Atomic cooling apparatus and production method therefor

Abstract

An atomic cooling apparatus according to one aspect of the present disclosure comprises: an optical structure that includes a cold atom generation chamber which cools and captures atoms and an ion pump unit which evacuates the inside of the cold atom generation chamber; a pair of light-incident substrates that are disposed at positions facing each other on outer surfaces of the optical structure and that can cause a pair of parallel light beams which travel in directions opposite to each other and which are circularly polarized light having the same rotation direction relative to the traveling direction to enter the cold atom generation chamber; and a diffraction element, inside the cold atom generation chamber, that diffracts at least one of the pair of parallel light beams to a side opposite to the incident side and that emits, into the cold atom generation chamber, the diffracted light that is circularly polarized light having a rotation direction opposite to that of the parallel light beam having entered, relative to the traveling direction, wherein inside the cold atom generation chamber, atoms are cooled and captured in the region where the pair of parallel light beams and the diffracted light overlap with each other.

Description

Atomic cooling device and manufacturing method thereof

[0001] The present disclosure relates to an atom cooling device used to cool and trap atoms and a method for manufacturing the same.

[0002] Using atoms cooled to cryogenic temperatures, atomic clocks, atomic interferometers, cooled-atom quantum computers, etc. Magneto-optical traps (MOTs) are known as a method for cooling atoms to cryogenic temperatures.

[0003] As an example of a magneto-optical trap, a technique is disclosed in Patent Document 1, in which an incident laser beam is diffracted using a diffraction grating, the diffracted beam intersects with the incident laser beam, and atoms are cooled and trapped at the center of the intersecting plane. This technique is called a grating magneto-optical trap (GMOT) or the like (see, for example, Patent Document 1).

[0004] To perform GMOT, a cooling chamber in which atoms are cooled and trapped is placed in an ultra-high vacuum (e.g., 10 －５ An example of a configuration for creating an ultra-high vacuum inside the cooling chamber is an ion pump.

[0005] For example, Patent Document 2 discloses a technique for integrating a cooling chamber, a diffraction grating, and an ion pump in order to reduce the size of a magneto-optical trap device.

[0006] U.S. Patent No. 10,278,275 U.S. Patent No. 9,960,025

[0007] The technology disclosed in Patent Document 2 has limitations on miniaturization due to the complicated arrangement of components. The present disclosure aims to provide an atomic cooling device with a simpler structure that can be easily miniaturized, and a manufacturing method thereof.

[0008] An atom cooling device according to one aspect of the present disclosure comprises: an optical structure including a cooled atom generation chamber that cools and captures atoms; and an ion pump unit that evacuates the inside of the cooled atom generation chamber; a pair of light incident substrates arranged at opposing positions on the outer surface of the optical structure, which are capable of incident into the cooled atom generation chamber a pair of parallel light beams that travel in opposing directions and are circularly polarized light beams whose electric field vectors rotate in the same direction as the direction of propagation; and a diffraction element inside the cooled atom generation chamber that diffracts at least one of the pair of parallel light beams to the side opposite to the incident side and emits diffracted light into the cooled atom generation chamber, which is circularly polarized light whose rotation direction is opposite to the direction of propagation of the incident parallel light beam.The atoms are cooled and captured in a region inside the cooled atom generation chamber where the pair of parallel light beams and the diffracted light overlap.

[0009] A method for manufacturing an atomic cooling device according to one aspect of the present disclosure is a method for manufacturing an atomic cooling device according to the above aspect, and includes joining the pair of light incident substrates to opposing positions on the outer surface of the optical structure by substrate bonding.

[0010] According to the present disclosure, it is possible to provide an atomic cooling device that has a simpler structure and is easily miniaturized, and a method for manufacturing the same.

[0011] 1 is a diagram illustrating a configuration of an atom cooling device according to an embodiment of the present disclosure; FIG. 2 is a diagram illustrating a configuration of an atom cooling device according to an embodiment of the present disclosure; FIG. 3 is a diagram illustrating a configuration of an atom cooling device according to an embodiment of the present disclosure; FIG. 4 is a diagram illustrating a first configuration example of a magneto-optical trap; FIG. 5 is a diagram illustrating a second configuration example of a magneto-optical trap; FIG. 6 is a diagram illustrating a modification of the third configuration example of a magneto-optical trap; FIG. 7 is a diagram illustrating a fourth configuration example of a magneto-optical trap; FIG. 8 is a diagram illustrating a fifth configuration example of a magneto-optical trap; FIG. 9 is a diagram illustrating a structure of a diffraction element; FIG. 10 is a diagram illustrating a first example of periodically arranged regions formed on a surface of a substrate of a diffraction element; FIG. 11 is a diagram illustrating a second example of periodically arranged regions formed on a surface of a substrate of a diffraction element; FIG. 12 is a diagram illustrating a diffraction pattern formed on one surface of a diffraction element having the first example of periodically arranged regions when parallel light is incident perpendicularly from the other surface side; FIG. 13 is a diagram illustrating a diffraction pattern formed on one surface of a diffraction element having the second example of periodically arranged regions when parallel light is incident perpendicularly from the one surface side; 1 is a diagram illustrating a diffraction pattern in a diffraction element employing a third example of a two-dimensional periodic array of dielectric nanostructures. FIG. 2 is a diagram for explaining the unit structure of a dielectric nanostructure. FIG. 3 is a diagram for explaining the unit structure of a dielectric nanostructure. FIG. 4 is a diagram for explaining a first example of a two-dimensional periodic array of dielectric nanostructures in a diffraction element. FIG. 5 is a diagram for explaining a second example of a two-dimensional periodic array of dielectric nanostructures in a diffraction element. FIG. 6 is a diagram for explaining a third example of a two-dimensional periodic array of dielectric nanostructures in a diffraction element. A conceptual diagram for explaining an example of operation for cooling and trapping atoms using an atom cooling device. A flowchart for explaining an example of operation when cooling and trapping atoms using an atom cooling device. A diagram for explaining a method for manufacturing an atom cooling device. A flowchart for explaining a method for manufacturing an atom cooling device.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, more detailed explanation than necessary, such as detailed explanation of already well-known matters and redundant explanation of substantially the same configuration, may be omitted.

[0013] 1A to 1C are diagrams showing the configuration of an atom cooling device 100 according to an embodiment of the present disclosure. Fig. 1A is a perspective view of the atom cooling device 100. As shown in Fig. 1A, the atom cooling device 100 has an overall shape similar to a rectangular parallelepiped having a longitudinal direction and a lateral direction.

[0014] In this specification, the longitudinal direction of the atomic cooling device 100 will be described as the x-direction, the lateral direction as the y-direction, and the thickness direction as the z-direction. The z-direction may also be referred to as the up-down direction. The side on which the diffraction element 22 (described later) is formed is the lower side in the z-direction, and the opposite side is the upper side.

[0015] Fig. 1B is a top view of the atom cooling device 100 as seen from the z-axis direction. Fig. 1C is a cross-sectional view taken along line AA in Fig. 1B. In Fig. 1B, the internal structure of the atom cooling device 100 is shown by dashed lines.

[0016] 1A to 1C, the atom cooling device 100 includes an optical structure 10 including a cooled-atom generation chamber 11 for cooling atoms and an ion pump unit 12 for evacuating the inside of the cooled-atom generation chamber 11, and a pair of light-incident substrates 20 that can input a pair of parallel beams of light into the cooled-atom generation chamber. The light-incident substrates 20 are bonded by substrate bonding to the outer surface of the optical structure 10 at positions facing each other.

[0017] The cold atom generation chamber 11 is a container capable of maintaining a vacuum inside. In this embodiment, the cold atom generation chamber 11 has an ultra-high vacuum (10 －５ Pa or less), and more preferably, 10 －６ It has the ability to maintain the temperature at or below 100 Pa.

[0018] 1B and 1C, the cold-atom generation chamber 11 is a substantially cylindrical space inside the optical structure 10, and both of its bottom surfaces are defined by the light-incident substrate 20. In other words, the cold-atom generation chamber 11 is an opening of the optical structure 10, and is sealed by the light-incident substrate 20. Note that the cold-atom generation chamber 11 is not particularly limited to a cylindrical shape, and may also be a rectangular parallelepiped shape.

[0019] A magneto-optical trap 200 for cooling and trapping atoms is configured in the cooled atom generation chamber 11. Details of the magneto-optical trap 200 will be described later.

[0020] The ion pump unit 12 operates by supplying a voltage between the electrodes 15 and 16 in a state where an external magnetic field is applied, and evacuates the inside of the cooled atom generation chamber 11. This creates a vacuum inside the cooled atom generation chamber 11. In Figures 1B and 1C, the area of ​​the ion pump unit 12 is indicated by dashed lines.

[0021] The electrode 15 is disposed at approximately the center of the atomic cooling device 100 in the thickness direction (z direction), and has a plate-like configuration that is disposed so as to penetrate the entire atomic cooling device 100. In the example shown in Fig. 1, the electrode 15 is formed in a rectangular parallelepiped shape. In the example shown in Fig. 1, the electrode 15 is disposed so as to protrude in the positive x direction from the other components of the atomic cooling device 100. This allows lead wires and the like that supply power to be connected via the electrode 15.

[0022] 1, the electrodes 16 are disposed on the upper and lower end faces in the thickness direction (z direction) of the atomic cooling device 100. The electrodes 16 are conductors formed on the upper and lower end faces of the atomic cooling device 100. For example, in the example shown in Fig. 1, the electrodes 16 are formed on the entire upper and lower end faces of the atomic cooling device 100 in areas where the light incident substrate 20 is not provided.

[0023] The ion pump unit 12 operates, for example, as follows. When a voltage is applied between the electrodes 15 and 16 in an externally applied magnetic field, plasma is generated inside the ion pump unit 12. The ions constituting the plasma are, for example, ions of nitrogen, oxygen, argon, hydrogen, etc. The ions in the plasma are directed toward at least one of the electrodes 15 and 16. A Ti film is pre-formed on the surface of the cathode electrode 16. When ions collide with Ti atoms, the Ti atoms scatter in all directions. In other words, they are sputtered. The sputtered Ti atoms form a Ti film on the inner wall of the ion pump unit 12. Furthermore, the sputtered Ti atoms chemically adsorb active gases. Even inert gases are ionized by collisions with electrons and trapped inside the cathode electrode 16 or in the Ti film on its surface. This increases the degree of vacuum inside the ion pump unit 12.

[0024] 1B and 1C, the ion pump section 12 has a substantially cylindrical space with both bottom surfaces disposed perpendicular to the z direction inside the optical structure 10, similar to the cooled atom generation chamber 11. The space of the ion pump section 12 may be cylindrical or rectangular, and is not particularly limited.

[0025] The connection section 13 is formed inside the optical structure 10 and spatially connects the cooled atom generation chamber 11 and the ion pump section 12. In Figures 1B and 1C, the area of ​​the connection section 13 is indicated by a dashed line.

[0026] An atom supply unit 14 is provided near the connection between the cooled atom generation chamber 11 and the connection unit 13. The atom supply unit 14 supplies atoms to be cooled to the cooled atom generation chamber 11. The atom supply unit 14 supplies atoms into the cooled atom generation chamber 11 when, for example, heat is applied from the outside. Examples of atoms to be cooled include: ７ Li, ８７ Rb, ８５ Rb, １３３ Examples include alkali metal atoms such as Cs.

[0027] The pair of light incident substrates 20 each have a substrate 21 made of a material transparent to the laser beam, such as glass. At least one of the pair of light incident substrates 20 has a diffraction element 22 that generates transmitted light and diffracted light based on one of the pair of laser beams traveling in opposite directions. The diffraction element 22 is formed on the inner surface of the substrate 21. The inner surface of the substrate 21 refers to the surface of the substrate 21 that is located inside the cold atom generation chamber 11, out of the front and back surfaces of the substrate 21.

[0028] 1, the diffraction element 22 is formed only on the upper side of the pair of upper and lower light incident substrates 20, and no diffraction element is formed on the lower side. That is, in the example shown in Fig. 1, of the pair of light incident substrates 20, the upper light incident substrate 20 has only the substrate 21, and the lower light incident substrate 20 has the substrate 21 and the diffraction element 22 arranged on the inner surface of the substrate 21.

[0029] The diffraction element 22 receives parallel light incident in a direction perpendicular to the diffraction element 22 and outputs, on the side opposite to the incident side, diffracted light that travels in an oblique direction at a predetermined diffraction angle with respect to the direction perpendicular to the diffraction element 22. In other words, the diffraction element 22 is a transmissive diffraction element.

[0030] An example of a transmissive diffraction element is a diffraction element in which dielectric nanostructures made of a dielectric material with a high refractive index are periodically arranged on a substrate. When the diffraction element 22 is placed inside the cooled atom generation chamber 11, it is desirable that the material of the diffraction element 22 (substrate and dielectric nanostructure) be made of a material that does not react with the alkali metal atoms or alkaline earth metal atoms to be cooled and captured. Details of the diffraction element 22 will be described later.

[0031] 1, the diffraction element 22 is disposed on the inner surface of the substrate 21, but the present disclosure is not limited to this. For example, the diffraction element 22 may be disposed on the outer surface of the substrate 21. Furthermore, in the example shown in FIG. 1, the diffraction element 22 is disposed on only one of the pair of light incident substrates 20, but the present disclosure is not limited to this. For example, the diffraction element 22 may be disposed on both substrates 21 of the pair of light incident substrates 20. The diffraction element 22 may be formed on the substrate 21.

[0032] <Configuration Example of Magneto-Optical Trap> Below, we will specifically explain configuration examples of the magneto-optical trap 200 configured in the cooled atom generation chamber 11. For ease of explanation, in Figures 2 to 7 showing the configuration examples of the magneto-optical trap 200 below, the substrate 21 is also shown.

[0033] (First Configuration Example) Fig. 2 is a diagram for explaining a first configuration example of the magneto-optical trap 200 configured in the cooled atom generation chamber 11. In the example shown in Fig. 2, similar to Fig. 1C, a diffraction element 22 is arranged only on the lower side of a pair of upper and lower substrates 21, and no diffraction element is arranged on the upper side.

[0034] 2, a first parallel light beam Lp1 and a second parallel light beam Lp2 are incident in opposing directions on the cooled atom generation chamber 11. The first parallel light beam Lp1 and the second parallel light beam Lp2 are a pair of parallel light beams generated by an external light source and optical elements, and this is also true for other configuration examples.

[0035] The propagation directions of the first parallel light Lp1 and the second parallel light Lp2 are perpendicular to the light incident substrate 20, which is formed and arranged in a planar shape. The first parallel light Lp1 is incident from the bottom side, i.e., the side where the diffraction element 22 is arranged. The second parallel light Lp2 is incident from the top side, i.e., the side where the diffraction element 22 is not arranged. The first parallel light Lp1 and the second parallel light Lp2 are either of a pair of parallel light beams traveling in opposite directions. The first parallel light Lp1 and the second parallel light Lp2 are circularly polarized light beams whose electric field vectors rotate in the same direction when facing their respective propagation directions. The first direction, which is the propagation direction of the first parallel light Lp1, and the second direction, which is the propagation direction of the second parallel light Lp2, are opposite directions and are along the central optical axis of the magneto-optical trap 200.

[0036] In the following description, the traveling direction of the first parallel light Lp1 is referred to as the first direction, and the traveling direction of the second parallel light Lp2 is referred to as the second direction. The first direction and the second direction are opposite directions. Note that in Figure 2, the first parallel light Lp1 and the second parallel light Lp2, which are parallel lights, are illustrated as solid arrows.

[0037] A quadrupole magnetic field is applied by a magnetic field generator (not shown) inside the cooled atom generation chamber 11. In addition to the pair of parallel beams, repump beams are also incident on the cooled atom generation chamber 11.

[0038] With these components, a magneto-optical trap 200 for cooling and trapping atoms is configured in the cooled atom generation chamber 11. In the following description, the three-dimensional region in which atoms are cooled and trapped in the magneto-optical trap 200 is referred to as a specific region Rs.

[0039] Based on the incidence of the first parallel light Lp1 traveling along the first direction, the diffraction element 22 emits diffracted light Ld, which is circularly polarized light with a rotation direction opposite to that of the first parallel light Lp1, at a predetermined diffraction angle toward the side opposite to the side on which the first parallel light Lp1 is incident on the diffraction element 22.

[0040] In the example shown in Fig. 2, the diffraction element 22 is formed in a circular shape with a first opening 221 at the center. The circular shape of the diffraction element 22 in the example shown in Fig. 2 is an example of a shape that is n-fold symmetric (n is an integer of 3 or more) with respect to the central optical axis. The circular first opening 221 provided in the center of the diffraction element 22 is provided to allow the first parallel light Lp1 to pass through. Note that the circular shapes of the diffraction element 22 and the first opening 221 shown in Fig. 2 are examples, and the shapes of the diffraction element and opening in the present disclosure are not limited to the example shown in Fig. 2.

[0041] The diffraction element 22 transmits the first parallel light Lp1, thereby emitting diffracted light Ld at a predetermined diffraction angle α with respect to the central optical axis of the magneto-optical trap. In the example shown in FIG. 2 , the diffraction element 22 emits diffracted light Ld that travels from its entire circumferential direction toward the specific region Rs. In FIG. 2 , four hollow arrows are used to illustrate a portion of the diffracted light Ld traveling from the entire circumferential direction toward the specific region Rs. The predetermined diffraction angle α may be adjusted as appropriate depending on the position of the diffraction element 22 so that the diffracted light Ld travels toward the specific region Rs.

[0042] The first parallel light Lp1 that passes through the first opening 221, the second parallel light Lp2 that passes through the substrate 21, and the diffracted light Ld that is emitted by the diffraction element 22 are incident on a specific region Rs in the cooled atom generation chamber 11. The specific region Rs is located approximately at the center of the pair of coils that make up the magnetic field generator. Atoms in the cooled atom generation chamber 11 are cooled and captured in the specific region Rs due to the radiation pressure caused by the pair of parallel light and diffracted light, as well as the influence of the quadrupole magnetic field.

[0043] As described above, the diffraction element 22 has a plurality of dielectric nanostructures 82 (see FIG. 13A described later) periodically arranged on a plane perpendicular to the traveling direction of the pair of parallel beams. This allows the diffraction element 22 to emit n-component diffracted beams, each with the same diffraction angle and diffraction efficiency, toward the central optical axis of the magneto-optical trap 200. Furthermore, the diffraction element 22 rotates the circularly polarized beam of the emitted diffracted beam in the opposite direction to the circularly polarized beam of the incident beam (here, the first parallel beam Lp1). Details of the diffraction element 22 having such properties will be described later.

[0044] When the specific region Rs is projected onto the plane P on which the diffraction element 22 is disposed, the position of the specific region Rs is the center position of the diffraction element 22. As a result, diffracted light Ld is incident on the specific region Rs from all circumferential directions of the diffraction element 22. Note that even if the diffraction element 22 does not have the circular shape exemplified in Fig. 2, it is sufficient that the position of the specific region Rs is configured to be the center position of the diffraction element 22 when the specific region Rs is projected onto the plane P on which the diffraction element 22 is disposed.

[0045] With this configuration, in the first configuration example, a pair of parallel beams, a first parallel beam Lp1 and a second parallel beam Lp2, traveling in opposite directions, are incident on the specific region Rs inside the cooled atom generation chamber 11. In addition to these, diffracted beam Ld traveling in an oblique direction with respect to the central optical axis is incident on the specific region Rs. The diffracted beam Ld is incident on the specific region Rs from all around the circumference of the diffraction element 22. The rotation directions of the circularly polarized beams of the first parallel beam Lp1 and the second parallel beam Lp2 are the same, and the rotation directions of the circularly polarized beams of the first parallel beam Lp1 and the diffracted beam Ld are opposite to each other.

[0046] As a result, atoms to be cooled and captured within the cooled atom generation chamber 11 are subjected to radiation pressure from the first collimated light Lp1, the second collimated light Lp2, and the diffracted light Ld that have passed through the first opening 221. The frequencies of these lights are set slightly lower than the resonant frequency of the atoms. Due to the Doppler effect, the frequency of light seen from the atoms is closer to the resonant frequency of the atoms in the direction opposite to the direction of the atoms' velocity than that of light traveling in the same direction. Therefore, the atoms are subjected to stronger radiation pressure from the light traveling in the opposite direction to the direction of their velocity. This causes the atoms to decelerate. Furthermore, due to the shift in the resonant frequency of the atoms caused by the magnetic field, the frequency of light traveling toward the center of the quadrupole magnetic field is closer to the resonant frequency of the atoms than the frequency of light traveling away from the center. Therefore, the atoms are subjected to stronger radiation pressure toward the center of the quadrupole magnetic field, and are concentrated near the center of the quadrupole magnetic field within the specific region Rs.

[0047] In order for atoms to be suitably trapped within the specific region Rs and at the center of the quadrupole magnetic field, the intensities of the first parallel light Lp1 and the second parallel light Lp2, as well as the optical characteristics (such as the diffraction efficiency and diffraction angle of the diffraction element 22) of the optical element generating the pair of parallel light beams and the diffraction element 22 must be appropriately set so as to maintain a balance between the intensities of the radiation pressures caused by the first parallel light Lp1, the second parallel light Lp2, and the diffracted light Ld incident on the specific region Rs. These parameters may be set through experiments or the like based on the atomic species to be cooled and trapped, the characteristics of the cooling laser beam used, and the like. This allows the magneto-optical trap 200 to efficiently cool and trap atoms in the specific region Rs.

[0048] (Second Configuration Example) The magneto-optical trap configured in the cooled atom generation chamber of the atom cooling device according to the present disclosure is not limited to the first configuration example described above, and can have a number of configurations. Below, a second configuration example of the magneto-optical trap 200 configured in the atom cooling device 100 according to the embodiment of the present disclosure will be described.

[0049] 3 is a diagram for explaining a second configuration example of the magneto-optical trap 200. Fig. 3 shows the laser light incident on the specific region Rs in the second configuration example. Fig. 3 is a schematic diagram of the inside of the cooled atom generation chamber 11 as viewed from the side.

[0050] As shown in FIG. 3, in the second configuration example of magneto-optical trap 200, a mirror 71 and a quarter-wave plate 72 are provided on the outer surface of substrate 21 opposite to substrate 21 on which diffraction element 22 is provided.

[0051] The mirror 71 is disposed perpendicular to the traveling direction (first direction) of the parallel light. The quarter-wave plate 72 is disposed adjacent to the mirror 71 on the side of the mirror 71 on which the parallel light Lp is incident.

[0052] As shown in FIG. 3, at least a part of the parallel light Lp incident from below passes through the specific region Rs and is incident on the mirror 71 and the quarter-wave plate 72 .

[0053] The mirror 71 reflects the collimated light Lp that has passed through the quarter-wave plate 72 and emits reflected light Lr that travels in a second direction opposite to the first direction. The quarter-wave plate 72 imparts a phase difference of π / 2 to the polarization components of the collimated light Lp. The light incident on the mirror 71 passes through the quarter-wave plate 72 both before and after reflection by the mirror 71, so that the rotation direction of the circularly polarized light of the reflected light Lr becomes the same as the rotation direction of the circularly polarized light of the collimated light Lp.

[0054] The diffraction element 22 is a transmissive diffraction element, similar to the first configuration example. The diffraction element 22 diffracts the parallel light Lp in the direction opposite to the incident side to emit diffracted light Ld. The diffraction element 22 is disposed on a plane P perpendicular to the first direction and the second direction.

[0055] The diffraction element 22 emits diffracted light Ld from all directions, traveling obliquely with respect to the central optical axis of the magneto-optical trap. At this time, the diffraction element 22 rotates the circularly polarized light of the incident light in the direction opposite to the direction of rotation of the circularly polarized light of the outgoing diffracted light.

[0056] The first opening 221 of the diffraction element 22 is provided to allow the parallel light Lp incident on the specific region Rs, the mirror 71 and the quarter-wave plate 72 to pass through.

[0057] As a result, in the second configuration example, the following light components are incident: collimated light Lp that has passed through the first opening 221 of the diffraction element 22; diffracted light Ld that is emitted from the diffraction element 22 based on the incidence of the collimated light Lp; and reflected light Lr that is the collimated light Lp reflected by the mirror 71 and the quarter-wave plate 72. The collimated light Lp travels along the first direction, and the reflected light Lr travels along the second direction. As a result, the collimated light Lp and the reflected light Lr are incident on the specific region Rs in directions opposite to each other.

[0058] The second configuration example can also achieve the same effect as the first configuration example. That is, a pair of parallel light beams, namely, parallel light beam Lp and reflected light beam Lr, traveling in opposite directions, are incident on the specific region Rs inside the cooled atom generation chamber 11. In addition, diffracted light beam Ld, which is emitted by the diffraction element 22 by transmitting the parallel light beam Lp and travels in a direction oblique to the first direction, is incident on the specific region Rs. The circularly polarized light of the parallel light beam Lp and the reflected light beam Lr rotates in the same direction, while the circularly polarized light of the parallel light beam Lp and the circularly polarized light of the diffracted light beam Ld rotate in opposite directions.

[0059] In this way, the atoms are subjected to radiation pressure in a direction toward the specific region Rs by the influence of the parallel light Lp, reflected light Lr, and diffracted light Ld incident on the specific region Rs, and the quadrupole magnetic field, and are suitably cooled and captured.

[0060] As in the first configuration example, the intensities of the parallel light Lp and the reflected light Lr, as well as the optical characteristics of the optical element 7 and the diffraction element 22 (such as the reflectance of the mirror 71 and the transmittance and diffraction angle of the diffraction element 22) may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the parallel light Lp, the reflected light Lr, and the diffracted light Ld incident on the specific region Rs, thereby enabling the magneto-optical trap 200 to efficiently cool and trap atoms in the specific region Rs.

[0061] (Third Configuration Example) Next, a third configuration example of magneto-optical trap 200 will be described. In the third configuration example, first and second parallel beams of light traveling in two mutually opposing directions are transmitted through diffraction element 22, which is a transmissive diffraction element, to emit diffracted beams.

[0062] Fig. 4 is a diagram for explaining a third configuration example of the magneto-optical trap 200. Fig. 4 shows the laser light incident on the specific region Rs in the third configuration example. Fig. 4 is a schematic diagram of the inside of the cooled atom generation chamber 11 as viewed from the side.

[0063] 4, in the third configuration example, a first parallel light beam Lp1 traveling along a first direction and a second parallel light beam Lp2 traveling along a second direction opposite to the first direction are incident from an external light source (not shown). The circularly polarized light beams of the first parallel light beam Lp1 and the second parallel light beam Lp2 rotate in the same direction.

[0064] As a result, a pair of parallel beams of light enters the cooled atom generating chamber 11 so as to face each other.

[0065] In the third configuration example, a diffraction element 22A is disposed on the upper substrate 21 A, and a diffraction element 22B is disposed on the lower substrate 21 B. The diffraction elements 22A and 22B are transmissive diffraction elements, as in the other configuration examples.

[0066] The diffraction element 22A diffracts the incident first parallel light Lp1 and emits first diffracted light Ld1 in a direction oblique to the central optical axis, which is incident on the specific region Rs. The diffraction element 22B diffracts the incident second parallel light Lp2 and emits second diffracted light Ld2 in a direction oblique to the central optical axis, which is incident on the specific region Rs. The rotation direction of the circularly polarized light of the first parallel light Lp1 and the first diffracted light Ld1 are opposite to each other. The rotation direction of the circularly polarized light of the second parallel light Lp2 and the second diffracted light Ld2 are opposite to each other.

[0067] The first openings 221A and 221B of the diffraction element 22 are provided to allow the first parallel light Lp1 and the second parallel light Lp2 to pass through, respectively.

[0068] The third configuration example can achieve the following effect. A pair of parallel light beams traveling in opposite directions, a first parallel light beam Lp1 that has passed through the first opening 221A and a second parallel light beam Lp2 that has passed through the first opening 221B, are incident on the specific region Rs within the cooled atom generation chamber 11. In addition to these, a first diffracted light beam Ld1 that is emitted by the diffraction element 22A after diffracting the first parallel light beam Lp1 and traveling in a direction oblique to the first direction, and a second diffracted light beam Ld2 that is emitted by the diffraction element 22B after diffracting the second parallel light beam Lp2 and traveling in a direction oblique to the second direction, are also incident on the specific region Rs. The first parallel light beam Lp1 and the second parallel light beam Lp2 have the same rotation direction of the circularly polarized light, and the rotation direction of the circularly polarized light of the first parallel light beam Lp1 and the second parallel light beam Lp2 is opposite to that of the first diffracted light beam Ld1 and the second diffracted light beam Ld2.

[0069] In this way, due to the influence of the first parallel light Lp1, the second parallel light Lp2, the first diffracted light Ld1, and the second diffracted light Ld2 incident on the specific region Rs, and the quadrupole magnetic field, the atoms are subjected to radiation pressure in the direction toward the specific region Rs, and are suitably cooled and captured.

[0070] In the third configuration example, the intensities of the first parallel light Lp1 and the second parallel light Lp2, the first diffracted light Ld1, and the second diffracted light Ld2 incident on the specific region Rs, and the optical characteristics of the diffractive elements 22A and 22B (e.g., the diffraction efficiency and diffraction angle of the diffractive elements 22A and 22B) may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the first parallel light Lp1, the second parallel light Lp2, the first diffracted light Ld1, and the second diffracted light Ld2. This allows the magneto-optical trap 200 to efficiently cool and trap atoms in the specific region Rs.

[0071] According to the third configuration example, the number of diffracted light components incident on the specific region Rs is increased compared to the other configuration examples, which makes it easier to maintain the balance of radiation pressure that cools and captures atoms in the specific region Rs. This is thought to enable cooling and capturing of more atomic species.

[0072] (Modification of the Third Configuration Example) A modification of the third configuration example will be described. Fig. 5 is a diagram for explaining a modification of the third configuration example of magneto-optical trap 200. The modification of the third configuration example of magneto-optical trap 200 differs from the third configuration example in that each of diffraction elements 22A and 22B does not have an opening.

[0073] 5 shows the laser light incident on the specific region Rs in a modified example of the third configuration example. FIG. 5 is a schematic diagram of the inside of the cooled atom generation chamber 11 as viewed from the side.

[0074] The diffraction element 22A transmits the first parallel light Lp1, which is the incident light, and emits the first transmitted light Lt1 traveling along the first direction on the side opposite to the side on which the first parallel light Lp1 is incident, and also emits the first diffracted light Ld1 traveling in a direction oblique to the first direction.

[0075] In this case, similarly to the third configuration example, the diffraction element 22A sets the rotation direction of the circularly polarized light of the incident first collimated light Lp1 and the rotation direction of the circularly polarized light of the outgoing first diffracted light Ld1 to be opposite to each other. The diffraction element 22A also sets the rotation direction of the circularly polarized light of the incident first collimated light Lp1 and the rotation direction of the circularly polarized light of the outgoing first transmitted light Lt1 to be the same. The first diffracted light Ld1 emitted by the diffraction element 22A is incident on the specific region Rs from all directions around its circumference.

[0076] The diffraction element 22B transmits the second parallel light Lp2, which is the incident light, and emits second transmitted light Lt2 traveling along the second direction on the side opposite to the side on which the second parallel light Lp2 is incident, and emits second diffracted light Ld2 traveling in a direction oblique to the second direction.

[0077] In this case, as in the third configuration example, the diffraction element 22B sets the rotation direction of the circularly polarized light of the incident second collimated light Lp2 and the rotation direction of the circularly polarized light of the outgoing second diffracted light Ld2 to be opposite to each other. The diffraction element 22B also sets the rotation direction of the circularly polarized light of the incident second collimated light Lp2 and the rotation direction of the circularly polarized light of the outgoing second transmitted light Lt2 to be the same. The second diffracted light Ld2 emitted by the diffraction element 22B is incident on the specific region Rs from all circumferential directions.

[0078] According to the modified example of the third configuration example, the following effect can be obtained. A pair of parallel light beams, the first transmitted light Lt1 and the second transmitted light Lt2, traveling in opposite directions, are incident on the specific region Rs inside the cooled atom generation chamber 11. In addition to these, a first diffracted light Ld1 traveling in a direction oblique to the first direction, which is obtained by diffracting the first parallel light Lp1 and output by the diffraction element 22A, and a second diffracted light Ld2 traveling in a direction oblique to the second direction, which is obtained by diffracting the second parallel light Lp2 and output by the diffraction element 22B, are also incident on the specific region Rs. The first transmitted light Lt1 and the second transmitted light Lt2 have the same rotation direction of the circularly polarized light, and the rotation direction of the circularly polarized light of the first transmitted light Lt1 and the second transmitted light Lt2 is opposite to each other.

[0079] In this way, due to the influence of the first transmitted light Lt1, the second transmitted light Lt2, the first diffracted light Ld1, and the second diffracted light Ld2 incident on the specific region Rs, and the quadrupole magnetic field, the atoms are subjected to radiation pressure in the direction toward the specific region Rs, and are suitably cooled and captured.

[0080] In a modification of the third configuration example, the intensities of the first transmitted light Lt1 and the second transmitted light Lt2 incident on the diffraction elements 22A and 22B, as well as the optical characteristics of the optical element 7 and the diffraction elements 22A and 22B (e.g., the diffraction efficiency and diffraction angle of the diffraction elements 22A and 22B) may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the first transmitted light Lt1, the second transmitted light Lt2, the first diffracted light Ld1, and the second diffracted light Ld2 incident on the specific region Rs. This allows the magneto-optical trap 200 to efficiently cool and trap atoms in the specific region Rs.

[0081] (Fourth Configuration Example) Next, a fourth configuration example of the magneto-optical trap 200 will be described. Fig. 6 is a diagram for explaining the fourth configuration example of the magneto-optical trap 200. The fourth configuration example of the magneto-optical trap 200 is a configuration example in which the diffraction element 22 of the first configuration example does not have the first opening 221. Fig. 6 is a schematic perspective view of the interior of the cooled atom generation chamber 11.

[0082] In the fourth configuration example, similarly to the first configuration example, a pair of parallel beams, a first parallel beam Lp1 and a second parallel beam Lp2, are incident on the cooled atom generation chamber 11 so as to face each other.

[0083] The diffraction element 22, which is a transmissive diffraction element, transmits incident light to emit transmitted light Lt and emits diffracted light Ld on the side opposite to the incident light side. The diffraction element 22 is disposed on the inner surface of the substrate 21, which is disposed perpendicular to the first direction and the second direction. In the example shown in FIG. 6 , the diffraction element 22 has a circular shape, but as described in the first configuration example, the present disclosure is not limited to this.

[0084] The diffraction element 22 emits diffracted light Ld traveling in a direction oblique to the first direction (the central optical axis of the magneto-optical trap) and transmitted light Lt traveling in a direction parallel to the central optical axis. At this time, the diffraction element 22 sets the rotation direction of the circularly polarized light of the incident first parallel light Lp1 and the circularly polarized light of the emitted diffracted light Ld to be opposite to each other. Furthermore, the diffraction element 22 sets the rotation direction of the circularly polarized light of the incident first parallel light Lp1 and the circularly polarized light of the emitted transmitted light Lt to be the same. The diffracted light Ld emitted by the diffraction element 22 is incident on the specific region Rs from all circumferential directions.

[0085] The fourth configuration example can achieve the following effects. A pair of parallel light beams, a transmitted light beam Lt and a second parallel light beam Lp2, traveling in opposite directions, are incident on the specific region Rs inside the cooled atom generation chamber 11. The transmitted light beam Lt is the first parallel light beam Lp1 transmitted by the diffraction element 22. In addition, diffracted light beam Ld, which travels obliquely with respect to the central optical axis of the magneto-optical trap and is emitted by the diffraction element 22 after diffracting the first parallel light beam Lp1 in the direction opposite to the incident side, is incident on the specific region Rs. The first parallel light beam Lp1, the transmitted light beam Lt, which is the first parallel light beam Lp1 transmitted by the diffraction element 22 without diffracting it, and the second parallel light beam Lp2 each have the same rotation direction of circular polarization. Meanwhile, the rotation direction of the circular polarization of the first parallel light beam Lp1, the transmitted light beam Lt, and the second parallel light beam Lp2 are opposite to each other.

[0086] In this way, due to the influence of the first parallel light Lp1, the second parallel light Lp2, the transmitted light Lt, and the diffracted light Ld incident on the specific region Rs, and the quadrupole magnetic field, the atoms are subjected to radiation pressure in the direction toward the specific region Rs, and are suitably cooled and captured.

[0087] In the fourth configuration example, the intensities of the transmitted light Lt and the second parallel light Lp2, as well as the optical characteristics (diffraction angle, diffraction efficiency, transmittance, etc.) of the optical element 7 and the diffraction element 22, may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the transmitted light Lt, the second parallel light Lp2, and the diffracted light Ld incident on the specific region Rs, thereby enabling the magneto-optical trap 200 to efficiently cool and trap atoms in the specific region Rs.

[0088] In the fourth configuration example, unlike the first configuration example, the diffraction element 22 does not have an opening, so the area of ​​the diffraction element 22 that receives the first parallel light Lp1 is larger than that of the first configuration example. This makes it possible to increase the volume of the specific region Rs formed by the overlapping of the light beams of each component of light. This makes it possible to increase the number of atoms that can be cooled and captured, and to improve the performance of cooling and supplementing atoms, compared to the other configuration examples.

[0089] 7 is a combination of the transmissive diffraction element described in the fourth configuration example with the mirror and λ / 4 wave plate in the second configuration example. In the fifth configuration example, parallel light Lp is incident on the cooled atom generation chamber 11 from below.

[0090] That is, in the fifth configuration example, the transmitted light Lt that is transmitted through the substrate of the diffraction element 22 due to the incidence of the parallel light Lp is incident on the specific region Rs, and at least a portion of the transmitted light Lt is incident on the mirror 71 and the quarter-wave plate 72 that are provided in positions facing the diffraction element 22 across the specific region Rs. With this configuration, in addition to the transmitted light Lt, reflected light Lr generated by the mirror 71 and the quarter-wave plate 72 is incident on the specific region Rs in a direction opposite to the transmitted light Lt.

[0091] 7 is a diagram illustrating a fifth configuration example of the magneto-optical trap 200 according to the embodiment of the present disclosure. This diagram is a schematic side view of the interior of the cooled atom generation chamber 11, showing the laser light incident on the specific region Rs. This configuration also provides the same effects as the fourth configuration example.

[0092] (Specific Example of Diffraction Element 22) The structure of the diffraction element 22, which is a transmission type diffraction element, will be described in detail below.

[0093] In the present disclosure, the diffraction element 22, which is a transmissive diffraction element, is configured by periodically arranging a plurality of unit structures of at least one type of dielectric nanostructure 82 on a substrate 81. FIG. 8 is a diagram for explaining the structure of the diffraction element 22. In the following description, it is assumed that the plurality of unit structures of the dielectric nanostructure 82 are arranged on the surface of the substrate 81 along the x and y directions, which are perpendicular to each other. The xy plane is a plane parallel to the surface of the substrate 81, and the direction perpendicular to the xy plane is the z direction. FIG. 8 shows the plurality of unit structures of the dielectric nanostructure 82 arranged along the x direction and extending from the substrate 81 in the z direction. Note that while FIG. 8 shows the plurality of unit structures of the dielectric nanostructure 82 arranged along the x direction, in reality, the plurality of unit structures of the dielectric nanostructure 82 are also arranged along the y direction. Furthermore, FIG. 8 schematically illustrates the structure of the diffraction element 22, and the shapes and sizes of each component are not accurate.

[0094] Fig. 8 is a cross-sectional schematic diagram of the diffraction element 22, showing a plurality of dielectric nanostructures 82 periodically arranged in a row along the x direction on a substrate 81. The example shown in Fig. 8 is an example of the structure of the diffraction element 22 of the present disclosure. The reason why the widths in the x direction of the unit structures of the dielectric nanostructure 82 in Fig. 8 are different from each other is because the respective unit structures, each having a rectangular parallelepiped shape, are arranged on the substrate 81 in different orientations, as will be described later.

[0095] However, the present disclosure is not limited to this, and a plurality of periodic arrangement regions Ra in which the arrangement directions of the plurality of unit structures of the dielectric nanostructure 82 differ from each other may be formed on the substrate 81 of the diffraction element 22. The periodic arrangement region Ra refers to a region in which the plurality of unit structures of the dielectric nanostructure 82 are periodically arranged according to a certain arrangement rule. Fig. 9A is a diagram showing a first example of the periodic arrangement region Ra formed on the surface of the substrate 81 of the diffraction element 22, and Fig. 9B is a diagram showing a second example of the periodic arrangement region Ra formed on the surface of the substrate 81 of the diffraction element 22. Figs. 9A and 9B show the surface of the substrate 81 as viewed from the z direction perpendicular to the substrate 81.

[0096] In the first example shown in FIG. 9A and the second example shown in FIG. 9B, four periodically arranged regions Ra1 to Ra4 are arranged on the surface of a substrate 81 of a circular diffraction element 22. FIG. 9A shows an example in which an opening O is provided around a center C, while FIG. 9B shows an example in which no opening is provided. The four periodically arranged regions Ra1 to Ra4 are arranged at positions that are four-fold symmetric with respect to each other with respect to the center C of the circular diffraction element 22. In other words, the four periodically arranged regions Ra1 to Ra4 are arranged at positions rotated 90 degrees from each other around the center C. When the specific region Rs is projected onto the surface of the substrate 81 of the diffraction element 22, the position of the specific region Rs is positioned so that it overlaps with the center C, allowing diffracted light emitted from the diffraction element 22 to be incident on the specific region Rs from all directions around the circular diffraction element 22.

[0097] Furthermore, the periodic arrangement regions Ra1 to Ra4 are arranged so that the x direction (a direction in which the arrangement angle differs depending on the period), which is one of the arrangement directions of the multiple unit structures of the dielectric nanostructure 82 that each of them has, is perpendicular to a line connecting the center C of the diffraction element 22 and the center of each of the periodic arrangement regions Ra1 to Ra4. As a result, for two adjacent periodic arrangement regions, for example, the periodic arrangement region Ra1 and the periodic arrangement region Ra2, the x direction in the periodic arrangement region Ra1 is a direction rotated 90 degrees around the center C from the x direction in the periodic arrangement region Ra2.

[0098] When circularly polarized parallel light is incident perpendicularly to one surface of a diffraction element 22 having the structure illustrated in Figures 9A and 9B, the diffraction pattern shown in Figures 10A and 10B is generated on the other surface. Figures 10A and 10B are diagrams illustrating the diffraction pattern formed on the other surface of a diffraction element 22 having the periodic array regions of Figures 9A and 9B when parallel light is incident perpendicularly from one surface. More specifically, when parallel light is incident perpendicularly from one surface of a diffraction element 22 having the periodic array regions of Figures 9A and 9B, the shapes of the transmitted light and diffracted light projected onto a predetermined surface parallel to the other surface of the diffraction element 22 and spaced apart from the other surface are as shown in Figures 10A and 10B. That is, Figures 10A and 10B schematically show how the transmitted light and diffracted light exit the diffraction element 22 based on the incidence of parallel light.

[0099] 10A and 10B, circularly polarized transmitted and diffracted light is generated in response to the incidence of circularly polarized parallel light. The direction of rotation of the circularly polarized light of the transmitted light is the same as that of the incident light, and the direction of rotation of the circularly polarized light of the diffracted light is opposite to that of the incident light.

[0100] Furthermore, the present disclosure is not limited to this, and only one periodic arrangement region Ra in which the arrangement directions of the unit structures of the dielectric nanostructure 82 differ from each other may be formed on the substrate 81 of the diffraction element 22. Figure 11 is a diagram showing a third example of a periodic arrangement region Ra formed on the surface of the substrate 81 of the diffraction element 22. As shown in Figure 11, the third example shows a diffraction element 22 having only one circular periodic arrangement region. Figure 11 shows the surface of the substrate 81 as viewed from the z direction perpendicular to the substrate 81.

[0101] 12 is a diagram illustrating a diffraction pattern in the diffraction element 22 employing the third example of the two-dimensional periodic arrangement of the dielectric nanostructures 82. As shown in Fig. 12, when circularly polarized parallel light is incident on the circular diffraction element 22 employing the third example of the periodic arrangement illustrated in Fig. 11, the cross-sectional beam shapes of the transmitted light and diffracted light are circular, similar to the cross-sectional beam shape of the incident parallel light.

[0102] 12, circularly polarized transmitted light and diffracted light are generated in response to the incidence of circularly polarized parallel light. The direction of rotation of the circularly polarized light of the transmitted light is the same as the direction of rotation of the circularly polarized light of the incident light, and the direction of rotation of the circularly polarized light of the diffracted light is opposite to the direction of rotation of the circularly polarized light of the incident light.

[0103] In the third example shown in Figures 11 and 12, the beam cross-sectional area of ​​the diffracted light is larger than that of the first example shown in Figures 9A and 10A and the second example shown in Figures 9B and 10B, so the volume of the specific region Rs (see Figures 3B, 5B, 6B, 7, 8, and 9), which is the region where the diffracted light overlaps, can be made relatively large. This makes it possible to capture a relatively large number of atoms in the specific region Rs.

[0104] 13A and 13B are diagrams for explaining the unit structure of the dielectric nanostructure 82. Fig. 13A shows a perspective view of the unit structure of the dielectric nanostructure 82 formed on a substrate 81. Fig. 13B shows a top view (viewed from the z direction) of the unit structure of the dielectric nanostructure 82.

[0105] The substrate 81 is made of an amorphous material or single crystal material that has high transmittance at least for the wavelength of the cooling laser light (the first parallel light Lp1, the second parallel light Lp2, the parallel light Lp, etc. in the above-described configuration example).

[0106] The dielectric nanostructure 82 is a nanometer-order structure formed of a dielectric material having a wavelength equal to or less than the target wavelength. The dielectric nanostructure 82 is formed of a material that has low absorption at the target wavelength and a higher refractive index than the substrate 81, such as Si, GaN, TiO2, a polymer, or a combination thereof. When the diffraction element 22 is placed inside the vacuum vessel 1, it is desirable that the material of the dielectric nanostructure 82 is one that does not easily react with the atoms to be cooled and captured.

[0107] As shown in Fig. 13A, the unit structure of the dielectric nanostructure 82 is formed, for example, in the shape of a rectangular parallelepiped. Note that, since the unit structure of the dielectric nanostructure 82 is a structure on the order of nanometers, it may not be formed into an accurate rectangular parallelepiped due to influences such as manufacturing errors. For this reason, the unit structure of the dielectric nanostructure 82 may actually take on shapes other than a rectangular parallelepiped, such as an elliptical cylinder, a polygonal cylinder, an elliptical cone, or a polygonal pyramid. The top and bottom surfaces of the unit structure of the dielectric nanostructure 82 have a shape having a major axis and a minor axis (for example, a rectangle, an ellipse, or a polygon similar to these).

[0108] The orientation angle θ represents the direction in which the unit structure of the dielectric nanostructure 82 faces relative to the substrate 81. In the example shown in Fig. 13B, the orientation angle θ represents the angle formed between the x direction of the substrate 81 and the long axis direction of the unit structure of the dielectric nanostructure 82.

[0109] The dielectric nanostructure 82 functions as a half-wave plate because each unit structure has a shape including a long side and a short side. With this shape, as shown in Figure 13A, the dielectric nanostructure 82, in response to circularly polarized incident light, emits output light 1, which is circularly polarized in the same direction as the incident light, and output light 2, which is circularly polarized in the opposite direction to the incident light.

[0110] Furthermore, due to the arrangement angle θ of the dielectric nanostructure 82, a phase difference occurs between the output light 1 and the output light 2 emitted from the dielectric nanostructure 82 and the incident light. The output light 1 has a phase difference of 0 with respect to the incident light, and the output light 2 has a phase difference of 2θ with respect to the incident light. Therefore, the phase difference between the output light 1 and the output light 2 is 2θ.

[0111] In this way, the dielectric nanostructure 82 functions to spatially change the phase of the incident light, thereby enabling the dielectric nanostructure 82 to generate diffracted light having a desired diffracted wavefront.

[0112] By suitably setting the arrangement angles of the plurality of dielectric nanostructures 82 in the diffraction element 22, the diffraction element 22 can emit diffracted light having a desired diffraction wavefront. Specifically, when the arrangement angles of two dielectric nanostructures 82 spaced apart in the x direction are θ1 and θ2, respectively, a phase difference of 2*(θ1-θ2) occurs between the positions of the two dielectric nanostructures 82. By suitably setting the arrangement positions and arrangement angles of the dielectric nanostructures 82 arranged on the substrate 81, this spatial phase difference can be manipulated, making it possible to emit diffracted light having a desired diffraction wavefront.

[0113] Fig. 14 is a diagram showing a first example of a two-dimensional periodic arrangement of dielectric nanostructures 82 in the diffraction element 22. The first example of the periodic arrangement shown in Fig. 14 corresponds to the example of the periodic arrangement used in the first example of the periodic arrangement region shown in Fig. 9A and the second example of the periodic arrangement region shown in Fig. 9B. The arrangement example shown in Fig. 14 is just one example, and the diffraction element of the present disclosure is not limited to the structure shown in Fig. 14. In practice, the arrangement of the dielectric nanostructures 82 may be adjusted as appropriate based on the diffraction angle, diffraction efficiency, etc. of the diffracted light Ld used in the magneto-optical trap 200.

[0114] Fig. 14 shows the surface as viewed from the z direction perpendicular to the substrate 81. As shown in Fig. 14, in the diffraction element 22, a plurality of unit structures of the dielectric nanostructure 82 are periodically arranged along the x direction and the y direction which are perpendicular to each other.

[0115] 14, the plurality of unit structures of the dielectric nanostructure 82 arranged along the x direction are arranged at different arrangement angles θ with respect to the x direction according to the period p. In the example shown in FIG. 14, the arrangement angle θ is the angle between the long axis direction of the unit structure of the dielectric nanostructure 82 and the x direction.

[0116] On the other hand, the multiple unit structures of the dielectric nanostructure 82 arranged along the y direction are arranged at approximately the same arrangement angle θ with respect to the y direction by the period p. Note that, although "approximately the same arrangement angle" is used here to allow for some deviation in angle due to the influence of manufacturing errors, etc., it is ideal that the arrangement angles are the same.

[0117] The coordinates of the unit structure of each dielectric nanostructure 82 in the xy plane are (x ａ , y ｂ ), the diffraction angle by the diffraction element 22 is α, and the wavelength of the parallel light incident on the diffraction element 22 is λ, the arrangement angle θ(x ａ , y ｂ ) can be expressed by the following formula (1). Note that a and b are positive integers and are values ​​indicating the period in which the unit structure of the dielectric nanostructure 82 is arranged. n1 is the refractive index of the diffracting medium, but here, because it is a vacuum, n １ can be considered as 1.

[0118] In addition, when a plurality of unit structures of the dielectric nanostructure 82 are arranged at equal intervals of period p in each of the x direction and the y direction, the coordinates (x ａ , y ｂ ) can be expressed by the following formula (2).

[0119] FIG. 15 is a diagram showing a second example of a two-dimensional periodic array of dielectric nanostructures 82 in a diffraction element 22. The second example of the periodic array shown in FIG. 15 corresponds to the third example of the periodic array region shown in FIG. 11. FIG. 15 is an image of a prototype diffraction element 22, viewed from the surface in the z direction perpendicular to the substrate 81, taken with a scanning electron microscope (SEM). In the second example of the periodic array shown in FIG. 15, the arrangement angle θ of the dielectric nanostructures 82 is designed by an inverse problem design process. With such a configuration, a diffraction element 22 that can be employed in the present disclosure can also be obtained.

[0120] As described above, the diffraction element 22 has a structure in which a dielectric nanostructure 82 that converts incident circularly polarized light into output light 1 that is circularly polarized in the same rotation direction and output light 2 that is circularly polarized in the opposite rotation direction is formed on a substrate 81. The diffraction element 22 may also have a periodic arrangement region Ra on the substrate 81 in which the dielectric nanostructures 82 are periodically arranged so that the arrangement angle varies periodically. This allows the diffraction element 22 to generate a phase difference in the output light depending on the location where the incident light is incident, and to emit diffracted light having a desired diffraction wavefront.

[0121] Furthermore, the diffraction element 22 may be designed so that, for incident circularly polarized light having a Gaussian beam shape, output light 1 having circular polarization in the same rotation direction and output light 2 having circular polarization in the opposite rotation direction are output, and output light 1 and output light 2 have flat-top beam shapes. The diffraction element 22 designed in this manner has a two-dimensional periodic array of dielectric nanostructures 82 as exemplified in Fig. 16. Fig. 16 is a diagram showing a third example of a two-dimensional periodic array of dielectric nanostructures 82 in the diffraction element 22.

[0122] A flat-top beam is a beam that has a uniform light intensity distribution across the laser cross section and a sharp drop in light intensity at the edge. By using such a diffraction grating 22, the emitted light 1 and emitted light 2 can be shaped to have a uniform intensity distribution, making it possible to capture a relatively large number of atoms more stably.

[0123] The above-described arrangement examples of the periodic arrangement regions Ra in the diffraction element 22 (FIGS. 9A, 9B, and 11) are merely examples, and the present disclosure is not limited thereto. In the present disclosure, for example, the diffraction element 22 may have n (n is an integer of 3 or greater) periodic arrangement regions Ra arranged at positions with n-fold symmetry relative to each other around the center C. That is, although an example of 4-fold symmetry is shown in FIGS. 9A and 9B, the present disclosure also includes diffraction elements having periodic arrangement regions arranged at positions with, for example, 3-fold symmetry or 5-fold or greater rotational symmetry.

[0124] Furthermore, when the n periodic array regions included in the diffraction element 22 are arranged at positions with n-fold symmetry with respect to each other, each periodic array region is arranged so that the x direction, which is one of the two directions in which the dielectric nanostructures are arranged, is perpendicular to a line passing through the center of symmetry and the center of each periodic array region. As a result, the x direction in a first periodic array region among the multiple periodic array regions is a direction obtained by rotating the x direction in a second periodic array region adjacent to the first periodic array region by 360 / n degrees.

[0125] 11 and 12, the diffraction element 22 employing the third example of the periodic arrangement has been described as emitting four diffracted beams, but the present disclosure is not limited thereto. By adjusting the arrangement angle of each dielectric nanostructure 82 on the substrate 81, the diffraction element 22 may be configured to emit three or five or more diffracted beams.

[0126] The number of unit structures 83 included in the diffraction element 22 is 10 １０ The number is preferably 1 or less because it is easy to design and manufacture the size of the optical elements used.

[0127] Furthermore, when the n periodically arranged regions included in the diffraction element 22 are arranged at positions with n-fold symmetry with respect to each other, n may be infinite. In this case, the arrangement angle θ(x ａ , y ｂ ) can be expressed by the following equation (10). In this case, the diffraction element 22 can be regarded as an axicon lens that focuses the incident laser light at a certain angle (diffraction angle α) around the optical axis of the incident laser light. The definitions of the parameters are the same as those in equation (1), and n １ can be considered as 1 due to the vacuum.

[0128] <Operation Example> Next, an operation example of the atom cooling device 100 will be described. Fig. 17 is a conceptual diagram for explaining an operation example of cooling atoms using the atom cooling device 100. As shown in Fig. 17, a pair of anti-Helmholtz coils 30 are arranged on a plane perpendicular to the traveling direction of a pair of parallel beams (first parallel beam Lp1 and second parallel beam Lp2) entering the cooled atom generation chamber 11, so as to sandwich the cooled atom generation chamber 11. The anti-Helmholtz coils 30 do not need to be fixed to the atom cooling device 100 at all times, and need only be arranged during operation.

[0129] The anti-Helmholtz coils 30 generate a quadrupole magnetic field inside the cooled atom generation chamber 11. In this state, a pair of parallel beams, a first parallel beam Lp1 and a second parallel beam Lp2, are supplied from the light source 40 to the cooled atom generation chamber 11. As a result, inside the cooled atom generation chamber 11, the first parallel beam Lp1, the transmitted beam Lt, and the diffracted beam Ld are incident on a specific region Rs, as shown in FIG. 2 , thereby cooling atoms.

[0130] FIG. 18 is a flowchart illustrating an example of the operation of cooling atoms using the atom cooling device 100.

[0131] In step S1, the ion pump unit 12 is operated to make the inside of the cooled atom generation chamber 11 a vacuum state (for example, 10 －５ Pa).

[0132] In step S2, the atom supply unit 14 is operated to supply atoms to be cooled into the cooled atom generation chamber 11. After the alkali metal atoms are supplied in step S2, the ion pump unit 12 is operated again to create a more preferable ultra-high vacuum state (10 －６ Pa or less). Furthermore, the operation of the ion pump unit 12 in step S1 and the supply of atoms in step S2 may be performed simultaneously.

[0133] In step S3, the anti-Helmholtz coil 30 is operated to generate a quadrupole magnetic field in a specific region inside the cooled atom generation chamber 11.

[0134] In step S4, light is emitted from the light source 40. As a result, a pair of parallel light and diffracted light enters the cooled atom generation chamber 11. As a result, the magneto-optical trap 200 shown in FIG. 2 and other figures is formed, and the atoms to be cooled are cooled in the specific region Rs.

[0135] <Manufacturing Method of Atom Cooling Device 100> A method for manufacturing the above-described atom cooling device 100 will be described below. Fig. 19 is a diagram for explaining the manufacturing method of the atom cooling device 100. Fig. 19 is an exploded perspective view showing the state in which the plurality of substrates 210 to 270 that are joined together by substrate bonding to form the atom cooling device 100 are disassembled.

[0136] The substrate 210 corresponds to the substrate 21 of the light incident substrate 20 shown in Fig. 1 etc. The substrate 210 is made of a material that is transparent to the incident laser light, such as glass.

[0137] The substrate 220 corresponds to the upper surface of the optical structure 10 shown in FIG. 1 . The substrate 220 is bonded to the underside of the substrate 210 by substrate bonding. Substrate bonding is a technique for bonding substrates together, and in the present disclosure, for example, substrate bonding is performed by microfabrication and anodic bonding. The substrate 220 is used as the electrode 16, and is therefore a plate-like member made of a conductive material suitable for bonding to other substrates, such as Si.

[0138] The substrate 220 has a circular first opening 221 formed therein to form the cooled atom generation chamber 11 .

[0139] Substrate 230 is formed to have the same size as substrate 220, and is joined to the underside of substrate 220 by substrate bonding. Substrate 230 is a plate-like member made of an insulating material and a material suitable for bonding to other substrates, such as glass.

[0140] The substrate 230 is formed with a circular first opening 231 for forming the cooled atom generation chamber 11, a circular second opening 232 for forming the ion pump section 12, and a third opening 233 for forming the connection section 13.

[0141] The substrate 240 is a substrate that constitutes the electrode 15, which is the anode of the ion pump section 12. The size of the substrate 240 in the x direction is formed to be larger than that of the substrate 230 by the amount that the electrode 15 protrudes from the side surface of the optical structure 10. The substrate 240 is bonded to the underside of the substrate 230 by substrate bonding so that the electrode 15 protrudes from the side surface of the optical structure 10. Since the substrate 240 is used as the electrode 15, it is made of a conductor and a material that is suitable for bonding to other substrates, such as Si.

[0142] The substrate 240 is formed with a first opening 241 for forming the cooled atom generation chamber 11 and a second opening 242 for forming the ion pump section 12 .

[0143] The substrate 250 is bonded to the underside of the substrate 240 by substrate bonding. The substrate 250 is a plate-like member made of an insulating material and a material suitable for bonding to other substrates, such as glass.

[0144] The substrate 250 is formed with a first opening 251 for forming the cooled atom generation chamber 11, a second opening 252 for forming the ion pump section 12, and a third opening 253 for forming the connection section 13.

[0145] The substrate 260 corresponds to the lower surface of the optical structure 10 shown in Fig. 1. The substrate 260 is bonded to the lower side of the substrate 250 by substrate bonding. The substrate 260 is used as the electrode 16, and is therefore a plate-like member made of a conductive material suitable for bonding to other substrates, such as Si.

[0146] The substrate 260 has a first opening 261 formed therein for forming the cooled atom generation chamber 11 .

[0147] The substrate 270 corresponds to the substrate 21 of the light incident substrate 20 shown in Fig. 1 etc. The substrate 270 is bonded to the lower side of the substrate 260 by substrate bonding. The substrate 270 is made of a material that is transparent to the incident laser light, such as glass.

[0148] The diffraction element 22 is disposed on a substrate 270 .

[0149] The atom cooling device 100 is manufactured by bonding these substrates 210 to 270 together by substrate bonding. Examples of substrate bonding include anodic bonding or low-temperature bonding via a metal film. With this configuration, the first openings 221, 231, 241, 251, and 261 are spatially connected to form the cylindrical cooled atom generation chamber 11 shown in FIG. 1. The cooled atom generation chamber 11 may be cylindrical or rectangular, and is not particularly limited in shape.

[0150] Similarly, by connecting the substrates 220 to 260 to each other, the second openings 232, 242, and 252 are spatially connected to form the cylindrical ion pump section 12 shown in Figure 1. The ion pump section 12 may be a rectangular parallelepiped shape other than a cylindrical shape, and is not particularly limited. It is preferable that a Ti film be formed on the surfaces of the substrates 220 and 260 exposed to the ion pump section 12, i.e., the surfaces exposed to the spaces of the second openings 232, 242, and 252.

[0151] Furthermore, the third opening 233 of the substrate 230 and the third opening 253 of the substrate 250 form the connection section 13 that connects the cooled atom generation chamber 11 and the ion pump section 12 to each other, as shown in FIG.

[0152] In this manner, the optical structure 10 is produced by bonding the substrates 220 to 260 together by substrate bonding.

[0153] The substrate 210 is bonded to the upper surface of the substrate 220, i.e., the outer surface of the optical structure 10, by substrate bonding so that the parallel light passing through the substrate 210 is incident on a specific region Rs within the cooled atom generation chamber 11.

[0154] The substrate 270 on which the diffraction element 22 is arranged is bonded to the lower surface of the substrate 260, i.e., the outer surface of the optical structure 10, so that the diffracted light Ld emitted by the diffraction element 22 is incident on a specific region Rs (see Figure 2, etc.).

[0155] In this way, the atom cooling device 100 according to the embodiment of the present disclosure is manufactured by bonding together substrates such as glass or Si, including the optical structure 10 including the cooled atom generation chamber 11 and the ion pump section 12, and the light incident substrate 20 including the diffraction element 22 for directing the laser light for atom cooling onto the specific region Rs in the cooled atom generation chamber 11. As a result, the atom cooling device 100 according to the embodiment of the present disclosure can be made smaller than when the cooling chamber for cooling atoms, the pump for evacuating the cooling chamber, and the diffraction element for directing the laser light for atom cooling onto the specific region Rs in the cooling chamber are each manufactured as a unit and then assembled together to manufacture an atom cooling device.

[0156] FIG. 20 is a flowchart for explaining a method for manufacturing the atomic cooling device 100.

[0157] In step S11, the optical structure 10 is produced by bonding together a plurality of substrates 220 to 260, each of which has at least one of first openings 221, 231, 241, 251, 261 corresponding to the cooled atom generation chamber 11 and second openings 232, 242, 252 corresponding to the ion pump section.

[0158] In step S12, a substrate 210 corresponding to the light incident substrate 20 and a substrate 270 are bonded by substrate bonding to a position on the outer surface of the optical structure 10 where the transmitted light and diffracted light travel toward a specific region Rs within the cooled atom generation chamber 11.

[0159] By the above steps, in the atomic cooling device 100 according to the embodiment of the present disclosure, the substrate preparation and the substrate bonding can be performed as separate steps, and therefore the device can be manufactured through a simple process.

[0160] <Modifications> The above-described embodiment is an example of the present disclosure, and the present disclosure is not limited to the above-described embodiment.

[0161] 1 and 19, the cold atom generation chamber 11 and the ion pump unit 12 have cylindrical internal spaces, but in the present disclosure, the internal spaces of the cold atom generation chamber and the ion pump unit may have other shapes, such as a rectangular parallelepiped shape. Accordingly, the first openings 221, 231, 241, 251, 261 and the second openings 232, 242, 252 formed in each of the substrates 210 to 270 that constitute the cold atom generation chamber 11 and the ion pump unit 12 do not have to be formed in a circular shape.

[0162] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2024-147581, filed on August 29, 2024, are incorporated herein by reference in their entirety.

[0163] The present disclosure is useful in atom refrigerators that cool and trap atoms.

[0164] 100 Atom cooling device 200 Magneto-optical trap 10 Optical structure 11 Cold atom generation chamber 12 Ion pump section 13 Connection section 14 Atom supply section 15, 16 Electrode 20 Light incident substrate 21, 21A, 21B Substrate 22, 22A, 22B Diffraction element 210, 220, 230, 240, 250, 260, 270 Substrate 221, 221A, 221B, 231, 241, 251, 261 First opening 232, 242, 252 Second opening 233, 253 Third opening 81 Substrate 82 Dielectric nanostructure

Claims

1. An atom cooling device comprising: an optical structure including a cooled atom generation chamber that cools and captures atoms, and an ion pump unit that evacuates the inside of the cooled atom generation chamber; a pair of light incident plates arranged at opposing positions on the outer surface of the optical structure and capable of incident into the cooled atom generation chamber a pair of parallel light beams that travel in opposing directions and are circularly polarized light beams whose electric field vectors rotate in the same direction relative to the direction of travel; and a diffraction element inside the cooled atom generation chamber that diffracts at least one of the pair of parallel light beams to the side opposite to the incident side, and emits diffracted light into the cooled atom generation chamber, which is circularly polarized light whose rotation direction is opposite to that of the incident parallel light beam, wherein atoms are cooled and captured in a region inside the cooled atom generation chamber where the pair of parallel light beams and the diffracted light overlap.

2. The atomic cooling device according to claim 1, wherein the pair of light incident substrates and the optical structure are bonded together with their respective surfaces in direct contact with each other.

3. An atomic cooling device according to claim 1 or 2, wherein the diffraction element has a plurality of dielectric nanostructures arranged with n-fold symmetry (n is an integer of 3 or more) on a substrate that is perpendicular to the traveling direction of the pair of parallel beams and is capable of transmitting the pair of parallel beams, and emits diffracted light of at least one of the pair of parallel beams to the region at a predetermined diffraction angle on the side opposite to the incident side, the diffracted light being circularly polarized light whose rotation direction is opposite to that of the incident parallel beams.

4. The atomic cooling device according to claim 3, wherein the diffraction element has the plurality of dielectric nanostructures on the surface of the substrate and an opening in the substrate, and emits diffracted light, which is circularly polarized light whose rotation direction is opposite to that of the incident one of the parallel light beams at a predetermined diffraction angle to the side opposite to the incident side, and the opening passes a portion of the incident one of the parallel light beams, and is configured so that the portion of the one of the parallel light beams that passed through the opening of the diffraction element, the parallel light beam that passed through the other of the pair of light incident substrates, and the diffracted light emitted by the diffraction element are incident on the region.

5. The atomic cooling device according to claim 3, wherein the diffraction element has the plurality of dielectric nanostructures on the surface of the substrate and an opening in the substrate, and emits diffracted light, which is circularly polarized light whose rotation direction is opposite to that of the one of the incident parallel light beams, at a predetermined diffraction angle to the side opposite to the incident side of the one of the pair of light incident substrates, and the opening passes a portion of the one of the incident parallel light beams, and further comprises a mirror and a quarter-wave plate on the inside or outside of the other of the pair of light incident substrates, which reflect a portion of the one of the parallel light beams that has passed through the opening to form the other of the pair of parallel light beams, and is configured so that the other portion of the one of the parallel light beams that has passed through the opening of the diffraction element, the other parallel light beam, and the parallel light emitted by the diffraction element are incident on the region.

6. An atomic cooling device as described in claim 3, comprising two diffraction elements each having the plurality of dielectric nanostructures on the surface of the substrate and an opening in the substrate, wherein each of the two diffraction elements is arranged inside each of the pair of light incident substrates, and the parallel light that has passed through the light incident substrate is emitted at a predetermined diffraction angle on the side opposite to the incident side as diffracted light that is circularly polarized and whose rotation direction is opposite to that of the incident parallel light, and the opening allows a portion of the incident parallel light to pass through, and the atomic cooling device is configured so that a portion of the parallel light that has passed through the opening of each of the two diffraction elements and the diffracted light emitted by each of the two diffraction elements are incident on the region.

7. An atomic cooling device as described in claim 3, comprising two diffraction elements each having a plurality of dielectric nanostructures on the surface of the substrate, each of the two diffraction elements being arranged inside each of the pair of light incident substrates, and emitting diffracted light, which is circularly polarized light whose rotation direction is opposite to that of the incident parallel light, at a predetermined diffraction angle on the side opposite to the incident side of the parallel light that has passed through the light incident substrate, and the substrate transmitting a portion of the parallel light, and configured so that a portion of the parallel light that has passed through each of the two diffraction elements and the diffracted light emitted by each of the two diffraction elements are incident on the region.

8. The atomic cooling device according to claim 3, wherein the diffraction element has the plurality of dielectric nanostructures on the surface of the substrate, and emits diffracted light, which is circularly polarized light whose rotation direction is opposite to that of the incident one of the parallel light beams at a predetermined diffraction angle on the side opposite to the incident side, the substrate transmits a portion of the one of the parallel light beams, and the portion of the one of the parallel light beams that has transmitted through the substrate of the diffraction element, the parallel light that has transmitted through the other of the pair of light incident substrates, and the diffracted light emitted by the diffraction element are incident on the region.

9. The atomic cooling device according to claim 3, wherein the diffraction element has the plurality of dielectric nanostructures on the surface of the substrate, and emits one of the parallel light beams that has passed through one of the pair of light incident substrates to the side opposite the incident side at a predetermined diffraction angle, the diffracted light being circularly polarized in the opposite rotation direction to that of the one of the parallel light beams that has passed through the substrate, and a portion of the one of the parallel light beams passes through the substrate, and further comprises a mirror and a quarter-wave plate on the inside or outside of the other of the pair of light incident substrates that reflect a portion of the one of the parallel light beams that has passed through the substrate to form the other of the pair of parallel light beams, and is configured so that the portion of the one of the parallel light beams that has passed through the substrate of the diffraction element, the other parallel light beam, and the parallel light emitted by the diffraction element are incident on the region.

10. The atomic cooling device according to claim 1, wherein the diffraction element is designed to receive circularly polarized incident light having a Gaussian beam shape, output a first output light having circular polarized light in the same rotational direction and a second output light having circular polarized light in the opposite rotational direction, and to have flat-top beam shapes for the first output light and the second output light.

11. An atom cooling device according to claim 1 or 2, wherein the diffraction element is arranged outside the cooled atom generation chamber instead of inside the chamber.

12. An atomic cooling device according to claim 1 or 2, wherein the optical structure is formed by a plurality of substrates on which at least one of a first opening corresponding to the cooled atom generation chamber and a second opening corresponding to the ion pump section is formed.

13. The atom cooling device according to claim 1 or 2, wherein the optical structure has an atom supply unit that supplies the atoms to be cooled to the inside of the cooled atom generation chamber.

14. A method for manufacturing an atomic cooling device according to claim 1, comprising bonding the pair of light incident substrates to opposing positions on the outer surface of the optical structure by substrate bonding.

15. The manufacturing method of claim 14, wherein the substrate bonding is anodic bonding.

16. The manufacturing method according to claim 15, wherein the substrate bonding is a low-temperature bonding via a metal film.

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