example 14. 14. The vapor cell of example 13, wherein the first exterior portion and the second exterior portion are adjacent to one another. Example 15. 14. The vapor cell of example 13, wherein the first exterior portion and the second exterior portion oppose one another. Example 16. The four outer portions include a third and a fourth outer portion, The stack of layers above is: a third set of tabs extending outwardly from the intermediate layer at the third outer portion of the body; and a fourth set of tabs extending outwardly from the intermediate layer at the fourth outer portion of the body; and Including, The vapor cell of any one of Example 13 or Example 14 to Example 15. Example 17. each tab of the third set is an integral part of the intermediate layer from which it extends; each tab of the fourth set is an integral part of the intermediate layer from which it extends; Vapor cell as described in Example 16. Example 18. the first, second, third, and fourth sets of tabs are aligned with centers of the first, second, third, and fourth outer portions, respectively; The vapor cell of Example 16 or Example 17. Example 19. the intermediate layer includes a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab in the first and third sets extends outwardly from a respective layer in the first subset of layers; each tab in the second and fourth sets extends outwardly from a respective layer in the second subset of layers; The vapor cell of any one of Example 16 or Example 17 to Example 18. Example 20. The first end layer comprises: an interior surface covering a first opening of the interior cavity adjacent the first end layer; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell according to any one of Example 1 or Example 2 to Example 19. Example 21. 21. The vapor cell of example 20, wherein the inner surface of the first end layer includes a reflective coating disposed thereon. Example 22. Example 22. The vapor cell of example 20 or example 21, wherein the exterior surface of the first end layer includes a reflective coating disposed thereon. Example 23. The vapor cell of any one of Examples 20 or 21-22, wherein the inner surface of the first end layer includes an antireflective coating disposed thereon. Example 24. The vapor cell of Example 20 or any one of Examples 21 to 23, wherein the exterior surface of the first terminal layer includes an antireflective coating disposed thereon. Example 25. The second terminal layer comprises: an interior surface covering a second opening of the interior cavity adjacent the second end layer; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell according to any one of Example 1 or Example 2 to Example 24. Example 26. 26. The vapor cell of example 25, wherein the inner surface of the second end layer includes a reflective coating disposed thereon. Example 27. Example 27. The vapor cell of example 25 or example 26, wherein the exterior surface of the second end layer includes a reflective coating disposed thereon. Example 28. The vapor cell of any one of Examples 25 or 26-27, wherein the inner surface of the second end layer includes an antireflective coating disposed thereon. Example 29. The vapor cell of Example 25 or any one of Examples 26 to 28, wherein the exterior surface of the second terminal layer includes an antireflective coating disposed thereon. Example 30. The vapor cell of any one of Examples 1 or 2 to 29, wherein at least one of the intermediate layers includes a plurality of holes between the internal cavity and an outer periphery of the intermediate layer. Example 31. 31. The vapor cell of example 30, wherein the plurality of holes extend through the intermediate layer. Example 32. the vapor cell configured to detect target radiation; each of the plurality of holes having a maximum dimension not exceeding a wavelength of the target radiation; The vapor cell of example 30 or example 31. Example 33. 33. The vapor cell of example 32, wherein the target radiation has a wavelength of at least 0.3 mm. Example 34. The vapor cell of any one of Example 1 or Example 2 to Example 33, wherein a joint between at least one pair of adjacent layers in the stack of layers includes an adhesive layer. Example 35. 35. The vapor cell of example 34, wherein the adhesion layer comprises silicon oxide. Example 36. each intermediate layer includes a through hole defining a portion of the internal cavity through that intermediate layer; At least two adjacent intermediate layers have respective through holes that differ from each other in either or both of shape and size; The vapor cell of any one of Example 1 or Example 2 to Example 35.

[0064] In some aspects of the described subject matter, a method for manufacturing a vapor cell can be illustrated by the following example. Example 37. 1. A method of manufacturing a vapor cell, comprising the steps of: obtaining a stack of layers bonded together, The stack of layers is: a first end layer formed of a first type of optically transparent dielectric material; intermediate layers formed of a dielectric material, extending in sequence from a leading intermediate layer to a trailing intermediate layer, said leading intermediate layer bonded to said first end layer, an internal cavity extending therethrough, said internal cavity including an opening defined by a surface of said trailing intermediate layer; Including, The method further comprises: disposing steam or a source of steam in the internal cavity; bonding a second terminal layer of the stack of layers to the rearmost intermediate layer to seal the vapor or vapor source within the first subset of the cavities, the second terminal layer being formed of a dielectric material; Including, the stack of layers, when including the bonded second terminal layer, defines a body of the vapor cell, the first terminal layer at a first end of the body, and the second terminal layer at an opposite second end of the body; A method for manufacturing a vapor cell. Example 38. 38. The method of claim 37, wherein bonding the second end layer includes covering an opening of the internal cavity with the second end layer to enclose the vapor or vapor source within the internal cavity. Example 39. Example 39. The method of example 37 or example 38, wherein the second terminal layer is formed of the first type of dielectric material. Example 40. The method of any one of Examples 37 or 38 to 39, wherein the first type of dielectric material comprises silicon oxide. Example 41. obtaining said stack of layers, removing material from a first wafer formed of the first type of dielectric material to produce the first terminal layer, the second terminal layer (when combined with Example 39), or both; removing material from a second wafer formed of a dielectric material to produce the intermediate layer; Including, The method according to any one of Example 37 or Examples 38 to 40. Example 42. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second, different type of dielectric material; and Including, The method according to any one of Example 37 or Examples 38 to 40. Example 43. obtaining said stack of layers, bonding layers of a first subset of layers and layers of a second subset of layers to each other alternately to form the intermediate layer; bonding the leading intermediate layer to the first distal layer; Including, The method described in Example 42. Example 44. obtaining said stack of layers, removing material from a first wafer formed of the first type of dielectric material to produce the first terminal layer, one or more of the first subset of layers, the second terminal layer (when combined with Example 39), or any combination thereof; removing material from a second wafer formed of the second type of dielectric material to produce one or more of the second subset of layers; Including, The method described in Example 42 or Example 43. Example 45. The method of any one of Example 42 or Example 43 to Example 44, wherein the second type of dielectric material is silicon. Example 46. The step of bonding the second end layer further comprises: modifying the surface of the last intermediate layer to include a first plurality of hydroxyl ligands; modifying a surface of the second terminal layer to include a second plurality of hydroxyl ligands; contacting the modified surfaces to form a seal around the opening of the internal cavity defined by metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contact of the two modified surfaces; Including, The method according to any one of Example 37 or Example 38 to Example 45. Example 47. The step of bonding the second end layer further comprises: activating one or both of the surfaces of the rearmost intermediate layer and the second terminal layer by exposing the respective surfaces of the layers to a plasma. The method described in Example 46. Example 48. The method of any one of Example 37 or Examples 38 to 47, wherein at least one of the intermediate layers includes a plurality of holes between the internal cavity and the outer periphery of the intermediate layer. Example 49. 49. The method of embodiment 48, wherein the plurality of holes extend through the intermediate layer. Example 50. the vapor cell is configured, at the time of manufacture, to detect target radiation; each of the plurality of holes having a maximum dimension not exceeding a wavelength of the target radiation; The method described in Example 48 or Example 49. Example 51. 51. The method of claim 50, wherein the target radiation has a wavelength of at least 0.3 mm. Example 52. obtaining said stack of layers, forming an adhesive layer on one or both sides of an intermediate layer to define a bonding surface for each of said intermediate layers; The method according to any one of Example 37 or Example 38 to Example 51. Example 53. 53. The method of embodiment 52, wherein the adhesion layer comprises silicon oxide. Example 54. The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at a first outer portion (or location) of the stack of layers (or body of the vapor cell); a second set of tabs extending outwardly from the intermediate layer at a second outer portion (or location) of the stack of layers (or body of the vapor cell); and Including, The method according to any one of Example 37 or Example 38 to Example 53. Example 55. the vapor cell is a first vapor cell; the first set of tabs defines a first mechanical joint configured to couple with a second vapor cell (e.g., a second instantiation of the first vapor cell); the second set of tabs defines a second mechanical joint configured to couple with a third vapor cell (e.g., a third instantiation of the first vapor cell); The steam process described in Example 54.

[0065] In some aspects of the described subject matter, the vapor cell system can be illustrated by the following example. Example 56. 1. A vapor cell system comprising: an array of interconnected vapor cells; Each of the linked vapor cells a stack of layers bonded together to define a body of said interconnected vapor cell; The stack of layers is: a first terminal layer at a first end of the body and formed of a first type of optically transparent dielectric material; a second terminal layer at an opposite second end of the body and formed of a dielectric material; and one or more intermediate layers formed of a dielectric material between the first terminal layer and the second terminal layer, the intermediate layers defining an interior cavity extending through the stack of layers between the first terminal layer and the second terminal layer; Including, Each of the coupled vapor cells further comprises: a first mechanical joint on a first exterior portion of the body; a second mechanical joint on a second exterior portion of the body; and a steam or steam source disposed in the internal cavity; Including, the first mechanical joint of at least one coupled vapor cell is coupled with a second mechanical joint of another coupled vapor cell; the second mechanical joint of the at least one coupled vapor cell is coupled with a first mechanical joint of another different coupled vapor cell; Vapor cell system. Example 57. 57. The vapor cell system of example 56, wherein the second terminal layer is formed of the first type of dielectric material. Example 58. The vapor cell system of example 56 or example 57, wherein the one or more intermediate layers include at least one layer formed of a second, different type of dielectric material. Example 59. The one or more intermediate layers are a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second, different type of dielectric material; and Including, The vapor cell system of example 56 or example 57. Example 60. 60. The vapor cell system of example 59, wherein the layers are ordered to alternate between the first type of dielectric material and the second type of dielectric material within the stack. Example 61. The vapor cell system of any one of Example 58 or Example 59 to Example 60, wherein the second type of dielectric material is silicon. Example 62. The vapor cell system of any one of Example 56 or Example 57 to Example 61, wherein the first type of dielectric material comprises silicon oxide. Example 63. the first mechanical joint includes a first set of tabs extending outwardly from the one or more intermediate layers at the first outer side (or location) of the body; the second mechanical joint includes a second set of tabs extending outwardly from the one or more intermediate layers at the second outer portion (or location) of the body; The vapor cell system of any one of Example 56 or Example 57 to Example 62. Example 64. each tab of the first set is an integral part of the intermediate layer from which it extends; each tab of the second set is an integral part of the intermediate layer from which it extends; The vapor cell system described in Example 63. Example 65. The vapor cell system of Example 63 or Example 64, wherein the first and second sets of tabs are aligned with the centers of the first and second outer portions, respectively. Example 66. the one or more intermediate layers include a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab in the first set extends outwardly from a respective layer in the first subset of layers; each tab in the second set extends outwardly from a respective layer in the second subset of layers; The vapor cell system of any one of Example 63 or Example 64 to Example 65. Example 67. A vapor cell system described in any one of Example 56 or Examples 57 to 66, wherein the body of the connected vapor cell has four outer parts defining a square cross-section of the body, and the four outer parts include the first and second outer parts. Example 68. 68. The vapor cell system of embodiment 67, wherein the first outer portion and the second outer portion are adjacent to each other. Example 69. 68. The vapor cell system of embodiment 67, wherein the first outer portion and the second outer portion are opposed to each other. Example 70. The four outer portions include a third and a fourth outer portion, Each connected vapor cell is a third mechanical joint on the third outer portion of the body; and a fourth mechanical joint on the fourth outer portion of the body; and Including, The vapor cell system of any one of Example 67 or Example 68 to Example 69. Example 71. the third mechanical joint includes a third set of tabs extending outwardly from the one or more intermediate layers at the third outer portion of the body; the fourth mechanical joint includes a fourth set of tabs extending outwardly from the one or more intermediate layers at the fourth outer portion of the body. The vapor cell system described in Example 70. Example 72. each tab of the third set is an integral part of the intermediate layer from which it extends; each tab of the fourth set is an integral part of the intermediate layer from which it extends; The vapor cell system described in Example 71. Example 73. The vapor cell system of example 71 or example 72, wherein the third and fourth sets of tabs are aligned with the centers of the third and fourth outer portions, respectively. Example 74. the one or more intermediate layers include a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab in the third set extends outwardly from a respective layer in the first subset of layers; each tab in the fourth set extends outwardly from a respective layer in the second subset of layers; The vapor cell system of any one of Example 71 or Example 72 to Example 73. Example 75. The first end layer comprises: an interior surface covering a first opening of the interior cavity adjacent the first end layer; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell system of any one of Example 56 or Example 57 to Example 74. Example 76. 76. The vapor cell system of example 75, wherein the inner surface of the first end layer includes a reflective coating disposed thereon. Example 77. Example 77. The vapor cell system of example 75 or example 76, wherein the exterior surface of the first terminal layer includes a reflective coating disposed thereon. Example 78. The vapor cell system of any one of Examples 75 or 76 to 77, wherein the inner surface of the first terminal layer includes an antireflective coating disposed thereon. Example 79. The vapor cell system of any one of Example 75 or Example 76 to Example 78, wherein the outer surface of the first terminal layer includes an antireflective coating disposed thereon. Example 80. The second terminal layer comprises: an interior surface covering a second opening of the interior cavity adjacent the second end layer; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell system of any one of Example 56 or Example 57 to Example 79. Example 81. 81. The vapor cell system of example 80, wherein the inner surface of the second end layer includes a reflective coating disposed thereon. Example 82. Example 82. The vapor cell system of Example 80 or Example 81, wherein the exterior surface of the second terminal layer includes a reflective coating disposed thereon. Example 83. The vapor cell system of any one of Example 80 or Example 81 to Example 82, wherein the inner surface of the second terminal layer includes an antireflective coating disposed thereon. Example 84. The vapor cell system of any one of Example 80 or Example 81 to Example 83, wherein the outer surface of the second terminal layer includes an antireflective coating disposed thereon. Example 85. A vapor cell system described in any one of Examples 56 or 57 to 84, wherein the one or more intermediate layers include at least one layer having a plurality of holes between the internal cavity and the outer periphery of the intermediate layer. Example 86. 86. The vapor cell system of embodiment 85, wherein the plurality of holes extend through the intermediate layer. Example 87. Each coupled vapor cell is configured to detect a respective target radiation; the plurality of holes associated with the coupled vapor cells each have a maximum dimension not exceeding a wavelength of the target radiation of the coupled vapor cells; The vapor cell system of example 85 or example 86. Example 88. 88. The vapor cell system of example 87, wherein the target radiation has a wavelength of at least 0.3 mm. Example 89. The vapor cell system of any one of Example 56 or Example 57 to Example 88, wherein the joint between at least one pair of adjacent layers in the stack of layers includes an adhesive layer. Example 90. 90. The vapor cell system of example 89, wherein the adhesion layer comprises silicon oxide. Example 91. each intermediate layer includes a through hole defining a portion of the internal cavity through that intermediate layer; At least two adjacent intermediate layers have respective through holes that differ from each other in either or both of shape and size; The vapor cell system of Example 56 or any one of Examples 57 to 90.

[0066] In some aspects of the described subject matter, the vapor cell can be illustrated by the following example. Example 92. a body defined by a stack of layers bonded together, the stack of layers defining an array of cavities, the array of cavities including a first subset of cavities extending through an intermediate layer of the stack of layers and a second subset of cavities extending completely through the stack of layers; a vapor or vapor source disposed in each of the first subset of cavities; Equipped with The stack of layers is: a first terminal layer at a first end of the body and formed of a first type of optically transparent dielectric material; a second terminal layer at an opposite second end of the body and formed of a dielectric material; the intermediate layer positioned between the first end layer and the second end layer and formed of a dielectric material; a vapor cell. Example 93. the array of cavities is at respective locations defined by a two-dimensional lattice including first and second lattice sites; a first subset of the cavities occupying respective first lattice sites and a second subset of the cavities occupying respective second lattice sites. Vapor cell as described in Example 92. Example 94. 94. The vapor cell of embodiment 93, wherein all of the first lattice sites are occupied by respective cavities of the first subset and all of the second lattice sites are occupied by respective cavities of the second subset. Example 95. The vapor cell of example 93 or example 94, wherein the two-dimensional lattice is a square lattice and the first lattice sites and the second lattice sites alternate in sequence along the rows and columns of the square lattice. Example 96. 93. A vapor cell as described in Example 92, wherein the cavities of the array are present at respective locations of a square lattice, and the first subset of cavities and the second subset of cavities alternate in sequence along the rows and columns of the square lattice. Example 97. each cavity of the first subset is bounded by a sidewall formed by the stack of layers, the sidewall having four exterior surfaces defining a square cross-section of the sidewall; Each cavity of the second subset has a square cross section. The vapor cell of Example 92 or any one of Examples 93 to 95. Example 98. The vapor cell of any one of Example 92 or Examples 93 to 97, wherein the second terminal layer is formed of the first type of dielectric material. Example 99. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second, different type of dielectric material; and Including, The vapor cell of Example 92 or any one of Examples 93 to 98. Example 100. 99. The vapor cell of embodiment 99, wherein the layers are ordered to alternate between the first type of dielectric material and the second type of dielectric material within the stack. Example 101. The vapor cell of example 99 or example 100, wherein the second type of dielectric material is silicon. Example 102. The vapor cell of Example 92 or any one of Examples 93 to 101, wherein the first type of dielectric material comprises silicon oxide. Example 103. The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at a first location on a periphery of the body; a second set of tabs extending outwardly from the intermediate layer at a second location on the periphery of the body; and Including, The vapor cell of example 92 or any one of examples 93 to 102. Example 104. each cavity of the first subset is bounded by a sidewall formed by the stack of layers, the sidewall including a corner defining a portion of the periphery of the body; the first location is a first corner of the periphery of the body and the second location is a second, different corner of the periphery of the body. Vapor cell as described in Example 103. Example 105. each cavity of the first subset is bounded by a sidewall formed by the stack of layers, the sidewall including a planar surface defining a portion of the periphery of the body; the first location is a first planar surface of the periphery of the body and the second location is a second, different planar surface of the periphery of the body; Vapor cell as described in Example 103. Example 106. the vapor cell is a first vapor cell; the first set of tabs defines a first mechanical joint configured to couple with a second vapor cell (e.g., a second instantiation of the first vapor cell); the second set of tabs defines a second mechanical joint configured to couple with a third vapor cell (e.g., a third instantiation of the first vapor cell); The vapor cell of any one of Example 103 or Example 104 to Example 105. Example 107. each tab of the first set is an integral part of the intermediate layer from which it extends; each tab of the second set is an integral part of the intermediate layer from which it extends; The vapor cell of example 103 or any one of examples 104 to 106. Example 108. the intermediate layer includes a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab in the first set extends outwardly from a respective layer in the first subset of layers; each tab in the second set extends outwardly from a respective layer in the second subset of layers; The vapor cell of example 103 or any one of examples 104 to 107. Example 109. A plurality of vapor cells, each corresponding to the vapor cell described in Example 103 or any one of Examples 104 to 108, wherein the first and second sets of tabs of each vapor cell are respectively connected to the second set of tabs of a first vapor cell and the first set of tabs of a second, different vapor cell. Example 110. each cavity of the first subset has a first opening adjacent the first end layer; The first end layer comprises: an inner surface covering the first openings of a first subset of the cavities; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell of example 92 or any one of examples 93 to 109. Example 111. 111. The vapor cell of example 110, wherein the inner surface of the first end layer includes a reflective coating disposed thereon. Example 112. The vapor cell of example 110 or example 111, wherein the exterior surface of the first terminal layer includes a reflective coating disposed thereon. Example 113. The vapor cell of any one of Example 110 or Example 111 to Example 112, wherein the inner surface of the first terminal layer includes an antireflective coating disposed thereon. Example 114. The vapor cell of Example 110 or any one of Examples 111 to 113, wherein the outer surface of the first terminal layer includes an antireflective coating disposed thereon. Example 115. each cavity of the first subset has a second opening adjacent the second end layer; The second terminal layer comprises: an inner surface covering the second openings of a first subset of the cavities; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell of example 92 or any one of examples 93 to 112. Example 116. 116. The vapor cell of example 115, wherein the inner surface of the second end layer includes a reflective coating disposed thereon. Example 117. Example 115 or Example 116. The vapor cell of Example 115 or Example 116, wherein the exterior surface of the second end layer includes a reflective coating disposed thereon. Example 118. The vapor cell of Example 115 or any one of Examples 116 to 117, wherein the inner surface of the second terminal layer includes an antireflective coating disposed thereon. Example 119. The vapor cell of Example 115 or any one of Examples 116 to 118, wherein the outer surface of the second terminal layer includes an antireflective coating disposed thereon. Example 120. each cavity of the first subset is surrounded by a sidewall formed by the stack of layers, the sidewall having one or more exterior surfaces defining at least a portion of a unit cell perimeter surrounding the cavity; for one or more cavities of the first subset, at least one of the intermediate layers includes a plurality of holes between the one or more cavities and a respective unit cell periphery of the cavity; The vapor cell of example 92 or any one of examples 93 to 119. Example 121. 121. The vapor cell of embodiment 120, wherein the plurality of holes extend through the at least one intermediate layer. Example 122. the vapor cell configured to detect target radiation; each of the plurality of holes having a maximum dimension not exceeding a wavelength of the target radiation; The vapor cell of example 120 or example 121. Example 123. 123. The vapor cell of embodiment 122, wherein the target radiation has a wavelength of at least 0.3 mm. Example 124. The vapor cell of any one of Example 92 or Example 93 to Example 123, wherein a joint between at least one pair of adjacent layers in the stack of layers includes an adhesive layer. Example 125. 125. The vapor cell of embodiment 124, wherein the adhesion layer comprises silicon oxide. Example 126. each intermediate layer includes a through hole defining a portion of the first subset of cavities through the intermediate layer; at least two adjacent intermediate layers have respective through holes that differ in shape and / or size relative to the cavities of the first subset; The vapor cell of example 92 or any one of examples 93 to 125. Example 127. each intermediate layer includes a through hole defining a portion of the second subset of cavities through the intermediate layer; at least two adjacent intermediate layers have respective through holes that differ in shape and / or size relative to the cavities of the second subset; The vapor cell of example 92 or any one of examples 93 to 126.

[0067] In some aspects of the described subject matter, a method for manufacturing a vapor cell can be illustrated by the following example. Example 128. 1. A method of manufacturing a vapor cell, comprising the steps of: obtaining a stack of layers bonded together and defining an array of cavities; the array of cavities includes a first subset of cavities extending through an intermediate layer of the stack of layers and a second subset of cavities extending completely through the stack of layers; The stack of layers is: a first end layer formed of a first type of optically transparent dielectric material; intermediate layers formed of a dielectric material and extending in sequence from a leading intermediate layer to a trailing intermediate layer, the leading intermediate layer being bonded to the first end layer, each of the first subset of cavities including an opening defined by a surface of the trailing intermediate layer; Including, The method further comprises: disposing a vapor or a source of vapor in each of a first subset of the cavities; bonding a second terminal layer of the stack of layers to the rearmost intermediate layer to seal the vapor or vapor source within the first subset of the cavities, the second terminal layer being formed of a dielectric material; Including, each cavity of the second subset extends through the second end layer; the stack of layers, when including the bonded second terminal layer, defines a body of the vapor cell, the first terminal layer at a first end of the body, and the second terminal layer at an opposite second end of the body; A method for manufacturing a vapor cell. Example 129. The method of example 128, wherein bonding the second terminal layer includes covering each opening of a first subset of the cavities with the second terminal layer to enclose the vapor or vapor source in the first subset of the cavities. Example 130. Example 128 or Example 129. The method of Example 128 or Example 129, wherein the second terminal layer is formed of the first type of dielectric material. Example 131. The method of any one of Example 128 or Examples 129 to 130, wherein the first type of dielectric material includes silicon oxide. Example 132. obtaining said stack of layers, removing material from a first wafer formed of the first type of dielectric material to produce the first terminal layer, the second terminal layer (when combined with embodiment 130), or both; removing material from a second wafer formed of a dielectric material to produce the intermediate layer; Including, The method according to any one of Example 128 or Example 129 to Example 131. Example 133. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second, different type of dielectric material; and Including, The method according to any one of Example 128 or Example 129 to Example 131. Example 134. obtaining said stack of layers, bonding layers of a first subset of layers and layers of a second subset of layers to each other alternately to form the intermediate layer; bonding the leading intermediate layer to the first distal layer; Including, The method described in Example 133. Example 135. obtaining said stack of layers, removing material from a first wafer formed of the first type of dielectric material to produce the first terminal layer, one or more of the first subset of layers, the second terminal layer (when combined with embodiment 130), or any combination thereof; removing material from a second wafer formed of the second type of dielectric material to produce one or more of the second subset of layers; Including, The method described in Example 133 or Example 134. Example 136. The method of any one of Example 133 or Example 134 to Example 135, wherein the second type of dielectric material is silicon. Example 137. The step of bonding the second end layer further comprises: modifying the surface of the last intermediate layer to include a first plurality of hydroxyl ligands; modifying a surface of the second terminal layer to include a second plurality of hydroxyl ligands; contacting the modified surfaces to form a seal around each opening of a first subset of the cavities defined by metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contact of the two modified surfaces; Including, The method according to any one of Example 128 or Example 129 to Example 136. Example 138. The step of bonding the second end layer further comprises: activating one or both of the surfaces of the rearmost intermediate layer and the second terminal layer by exposing the respective surfaces of the layers to a plasma. The method described in Example 137. Example 139. each cavity of the first subset is surrounded by a sidewall formed by the stack of layers, the sidewall having one or more exterior surfaces defining at least a portion of a unit cell perimeter surrounding the cavity; for one or more cavities of the first subset, at least one of the intermediate layers includes a plurality of holes between the one or more cavities and a respective unit cell periphery of the cavity; The method according to any one of Example 128 or Example 129 to Example 138. Example 140. 140. The method of embodiment 139, wherein the plurality of holes extend through the at least one intermediate layer. Example 141. the vapor cell is configured, at the time of manufacture, to detect target radiation; each of the plurality of holes having a maximum dimension not exceeding a wavelength of the target radiation; The method described in Example 139 or Example 140. Example 142. 142. The method of claim 141, wherein the target radiation has a wavelength of at least 0.3 mm. Example 143. obtaining said stack of layers, forming an adhesive layer on one or both sides of an intermediate layer to define a bonding surface for each of said intermediate layers; The method according to any one of Example 128 or Example 129 to Example 142. Example 144. 144. The method of embodiment 143, wherein the adhesion layer comprises silicon oxide. Example 145. The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at a first location on a periphery of the stack of layers (or the body of the vapor cell); a second set of tabs extending outwardly from the intermediate layer at a second location on the periphery of the stack of layers (or the body of the vapor cell); and Including, The method according to any one of Example 128 or Example 129 to Example 144. Example 146. the vapor cell is a first vapor cell; the first set of tabs defines a first mechanical joint configured to couple with a second vapor cell (e.g., a second instantiation of the first vapor cell); the second set of tabs defines a second mechanical joint configured to couple with a third vapor cell (e.g., a third instantiation of the first vapor cell); The method described in Example 145.

[0068] In some aspects of the described subject matter, the vapor cell can be illustrated by the following example. Example 147. 1. A vapor cell comprising: a body defined by a stack of layers bonded together, the stack of layers including: a first terminal layer at a first end of the body and formed of a first type of optically transparent dielectric material; a second terminal layer at an opposite second end of the body and formed of a dielectric material; and intermediate layers formed of a dielectric material between the first and second terminal layers, the intermediate layers defining an internal cavity extending through the body between the first and second terminal layers, each intermediate layer including a through hole defining a portion of the internal cavity through the intermediate layer; a steam or steam source disposed in the internal cavity; A vapor cell comprising: Example 148. The vapor cell of Example 147, wherein each through-hole is equal in shape and size. Example 149. The vapor cell of example 147, wherein at least two adjacent intermediate layers have respective through holes that differ from one another in either or both of shape and size. Example 150. the through holes are circular and aligned along a direction perpendicular to the stack of layers; the through holes vary in size to define a spherical volume for the interior cavity; Vapor cell as described in Example 147. Example 151. The vapor cell of any one of Example 147 or Example 148 to Example 150, wherein the second terminal layer is formed of the first type of dielectric material. Example 152. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second, different type of dielectric material; Including, The vapor cell of any one of Example 147 or Example 148 to Example 151. Example 153. 153. The vapor cell of embodiment 152, wherein the layers are ordered to alternate between the first type of dielectric material and the second type of dielectric material within the stack. Example 154. The vapor cell of example 152 or example 153, wherein the second type of dielectric material is silicon. Example 155. The vapor cell of Example 147 or any one of Examples 148 to 154, wherein the first type of dielectric material comprises silicon oxide. Example 156. The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at a first exterior portion (or location) of the body; a second set of tabs extending outwardly from the intermediate layer at a second outer portion (or location) of the body; Including, The vapor cell of any one of Example 147 or Example 148 to Example 155. Example 157. the vapor cell is a first vapor cell; the first set of tabs defines a first mechanical joint configured to couple with a second vapor cell (e.g., a second instantiation of the first vapor cell); the second set of tabs defines a second mechanical joint configured to couple with a third vapor cell (e.g., a third instantiation of the first vapor cell); Vapor cell as described in Example 156. Example 158. each tab of the first set is an integral part of the intermediate layer from which it extends; each tab of the second set is an integral part of the intermediate layer from which it extends; The vapor cell of example 156 or example 157. Example 159. A vapor cell described in Example 156 or any one of Examples 157 to 158, wherein the first and second sets of tabs are aligned with the centers of the first and second outer portions, respectively. Example 160. the intermediate layer includes a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab in the first set extends outwardly from a respective layer in the first subset of layers; each tab in the second set extends outwardly from a respective layer in the second subset of layers; The vapor cell of Example 156 or any one of Examples 157 to 159. Example 161. A plurality of vapor cells, each corresponding to the vapor cell described in Example 156 or any one of Examples 157 to 160, wherein a first and second set of tabs of each vapor cell are respectively connected to the second set of tabs of a first vapor cell and the first set of tabs of a second, different vapor cell. Example 162. the body having four outer portions defining a square cross section thereof, the four outer portions including first and second outer portions; The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at the first outer portion of the body; a second set of tabs extending outwardly from the intermediate layer at the second outer portion of the body; and Including, The vapor cell of any one of Example 147 or Example 148 to Example 161. Example 163. 163. The vapor cell of embodiment 162, wherein the first outer portion and the second outer portion are adjacent to one another. Example 164. 163. The vapor cell of embodiment 162, wherein the first outer portion and the second outer portion oppose each other. Example 165. The four outer portions include a third and a fourth outer portion, The stack of layers above is: a third set of tabs extending outwardly from the intermediate layer at the third outer portion of the body; and a fourth set of tabs extending outwardly from the intermediate layer at the fourth outer portion of the body; and Including, The vapor cell of Example 162 or any one of Example 163 to Example 164. Example 166. each tab of the third set is an integral part of the intermediate layer from which it extends; each tab of the fourth set is an integral part of the intermediate layer from which it extends; Vapor cell as described in Example 165. Example 167. A vapor cell as described in Example 165 or Example 166, wherein the first, second, third, and fourth sets of tabs are aligned with the centers of the first, second, third, and fourth outer portions, respectively. Example 168. the intermediate layer includes a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab in the first and third sets extends outwardly from a respective layer in the first subset of layers; each tab in the second and fourth sets extends outwardly from a respective layer in the second subset of layers; The vapor cell of example 165 or any one of example 166 to example 167. Example 169. The first end layer comprises: an interior surface covering a first opening of the interior cavity adjacent the first end layer; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell of any one of example 147 or example 148 to example 168. Example 170. 169. The vapor cell of embodiment 169, wherein the inner surface of the first end layer includes a reflective coating disposed thereon. Example 171. The vapor cell of example 169 or example 170, wherein the exterior surface of the first terminal layer includes a reflective coating disposed thereon. Example 172. The vapor cell of any one of Example 169 or Example 170 to Example 171, wherein the inner surface of the first terminal layer includes an antireflective coating disposed thereon. Example 173. The vapor cell of any one of Example 169 or Example 170 to Example 172, wherein the outer surface of the first terminal layer includes an antireflective coating disposed thereon. Example 174. The second terminal layer comprises: an interior surface covering a second opening of the interior cavity adjacent the second end layer; an outer surface opposite said inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; The vapor cell of example 147 or any one of examples 148 to 173. Example 175. 175. The vapor cell of embodiment 174, wherein the inner surface of the second end layer includes a reflective coating disposed thereon. Example 176. The vapor cell of example 174 or example 175, wherein the exterior surface of the second end layer includes a reflective coating disposed thereon. Example 177. The vapor cell of any one of Example 174 or Example 175 to Example 176, wherein the inner surface of the second terminal layer includes an antireflective coating disposed thereon. Example 178. The vapor cell of any one of Example 174 or Example 175 to Example 177, wherein the outer surface of the second terminal layer includes an antireflective coating disposed thereon. Example 179. A vapor cell described in any one of Examples 147 or 148 to 178, wherein at least one of the intermediate layers includes a plurality of holes between the internal cavity and the outer periphery of the intermediate layer. Example 180. 179. The vapor cell of embodiment 179, wherein the plurality of holes extend through the intermediate layer. Example 181. the vapor cell configured to detect target radiation; each of the plurality of holes having a maximum dimension not exceeding a wavelength of the target radiation; The vapor cell of example 179 or example 180. Example 182. 182. The vapor cell of embodiment 181, wherein the target radiation has a wavelength of at least 0.3 mm. Example 183. The vapor cell of any one of Example 147 or Example 148 to Example 182, wherein a joint between at least one pair of adjacent layers in the stack of layers includes an adhesive layer. Example 184. 184. The vapor cell of embodiment 183, wherein the adhesion layer comprises silicon oxide. Example 185. The body includes an outer shape, each layer in the stack of layers includes a peripheral surface defining a cross-section of a profile at the location of the layer; The vapor cell of any one of Example 147 or Example 148 to Example 184. Example 186. 186. The vapor cell of embodiment 185, wherein the cross-section of the profile is constant along the stack of layers. Example 187. 186. The vapor cell of embodiment 185, wherein at least two adjacent intermediate layers have respective outer peripheries that differ from one another in either or both of shape and size. Example 188. A vapor cell as described in Example 185 (excluding the features described in Examples 162 to 168), wherein the cross-section is circular in shape and varies in size along the stack of layers to define a spherical outline for the body.

[0069] In some aspects of the described subject matter, a method for manufacturing a vapor cell can be illustrated by the following example. Example 189. 1. A method of manufacturing a vapor cell, comprising the steps of: obtaining a stack of layers bonded together, The stack of layers is: a first end layer formed of a first type of optically transparent dielectric material; intermediate layers formed of a dielectric material, extending in sequence from a leading intermediate layer to a trailing intermediate layer, said leading intermediate layer being bonded to said first end layer, an internal cavity extending therethrough, said internal cavity including an opening defined by a surface of said trailing intermediate layer, each intermediate layer including a through hole defining a portion of said internal cavity therethrough; Including, The method further comprises: disposing steam or a source of steam in the internal cavity; bonding a second terminal layer of the stack of layers to the rearmost intermediate layer to seal the vapor or vapor source within the first subset of the cavities, the second terminal layer being formed of a dielectric material; Including, the stack of layers, when including the bonded second terminal layer, defines a body of the vapor cell, the first terminal layer at a first end of the body, and the second terminal layer at an opposite second end of the body; A method for manufacturing a vapor cell. Example 190. The method of example 189, wherein each through hole is equal in shape and size. Example 191. The method of example 189, wherein at least two adjacent intermediate layers have respective through holes that differ from each other in either or both of shape and size. Example 192. the through holes are circular and aligned along a direction perpendicular to the stack of layers; the through holes vary in size to define a spherical volume for the interior cavity; The method described in Example 191. Example 193. A method as described in any one of Example 189 or Example 190 to Example 192, wherein the step of bonding the second terminal layer includes a step of covering an opening of the internal cavity with the second terminal layer to enclose the vapor or vapor source within the internal cavity. Example 194. The method of any one of Example 189 or Example 190 to Example 193, wherein the second terminal layer is formed of the first type of dielectric material. Example 195. The method of any one of Example 189 or Example 190 to Example 194, wherein the first type of dielectric material includes silicon oxide. Example 196. obtaining said stack of layers, removing material from a first wafer formed of the first type of dielectric material to produce the first terminal layer, the second terminal layer (when combined with embodiment 194), or both; removing material from a second wafer formed of a dielectric material to produce the intermediate layer; Including, The method according to any one of Example 189 or Example 190 to Example 195. Example 197. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second, different type of dielectric material; and Including, The method according to any one of Example 189 or Example 190 to Example 195. Example 198. obtaining said stack of layers, bonding layers of a first subset of layers and layers of a second subset of layers to each other alternately to form the intermediate layer; bonding the leading intermediate layer to the first distal layer; Including, The method described in Example 197. Example 199. obtaining said stack of layers, removing material from a first wafer formed of the first type of dielectric material to produce the first terminal layer, one or more of the first subset of layers, the second terminal layer (when combined with embodiment 194), or any combination thereof; removing material from a second wafer formed of the second type of dielectric material to produce one or more of the second subset of layers; Including, The method described in Example 197 or Example 198. Example 200. The method of any one of Example 197 or Example 198 to Example 199, wherein the second type of dielectric material is silicon. Example 201. The step of bonding the second end layer further comprises: modifying the surface of the last intermediate layer to include a first plurality of hydroxyl ligands; modifying a surface of the second terminal layer to include a second plurality of hydroxyl ligands; contacting the modified surfaces to form a seal around the opening of the internal cavity defined by metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contact of the two modified surfaces; Including, The method according to any one of Example 189 or Example 190 to Example 200. Example 202. The step of bonding the second end layer further comprises: activating one or both of the surfaces of the last intermediate layer and the second terminal layer by exposing the respective surfaces of the layers to a plasma; Including, The method described in Example 201. Example 203. The method of any one of Example 189 or Example 190 to Example 202, wherein at least one of the intermediate layers includes a plurality of holes between the internal cavity and the outer periphery of the intermediate layer. Example 204. 204. The method of claim 203, wherein the plurality of holes extend through the intermediate layer. Example 205. the vapor cell is configured, at the time of manufacture, to detect target radiation; each of the plurality of holes having a maximum dimension not exceeding a wavelength of the target radiation; The method described in Example 203 or Example 204. Example 206. 206. The method of claim 205, wherein the target radiation has a wavelength of at least 0.3 mm. Example 207. obtaining said stack of layers, forming an adhesive layer on one or both sides of an intermediate layer to define a respective bonding surface of said intermediate layer; Including, The method according to any one of Example 189 or Example 190 to Example 206. Example 208. 208. The method of embodiment 207, wherein the adhesion layer comprises silicon oxide. Example 209. The stack of layers above is: a first set of tabs extending outwardly from the intermediate layer at a first outer portion of the stack of layers (or the body of the vapor cell); a second set of tabs extending outwardly from the intermediate layer at a second outer portion of the stack of layers (or the body of the vapor cell); and Including, The method according to any one of Example 189 or Example 190 to Example 208. Example 210. the vapor cell is a first vapor cell; the first set of tabs defines a first mechanical joint configured to couple with a second vapor cell (e.g., a second instantiation of the first vapor cell); the second set of tabs defines a second mechanical joint configured to couple with a third vapor cell (e.g., a third instantiation of the first vapor cell); The method described in Example 209. Example 211. The body includes an outer shape, each layer in the stack of layers includes a peripheral surface that defines a cross-section of a profile at the location of the layer; The method according to any one of Example 189 or Example 190 to Example 210. Example 212. 212. The method of claim 211, wherein the cross-section of the profile is constant along the stack of layers. Example 213. The method of example 211, wherein at least two adjacent intermediate layers have respective outer perimeters that differ from one another in either or both of shape and size. Example 214. The method of embodiment 211, wherein the cross-section is circular in shape and varies in size along the stack of layers to define a spherical contour for the body.

[0070] Although this specification contains many details, these should not be understood as limitations on the scope that may be set forth in the claims, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this specification or illustrated in the drawings in the context of separate implementations may also be combined. Conversely, various additional features that are described in the specification or illustrated in the drawings in the context of a single implementation may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0071] Similarly, although the figures depict operations in a particular order, this should not be understood as requiring that such operations be performed in the particular order or sequence shown, or that all of the illustrated operations be performed, to achieve desirable results. In certain situations, multitasking and parallel processing may be beneficial. Furthermore, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the program components and systems described as a whole may be integrated into a single product or packaged into multiple products.

[0072] Although several embodiments have been described, it will be understood that various modifications may be made and, therefore, other embodiments are within the scope of the following claims. [Explanation of symbols]

[0073] 600 Exemplary Vapor Cell 608 Main Unit 610 layer stack 612a First subset of cavities 612b Second subset of cavities 614 Middle Class 614a First subset of layers Second subset of layer 614b 616 First End Layer 618 First End 620 Second End Layer 622 Second End 624a 1st set of tabs 624b Second set of tabs 626a 1st place 626b Second location 628 Outer periphery of the body 630 Side wall 632 Cavity unit cell periphery

Claims

1. 1. A vapor cell comprising: a body defined by a stack of layers bonded together; The stack of layers comprises: a first terminal layer at a first end of the body and formed of a first type of optically transparent dielectric material; a second terminal layer at an opposite second end of the body and formed of a dielectric material; a plurality of intermediate layers between the first end layer and the second end layer and formed of a dielectric material, the plurality of intermediate layers defining an interior cavity extending through the body between the first end layer and the second end layer; a first set of tabs extending outwardly from the intermediate layer at a first exterior portion of the body; a second set of tabs extending outwardly from the intermediate layer at a second outer portion of the body; The vapor cell comprises: a steam or steam source disposed in the internal cavity; A vapor cell comprising:

2. The vapor cell of claim 1 , wherein the second terminal layer is formed of the first type of dielectric material.

3. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second type of dielectric material different from the first type of dielectric material; The vapor cell of claim 1 or 2, comprising:

4. The vapor cell of claim 3 , wherein the stack of layers is ordered to alternate between the first type of dielectric material and the second type of dielectric material.

5. the intermediate layer includes a first subset of layers and a second subset of layers that alternate in sequence along the stack of layers; each tab of the first set extends outwardly from a respective layer in the first subset of layers; each tab of the second set extends outwardly from a respective layer in the second subset of layers; 3. The vapor cell according to claim 1 or 2.

6. the first and second sets of tabs are aligned with centers of the first and second outer portions, respectively; 3. The vapor cell according to claim 1 or 2.

7. the vapor cell is a first vapor cell; the first set of tabs defines a first mechanical joint configured to couple with a second vapor cell; a second set of tabs defining a second mechanical joint configured to couple with a third vapor cell; 3. The vapor cell according to claim 1 or 2.

8. At least one of the intermediate layers includes a plurality of holes between the interior cavity and an outer periphery of the intermediate layer.

3. The vapor cell according to claim 1 or 2.

9. the plurality of holes extending through the intermediate layer; The vapor cell of claim 8 .

10. the vapor cell is configured to detect target radiation; each of the plurality of holes having a maximum dimension not exceeding a wavelength of the target radiation; The vapor cell of claim 8 .

11. The first end layer comprises: an interior surface covering a first opening of the interior cavity adjacent the first end layer; an outer surface opposite the inner surface; Including, one or both of the inner surface and the outer surface have an optical coating disposed thereon; 3. The vapor cell according to claim 1 or 2.

12. the body has four outer portions defining a square cross section of the body, the four outer portions including a first and a second outer portion; 3. The vapor cell according to claim 1 or 2.

13. The vapor cell of claim 12 , wherein the first outer portion and the second outer portion are adjacent to one another.

14. The vapor cell of claim 12 , wherein the first exterior portion and the second exterior portion oppose one another.

15. the four outer portions include a third and a fourth outer portion; The stack of layers comprises: a third set of tabs extending outwardly from the intermediate layer at the third outer portion of the body; and a fourth set of tabs extending outwardly from the intermediate layer at the fourth outer portion of the body; and Including, The vapor cell of claim 12.

16. the first, second, third, and fourth sets of tabs are aligned with centers of the first, second, third, and fourth outer portions, respectively; 16. The vapor cell of claim 15.

17. 1. A method of manufacturing a vapor cell, comprising the steps of: obtaining a stack of layers bonded together, The stack of layers comprises: a first terminal layer formed of a first type of optically transparent dielectric material; intermediate layers formed of a dielectric material, extending in sequence from a leading intermediate layer to a trailing intermediate layer, the leading intermediate layer being bonded to the first end layer, an internal cavity including an opening extending through the intermediate layers and defined by a surface of the trailing intermediate layer; a first set of tabs extending outwardly from the intermediate layer at a first perimeter of the stack of layers; a second set of tabs extending outwardly from the intermediate layer at a second perimeter of the stack of layers; and Including, The method further comprises: disposing steam or a source of steam in the internal cavity; bonding a second terminal layer of the stack of layers to the rearmost intermediate layer to seal the vapor or vapor source within the interior cavity, the second terminal layer being formed of a dielectric material; Including, the stack of layers, when including the bonded second terminal layer, defines a body of the vapor cell, the first terminal layer at a first end of the body, and the second terminal layer at an opposite second end of the body. A method for manufacturing a vapor cell.

18. bonding the second end layer includes covering an opening of the internal cavity with the second end layer to enclose the vapor or vapor source in the internal cavity.

20. The method of claim 17.

19. the second terminal layer is formed of the first type of dielectric material; 19. The method according to claim 17 or 18.

20. The intermediate layer is a first subset of layers formed of the first type of dielectric material; a second subset of layers formed of a second type of dielectric material different from the first type of dielectric material; Including, 19. The method according to claim 17 or 18.

21. The step of obtaining a stack of layers comprises: bonding layers of the first subset of layers and layers of the second subset of layers to one another in an alternating manner to form the intermediate layer; bonding the leading intermediate layer to the first distal layer; Including, 21. The method of claim 20.

22. The step of obtaining a stack of layers comprises: removing material from a first wafer formed of the first type of dielectric material to produce the first terminal layer, one or more of the first subset of layers, or one or more of the first terminal layer and the first subset of layers; removing material from a second wafer formed of the second type of dielectric material to produce one or more of the second subset of layers; Including, 21. The method of claim 20.

23. The step of bonding the second end layer further comprises: modifying the surface of the last intermediate layer to include a first plurality of hydroxyl ligands; modifying a surface of the second terminal layer to include a second plurality of hydroxyl ligands; contacting the modified surfaces to form a seal around an opening of the internal cavity defined by metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contact of the two modified surfaces; Including, 19. The method according to claim 17 or claim 18.

24. The step of bonding the second end layer further comprises: activating one or both of the surfaces of the rearmost intermediate layer and the second terminal layer by exposing the respective surfaces of the layers to a plasma.

24. The method of claim 23.

25. At least one of the intermediate layers includes a plurality of holes between the interior cavity and an outer periphery of the intermediate layer.

19. The method according to claim 17 or claim 18.

26. The method of claim 25 , wherein the plurality of holes extend through the intermediate layer.

27. The step of obtaining a stack of layers comprises: forming an adhesive layer on one or both sides of an intermediate layer to define a respective bonding surface of said intermediate layer; 19. The method according to claim 17 or claim 18.

28. 1. A vapor cell system comprising: an array of interconnected vapor cells; Each of the coupled vapor cells comprises: a stack of layers bonded together to define a body of said interconnected vapor cell; The stack of layers comprises: a first terminal layer at a first end of the body and formed of a first type of optically transparent dielectric material; a second terminal layer at an opposite second end of the body and formed of a dielectric material; one or more intermediate layers between the first and second end layers and formed of a dielectric material, the intermediate layers defining an interior cavity extending through the stack of layers between the first and second end layers; Including, Each of the coupled vapor cells further comprises: a first mechanical joint on a first exterior portion of the body; a second mechanical joint on a second exterior portion of the body; and a steam or steam source disposed in the internal cavity; Including, the first mechanical joint of at least one coupled vapor cell is coupled to the second mechanical joint of another coupled vapor cell; the second mechanical joint of the at least one coupled vapor cell is coupled with the first mechanical joint of another different coupled vapor cell; Vapor cell system.

29. the first mechanical joint includes a first set of tabs extending outwardly from the one or more intermediate layers at the first outer side of the body; the second mechanical joint includes a second set of tabs extending outwardly from the one or more intermediate layers at the second outer portion of the body.

30. The vapor cell system of claim 28.

30. the one or more intermediate layers include at least one layer having a plurality of holes between the interior cavity and an outer periphery of the intermediate layer; 30. The vapor cell system of claim 28 or 29.

Images