Method for removing alkaline earth metals from optical components and optical components

Abstract

Provided is an optical member that is used in an environment in which at least a portion is in contact with an alkaline earth metal gas, has at least a dielectric multilayer film and an alumina layer on an optical path, and the most surface on the side in contact with the alkaline earth metal gas is coated with the alumina layer. Also provided is a method for removing an alkaline earth metal adhering to an optical member, which includes a heating step of sublimating the alkaline earth metal adhering to the optical member by heating the optical member at a heating temperature of 200°C or higher after the optical member has been used in an environment in which at least a portion is in contact with an alkaline earth metal gas.

Description

Technical Field

[0001] This invention relates to optical components and methods for removing alkaline earth metals adhering to optical components. Background Technology

[0002] Patent Document 1 discloses that "atomic gas is generated from an atomic source in a high-temperature bath (116) by heating it with a heater (108). The atomic gas is captured and cooled by a magneto-optical trap formed by a laser (130) reflected by a right-angled conical mirror (102) and a magnetic field formed by a magnetic field generating device (112). The captured and cooled atoms are output from the opening (106) to the outside of a low-speed atomic beam generating device (100) by the laser (132) which acts as a driving laser. Thus, a low-speed atomic beam is formed. (Abstract)" Non-patent document 1 describes "We demonstrate strontium (Sr) atomic vapor cells having a total external volume of 0.63cm 3 that can operate above 300°C for times exceeding 380h. Thecells are fabricated using micromachined silicon frames anodically bonded to glass windows that have a 20 - nm thick protective layer of Al2O3 deposited on the interior surfaces. The presence of Sr vapor in the cell is confirmed through laser absorption spectroscopy for the 1 S0→ 1P1 transition in Sr at 461 nm. Measurements of sub-Doppler linewidths indicated negligible (<3 MHz) broadening of this transition from residual background gas collisions. This compact and manufacturable, high-temperature atomic vapor cell can enable narrow-line optical frequency references based on strontium and other alkaline earth species. (Opening paragraph) "We demonstrate a strontium (Sr) atomic vapor unit with a total external volume of 0.63 cm³." 3 It can operate for over 380 hours at temperatures above 300°C. The atomic vapor unit is fabricated using a micromachining silicon framework and is anoly bonded to a glass window, which has 20 atoms deposited on its inner surface. - A nm-thick Al2O3 protective layer. This was achieved by studying the strontium at 461 nm. 1 S0→ 1 Laser absorption spectroscopy analysis of the P1 transition confirmed the presence of strontium vapor in the atomic vapor unit. Sub-Doppler linewidth measurements showed that the broadening of this transition caused by collisions with residual background gas was negligible (<3 MHz). This compact and easily fabricated high-temperature atomic vapor unit can be used to realize narrow-linewidth optical frequency reference sources based on strontium and other alkaline earth metals. (Opening paragraph) As shown in Patent Document 1, the optical lattice clock uses a mirror as an optical component. Existing technical documents Patent documents Patent Document 1: WO2022 / 113717 Non-patent literature Non-Patent Literature 1: Jacob M. Pate, John Kitching, AND Matthew T. Hummon, Microfabricated strontium atomic vapor cells, Optics Letters, Vol.48, No.2 / 15 (2023). Summary of the Invention Solution for solving the problem

[0003] In a first aspect of the invention, an optical component is provided for use in an environment where at least a portion is in contact with an alkaline earth metal gas. The optical component has at least a dielectric multilayer film and an alumina layer on its optical path. The outermost surface of the optical component on the side in contact with the alkaline earth metal gas is covered with the alumina layer.

[0004] In the above, the optical component may have one or more functions such as a mirror, lens, prism, antireflector, phase difference plate, and polarizer.

[0005] In the above context, alkaline earth metal gases may contain strontium atoms.

[0006] In the above, the alumina layer may have a thickness of 50 to 150 nm.

[0007] In the above, the dielectric multilayer film can be formed by alternating layers of transparent high-refractive-index layers and transparent low-refractive-index layers with a refractive index lower than that of the high-refractive-index layers.

[0008] In the above, the high refractive index layer can be selected from tantalum oxide, titanium oxide, zirconium dioxide, zinc selenide, and hafnium oxide. The low refractive index layer can be selected from silicon dioxide and magnesium fluoride.

[0009] In the above, it may be that a substrate is provided, and a dielectric multilayer film is formed on the substrate.

[0010] In the above, the substrate can be an alumina substrate.

[0011] In the above, the optical components may be used in an environment with a pressure of less than 1 atmosphere.

[0012] In the above, the optical components may be used in high-temperature environments above 200°C.

[0013] In a second aspect of the present invention, a low-speed atomic beam generating apparatus is provided, which includes any of the optical components described above as a mirror or window.

[0014] In a third aspect of the present invention, a method for removing alkaline earth metals adhering to an optical component of any of the above-described embodiments is provided. The removal method includes a heating step, wherein after using the optical component in an environment in which at least a portion is in contact with an alkaline earth metal gas, the alkaline earth metals adhering to the optical component are sublimated by heating the optical component at a heating temperature of 200°C or higher.

[0015] In the above, the heating process may be carried out in the range of 250 to 500°C.

[0016] In the above, the heating process can be carried out with a heating time ranging from 5 to 15 hours.

[0017] In the fourth aspect of the present invention, a method for preventing the adhesion of alkaline earth metal gases is provided, by using the optical component of any of the above in an environment at a temperature of 200°C or higher where at least a portion is in contact with the alkaline earth metal gas, thereby preventing the alkaline earth metal from adhering to the optical component while using the optical component.

[0018] Furthermore, the above summary of the invention does not enumerate all the essential features of the invention. Additionally, sub-combinations of these feature groups can also constitute inventions. Attached Figure Description

[0019] Figure 1 The first example of optical device 1 is shown. Figure 2 The second example of optical device 1 is shown. Figure 3 The third example of optical device 1 is shown. Figure 4 The fourth example of optical device 1 is shown. Figure 5 The fifth example of optical device 1 is shown. Figure 6 An example of the configuration of an optical lattice clock 10 is shown. Figure 7 This is an example of the configuration of a low-speed atomic beam generating device 100. Figure 8 This is an example of the configuration of a low-speed atomic beam generating device 100. Figure 9 This is an example of the configuration of a low-speed atomic beam generating device 100. Figure 10 An example of the layered structure of the optical component 500 according to this embodiment is shown in a schematic diagram. Figure 11 An example of a process for removing alkaline earth metals attached to the optical component 500 involved in this embodiment is shown. Figure 12 The comparison between the evaluation substrate and the spectral characteristics obtained through simulation is shown. Figure 13 The variation of the reflectivity of the evaluation substrate over time is shown. Explanation of reference numerals in the attached figures 1. Optical device 2. Nuclear Furnace 3. Laser cooling section 4 atoms 5. Vacuum Chamber 6. Laser 7. Optical components (windows) 8 heaters 9. Temperature sensor 10 Optical Lattice Clocks 11 Optical components (mirrors) 12 Distributor Atomic Source 20 Physical Package 40 Optical System Device 60 Control device 80 Computers 100 Low-speed atomic beam generation device 102 Right-angled right-circular conical reflector 104 Optical Window 106 Opening 108 heater 110 Samples 112 Magnetic field generating device 116 High Temperature Bath 118 Flange 120 Heat radiation shielding component 122 Thermal Insulation Support Rod 124 Cooling Filter Window 126 Vacuum-resistant window 128 Vacuum-resistant electrical connector 130 laser 132 laser 134 laser 500 optical components 510 base plate 520 dielectric multilayer film 530 alumina layer Detailed Implementation

[0020] The present invention will now be described through embodiments thereof, but these embodiments do not limit the scope of the invention as defined in the claims. The combinations of features described in the embodiments are not necessarily all necessary for the solution of the invention. Furthermore, embodiments will be described with reference to the accompanying drawings; however, in the drawings, the same reference numerals are sometimes used for the same or similar parts, and repeated descriptions are omitted.

[0021] An example of an optical device using the optical components described in this embodiment will be explained.

[0022] Figure 1 The first example of optical device 1 is shown. In this example, optical device 1 is a laser cooling device. Optical device 1 includes, for example, a nuclear furnace 2, a laser cooling section 3, a vacuum cavity 5, and an optical component (window) 7.

[0023] Atomic furnace 2 heats the atoms. As a result, atoms 4 are ejected from atomic furnace 2 with a certain velocity (e.g., several hundred m / s). The atoms can be, for example, alkaline earth metals such as strontium.

[0024] The laser cooling section 3 cools the atoms emitted from the atomic furnace 2. For example, in the laser cooling section 3, a magnetic field gradient and a corresponding laser 6 act on the atom 4, and the Doppler frequency shift caused by deceleration is compensated by a Zeeman frequency shift. The frequency of the laser 6 is always set to match the resonant frequency of the atom 4. Thus, the atom 4 is decelerated, and cooling is performed.

[0025] Vacuum cavity 5 provides space for atoms to move. Vacuum cavity 5 can be maintained at a high vacuum. Vacuum cavity 5 is provided with an optical component (window) 7 through which laser 6 is incident. Here, by using optical device 1, atoms (e.g., alkaline earth metal atoms such as strontium) collide with the inside of optical component (window) 7, resulting in atomic deposition. As a result, there is a risk that the optical properties (e.g., transmittance) of optical component (window) 7 may deteriorate.

[0026] As will be described later, the optical component (window) 7 may also be an example of the optical component in this embodiment. Therefore, the optical component (window) 7 is resistant to alkaline earth metal gases such as strontium, and can easily remove alkaline earth metal atoms. The removal method will be described later.

[0027] Figure 2 The second example of optical device 1 is shown. In this example, optical device 1 not only has… Figure 1 The optical device 1 also includes a heater 8 and a temperature sensor 9. As will be described later, alkaline earth metal atoms such as strontium can be easily removed from the optical component (window) 7 using the heater 8 and the like.

[0028] Figure 3 The third example of optical device 1 is shown. In this example, optical device 1 not only has… Figure 1 The optical device 1 includes an optical component (mirror) 11. In this example, laser 6 incident from the optical component (window) 7 is reflected by the optical component (mirror) 11 and then irradiates the atom 4. As will be described later, the optical component (window) 7 and / or the optical component (mirror) 11 may be an example of the optical component in this embodiment.

[0029] In this example, by using optical device 1, atoms (e.g., alkaline earth metal atoms such as strontium) collide with the inner side of optical component (window) 7 and the reflective surface of optical component (mirror) 11, causing further atomic deposition. As a result, there is a risk of deterioration in the optical properties (e.g., transmittance and reflectance) of optical component (window) 7 and optical component (mirror) 11. The removal method will be described later.

[0030] Figure 4 The fourth example of optical device 1 is shown. In this example, optical device 1 not only has… Figure 3 The optical device 1 also includes a heater 8 and a temperature sensor 9. As described above, strontium and other alkaline earth metal atoms at the optical components (windows) 7 and (mirrors) 11 can be easily removed using the heater 8 or the like.

[0031] Figure 5 The fifth example of optical device 1 is shown. This example of optical device 1 is an atom trapping device that uses magneto-optical trapping or optical bipolar trapping techniques to trap atoms. In this example of optical device 1, atoms released from the atom source 12 in the distributor are irradiated by an optical component (mirror) 11 with a laser 6 introduced from an optical component (window) 7. In this example, alkaline earth metal gases such as strontium may also collide, leading to further deposition and a risk of deterioration in the optical properties (e.g., transmittance and reflectance) of the optical component (window) 7 and the optical component (mirror) 11.

[0032] Next, as an example of an object using the optical components involved in this embodiment, an optical lattice clock will be described. The optical lattice clock is a high-precision atomic clock proposed in 2001 by Hidetoshi Katori, one of the inventors of this application. The optical lattice clock encloses a cluster of atoms within an optical lattice formed by a laser, measuring the resonant frequency of the atomic cluster. According to the optical lattice clock, time can be measured with an accuracy of 18 bits, far exceeding the accuracy of existing cesium clocks.

[0033] Figure 6 An example of the configuration of an optical lattice clock is shown. The optical lattice clock 10 includes, for example, a physical package 20, an optical system device 40, a control device 60, and a computer 80.

[0034] Physical package 20 is a device for capturing clusters of atoms from a low-speed atomic beam and enclosing these clusters within an optical lattice to induce clock transitions. Physical package 20 includes a low-speed atomic beam generating device 100 for generating the low-speed atomic beam.

[0035] The optical system device 40 includes optical equipment such as an atom-trapping laser source, a clock transition-excited laser source, and a laser frequency control device. The optical system device 40 transmits the laser to the physical package 20. Furthermore, the optical system device 40 receives fluorescence signals emitted by the atomic clusters within the physical package 20 and converts them into electrical signals. The optical system device 40 performs feedback control and other processes on the laser source frequency to match the resonant frequencies of the atoms.

[0036] The control device 60 controls the physical package 20 and the optical system device 40. The control device 60 performs actions such as controlling the operation of the physical package 20, controlling the operation of the optical system device 40, and performing analytical processing such as frequency analysis of the clock transitions obtained from measurements. Through the cooperation of the physical package 20, the optical system device 40, and the control device 60, the function of the optical lattice clock 10 is realized.

[0037] Computer 80 can be a general-purpose computer containing a processor and memory. The functions of computer 80 are implemented by software executed by the hardware containing the processor and memory. Computer 80 can be equipped with software to control the optical lattice clock 10. Alternatively, computer 80 can also be a special-purpose computer designed specifically for the use of the optical lattice clock, or it can be special-purpose hardware implemented by special circuitry.

[0038] The computer 80 is connected to the control device 60 and can control not only the control device 60, but also the entire optical lattice clock 10, including the physical package 20 and the optical system device 40. Furthermore, the computer 80 provides the user interface (UI) for the optical lattice clock 10. Users can use the computer 80 to start the optical lattice clock 10, measure time, and confirm results.

[0039] The computer 80 can be a personal computer, tablet computer, smartphone, workstation, server computer, or general-purpose computer, or it can be a computer system composed of multiple computers connected together.

[0040] Computer 80 can be implemented by a single device or by multiple devices with shared functions. For example, computer 80 can be a server-client system, or it can provide cloud services to users utilizing the methods of this embodiment. Computer 80 can function by executing programs on the computer.

[0041] Sometimes, a system that includes the physical package 20 and the components required for controlling the physical package 20 is referred to as a "physical package system". The components required for control can be included in the control device 60 or the computer 80, or they can be included in the physical package 20. In addition, some or all of the functions of the control device 60 can also be included in the physical package 20.

[0042] Next, the low-speed atomic beam generation device 100 will be described.

[0043] Figure 7 This is an example of the configuration of a low-speed atomic beam generating apparatus 100. The axis parallel to the long side of the low-speed atomic beam generating apparatus 100 is defined as the X-axis. The low-speed atomic beam generating apparatus 100 includes a high-temperature section and a room-temperature section.

[0044] The high-temperature section includes a right-angled conical reflector 102, an optical window 104, an opening 106, a heater 108, a sample 110, a magnetic field generating device 112, a thermometer 114, and a high-temperature bath 116. The room-temperature section includes a flange 118, a heat radiation shield 120, a heat-insulating support rod 122, a cooling filter window 124, a vacuum-resistant window 126, and a vacuum-resistant electrical connector 128.

[0045] The high-temperature tank 116 has a shape that is axially symmetric with respect to the X-axis. For example, the high-temperature tank 116 may have a shape that is 2n (n is an integer greater than 2) axially symmetric with respect to the X-axis. As an example, the high-temperature tank 116 may have a cylindrical shape.

[0046] The high-temperature bath 116 includes a sample 110 that serves as an atomic source, an optical window 104 disposed at one end for laser transmission, and a right-angled conical mirror 102 disposed at the other end. Inside the high-temperature bath 116, an axisymmetric space is formed with respect to the X-axis, and the right-angled conical mirror 102 is disposed on its inner surface in a manner opposite to the optical window 104 disposed at one end.

[0047] In the case where the high-temperature tank 116 has a shape that is 4-fold symmetrical with respect to the X-axis, a right-angled right-square pyramidal reflector is provided instead of a right-angled right-circular conical reflector 102. The right-angled right-circular conical reflector 102 causes the laser 130 incident from the optical window 104 into the space inside the high-temperature tank 116 to be reflected toward the optical window 104.

[0048] An opening 106 is formed at the vertex of the right-angled conical mirror 102. The opening 106 is a hole formed at its vertex. Since the vertex is located on the X-axis, the opening 106 is also located on the X-axis. As described above, the atomic beam exits from the opening 106 to the outside of the high-temperature tank 116.

[0049] A thermometer 114 is installed on the side of the high-temperature bath 116 to measure the temperature of the high-temperature bath 116. The thermometer 114 can be, for example, a thermocouple thermometer or a resistance thermometer using platinum or the like. A heater 108 for heating the high-temperature bath and a magnetic field generating device 112 for generating a magnetic field are installed on the outer peripheral surface of the high-temperature bath 116.

[0050] The magnetic field generating device 112 generates a magnetic field inside the high-temperature bath 116 for trapping atoms using the magneto-optical trap (MOT) method. The magnetic field generating device 112 can be disposed on the outer peripheral surface of the high-temperature bath 116 and / or the inner surface of the thermal radiation shield 120.

[0051] The magnetic field generating device 112 is, for example, a coil. The coil is, for example, an anti-Helmholtz coil having a shape axially symmetric with respect to the X-axis and current flowing anti-symmetrically with respect to its central axis. To generate a larger gradient magnetic field, for example, it is necessary to wind a wire with a larger diameter with more turns to allow a larger current to flow. Of course, other types of coils can also be used.

[0052] When the set temperature of the high-temperature bath 116 is below 250°C, coated copper wire or the like that can withstand that temperature is used as the coil. When the low-speed atomic beam generating apparatus 100 is used in a high-temperature environment, such as when the set temperature of the high-temperature bath 116 is 270°C, for example, uncoated copper wire is used as the coil. For example, a bobbin made of alumina ceramic or the like is used, and grooves are formed on the bobbin to prevent adjacent copper wires from contacting each other. The copper wires are wound onto the bobbin using these grooves as guides.

[0053] As another example, the magnetic field generating device 112 can also be a permanent magnet. A permanent magnet can be, for example, a pair of permanent magnets that are axially symmetric rings and antisymmetrically magnetized relative to their central axis. As another example, a permanent magnet can also be a permanent magnet with an axially symmetric cylindrical shape covering the high-temperature tank 116 and magnetized in the radial direction.

[0054] The magnetic field generating device 112 can be a permanent magnet having a Curie temperature that is sufficiently large compared to the set temperature. For example, the magnetic field generating device 112 can be a samarium cobalt magnet, an alnico magnet, or a strontium ceramic magnet.

[0055] The magnetic field generating device 112 forms a quadrupole magnetic field distribution suitable for the right-angled right-circular conical reflector 102. In the case where a right-angled right-square pyramidal reflector is used instead of the right-angled right-circular conical reflector 102, two pairs of anti-Helmholtz coils or four permanent magnets that form a two-dimensional quadrupole magnetic field distribution and are separately arranged in a direction perpendicular to the central axis are used as the magnetic field generating device 112.

[0056] As another example, the magnetic field generating device 112 may consist of 2n (n is an integer of 2 or more) rectangular or saddle-shaped coils of equal shape disposed on the side of the high-temperature bath 116 surrounding a 2n (n is an integer of 2 or more) axis of rotational symmetry (on the outer peripheral surface of the high-temperature bath 116). For example, the control device 60 generates a two-dimensional quadrupole magnetic field from the magnetic field generating device 112 by causing the currents of the coils facing each other across the 2n axis of rotational symmetry to flow in opposite directions.

[0057] As another example, the magnetic field generating device 112 can also consist of 2n identically shaped quadrangular prisms or circular arc-shaped permanent magnets (permanent magnets with a cross-section having four sides or circular arcs) disposed on the side of the high-temperature tank 116 surrounding the 2n rotational symmetry axis (on the outer circumferential surface of the high-temperature tank 116). The permanent magnets are magnetized in a direction angular to the symmetry axis (circumferentially surrounding the symmetry axis). Furthermore, the permanent magnets facing each other across the 2n rotational symmetry axis have opposite magnetization directions. This creates a quadrupole magnetic field.

[0058] Heater 108 heats high-temperature bath 116 to bring it to a set temperature. For example, heater 108 heats a portion or the entire high-temperature bath 116. Through heating by heater 108, the state of the atomic source changes from solid to gaseous, thereby generating atomic gas and releasing it into the interior space of high-temperature bath 116.

[0059] Heating by heater 108 prevents atomic gas from condensing again when it collides with the inner wall of optical window 104 or high-temperature tank 116. The effect of changing the state of the atomic source from solid to gaseous can be achieved not only by heater 108, but also by ablation using laser.

[0060] The heater 108 can also replace the position shown in the figure / and is instead positioned near the right-angled conical mirror 102 (e.g., on the back side of the right-angled conical mirror 102). This allows for efficient heating of only a portion of the right-angled conical mirror 102 in the alkaline earth metal removal method described later.

[0061] The sample 110 contains an atomic source and is housed in a small chamber located on the side of the inner wall of the high-temperature bath 116. The sample 110 can be inserted and removed through the opening 106, or by disassembling the low-speed atomic beam generating device 100 and removing the optical window 104. The sample 110 is, for example, an alkaline earth metal, such as strontium.

[0062] The high-temperature bath 116 is made of a material that does not chemically react with or alloy with the atomic gas at the set temperature. The temperature of the high-temperature bath 116 is set such that the saturated vapor pressure of the sample 110 is sufficiently high compared to the vacuum level of the environment in which the sample 110 is placed, while the saturated vapor pressure of the heated parts, such as the high-temperature bath 116, is sufficiently low. For example, when the atomic source is strontium, the set temperature of the high-temperature bath 116 is set to 270°C or higher.

[0063] The right-angled right-circular conical reflector 102 reflects the laser 130. Details regarding the material of the right-angled right-circular conical reflector 102 will be described later.

[0064] The material of the high-temperature bath 116 can be, for example, a material with low vapor pressure when heated to a set temperature and with suppressed gas release under ultra-high vacuum. Examples of materials for the high-temperature bath 116 include aluminum, aluminum-coated metals, aluminum-coated insulators, silver, silver-coated metals, silver-coated insulators, SUS (stainless steel), or glass with an optical multilayer coating. Insulators can be, for example, ceramics (e.g., high-purity alumina) or glass.

[0065] Alternatively, the material of the high-temperature tank 116 can be the same as that of the right-angled conical mirror 102, or they can be different materials. For example, if the material of the right-angled conical mirror 102 is the same as that of the high-temperature tank 116, the surface that functions as the right-angled conical mirror 102 can be mechanically ground to make it into a mirror surface.

[0066] As the material for the optical window 104, a material that maintains translucency at a set temperature (e.g., sapphire) is used. A film capable of maintaining translucency at a set temperature (e.g., an anti-reflective film) may also be formed on the optical window 104, including the sapphire substrate. For example, a dielectric multilayer film 520 (described later) can be formed on the optical window 104 using electron beam evaporation (as an example, a titanium dioxide / silicon dioxide multilayer film). Furthermore, an aluminum oxide layer 530 (described later) can be formed on the dielectric multilayer film 520.

[0067] The thermal radiation shield 120 is provided to prevent thermal radiation to components disposed around the low-speed atomic beam generating apparatus 100. The thermal radiation shield 120 is configured to cover part or all of the heater 108, the magnetic field generating device 112, and the high-temperature tank 116. The heater 108, the magnetic field generating device 112, and the high-temperature tank 116 can be disposed within the space surrounded by the thermal radiation shield 120.

[0068] For example, the heat radiation shield 120 may use a material with low surface emissivity (e.g., mirror-finished aluminum or mirror-finished stainless steel). Multiple heat radiation shields 120 may also be stacked. For example, when using a double-layer sheet, by making the outer sheet from a material with high magnetic permeability such as permalloy, it can serve as both a heat radiation shield and an electromagnetic shield.

[0069] The windows are arranged in the order of optical window 104, cooling filter window 124, and vacuum-resistant window 126 on the X-axis. The optical window 104 is disposed at one end of the high-temperature tank 116 opposite to the right-angled right-circular conical reflector 102.

[0070] The vacuum-resistant window 126 can be made of materials such as Pyrex (registered trademark) glass or quartz glass. Alternatively, an anti-reflective film or other film that maintains translucency can be applied to the surface of the vacuum-resistant window 126.

[0071] A cooling filter window 124 is positioned between the optical window 104 and the vacuum-resistant window 126 in the optical path of the laser incident on the optical window 104, preventing heat from flowing from the optical window 104 to the vacuum-resistant window 126. The material of the cooling filter window 124 can be, for example, the same material as the vacuum-resistant window 126.

[0072] The heat insulation support rod 122 extends from the high-temperature tank 116 to the flange 118. A material with low thermal conductivity is used as the material for the heat insulation support rod 122 to prevent heat from flowing from the high-temperature section to the room-temperature section, thereby improving the thermal efficiency of the heater in the high-temperature section and maintaining the temperature stability of the room-temperature section. For example, magnesium oxide or talc ceramic can be used as the material for the heat insulation support rod 122.

[0073] The vacuum-resistant electrical connector 128 is a hermetic connector used for receiving and transmitting electrical signals between vacuum space and atmospheric space. The vacuum-resistant electrical connector 128 is used, for example, for signal input / output of the thermometer 114, supplying current to the heater 108, and supplying current to the magnetic field generating device 112.

[0074] Flange 118 is a component used to assemble the low-speed atomic beam generation device 100 into the physical package 20. The physical package 20 includes a vacuum container, and the high-temperature bath 116 of the low-speed atomic beam generation device 100 is used in an ultra-high vacuum environment, with the interior of the high-temperature bath 116 maintained at an ultra-high vacuum. For this purpose, flange 118 has a sealing mechanism for sealing the vacuum, such as a metal gasket. Furthermore, heat may be transferred from the high-temperature part to flange 118. To address this, a water-cooling mechanism can also be provided on flange 118.

[0075] The following is for reference Figure 8 To illustrate the operation of the low-speed atomic beam generating device 100.

[0076] Figure 8 This is an example of the configuration of a low-speed atomic beam generation device 100. For example... Figure 7 and Figure 8As shown, laser 130 is incident on the low-speed atomic beam generating apparatus 100 from the outside through a vacuum-resistant window 126. Laser 130 has circular polarization (e.g., σ+). The laser 130 incident on the low-speed atomic beam generating apparatus 100 is incident on a cooling filter window 124 and an optical window 104, and is reflected twice by a right-angled conical mirror 102 within a high-temperature tank 116, becoming reflected light. The reflected laser 134 has circular polarization (e.g., σ-) opposite to its path, and is incident on the low-speed atomic beam generating apparatus 100 from the outside through the optical window 104, cooling filter window 124, and vacuum-resistant window 126.

[0077] A gradient magnetic field is formed inside the high-temperature tank 116 by means of a magnetic field generating device 112. For example, the same gradient magnetic field is formed along the X-axis. By means of the reflected laser 134 and the magnetic field formed by the magnetic field generating device 112, a trapping space for trapping atoms is formed inside the high-temperature tank 116, thereby realizing a magneto-optical trap (MOT) for trapping atoms.

[0078] The atomic source is heated by the heater 108, thereby causing the atoms to evaporate and be released into the space inside the high-temperature tank 116. The atomic gas is then captured and cooled inside the high-temperature tank 116 using a magneto-optical trap.

[0079] like Figure 7 and Figure 8 As shown, laser 132 is incident along the X-axis from the outside of the low-speed atomic beam generating apparatus 100 through the vacuum window 126 into the low-speed atomic beam generating apparatus 100. Laser 132 is a push laser, causing atoms that have been captured and cooled by a magneto-optical trap in the high-temperature tank 116 to exit from the opening 106 to the outside of the high-temperature tank 116. The atoms exited in this way form a low-speed atomic beam. In addition, the thermal radiation shield 120 has an opening formed on the X-axis, and the low-speed atomic beam emitted from the high-temperature tank 116 exits from the opening formed in the thermal radiation shield 120 to the outside of the thermal radiation shield 120.

[0080] According to the low-speed atomic beam generating apparatus 100, the entire high-temperature chamber 116, including the optical window 104, is heated, except for the sample 110. Therefore, even for elements whose saturated vapor pressure is low at room temperature, making it impossible to obtain sufficient atomic gas, sufficient atomic gas can be obtained by increasing the saturated vapor pressure through heating. According to the low-speed atomic beam generating apparatus 100, a high-flow-rate cooled atomic beam can be generated by utilizing a magneto-optical trap. Elements other than strontium can also be used as elements with low saturated vapor pressure at room temperature. For example, other alkaline earth metals or ytterbium can also be used as atomic sources.

[0081] In the magneto-optical trap, it is preferable to have a strong and uniform gradient magnetic field that contributes to the trap, so as to capture clusters of cooled atoms throughout the region where the laser crosses after being reflected by the right-angled conical mirror 102. For this purpose, when using a permanent magnet as the magnetic field generating device 112, it is preferable to use a cylindrical magnet covering the high-temperature tank 116, wherein the length in the height direction of the cylinder is longer than the inner diameter of the cylinder, and the magnet is magnetized in the radius direction. When using a coil as the magnetic field generating device 112, it is preferable to use an antisymmetric tetracoil that forms an antisymmetric current distribution relative to the center point of the coil and includes a total of four current bands, or an antisymmetric coil that includes an even number of current bands (six or more).

[0082] Regarding the miniaturization of low-speed atomic beam generation devices, the length of the thermal insulation support rod 122, which bears the main heat conduction between the high-temperature section and the room-temperature section, becomes an important parameter. As for the material of the thermal insulation support rod 122, magnesium oxide (MgO) is suitable considering the low outgassing in a UHV environment. From the viewpoint of heat release, the number of thermal insulation support rods 122 is preferably three. Of course, this number is just an example, and a number other than three is also possible.

[0083] Figure 9 This is an example of the configuration of a low-speed atomic beam generation device 100. (See reference...) Figure 9 This is to illustrate the insertion and removal of sample 110.

[0084] The sample 110 can be accessed from the vicinity of the outer periphery of the optical window 104. For example, as indicated by reference numeral Y, the vacuum-resistant window 126 is detachably disposed in the low-speed atomic beam generating apparatus 100. The vacuum-resistant window 126 can be detached, and the sample 110 can be removed from the chamber containing the sample 110 using a suitable clamp on the side of the high-temperature bath 116. Alternatively, the vacuum-resistant window 126 can be detached, and the sample 110 can be placed into the low-speed atomic beam generating apparatus 100 and stored in the chamber using a clamp.

[0085] Figure 10 An example of the layered structure of the optical component 500 according to this embodiment is shown schematically. The optical component 500 is used in an environment in which at least a portion is in contact with an alkaline earth metal gas. The optical component 500 may have one or more functions such as a mirror, lens, prism, window (also called a window), phase retardation plate, and polarizing plate.

[0086] For example, optical component 500 could be Figures 1-5The optical components 500 include the optical element (window) 7 and / or the optical element (mirror) 11 of the optical device 1 (i.e., laser cooling device or atom trapping device). The optical element 500 can be used in higher temperature environments (e.g., above 200°C). For example, the optical element 500 may be... Figure 7 The right-angled conical mirror 102 of the low-speed atomic beam generation device 100 involved. When used in high-temperature environments (e.g., above 200°C), the optical component 500 prevents the adhesion of alkaline earth metal gases.

[0087] Optical component 500 has Figure 10 The layer structure shown is as follows. The optical component 500 includes a substrate 510, a dielectric multilayer film 520, and an aluminum oxide layer 530.

[0088] The substrate 510 provides the optical component 500 with basic structure and strength. The substrate 510 can be a substrate that provides the optical component 500 with basic optical functions such as reflection, transmission, or phase shifting. If the dielectric multilayer film 520 can perform its full optical function, the substrate 510 may not have an optical function.

[0089] The substrate 510 can be aluminum oxide (sapphire substrate), silicon oxide (quartz substrate), glass, or metal. When the optical component 500 is an optical component (mirror) 11 or a right-angled conical mirror 102, the substrate 510 can be an aluminum oxide substrate with better thermal conductivity than other materials.

[0090] The substrate 510 forms the structural basis of the optical component 500, but it does not necessarily need to be plate-shaped. The substrate 510 can be matched to the shape of the optical component 500 in any shape. For example, in the case where the optical component 500 is... Figures 1-5 In the case of optical components (windows) 7 and / or optical components (mirrors) 11, the substrate 510 is a flat plate. For example, in the case where the optical component 500 is a right-angled right conical mirror 102, the substrate 510 is as follows: Figure 7 It is a cylindrical shape with a right-angled, straight conical recess, as shown in the figure. The optical component 500 may also not have a substrate 510.

[0091] The surface roughness of the optical path side surface of substrate 510 can be sufficiently small relative to the wavelength of the incident light (e.g., laser 6 or laser 130). For example, the optical path side surface of substrate 510 can be polished.

[0092] The thickness of the substrate 510 can be 0.1 to 8.0 mm, preferably 1.0 to 3.0 mm. By ensuring a certain thickness, the strength of the optical component 500 can be guaranteed. By keeping the thickness from being too large, thermal expansion during the heating process of the optical component 500 can be suppressed.

[0093] The dielectric multilayer film 520 imparts optical functionality to the optical component 500. The dielectric multilayer film 520 is formed on the substrate 510. For example, the dielectric multilayer film 520 may have the function of reflecting laser 130 used by the low-speed atomic beam generating device 100 or laser 6 used by the optical device 1 through interference. In this case, the optical component 500 functions as a mirror (e.g., optical component (mirror) 11 and right-angled conical mirror 102).

[0094] Instead, the dielectric multilayer film 520 can have an anti-reflective function. In this case, the optical component 500 can function as a window (e.g., optical component (window) 7 and optical window 104) with an anti-reflective film, a lens, and / or a prism. Alternatively, the dielectric multilayer film 520 can have a phase-shifting function or a polarization function. In this case, the optical component 500 can be a phase-shifting plate or a polarizing plate.

[0095] The dielectric multilayer film 520 is disposed at least in the optical path of the optical component 500. For example, the dielectric multilayer film 520 is disposed at least in the optical path of the optical component (mirror) 11 (e.g., the portion irradiated by the laser 6). For example, the dielectric multilayer film 520 is disposed at least in the optical path of the right-angled conical mirror 102 (e.g., the portion irradiated by the laser 130). The dielectric multilayer film 520 may be disposed on the entire reflecting surface of the optical component (mirror) 11 and the right-angled conical mirror 102.

[0096] The dielectric multilayer film 520 is formed by stacking multiple dielectric layers. For example, the dielectric multilayer film 520 may be formed by alternating layers of a high refractive index layer that is transparent (e.g., has a transmittance of 90% or more) to the target wavelength light (e.g., laser 6 or laser 130) and a low refractive index layer that is transparent (e.g., has a transmittance of 90% or more) to the target wavelength light (e.g., laser 6 or laser 130) and has a lower refractive index than the high refractive index layer.

[0097] The dielectric multilayer film 520 can be a multilayer film comprising 5 to 200 dielectric layers. For example, the dielectric multilayer film 520 can be formed by alternating layers of high-refractive-index and low-refractive-index layers, totaling approximately 50 to 100 layers. By having multiple layers with different refractive indices in this way, the dielectric multilayer film 520 can achieve excellent optical performance (e.g., high reflectivity or high transmittance). For example, according to the dielectric multilayer film 520, a reflectivity close to 100% can be achieved.

[0098] For example, the high-refractive-index layer and the low-refractive-index layer are each formed with a thickness that enables the desired optical function of the dielectric multilayer film 520. When the optical component 500 is an optical component (mirror) 11 or a right-angled conical mirror 102, the high-refractive-index layer and the low-refractive-index layer are each formed with a thickness that would cause the laser 6 or laser 130 to be reflected by multi-beam interference. For example, when the optical component 500 is an anti-reflective film, the high-refractive-index layer and the low-refractive-index layer are each formed with a thickness that would cancel out the reflection of the laser 6 or laser 130 by multi-beam interference.

[0099] The high-refractive-index layer can be a layer of materials selected from tantalum oxide, titanium oxide, zirconium dioxide, zinc selenide, and hafnium oxide. The low-refractive-index layer can be a layer of materials selected from silicon dioxide and magnesium fluoride.

[0100] The layer in the dielectric multilayer film 520 that contacts the alumina layer 530 is preferably tantalum oxide (a high refractive index layer). Because tantalum oxide has a smaller lattice difference with alumina, it is less prone to deformation during subsequent heating processes.

[0101] The dielectric multilayer film 520 may also have three or more layers. For example, the dielectric multilayer film 520 may also be a layer formed by regularly stacking high refractive index layer, low refractive index layer and intermediate refractive index layer (the layer with the intermediate refractive index between the high refractive index layer and the low refractive index layer).

[0102] The dielectric multilayer film 520 can be formed by physical evaporation methods such as vacuum evaporation, sputtering, or ion plating. For example, the dielectric multilayer film 520 can be formed by electron beam evaporation.

[0103] The alumina layer 530 protects the surfaces of the optical component 500 that come into contact with alkaline earth metal gases. For example, if the optical component 500, such as the optical component (window) 7 and the optical component (mirror) 11 of the optical device 1, is used in an environment where it is in contact with alkaline earth metal gases, alkaline earth metal atoms will continuously deposit on the surface if the gases collide with it and the device continues to be used, causing a gradual deterioration in properties such as reflectivity. To address this, by forming the alumina layer 530, resistance to alkaline earth metal gases can be achieved, and the alkaline earth metal gases adhering to the surface of the optical component 500 can be easily removed by the method described later.

[0104] The optical components 500 of the low-speed atomic beam generating apparatus 100, such as the right-angled conical mirror 102 and optical window 104, used in environments exposed to alkaline earth metal gases, may also experience the following: High-temperature alkaline earth metal gases may collide with their surfaces, chemically reducing the surface of the optical components 500, reacting chemically with the surface, or diffusing into the interior of the optical components 500, causing a gradual deterioration in properties such as reflectivity and transmittance. To address this, forming an alumina layer 530 provides resistance to alkaline earth metal gases, preventing performance degradation.

[0105] It is known that the alumina layer 530 has low chemical reactivity with alkaline earth metal gases. Therefore, by pre-applying the alumina layer 530 to the surface of the optical component 500, alkaline earth metals can be more easily removed by sublimation compared to the case where the alumina layer 530 is not present in the heating process described later. By using the alumina layer 530, optical interference with the dielectric multilayer film 520 can be minimized, allowing the dielectric multilayer film 520 to fully exert its excellent optical properties (e.g., high reflectivity or high transmittance).

[0106] The alumina layer 530 is disposed at least in the optical path of the optical component 500. For example, the alumina layer 530 is disposed at least in the optical path of the optical component (window) 7 and the optical component (mirror) 11 (e.g., the entire portion irradiated by the laser 6) or the optical path of the right-angled conical mirror 102 (e.g., the entire portion irradiated by the laser 130).

[0107] The alumina layer 530 may be disposed on the entire surface of the optical component 500 (e.g., optical component (window) 7, optical component (mirror) 11 and / or right-angled conical mirror 102) that is in contact with the alkaline earth metal. The alumina layer 530 may be disposed only on the optical path portion of the surface of the optical component 500 (e.g., optical component (window) 7, optical component (mirror) 11 and / or right-angled conical mirror 102) that is in contact with the alkaline earth metal, and not disposed outside the optical path portion.

[0108] As described above, the alumina layer 530 covers the outermost surface of the optical component 500 on the side in contact with the alkaline earth metal gas. As a result, during the use of the optical component 500 in an alkaline earth metal gas atmosphere, alkaline earth metals are deposited onto the surface of the alumina layer 530.

[0109] The alumina layer 530 can have any thickness without impairing the function of the dielectric multilayer film 520, etc. For example, the alumina layer 530 can have a thickness of 50 to 150 nm, preferably 70 to 130 nm.

[0110] If the alumina layer 530 is too thin, its performance as a protective film may be insufficient; if the alumina layer 530 is too thick, its light absorption may adversely affect the performance of the optical component 500. As long as the alumina layer 530 is at least partially disposed on the outermost surface of the optical component 500, the desired performance can be achieved, and the film thickness is not particularly limited.

[0111] The aluminum oxide layer 530 can have a uniform film thickness. Therefore, there is no risk that the aluminum oxide layer 530 will adversely affect the function of the optical component 500.

[0112] The alumina layer 530 can be formed by physical vapor deposition methods such as vacuum evaporation, sputtering, or ion plating. For example, the alumina layer 530 can be formed by ion beam sputtering.

[0113] The layer composition of optical component 500 is not limited to Figure 10 As shown. Depending on the needs, additional layers may be added based on the above configuration.

[0114] Figure 11 This section illustrates an example of a process for removing alkaline earth metals adhering to the optical component 500 according to this embodiment. The alkaline earth metals adhering to the optical component can be removed by performing each of the processes S100 to S200.

[0115] First, in S100, an optical component 500 is used in an environment where at least a portion is in contact with an alkaline earth metal gas. For example, an optical component (window) 7 and an optical component (mirror) 11 will be included. Figures 1-5 The optical device 1 involved is used as an optical component 500.

[0116] Alkaline earth metal gases are not particularly limited, but can be elements with low vapor pressure at room temperature (25°C), for example, those exhibiting a vapor pressure of 10. -5 The temperature of Pa can be above 250°C. As an example, alkaline earth metal gases can contain strontium atoms.

[0117] Optical component 500 can operate at less than 1 atmosphere (e.g., 10 atmospheres). 2 Pa or less, preferably 10 Pa -1 Pa or less, more preferably 10 Pa -5 Used in environments with a pressure below 1000 Pa.

[0118] In the optical device 1, alkaline earth metals are used as atoms 4. During use, the alkaline earth metals sublimate within the vacuum chamber 5. As a result, a portion of the gas atoms of the alkaline earth metals are deposited onto the alumina layer 530 of the optical component 500, which is used as an optical component (window) 7 and / or an optical component (mirror) 11.

[0119] When alkaline earth metals are deposited in large quantities in optical components 500, the performance of optical components 500 will decrease. For example, the reflectivity of optical components (window) 7, optical components (mirrors) 11 and / or right-angled conical mirror 102 will decrease.

[0120] Pretreatment to specifically remove oxygen from the atmosphere can also be performed before S100. For example, the entire high-temperature bath 116 can be heated to around 100°C. This prevents the oxidation of alkaline earth metals such as strontium by oxygen.

[0121] Next, in S200, a heating process is performed to heat the optical component 500. The alkaline earth metals such as strontium adhering to the optical component 500 sublimate by heating and are easily removed from the alumina layer 530.

[0122] The heating process can target only the optical component 500. In the heating process, the entire optical component 500 can be heated, or only the optical path portion of the optical component 500 can be heated. Removing alkaline earth metals from the optical path portion improves the performance of the optical component 500, reduces energy and time losses during heating of other parts, and lowers the risk of thermal degradation of the optical component 500.

[0123] For example, in Figure 2 and Figure 4 In the optical device 1 involved, a heater 8 can be used to heat the optical component 500, which is used as an optical component (window) 7 and / or an optical component (mirror) 11. Within the low-speed atomic beam generation apparatus 100, the high temperature maintains a relatively low risk of alkaline earth metal adhesion, but by providing an alumina layer 530 on the optical component 500, deposition can be prevented. Thus, a method for preventing the adhesion of alkaline earth metal gases can be provided, by using the optical component of this embodiment in a high-temperature environment (e.g., above 200°C) where at least a portion is in contact with alkaline earth metal gases, thus preventing the adhesion of alkaline earth metals to the optical component while using it.

[0124] Alternatively, the environment containing the optical component 500 (e.g., a vacuum cavity 5 containing the optical component (window) 7 and / or the optical component (mirror) 11) can be used as the object to be heated. This allows alkaline earth metals to be removed from the entire environment containing the optical component 500.

[0125] The heating process can be performed under conditions where the vapor pressure of the alkaline earth metal exceeds the vacuum level of the environment in which the optical component 500 is disposed. For example, the optical component 500 can be placed under a pressure of less than 1 atmosphere (e.g., 10). 2 Pa or less, preferably 10 Pa -1 Pa or less, and preferably 10 Pa-5 In an environment below Pa, the metal is heated at a temperature at which alkaline earth metals will sublimate.

[0126] The heating process can be performed under conditions where the vapor pressure of the alkaline earth metal is at least 0.8 times, preferably at least 1 times, and more preferably at least 2 times, the vacuum level of the environment. The heating process can be performed at a maximum temperature of 500°C or lower. For example, the heating process can be performed at a maximum temperature of 200°C or higher, preferably 250–500°C, more preferably 280–420°C, and even more preferably 300–400°C.

[0127] By heating the optical component 500 at a certain temperature under vacuum conditions, alkaline earth metals adhering to it can be rapidly sublimated and removed efficiently. On the other hand, if the heating temperature is too high, the optical component 500 may deteriorate or have its performance adversely affected.

[0128] The heating process may include a heating phase (i.e., heating) and a cooling phase (i.e., cooling). Furthermore, the heating process may include a holding phase in which the temperature is maintained at approximately a certain level between the heating and cooling phases.

[0129] During the heating phase, the temperature can be increased at a certain rate. For example, heating can be carried out at a rate of 10–200°C / hour, preferably at a rate of 50–150°C / hour. During the cooling phase, cooling can be carried out at a certain rate. The cooling rate can be slower than the heating rate.

[0130] For example, the cooling rate can be 20% to 80% of the heating rate, preferably 30% to 70%, and more preferably 40% to 60%. As an example, the heating rate could be +100°C / hour and the cooling rate -50°C / hour. For example, during the cooling phase, cooling can be performed at a rate of -180 to -10°C / hour, preferably -100 to -40°C / hour.

[0131] The heating time in the heating process can be in the range of 1 to 30 hours, preferably in the range of 5 to 15 hours. If the time is too short, there is a risk of insufficient removal of alkaline earth metals. Even if the time is too long, the removal of alkaline earth metals will reach saturation, thus increasing waste.

[0132] Here, "heating time" can be the time during which the set temperature is higher than the ambient temperature. For example, heating time can be the time from the start of the heating phase (heating) to the completion of the cooling phase (cooling). Alternatively, heating time can be the time during which the temperature of the optical component 500 is maintained above the temperature at which sublimation of alkaline earth metals substantially occurs (e.g., 200°C).

[0133] Thus, according to this embodiment, by providing an aluminum oxide layer 530 on the surface of the optical component 500 in advance on the basis of the dielectric multilayer film 520, the alkaline earth metals deposited on the optical component 500 can be easily removed by heating.

[0134] After heating in S200 (removal of alkaline earth metals), S100 (use of optical component 500) can be performed again. S100 and S200 can also be performed alternately. For example, the performance of optical component 500 can be restored by performing cleaning by heating after a certain number of uses / hours.

[0135] For example, the combination of using the optical component 500 and the heating process can be repeated a certain number of times (e.g., up to 10 times, preferably up to 5 times). This allows the performance of the optical component 500 to be maintained through simple cleaning, and also extends its service life. After exceeding a certain number of uses, the optical component 500 can be disassembled for a more thorough cleaning that requires more resources and time, or it can be replaced with a new one.

[0136] In a variation of this embodiment, the optical component 500 may replace the alumina layer 530, or a tantalum oxide layer may be provided instead. Like alumina, tantalum oxide has a lattice constant significantly different from that of alkaline earth metals and is not reactive with them. On the other hand, the alumina layer exhibits superior laser resistance compared to the tantalum oxide layer.

[0137] This section primarily describes examples of applying the optical component 500 of this embodiment to the optical component (window) 7 and / or optical component (mirror) 11 of the optical device 1 used as a laser cooling device or an atom trapping device, and to the right-angled conical mirror 102 of the low-speed atomic beam generating device 100 of the optical lattice clock 10. The optical components of this embodiment are not limited to these examples; a wide variety of optical components can be applied to environments in contact with alkaline earth metal gases. For example, the optical components described in this embodiment can be used as mirrors, lenses, prisms, windows, phase retardation plates, or polarizing plates in atomic clock devices other than optical lattice clocks, atomic interferometer devices, particle accelerators, quantum computers, vacuum cavities, etc.

[0138] Hereinafter, embodiments of this implementation method, etc., will be described.

[0139] [Example] A 68-layer film was applied to the optically polished surface of a 2mm thick sapphire substrate. Layers 1 through 67 were formed by alternating layers of a high-refractive-index layer (Ta₂O₅) and a low-refractive-index layer (SiO₂) using ion beam sputtering. The thickness of the high-refractive-index and low-refractive-index layers was set to 1 / 4 of the wavelength λ of the laser used later. The outermost layer (layer 68) was formed by ion beam sputtering of an alumina film.

[0140] The aluminum oxide film is formed under the following conditions. • Film thickness: 85nm (no phase difference) • Target material: Al2O3 • Ion gun working gas: Argon (Ar) gas, purity 99.9999%, flow rate: 18 sccm • The working gas of the neutralizer used for plasma neutralization in the ion gun: Ar gas, purity: 99.9999%, flow rate: 8 sccm • Gas flowing into the target: O2 gas, purity: 99.9999%, flow rate: 35 sccm • Intracavitary temperature during film formation: 100℃

[0141] The spectral characteristics of the substrate after film deposition were evaluated. The spectral characteristics obtained through simulation were compared with those of a substrate deposited under the same conditions as described above. Based on the comparison results, the film thickness of each layer of the dielectric multilayer film was corrected, and film deposition was performed again under the same conditions as described above. The substrate deposited with the corrected film thickness was selected as the evaluation substrate.

[0142] Figure 12 The comparison between the evaluation substrate and the spectral characteristics obtained through simulation is shown. Figure 12 The vertical axis represents reflectivity (%), and the horizontal axis represents wavelength (nm). For example... Figure 12 As shown, the spectral characteristics (measurement value in the figure) of the evaluation substrate provided with dielectric multilayer films (layers 1 to 67) and an alumina layer (layer 68) are almost identical to the reflective spectral characteristics (design value in the figure) obtained by simulation.

[0143] Configure the evaluation substrate to Figure 4 The change in reflectivity of the optical component 11 shown was measured while strontium atoms 4 were emitted from the atomic furnace 2.

[0144] Figure 13 The variation of the reflectivity of the evaluation substrate over time is shown. Figure 13The vertical axis represents reflectivity (%), and the horizontal axis represents elapsed time (number of days). The solid line represents the log data for reflectivity. The light-colored area indicates the period when the atomic beam furnace of the low-speed atomic beam generation device (set to 490°C) is on. The dark-colored area indicates the period when the evaluation substrate was heated by setting the mirror heater (heater 108) to 300°C.

[0145] As shown in the figure, during the period when the atomic beam furnace is on, strontium adheres to the surface of the evaluation substrate, causing a decrease in reflectivity. However, the reflectivity immediately recovers when the mirror heater is activated. This means that the strontium adhering to the surface of the evaluation substrate is sublimated and removed by the mirror heater. Thus, according to this embodiment, alkaline earth metals deposited on optical components used in an environment in contact with alkaline earth metal gases can be removed quickly and easily.

[0146] Furthermore, as shown in the figure, the recovery of reflectivity becomes increasingly sluggish when a heating process is applied. However, it is shown that the reflectivity is fully recovered after at least about 5 cycles.

[0147] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. Those skilled in the art will obviously be able to make various modifications or improvements to the above embodiments. Furthermore, to the extent that there is no technical contradiction, the matters described for a particular embodiment can be applied to other embodiments. Additionally, each constituent element may have the same features as other constituent elements with the same name but different reference numerals. It is obvious from the claims that such modifications or improvements are also included within the technical scope of the present invention.

[0148] It should be noted that the execution order of actions, processes, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, description, and drawings can be arbitrary, unless specifically stated as "before" or "prior to," and as long as the output of a previous process is not used in a subsequent process. Even if terms such as "firstly" or "nextly" are used for convenience in describing the flow of actions in the claims, description, and drawings, it does not mean that they must be performed in that order.

Claims

1. An optical component used in an environment where at least a portion is in contact with an alkaline earth metal gas, characterized in that, The optical path has at least a dielectric multilayer film and an aluminum oxide layer. The outermost surface of the side in contact with the alkaline earth metal gas is covered by the alumina layer.

2. The optical component according to claim 1, wherein, It has one or more functions as a mirror, lens, prism, window, phase difference plate, and polarizer.

3. The optical component according to claim 1, wherein, The alkaline earth metal gas contains strontium atoms.

4. The optical component according to claim 1, wherein, The alumina layer has a thickness of 50–150 nm.

5. The optical component according to claim 1, wherein, The dielectric multilayer film is formed by alternating layers of transparent high-refractive-index layers and transparent low-refractive-index layers with a refractive index lower than that of the high-refractive-index layers.

6. The optical component according to claim 5, wherein, The high refractive index layer is selected from tantalum oxide, titanium oxide, zirconium dioxide, zinc selenide, and hafnium oxide. The low refractive index layer is selected from silicon dioxide and magnesium fluoride.

7. The optical component according to claim 1, wherein, It has a substrate on which the dielectric multilayer film is formed.

8. The optical component according to claim 7, wherein, The substrate is an alumina substrate.

9. The optical component according to claim 1, wherein, The optical components are used in environments with a pressure of less than one atmosphere.

10. The optical component according to claim 1, wherein, The optical components are used in high-temperature environments above 200°C.

11. A low-speed atomic beam generation device, characterized in that, The optical component described in any one of claims 1 to 10 is used as a reflector or window.

12. A method for removing alkaline earth metals, specifically a method for removing alkaline earth metals adhering to an optical component according to any one of claims 1 to 10, characterized in that... It includes a heating process in which, after using the optical component in an environment where at least a portion of it is in contact with an alkaline earth metal gas, the alkaline earth metal attached to the optical component is sublimated by heating the optical component at a heating temperature of 200°C or higher.

13. The removal method according to claim 12, wherein, The heating process is carried out at a temperature range of 250 to 500°C.

14. The removal method according to claim 12, wherein, The heating process is carried out over a period of 5 to 15 hours.

15. A method for preventing the adhesion of alkaline earth metal gases, characterized in that, By using the optical component of any one of claims 1 to 10 in an environment of 200°C or higher where at least a portion is in contact with an alkaline earth metal gas, the alkaline earth metal is prevented from adhering to the optical component while using the optical component.

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