Reflector, optical resonator, and quantum device

Abstract

A reflector 1 comprises dielectric multilayer films 2, 3 and a conductive layer 4. The dielectric multilayer films 2, 3 have a plurality of films laminated so as to reflect electromagnetic waves 6 made incident from a prescribed direction. The conductive layer 4 is positioned along the dielectric multilayer films 2, 3 outside or inside the dielectric multilayer films 2, 3, and has permeability of an electromagnetic wave 6 including a peak wavelength at which the reflectance is at its maximum when the dielectric multilayer films 2, 3 reflect the electromagnetic wave 6 made incident from the prescribed direction.

Description

Reflectors, optical resonators, and quantum devices

[0001] This disclosure relates to reflectors, optical resonators, and quantum devices. This application claims priority to Japanese Patent Application No. 2024-218190, filed in Japan on December 12, 2024, and the entire disclosure of said application is incorporated herein by reference.

[0002] As described in Patent Document 1, TiO ２ and SiO ２ A reflecting mirror is known that has a dielectric multilayer film in which two layers are alternately stacked.

[0003] Japanese Patent Publication No. 2007-133325

[0004] When a non-conductive dielectric multilayer film is used in a reflector, stray charges may be generated on the surface of the reflector. The generation of these stray charges disturbs the electric field near the surface of the reflector. This disturbance in the electric field affects the performance of the device equipped with the reflector.

[0005] The purpose of this disclosure is to provide a mirror, an optical resonator, and a quantum device that have high reflectivity while reducing electric field disturbance.

[0006] (1) A reflecting mirror according to one embodiment of the present disclosure comprises a dielectric multilayer film and a conductive layer. The dielectric multilayer film has a plurality of films stacked to reflect electromagnetic waves incident from a predetermined direction. The conductive layer is located outside or inside the dielectric multilayer film along the dielectric multilayer film and has transmittance of electromagnetic waves including the peak wavelength at which the reflectance is maximum when the dielectric multilayer film reflects electromagnetic waves incident from the predetermined direction.

[0007] (2) In the reflecting mirror described in (1) above, the conductive layer may be positioned to include a node of a standing wave formed by an electromagnetic wave having the peak wavelength incident from the predetermined direction.

[0008] (3) In the reflecting mirror described in (1) or (2) above, the conductive layer may be located outside the dielectric multilayer film and along the dielectric multilayer film.

[0009] (4) In the reflecting mirror described in any one of (1) to (3) above, the dielectric multilayer film may include a portion in which a plurality of high refractive index layers and a plurality of low refractive index layers are stacked alternately.

[0010] (5) In the reflecting mirror described in (4) above, the conductive layer may be in contact with the side on which the electromagnetic wave is incident to one of the plurality of high refractive index layers.

[0011] (6) In the reflector described in any one of (1) to (5) above, the conductive layer may be electrically connected to an electrode that controls the potential of the conductive layer to a specific potential.

[0012] (7) In the reflecting mirror described in (6) above, the dielectric multilayer film may be provided with the electrodes.

[0013] (8) In the reflecting mirror described in any one of (1) to (7) above, the conductive layer may be an oxide-based conductive material, an organic conductive material, a carbon-based conductive material, a semiconductor-based conductive material, or a metallic material.

[0014] (9) In the reflecting mirror described in any one of (1) to (8) above, the conductive layer may be configured as a film.

[0015] (10) In the reflector described in any one of (1) to (8) above, the conductive layer may be patterned.

[0016] (11) An optical resonator according to one embodiment of the present disclosure comprises a plurality of reflectors. One or more of the plurality of reflectors are the reflectors described in any one of (1) to (10) above.

[0017] (12) A quantum device according to one embodiment of the present disclosure comprises a mirror as described in any one of (1) to (10) above, or an optical resonator as described in (11) above.

[0018] According to a reflecting mirror, optical resonator, and quantum device according to one embodiment of this disclosure, electric field disturbance is reduced while maintaining high reflectivity.

[0019] It is a schematic diagram showing a configuration example of a mirror according to the present disclosure. It is a graph showing an example of the electric field strength distribution in the normal direction of the mirror. It is a graph obtained by expanding the range of Z from 0 nm to 400 nm in FIG. 2A. It is a graph showing an example of the wavelength characteristics of the electromagnetic wave loss in the mirror. It is a schematic diagram showing a configuration example of an optical resonator using the mirror. It is a schematic diagram showing an example of a patterned conductive layer. It is a cross-sectional view taken along the line A-A in FIG. 5A.

[0020] (Configuration Example of Mirror 1) As shown in FIG. 1, the mirror 1 according to an embodiment of the present disclosure includes a first dielectric film 2, a second dielectric film 3, and a conductive layer 4. In the mirror 1, the first dielectric film 2 and the second dielectric film 3 constitute a dielectric multilayer film to be described later. The mirror 1 has a reflection surface that specularly reflects an electromagnetic wave incident from a predetermined direction with respect to the dielectric multilayer film. Specular reflection means that the incident angle and the reflection angle are equal with respect to the reflection surface. The reflection surface is a surface along the first dielectric film 2 and the second dielectric film 3 that constitute the dielectric multilayer film.

[0021] The mirror 1 further includes a substrate 5, although not essential. The substrate 5 has a substrate surface extending along the XY plane. The mirror 1 reflects an electromagnetic wave incident in the normal direction of the substrate surface of the substrate 5.

[0022] The reflection spectrum of the electromagnetic wave by the mirror 1 has a peak wavelength at which the reflectivity is maximum. The peak wavelength is determined based on the structure and physical properties of the first dielectric film 2 and the second dielectric film 3, as will be described later. Further, the peak wavelength changes according to the incident angle of the electromagnetic wave incident from a predetermined direction with respect to the reflection surface. The structure of the dielectric film includes the thickness of the dielectric film and the number of stacked layers. The physical properties of the dielectric film include the reflectivity, refractive index, and transmittance of the dielectric film.

[0023] <Dielectric Multilayer Film> The reflector 1 is equipped with a dielectric multilayer film that specularly reflects electromagnetic waves incident from a predetermined direction. The dielectric multilayer film includes a film in which a first dielectric film 2 and a second dielectric film 3 are alternately stacked one layer at a time. The dielectric multilayer film may be a distributed Bragg reflector. The dielectric multilayer film may be composed of a portion in which the first dielectric film 2 and the second dielectric film 3 are alternately stacked and other portions, or it may be composed of only the portion in which the first dielectric film 2 and the second dielectric film 3 are alternately stacked. When the reflector 1 is equipped with a substrate 5, the first dielectric film 2 and the second dielectric film 3 are located along the substrate surface of the substrate 5 and are alternately stacked one layer at a time on the substrate surface. When the substrate surface of the substrate 5 is planar, the first dielectric film 2 and the second dielectric film 3 are stacked in the direction normal to the substrate surface, i.e., in the Z-axis direction in Figure 1. In this case, the Z-axis direction is also referred to as the stacking direction of the dielectric multilayer film. If the substrate surface of the substrate 5 includes a concave or convex surface, the first dielectric film 2 and the second dielectric film 3 are positioned along the substrate surface and are stacked in the direction normal to each position on the substrate surface. The number of layers of the first dielectric film 2 and the second dielectric film 3 is assumed to be N layers. Specifically, the first dielectric film 2 and the second dielectric film 3 are stacked on the substrate 5 in the following order, starting from the side furthest from the substrate surface of the substrate 5: first dielectric film 2-1, second dielectric film 3-1, first dielectric film 2-2, second dielectric film 3-2, ..., first dielectric film 2-N, second dielectric film 3-N. N is a natural number and is determined by the desired reflectance. In some embodiments, N may be 20 or more, 40 or more, or 80 or more. In some embodiments, N may be 400 or less, or 200 or less. The number of layers of the second dielectric film 3 may be the same as the number of layers of the first dielectric film 2. The number of layers in the second dielectric film 3 may be one less than the number of layers in the first dielectric film 2. In other words, the reflecting mirror 1 does not need to have the second dielectric film 3-N below the first dielectric film 2-N.

[0024] The substrate 5 may be made of any material. For example, SiO ２may include various materials such as silicon or sapphire. When light is desired to be incident from the side of the substrate 5 or when light is desired to be emitted from the side of the substrate 5, a material having transparency at the wavelength of the incident or emitted light is used. The substrate 5 may be composed of a single material, or may be composed of a combination of a plurality of materials. For example, the entire object obtained by forming a film such as glass or alumina on a silicon crystal plate may be used as the substrate 5.

[0025] After forming a dielectric multilayer film on the substrate 5, part or all of the substrate 5 may be removed. For example, part or all of the substrate 5 may be removed by the method described in Ding, S. W. et al. (2025). High Finesse Buckled Microcavities. ArXiv. That is, the mirror 1 of the present disclosure may not have the substrate 5. When the mirror 1 has the substrate 5, the substrate 5 may have holes in part so that the dielectric multilayer film is exposed when viewed from the substrate 5 toward the dielectric multilayer film. The substrate 5 may be configured such that both surfaces are flat, or one or both surfaces may be configured to be concave or convex. The substrate 5 may be configured such that at least the surface on which the dielectric multilayer film is formed, that is, the upper surface is concave or convex.

[0026] In one embodiment of the present disclosure, the material of the first dielectric film 2 is Ta ２ O ５ Let's assume it is. For example, the refractive index of Ta ２ O ５ with respect to an electromagnetic wave having a wavelength of 800 nm is 2.10. Also, in one embodiment of the present disclosure, the material of the second dielectric film 3 is SiO ２ Let's assume it is. For example, the refractive index of SiO ２ with respect to an electromagnetic wave having a wavelength of 800 nm is 1.45. The materials of the first dielectric film 2 and the second dielectric film 3 may be various other materials as long as they are a combination of materials having different refractive indices from each other. In the present disclosure, the first dielectric film 2 having a relatively high refractive index is also referred to as a high refractive index layer. The high refractive index layer is, for example, Ta ２ O ５、 TiO ２ or HfO ２This may also be the case. The second dielectric film 3, which has a relatively low refractive index, is also called the low refractive index layer. The low refractive index layer is, for example, SiO ２ MgF ２ or Al ２ O ３ This may also be the case. The dielectric multilayer film is configured such that multiple high refractive index layers and multiple low refractive index layers are arranged alternately in the stacking direction.

[0027] As illustrated in Figure 1, when the dielectric multilayer film is positioned along the substrate surface of the planar substrate 5 in the reflector 1, the reflector 1 reflects electromagnetic waves 6 incident in the positive Z-axis direction to each layer extending along the XY plane in the negative Z-axis direction. In other words, electromagnetic waves 6 are incident perpendicularly to the reflection surface along the XY plane and reflected perpendicularly. The incident electromagnetic waves 6 are reflected at the interface of each layer in the reflector 1. When the conductive layer 4 is located on the surface of the reflector 1, a portion of the electromagnetic waves 6 incident in the positive Z-axis direction is reflected in the negative Z-axis direction at the surface of the conductive layer 4. The surface of the reflector 1 is the surface located on the side of the reflector 1 furthest from the substrate surface of the substrate 5. The surface of the conductive layer 4 is the surface of the conductive layer 4 furthest from the substrate surface of the substrate 5. A further portion of the electromagnetic waves 6 that propagate in the positive Z-axis direction without being reflected at the surface of the conductive layer 4 is reflected in the negative Z-axis direction at the interface between the conductive layer 4 and the first dielectric film 2-1. A portion of the electromagnetic wave 6 that propagates in the positive Z-axis direction without being reflected at the interface between the conductive layer 4 and the first dielectric film 2-1 is reflected at the interface between the first conductive film 2-1 and the second conductive film 3-1. Similarly, the electromagnetic wave 6 is reflected in the negative Z-axis direction at the interfaces between each layer of the first conductive film 2 and each layer of the second conductive film 3.

[0028] The first dielectric film 2 is configured such that the thickness of each of the first dielectric film 2-1 to N is 1 / 4 of the value obtained by dividing the peak wavelength of the reflection spectrum of the reflector 1 by the refractive index of the first dielectric film 2 for electromagnetic waves of the peak wavelength. The second dielectric film 3 is configured such that the thickness of each of the second dielectric film 3-1 to N is 1 / 4 of the value obtained by dividing the peak wavelength of the reflection spectrum of the reflector 1 by the refractive index of the second dielectric film 3 for electromagnetic waves of the peak wavelength. Furthermore, depending on the relative magnitudes of the refractive index of the first dielectric film 2 and the refractive index of the second dielectric film 3, the phase shifts by π when electromagnetic waves traveling from the first dielectric film 2 to the second dielectric film 3 are reflected and when electromagnetic waves traveling from the second dielectric film 3 to the first dielectric film 2 are reflected. Therefore, by configuring the thicknesses of the first dielectric film 2 and the second dielectric film 3 as described above, the phases of the electromagnetic waves 6 of the peak wavelength when they are reflected at the interface of each layer of the reflector 1 and travel in the negative Z-axis direction are aligned. As a result, the electromagnetic waves with peak wavelengths reflected by the reflector 1 reinforce each other, maximizing the reflectivity of the electromagnetic waves with peak wavelengths in the dielectric multilayer film. Conversely, the thicknesses of the first dielectric film 2 and the second dielectric film 3 in the reflector 1 are determined so that the peak wavelength of the reflection spectrum becomes the desired wavelength. The peak wavelength may be, for example, in the ultraviolet region, the visible region, the near-infrared region, or the infrared region.

[0029] When the incident angle of the electromagnetic wave 6 is not perpendicular to the reflecting surface, the peak wavelength of the reflection spectrum of the reflector 1 changes depending on the incident angle. This amount of change is given by the combination of refractive indices derived from the dielectric constants of the dielectric multilayer film or conductive film used and the specific incident angle. Therefore, the thicknesses of the first dielectric film 2 and the second dielectric film 3 may be designed so that the desired peak wavelength is obtained at a specific incident angle. More specifically, the refractive index n of the i-th dielectric film among the dielectric films constituting the dielectric multilayer film. ｉ is the relative permittivity ε ｒ，ｉ (In the case of non-magnetic) Relational equation n ｉ =√ε ｒ，ｉ It is determined by calculations according to the formula. Also, the angle of incidence of the electromagnetic wave when it is incident from the (i-1)th dielectric film to the i-th dielectric film is θ. ｉ－１ Therefore, the refractive index n of the incident medium ｉ－１ In contrast, the propagation angle θ within each layerｉ is the relationship n ｉ－１ sinθ ｉ－１ = n ｉ sinθ ｉ It is determined by calculations following the formula. The same applies when a conductive film is used instead of a dielectric film in a certain layer.

[0030] In one embodiment, a specific propagation angle θ ｉ At the target peak wavelength λ ｔ To obtain this, for example, the relational expression d that represents the 1 / 4 wavelength condition ｉ n ｉ / cosθ ｉ = λ ｔ Each layer has a thickness d such that it satisfies / 4. ｉ , incident angle θ ｉ and refractive index n ｉ These may be designed. Since these relationships are based on well-known thin-film multilayer theory, those skilled in the art can find appropriate combinations of each parameter.

[0031] <Conductive Layer 4> The conductive layer 4 has both conductivity and transparency to electromagnetic waves 6, including the peak wavelength. The conductive layer 4 is located outside the dielectric multilayer film, that is, along the surface of the reflector 1, that is, along the surface of the substrate 5. The conductive layer 4 may be configured as a film along the surface of the reflector 1 or the surface of the substrate 5. The conductive layer 4 is not limited to being outside the dielectric multilayer film, but may also be located inside the dielectric multilayer film along the surface of the substrate 5. When the conductive layer 4 is located inside the dielectric multilayer film, it is in contact with the front side of any of the second dielectric films 3-1 to N that are located inside the first dielectric film 2-1 located on the surface of the reflector 1, that is, the side of the substrate 5 that is farther from the substrate surface. When the reflector 1 does not have a substrate 5, the conductive layer 4 is in contact with the side of any of the second dielectric films 3-1 to N that is incident on by the electromagnetic waves 6. As will be described later, when an optical resonator is constructed using the reflector 1, the electromagnetic waves may be incident from the opposite side, that is, from the side where the second dielectric film 3-N is located in the example of Figure 1, in the negative Z-axis direction. Furthermore, even if the reflector 1 includes a substrate 5, if the substrate 5 is made of a material that transmits electromagnetic waves, or if there are holes in the substrate 5 that allow electromagnetic waves to pass through, the electromagnetic waves may be incident from the side where the substrate 5 is located. When electromagnetic waves are incident on the reflector 1 in the negative Z-axis direction, the conductive layer 4 is located in contact with the surface on the positive Z-axis side of any of the second dielectric films 3-1 to N.

[0032] In the reflector 1, the conductive layer 4 functions to prevent the accumulation of stray charges in the dielectric multilayer film, which is an insulating film, by being conductive. If the reflector 1 does not have a conductive layer 4, stray charges may accumulate in the dielectric multilayer film, which is an insulating film. When stray charges accumulate in the dielectric multilayer film, the accumulated stray charges disturb the electric field near the surface of the dielectric multilayer film, i.e., the surface of the reflector 1. When the reflector 1 is applied to a device, disturbance in the electric field near the surface of the reflector 1 destabilizes the operation of the device. For example, when the reflector 1 is applied to an ion trap, the stray charges on the reflector 1 disturb the electric field near the surface of the reflector 1, heating the ions trapped near the surface of the reflector 1. Such phenomena become a constraint on the miniaturization of the device.

[0033] However, by providing a conductive layer 4 in the reflector 1 according to this disclosure, stray charges are less likely to move from the dielectric multilayer film to the conductive layer 4 and accumulate in the dielectric multilayer film. Therefore, the reflector 1 according to this disclosure can reduce the accumulation of stray charges in the dielectric multilayer film while maintaining high reflectivity, reduce disturbances in the electric field near the surface of the reflector 1, and improve the operational stability of the device to which the reflector 1 is applied.

[0034] The conductive layer 4 may be controlled to a specific potential. The conductive layer 4 may be in electrical contact with an electrode controlled to a specific potential. The conductive layer 4 may be controlled to reach the ground potential by being in electrical contact with a grounded electrode, i.e., by being grounded.

[0035] The reflector 1 may be provided with electrodes that are conductive with the conductive layer 4. The dielectric multilayer film may also be provided with electrodes. The electrodes may be connected to an external power source or ground point so as to be controlled to a specific potential. When the conductive layer 4 is located on the surface of the reflector 1, the electrodes may be placed at any position on the surface of the reflector 1 within a range that does not obstruct electromagnetic waves incident on the reflector 1, or within a range that can suppress the reduction of the reflectivity of electromagnetic waves. When the conductive layer 4 is located as an inner layer of the dielectric multilayer film of the reflector 1 and extends to the edge of the substrate 5, the electrodes may be located at the edge of the substrate 5 and be conductive with the conductive layer 4. Even when the conductive layer 4 is located as an inner layer of the dielectric multilayer film of the reflector 1, the electrodes may be placed at any position on the surface of the reflector 1 and be conductive with the conductive layer 4 via wiring extending in the Z-axis direction.

[0036] The reflector 1 does not necessarily have electrodes that are electrically connected to the conductive layer 4. In this case, the conductive layer 4 may have a connection portion that can be connected to an external electrode for electrical connection. The external electrode may be controlled to a specific potential by being connected to a power source or ground point, etc.

[0037] When the conductive layer 4 is located on the surface of the reflector 1, the potential of the surface of the reflector 1 stabilizes at the potential of the conductive layer 4. Even when the conductive layer 4 is located as an internal layer of the dielectric multilayer film, the surface of the reflector 1 capacitively couples with the conductive layer 4 via the first dielectric film 2 or the second dielectric film 3 located on the surface side of the conductive layer 4, thereby stabilizing the potential of the surface of the reflector 1 at or near the potential of the conductive layer 4. The stabilization of the surface of the reflector 1 at a specific potential reduces disturbances in the electric field near the surface of the reflector 1. As a result, the operational stability of the device to which the reflector 1 is applied is improved.

[0038] The conductive layer 4 is configured to have high transmittance at the peak wavelength in order to reduce the loss of the peak wavelength component in the reflector 1. The conductive layer 4 may be composed of a transparent material that has high transmittance at the peak wavelength.

[0039] As described above, the conductive layer 4 may be configured to have a thickness that is small, as long as it has sufficient conductivity to reduce the accumulation of stray charges on the surface of the reflector 1 or to stabilize the potential on the surface of the reflector 1. The conductive layer 4 may be configured such that its thickness is sufficiently thin compared to the respective thicknesses of the first dielectric film 2 and the second dielectric film 3. When an electromagnetic wave 6 passes through the conductive layer 4, the phase of the electromagnetic wave 6 changes by the thickness of the conductive layer 4. The thickness of the first dielectric film 2 or the second dielectric film 3 in contact with the conductive layer 4 may be adjusted to match the thickness of the conductive layer 4 so that the phase of the electromagnetic wave 6 passing through the conductive layer 4 and the phase of the electromagnetic wave 6 not passing through the conductive layer 4 are aligned. In one embodiment, the thickness of the conductive layer 4 may typically be 5 nm or more and 100 nm or less, more typically 5 nm or more and 80 nm or less, and more typically 5 nm or more and 50 nm or less.

[0040] In one embodiment of this disclosure, the conductive layer 4 is made of ITO (Indium Tin Oxide). ITO has both conductivity and transparency. Regarding the conductivity of ITO, when the film thickness of ITO is 10 nm, its sheet resistance is, for example, about 100 Ω / sq, but varies depending on the ITO deposition conditions. For example, the refractive index of ITO for electromagnetic waves with a wavelength of 800 nm is 1.60, but varies depending on the ITO deposition conditions. The refractive index of the conductive layer 4 may be smaller than the refractive index of the first dielectric film 2 and larger than the refractive index of the second dielectric film 3, provided that the refractive index of the first dielectric film 2 is greater than the refractive index of the second dielectric film 3.

[0041] The conductive layer 4 is not limited to ITO, but may be made of various other materials that possess both conductivity and permeability. The material of the conductive layer 4 may include oxide-based conductive materials other than ITO, such as TFO (Tin Fluorine Oxide), AZO (Aluminum-doped Zinc Oxide), or GZO (Gallium-doped Zinc Oxide). The material of the conductive layer 4 may include, for example, organic conductive materials, carbon-based conductive materials, or semiconductor-based conductive materials. Organic conductive materials may include PEDOT:PSS (Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), etc. Carbon-based conductive materials may include graphene or carbon nanotubes, etc. The conductivity or permeability of semiconductor-based conductive materials can be controlled by the amount of doping.

[0042] The material of the conductive layer 4 may include, for example, a metallic material. Generally, metallic materials are not permeable. When a metallic material is used as the material for the conductive layer 4, the metallic material may be formed as a thin film to the extent that it is permeable.

[0043] (Function of Reflector 1) Figures 2A and 2B show an example of the energy density distribution of an electromagnetic wave 6 at its peak wavelength when it is incident on the reflector 1 illustrated in Figure 1 in the positive Z-axis direction and reflected by the first dielectric film 2 and the second dielectric film 3. The horizontal axis of the graphs in Figures 2A and 2B represents the distance Z from the surface of the reflector 1 toward the substrate surface of the substrate 5. Assume that Z = 0 at the surface of the reflector 1. The vertical axis represents the energy density of the electromagnetic wave 6 at each position in the Z-axis direction, i.e., the square of the absolute value of the electric field strength of the electromagnetic wave 6. In the reflector 1 in Figures 2A and 2B, the number of layers of the first conductive film 2 and the second conductive film 3 is 10. Figure 2B is an enlarged graph of the graph in Figure 2A, showing the range of Z from 0 nm to 400 nm.

[0044] Electromagnetic waves 6 that enter from the surface of the reflector 1 and travel in the positive Z-axis direction are reflected in the negative Z-axis direction at the interfaces of each layer, and are attenuated as they approach the substrate surface of the substrate 5, that is, as they travel to a position where the Z value is large. The number of layers of the first conductive film 2 and the second conductive film 3 are not limited to the 10 layers exemplified in Figures 2A and 2B. The number of layers of the first conductive film 2 and the second conductive film 3 may be set such that the energy of the electromagnetic waves 6 that reach the substrate surface of the substrate 5 from the electromagnetic waves 6 traveling in the positive Z-axis direction is sufficiently small.

[0045] The first dielectric film 2 and the second dielectric film 3 are each Ta ２ O ５ and SiO ２ In this case, the electromagnetic wave 6 incident on the reflector 1 generates a standing wave in which the interface on the surface side of the first dielectric film 2 becomes a node and the interface on the surface side of the second dielectric film 3 becomes an antinode. For example, in the graphs of Figures 2A and 2B, a standing wave is generated in which the interface between the conductive layer 4 and the first dielectric film 2-1, and the interface between the second dielectric film 3-1 and the first dielectric film 2-2 become nodes, and the interface between the first dielectric film 2-1 and the second dielectric film 3-1, and the interface between the first dielectric film 2-2 and the second dielectric film 3-2 become antinodes. The energy density of the electromagnetic wave 6, which is thus a standing wave, is at a minimum at the interface on the surface side of the first dielectric film 2, i.e., at the node, and at a maximum at the interface on the surface side of the second dielectric film 3, i.e., at the antinode.

[0046] When the conductive layer 4 is in contact with the surface side of the first dielectric film 2-1, standing waves are generated such that the interface between the conductive layer 4 and the first dielectric film 2-1 forms nodes. In other words, the nodes of the standing waves of the electromagnetic waves 6 are located in or near the conductive layer 4. Because the nodes of the standing waves of the electromagnetic waves 6 are located in or near the conductive layer 4, the energy density of the electromagnetic waves 6 in the conductive layer 4 becomes a minimum or close to a minimum. The low energy density of the electromagnetic waves 6 in the conductive layer 4 reduces the loss of the electromagnetic waves 6 in the conductive layer 4.

[0047] Even when the conductive layer 4 is in contact with any of the surfaces of the first dielectric films 2-2 to N, standing waves are generated such that the nodes are located at the interface between the conductive layer 4 and any of the first dielectric films 2-2 to N. In this case as well, the nodes of the standing waves of the electromagnetic wave 6 are located in or near the conductive layer 4. As a result, the loss of the electromagnetic wave 6 in the conductive layer 4 is reduced.

[0048] From the above, when the conductive layer 4 is located on the surface side of a single high refractive index layer, that is, on the side farther from the substrate 5 in the stacking direction of the dielectric multilayer film, the nodes of the standing waves of the electromagnetic wave 6 are located in or near the conductive layer 4. In other words, the conductive layer 4 is positioned in the stacking direction of the dielectric multilayer film so as to include the nodes of the standing waves of the electromagnetic wave 6 at its peak wavelength. The location of the nodes of the standing waves of the electromagnetic wave 6 in or near the conductive layer 4 reduces the loss of the electromagnetic wave 6 in the conductive layer 4.

[0049] On the other hand, when the conductive layer 4 is in contact with any of the surfaces of the second dielectric films 3-1 to N, standing waves are generated such that the interface between the conductive layer 4 and any of the second dielectric films 3-1 to N is at an antinode. In this case, the antinode of the standing wave of the electromagnetic wave 6 is located in or near the conductive layer 4. Because the antinode of the standing wave of the electromagnetic wave 6 is located in or near the conductive layer 4, the energy density of the electromagnetic wave 6 in the conductive layer 4 becomes maximum or close to maximum. The high energy density of the electromagnetic wave 6 in the conductive layer 4 leads to a large loss of the electromagnetic wave 6 in the conductive layer 4.

[0050] As described above, the magnitude of the loss of electromagnetic waves 6 in the conductive layer 4 differs depending on whether the node or antinode of the standing wave of the electromagnetic wave 6 is located in or near the conductive layer 4. In other words, the position of the conductive layer 4 affects the reflection spectrum of the electromagnetic wave 6. The graph in Figure 3 shows examples of reflection spectra when the position of the conductive layer 4 is a node of the standing wave of the electromagnetic wave 6, and examples of reflection spectra when the position of the conductive layer 4 is an antinode of the standing wave of the electromagnetic wave 6. For reference, an example of the reflection spectrum when the reflector 1 does not have a conductive layer 4 is also shown alongside the graph in Figure 3. The horizontal axis of the graph in Figure 3 represents the wavelength of the electromagnetic wave 6. The vertical axis represents the magnitude of the loss when each wavelength component of the electromagnetic wave 6 is reflected by the reflector 1. The smaller the loss in the reflector 1, the higher the reflectivity of the reflector 1.

[0051] In the graph of Figure 3, when the reflector 1 is equipped with a conductive layer 4, and the position of the conductive layer 4 is a node of the standing wave of the electromagnetic wave 6, the peak wavelength of the reflection spectrum is approximately 810 nm. The shift in peak wavelength is caused by the thickness of the conductive layer 4. The loss at the peak wavelength is approximately 5 × 10⁻⁶. －６ Therefore, the reflectance at the peak wavelength is approximately 99.9995%. On the other hand, in the reflection spectrum when the position of the conductive layer 4 is an antinode of the standing wave of the electromagnetic wave 6, the loss is 10 in the wavelength range from approximately 730 nm to approximately 890 nm. －３ The value remains almost constant on the order of . The loss of the 810 nm electromagnetic wave 6 when the position of the conductive layer 4 is an antinode of the standing wave of the electromagnetic wave 6 is approximately 10 times the loss of the 810 nm electromagnetic wave 6 when the position of the conductive layer 4 is a node of the standing wave of the electromagnetic wave 6. －３ It has doubled. In other words, because the position of the conductive layer 4 is at a node of the standing wave of the electromagnetic wave 6, the loss of the electromagnetic wave 6 is greatly reduced.

[0052] The peak wavelength of the reflection spectrum when the reflector 1 does not have a conductive layer 4 is approximately 800 nm. The loss at the peak wavelength is 10 －６The following is true, and the reflectance at the peak wavelength is 99.9999% or higher. In a comparison between the case where the reflector 1 has a conductive layer 4 and the case where it does not, the loss at the peak wavelength in the reflection spectrum of the reflector 1 is greater than in the case where the conductive layer 4 is not present, even when the position of the conductive layer 4 is a node of the standing wave of the electromagnetic wave 6. However, the loss is 10 －６ For applications where a thickness of this order is acceptable, a reflector 1 equipped with a conductive layer 4 can be used. Furthermore, by making the conductive layer 4 even thinner, it is possible to further reduce losses due to the conductive layer 4.

[0053] As described above, the presence of the conductive layer 4 in the reflector 1 according to this disclosure increases the loss of peak wavelength electromagnetic waves 6, but it can reduce stray charges or stabilize the potential. In other words, if the loss of peak wavelength electromagnetic waves 6 can be tolerated to the extent that the peak wavelength reflectivity required for the performance of the reflector 1 is achieved, then providing the conductive layer 4 on the reflector 1 reduces stray charges or stabilizes the potential in the reflector 1. And by achieving a reduction in stray charges or stabilization of the potential in the reflector 1, disturbances in the electric field near the surface of the reflector 1 become less likely to occur, and the operation of the device using the reflector 1 can be stabilized. In addition, by reducing the loss of electromagnetic waves 6 due to the conductive layer 4, the reflectivity of the reflector 1 is maintained at a high reflectivity. Therefore, the reflector 1 according to this disclosure can reduce disturbances in the electric field near the surface while maintaining high reflectivity.

[0054] In this disclosure, the reflector 1 may have only one conductive layer 4, or it may have two or more conductive layers 4. Preferably, all conductive layers 4 are located in the range corresponding to the nodes of the standing waves of the electromagnetic wave, as described above. When the reflector 1 has two or more conductive layers 4, the thickness of each of the two or more conductive layers 4 can be made thinner compared to when there is only one conductive layer 4. By making the thickness of the conductive layers 4 thinner, the conductive layers 4 are arranged only in the range close to the nodes of the standing waves of the electromagnetic wave, and the loss of electromagnetic waves due to the conductive layers 4 is reduced. In addition, by placing a portion of two or more conductive layers 4 in the deep part of the dielectric multilayer film where electromagnetic waves are greatly attenuated, the loss of electromagnetic waves due to the conductive layers 4 is reduced. When there are two or more conductive layers 4, even if the loss of electromagnetic waves due to the conductive layers 4 is about the same, the accumulation of stray charges can be reduced more efficiently and potential stability can be achieved compared to when there is only one conductive layer 4.

[0055] (Manufacturing Method) The dielectric multilayer film and the conductive layer 4 can be manufactured by methods known to those skilled in the art. For example, they are formed on the substrate 5 by vacuum deposition technology. More specifically, various deposition methods are known, such as DC or RF sputtering, chemical vapor deposition (CVD), electron beam deposition, or ion beam sputtering. If the reflector 1 does not have a substrate 5, the substrate 5 may be removed after the dielectric multilayer film and the conductive layer 4 have been formed. At least a portion of the substrate 5 may be removed, or the substrate 5 may be left as is.

[0056] Alternatively, a commercially available dielectric multilayer film may be purchased and a conductive layer 4 may be further formed on it using the method described above. If the conductive layer 4 is formed of an organic conductive material, it may be prepared by known methods such as a solution process like spin coating or chemical vapor deposition.

[0057] (Application Examples of Reflector 1) The reflector 1 according to this disclosure may be applied to various devices. For example, the reflector 1 according to this disclosure may be used in an optical resonator 10. As shown in Figure 4, the optical resonator 10 may be equipped with two reflectors 1, and configured so that the two reflectors 1 face each other. In this case, electromagnetic waves 6 generate standing waves between the two reflectors 1. The optical resonator 10 is configured such that the positions of the conductive layer 4 of the reflectors 1 are nodes of the standing waves. By configuring the optical resonator 10 so that the positions of the conductive layer 4 of the reflectors 1 are nodes of the standing waves, the reflectance necessary for the operation of the optical resonator 10 is secured, and disturbances in the electric field near the surface of the reflectors 1 are less likely to occur.

[0058] The optical resonator 10 may comprise three or more reflectors 1, or it may be configured by combining three or more reflectors 1. In the optical resonator 10, for example, the three reflectors 1 may be arranged so as to correspond to the sides of a triangular prism with an equilateral triangle as its base. In this case, electromagnetic waves 6 are incident on each reflector 1 at an angle of 60 degrees, that is, at an angle of inclination of 30 degrees from the normal direction of the reflective surface of each reflector 1, causing the electromagnetic waves 6 to generate standing waves between the three reflectors 1. The optical resonator 10 may be configured by combining one or more reflectors 1 according to the present disclosure with reflectors of a different form from the reflectors 1 according to the present disclosure. In other words, the optical resonator 10 may be configured comprising one or more reflectors 1.

[0059] The optical resonator 10 may consist of two reflecting mirrors 1, three reflecting mirrors 1, or four or more reflecting mirrors 1. Taking into account the stabilization conditions of the optical resonator 10, at least one of the reflecting mirrors 1 may be a concave mirror. All of the reflecting mirrors 1 may be concave mirrors, or a combination of concave mirrors 1 and plane mirrors 1 may be used. The reflecting mirrors 1 may be configured as convex mirrors instead of plane mirrors. The stabilization conditions of the optical resonator 10 are known to those skilled in the art (see, for example, Chapter 4.4 of Photonics Optical Electronics in Modern Communications Sixth Edition by Amnon YARIV and Pochi YEH, Oxford University Press, 2007 (ISBN 0195179463)), so those skilled in the art can construct the optical resonator 10 using appropriate reflecting mirrors 1.

[0060] The reflector 1 or optical resonator 10 according to this disclosure may be applied to various quantum devices, such as quantum computers, quantum repeaters, or devices that process quantum information via a resonator QED (Quantum Electrodynamics). Furthermore, the reflector 1 or optical resonator 10 according to this disclosure may be applied to quantum devices such as quantum sensors or quantum light sources. The quantum computer may be an ion trap type, a semiconductor (quantum dot) type, or a neutrally cooled atomic type equipped with an optical trap. In other words, the quantum device may include the reflector 1 or optical resonator 10. The operation of the quantum device equipped with the reflector 1 or optical resonator 10 is stable because disturbances in the electric field near the surface of the reflector 1 according to this disclosure are less likely to occur.

[0061] Stable operation of a quantum device may refer, for example, to the electric field trapping ions in an ion-trap type quantum device not being disturbed by floating charges on the dielectric surface, allowing ions to be trapped for extended periods. Stable operation of a quantum device may also refer to the stabilization of the accuracy of quantum state control by reducing the influence of the dielectric or floating charges through the conductive layer 4 when controlling the quantum state of a neutral atom trapped by light. Furthermore, stable operation of a quantum device may refer to improving the sensitivity or achieving temporal stabilization of a quantum sensor by reducing unwanted electric field disturbances caused by floating charges on the dielectric surface.

[0062] A quantum computer may include an ion trap and an optical resonator 10. A quantum repeater may also include an ion trap and an optical resonator 10. In either case, by using the reflector 1 of this disclosure in the optical resonator 10, the charge of the reflector 1 can be reduced by the conductive layer 4, and as a result, the influence on the trap potential is reduced even when the reflector 1 is brought close to ions trapped in the ion trap.

[0063] The mirror 1 or optical resonator 10 incorporated into the quantum device described above may be used to control the quantum state in the quantum device, or to read out the quantum state. Alternatively, it may be used to promote or suppress the emission of light from a system in an excited state. Furthermore, it may be used to focus light emitted from a system in an excited state. The quantum state or excited state is, for example, the quantum state or excited state of an ion trapped in an ion trap. It may also be used to implement technologies based on resonator QED.

[0064] (Modifications of the conductive layer 4) As described above, the conductive layer 4 has both conductivity and permeability. To increase the permeability of the conductive layer 4, the material of the conductive layer 4 may be patterned, for example, as shown in Figures 5A and 5B. The pattern of the conductive layer 4 is not limited to the illustrated stripe shape, but may include various other patterns such as a grid. Also, when the conductive material is formed as the conductive layer 4 in a thin film thickness, the conductive material may be scattered in an island-like manner along the plane direction of the substrate 5 rather than being connected in a film shape. The pattern of the conductive layer 4 may include a pattern that electrically connects the conductive material scattered in an island-like manner.

[0065] By positioning the conductive layer 4 only in a portion of the surface of the reflector 1 in a plan view, the loss due to the conductive layer 4 is reduced across the entire reflective surface of the reflector 1. In other words, the transmittance of electromagnetic waves 6 through the conductive layer 4 is increased.

[0066] On the other hand, even if only a portion of the surface of the reflector 1 is covered by the conductive layer 4, stray charges are less likely to move from the dielectric multilayer film to the pattern of the conductive layer 4 and accumulate in the dielectric multilayer film. Also, even if only a portion of the surface of the reflector 1 is covered by the conductive layer 4, the surface of the reflector 1 becomes more stable at the potential of the conductive layer 4. As a result, even if only a portion of the surface of the reflector 1 is covered by the conductive layer 4, disturbances in the electric field near the surface of the reflector 1 are reduced. In other words, even if only a portion of the surface of the reflector 1 is covered by the conductive layer 4, the conductivity required for the conductive layer 4 is ensured.

[0067] From the above, by patterning the material of the conductive layer 4, the conductivity required for the reflecting mirror 1 according to this disclosure is ensured while the transmittance is enhanced.

[0068] While embodiments relating to this disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications or alterations are within the scope of this disclosure. For example, the functions included in each component can be rearranged in a logically consistent manner, and multiple components can be combined into one or separated.

[0069] All of the constituent elements described in this disclosure can be combined in any combination, except for any combination in which these features are mutually exclusive. Furthermore, each of the features described in this disclosure can be replaced by an alternative feature that serves the same, equivalent, or similar purpose, unless expressly disregarded. Thus, unless expressly disregarded, each of the disclosed features is merely one example of a comprehensive set of identical or equivalent features.

[0070] Furthermore, the embodiments relating to this disclosure are not limited to any specific configuration of the embodiments described above. The embodiments relating to this disclosure can be extended to all novel features described in this disclosure, or combinations thereof.

[0071] 1. Reflecting mirror 2. 2-1 to 10, 2-N First dielectric film 3. 3-1 to 10, 3-N Second dielectric film 4. Conductive layer 5. Substrate 6. Electromagnetic wave 10. Optical resonator

Claims

1. A reflector comprising a dielectric multilayer film and a conductive layer, wherein the dielectric multilayer film has a plurality of films stacked to reflect electromagnetic waves incident from a predetermined direction, and the conductive layer is located outside or inside the dielectric multilayer film along the dielectric multilayer film and has transmittance of electromagnetic waves including the peak wavelength at which the reflectance is maximum when the dielectric multilayer film reflects electromagnetic waves incident from the predetermined direction.

2. The reflector according to claim 1, wherein the conductive layer is positioned to include a node of a standing wave formed by an electromagnetic wave having the peak wavelength incident from the predetermined direction.

3. The reflector according to claim 1 or 2, wherein the conductive layer is located outside the dielectric multilayer film and along the dielectric multilayer film.

4. The reflecting mirror according to claim 1 or 2, wherein the dielectric multilayer film includes a portion in which a plurality of high refractive index layers and a plurality of low refractive index layers are stacked alternately.

5. The reflector according to claim 4, wherein the conductive layer is in contact with the side on which electromagnetic waves are incident to one of the plurality of high refractive index layers.

6. The reflector according to claim 1 or 2, wherein the conductive layer is electrically connected to an electrode that controls the potential of the conductive layer to a specific potential.

7. The reflector according to claim 6, wherein the dielectric multilayer film comprises the electrodes.

8. The reflector according to claim 1 or 2, wherein the conductive layer is an oxide-based conductive material, an organic conductive material, a carbon-based conductive material, a semiconductor-based conductive material, or a metallic material.

9. The reflector according to claim 8, wherein the conductive layer is configured as a film.

10. The reflector according to claim 8, wherein the conductive layer is patterned.

11. An optical resonator comprising a plurality of reflectors, wherein one or more of the plurality of reflectors are the reflectors described in claim 1 or 2.

12. A quantum device comprising the optical resonator described in claim 11.

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