Optical element and method for manufacturing an optical element

Abstract

The present invention provides an optical element and a method for manufacturing an optical element that can improve the design freedom of a metasurface. [Solution] The optical element comprises a substrate and a metasurface formed on the substrate. The metasurface has a first metaatom capable of transmitting light and a second metaatom capable of transmitting light and having a different refractive index from the first metaatom. The material composition of the first metaatom is the same as the material composition of the substrate.

Description

Technical Field

[0001] The present disclosure relates to an optical element and a method for manufacturing the optical element.

Background Art

[0002] Various devices such as mirrorless cameras, smartphones, microscopes, and semiconductor exposure apparatuses have an optical system for condensing desired light. Various lenses are used in those optical systems. In the optical systems using these lenses, optical design is performed using a plurality of lenses, and high-precision light collection with various aberrations corrected is realized.

[0003] In recent years, devices such as mirrorless cameras and smartphones have been required to be further miniaturized. However, in a conventional optical system using a lens that refracts and condenses light with a curved surface shape and the refractive index of a medium, there is a limit to reducing the size of the optical system, and there is a trade-off relationship between high-precision light collection with various aberrations corrected and miniaturization of the optical system.

[0004] Regarding such problems, Patent Document 1 states that by adopting an optical system configuration combining a refractive lens and an optical element having a metasurface, the thickness of the optical system can be reduced and the aberration problem can be improved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, conventional optical elements with metasurfaces have limited design flexibility for the metasurface. Given the wide range of needs for optical elements with metasurfaces, there is a demand for improved design flexibility for the metasurface. [Means for solving the problem]

[0007] Therefore, the object of this disclosure is to provide an optical element and a method for manufacturing an optical element that can improve the design freedom of a metasurface.

[0008] According to one aspect of the present disclosure, an optical element is provided, comprising a substrate and a metasurface formed on the substrate, wherein the metasurface comprises a first metaatom capable of transmitting light and a second metaatom capable of transmitting light and having a different refractive index from the first metaatom, and the material composition of the first metaatom is the same as the material composition of the substrate.

[0009] In another aspect of this disclosure, a method for manufacturing an optical element is provided, comprising the steps of: forming a first metaatom on the surface of a substrate by processing the surface of the substrate; and forming a second metaatom having a different refractive index from the first metaatom on the substrate on which the first metaatom is formed.

[0010] In other aspects of this disclosure, there is an optical element having a metasurface, wherein the metasurface has a solid medium capable of transmitting light, the medium having at least a first metaatom, a second metaatom, and a third metaatom, the first metaatom, the second metaatom, and the third metaatom having different refractive indices, and the first metaatom comprising a silicon oxide or a metal oxide or a plastic resin.

[0011] In other aspects of this disclosure, a method for manufacturing an optical element is provided, comprising the steps of: forming a first metaatom on the surface of a substrate by processing the surface of the substrate; forming a second metaatom having a refractive index different from that of the first metaatom on the surface on which the first metaatom is formed; and forming a third metaatom having a refractive index different from that of the first metaatom and the second metaatom on the surface on which the first metaatom and the second metaatom are formed. [Effects of the Invention]

[0012] According to this disclosure, the design freedom of metasurfaces can be improved. [Brief explanation of the drawing]

[0013] [Figure 1A] This is a perspective view showing an optical element according to a first embodiment of the present disclosure. [Figure 1B] This is a cross-sectional view showing an optical element according to a first embodiment of the present disclosure. [Figure 2] This is a flowchart showing the steps for a method of manufacturing an optical element according to the first embodiment of this disclosure. [Figure 3A] This is a cross-sectional view showing a process for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3B] This is a cross-sectional view showing a process for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3C] This is a cross-sectional view showing a process for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3D] This is a cross-sectional view showing a process for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3E] This is a cross-sectional view showing a process for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3F] This is a cross-sectional view showing a process for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3G] This is a cross-sectional view showing a process for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3H]It is a process cross-sectional view showing a method for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 3I] It is a process cross-sectional view showing a method for manufacturing an optical element according to a first embodiment of the present disclosure. [Figure 4A] It is a perspective view showing an optical element according to a second embodiment of the present disclosure. [Figure 4B] It is a cross-sectional view showing an optical element according to a second embodiment of the present disclosure. [Figure 5A] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5B] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5C] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5D] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5E] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5F] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5G] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5H] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5I] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5J] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5K] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 5L] It is a process cross-sectional view showing a method for manufacturing an optical element according to a second embodiment of the present disclosure. [Figure 6] It is a cross-sectional view showing an optical element according to a third embodiment of the present disclosure. [Figure 7]This is a cross-sectional view showing another example of a configuration relating to a metaatom in an optical element according to a third embodiment of the present disclosure. [Figure 8] This is a cross-sectional view showing an example in which the peripheral region of an optical element according to a third embodiment of this disclosure is filled with a solid. [Figure 9] This is a flowchart showing the steps for a method of manufacturing an optical element according to a third embodiment of the present disclosure. [Figure 10A] This is a cross-sectional view showing a process for manufacturing an optical element according to a third embodiment of the present disclosure. [Figure 10B] This is a cross-sectional view showing a process for manufacturing an optical element according to a third embodiment of the present disclosure. [Figure 10C] This is a cross-sectional view showing a process for manufacturing an optical element according to a third embodiment of the present disclosure. [Figure 10D] This is a cross-sectional view showing a process for manufacturing an optical element according to a third embodiment of the present disclosure. [Figure 10E] This is a cross-sectional view showing a process for manufacturing an optical element according to a third embodiment of the present disclosure. [Figure 11] This is a cross-sectional view showing an optical element according to a fourth embodiment of the present disclosure. [Modes for carrying out the invention]

[0014] [First Embodiment] An optical element and a method for manufacturing an optical element according to the first embodiment of this disclosure will be described with reference to Figures 1A to 3I.

[0015] First, the configuration of the optical element according to this embodiment will be described using Figures 1A and 1B. Figure 1A is a perspective view showing the optical element 100 according to this embodiment. Figure 1B is a cross-sectional view showing the optical element 100 according to this embodiment.

[0016] As shown in Figures 1A and 1B, the optical element 100 according to this embodiment has a substrate 2 and a metasurface 300 formed on the surface of the substrate 2. The metasurface 300 is composed of a plurality of metaatom groups, specifically having at least a first metaatom group 310 and a second metaatom group 320 that is different from the first metaatom group 310. Here, a metaatom group is a group of metaatoms. A metaatom is an artificially created structure that has a size that is sufficiently small with respect to the wavelength of the target light that the optical element 100 is targeting. The first metaatom group 310 is a group of first metaatoms 310a. The second metaatom group 320 is a group of second metaatoms 320a. The substrate 2 refers to the portion directly below each of the plurality of first metaatoms 310a and the plurality of second metaatoms 320a, and the portion connecting these directly below portions.

[0017] The metasurface 300 includes voids 360. Specifically, there are voids 360 between the first metaatoms 310a and the first metaatoms 310a, between the first metaatoms 310a and the second metaatoms 320a, and between the second metaatoms 320a and the second metaatoms 320a. These voids 360 included in the metasurface 300 are filled with, for example, air.

[0018] The multiple meta-atom groups in the optical element 100 are distinguished by the material composition of each meta-atom. Specifically, the first meta-atom 310a constituting the first meta-atom group 310 and the second meta-atom 320a constituting the second meta-atom group 320 are composed of materials with different refractive indices with respect to the target light of the optical element 100. As a result, the first meta-atom group 310 and the second meta-atom group 320 are composed of materials with different refractive indices with respect to the target light of the optical element 100. For example, the refractive index of the first meta-atom group 310 is smaller than that of the second meta-atom group 320.

[0019] Furthermore, the material composition of the first metaatom group 310 is the same as the material composition of the substrate 2. Here, having the same material composition means that the majority or main parts of the material composition that govern the optical properties of the two objects of interest are the same. Differences in surface or internal alteration of the objects due to processing or other treatments do not prevent the material composition from being the same.

[0020] The effect of metasurfaces on light changes with wavelength, angle of incidence, and polarization. Therefore, while it is possible to optimize them for specific incidence conditions, it is difficult to accommodate a wide range of incidence conditions. For this reason, currently, commercially available optical elements with metasurfaces are limited to products with restricted incidence conditions, such as TOF (Time of Flight) sensors using monochromatic lasers.

[0021] One reason why it is difficult to accommodate a wide range of incidence conditions is that there are few methods for forming metasurfaces and few materials that can be selected as metasurface materials, resulting in low design flexibility for metasurfaces. There is a wide range of needs for optical elements with metasurfaces, such as achromatic lenses that can accommodate a wide spectral range and large field of view (FOV) lenses that can accommodate a wide incidence angle, and there is a need to improve the design flexibility of metasurfaces.

[0022] In this embodiment, the material composition of the first meta-atom group 310, which is at least one of the multiple meta-atom groups in the optical element 100, is the same as the material composition of the substrate 2. Since there are many materials that can be selected for the substrate 2, there are also many materials that can be selected as the material for the first meta-atom group 310, which has the same material composition as the substrate 2. Therefore, according to this embodiment, the design freedom of the meta-surface 300 can be improved.

[0023] Furthermore, it is more preferable that the first meta-atom group 310, which has the same material composition as the substrate 2, is formed continuously with the substrate 2. In this case, the first meta-atom group 310 can be formed by processing the substrate 2, making it possible to select the material composition of the first meta-atom group 310 without being restricted by the film formation method. As a result, the material composition of the first meta-atom group 310 can be selected from a wider range, thereby improving the design freedom of the meta-surface 300. Here, "formed continuously" means that the first meta-atom group 310 and the substrate 2 have no interface and are an integral structure, and that the first meta-atom group 310 is composed of a part of the surface shape of the substrate 2.

[0024] Furthermore, it is preferable that the metasurface 300 has three or more types of media that can transmit and propagate the target light of the optical element 100. In this embodiment, the metasurface 300 has three types of media: a first metaatom group 310 as the first medium, a second metaatom group 320 as the second medium, and a medium such as air in the void 360 as the third medium. The first medium, the second medium, and the third medium can transmit and propagate the target light of the optical element 100, and have different refractive indices with respect to the target light of the optical element 100. By having three or more types of media in the metasurface 300 in this way, the number of combinations of media constituting the metasurface 300 is increased, and the design freedom of the metasurface 300 can be improved.

[0025] The substrate 2, metasurface 300, and first and second metaatoms 310a and 320a of the optical element 100 according to this embodiment will be described in detail below.

[0026] The substrate 2 is transparent to light of a desired wavelength, which is the target wavelength of the optical element 100, and serves as the basis for forming the metasurface 300 on its surface. Specifically, the substrate 2 is a substrate such as a glass substrate, resin substrate, or silicon substrate. The size and thickness of the substrate 2 can be appropriately selected according to the application of the optical element 100.

[0027] The material of the substrate 2 can be selected in various ways depending on the application of the optical element 100. For example, if the optical element 100 targets visible light with a wavelength of 400 nm to 800 nm, it is preferable to select a material containing a metal oxide as the material of the substrate 2. Specifically, it is preferable to select a material containing at least one oxide from among La, Nb, W, Ti, K, Na, and Li as the material of the substrate 2. Alternatively, in this case, it is preferable to select a material that is a resin containing a cycloolefin or a resin containing a polyolefin as the material of the substrate 2. Considering the performance of the optical element 100, it is preferable that the substrate 2 has a transmittance of at least 60% for visible light with a wavelength of 400 nm to 800 nm, which is the target light of the optical element 100.

[0028] On the other hand, when the wavelength of the light targeted by the optical element 100 is longer than visible light, it is preferable that the material of the substrate 2 be a material containing at least one of the following: polycrystalline silicon, Ge, ZnSe, SeS, ZnS, CaF2, sapphire, and chalcogenide glass.

[0029] Furthermore, when the wavelength of the light targeted by the optical element 100 is shorter than visible light, it is preferable that the material of the substrate 2 be a material containing at least one fluoride from among Al, Mg, Ca, Ba, and Sr. Specifically, when the wavelength of the light targeted is shorter than visible light, it refers to ultraviolet light between 257 nm and 360 nm.

[0030] In addition, depending on the application, one oxide, nitride, or oxynitride of Si, Al, Ti, Hf, Ta, and Nb may be selected as the material for base material 2.

[0031] The metasurface 300 is an optical surface provided on the surface of the substrate 2, and in this embodiment, it has a first metaatom group 310 and a second metaatom group 320. The first metaatom group 310 and the second metaatom group 320 are composed of materials with different refractive indices with respect to the target light of the optical element 100.

[0032] The first meta-atom group 310 is a group of multiple first meta-atoms 310a. Similarly, the second meta-atom group 320 is a group of multiple second meta-atoms 320a. The first meta-atom group 310 and the second meta-atom group 320 are distinguished by the material composition of the first meta-atom 310a and the material composition of the second meta-atom 320a.

[0033] Furthermore, it is preferable that the metasurface 300 has three or more types of media that can transmit and propagate the target light of the optical element 100. In this embodiment, the metasurface 300 has three types of media: a first metaatom group 310 as the first medium, a second metaatom group 320 as the second medium, and a medium such as air in the void 360 as the third medium.

[0034] The first meta-atom group 310 has the same material composition as the substrate 2, and, similar to the substrate 2, the material can be appropriately selected depending on the wavelength of the target light of the optical element 100. That is, when the optical element 100 targets visible light between 400 nm and 800 nm, it is preferable to select a material containing a metal oxide as the material for the first meta-atom group 310. In this case, specifically, it is preferable to select a material containing at least one oxide from among La, Nb, W, Ti, K, Na, and Li as the material for the first meta-atom group 310. Alternatively, in this case, a material containing either a resin containing a cycloolefin or a resin containing a polyolefin can be selected as the material for the first meta-atom group 310.

[0035] On the other hand, when the wavelength of the target light of the optical element 100 is longer than the wavelength of visible light, it is preferable that the material of the first metaatom group 310 be a material containing at least one of polycrystalline silicon, Ge, ZnSe, SeS, ZnS, CaF2, sapphire, and chalcogenide glass.

[0036] Furthermore, if the wavelength of the light targeted by the optical element 100 is shorter than visible light, the material of the first metaatom group 310 may be selected from materials containing at least one fluoride from among Al, Mg, Ca, Ba, and Sr.

[0037] In addition, as the material for the first metaatom group 310, one oxide, nitride, or oxynitride of Si, Al, Ti, Hf, Ta, and Nb may be selected.

[0038] The material for the second metaatom group 320 may be selected from any one oxide, nitride, or oxynitride of Si, Al, Ti, Hf, Ta, and Nb. Alternatively, the material for the second metaatom group 320 may be selected from a material containing at least one fluoride from Al, Mg, Ca, Ba, and Sr.

[0039] As a third medium that can transmit and propagate a third type of light to the first meta-atom group 310 and the second meta-atom group 320, the following can be selected: air, water, vacuum, plastic resins such as thermoplastic resins, Si oxide, MgF2, porous material, etc. The third medium can fill the void 360. The third medium has a different refractive index from the first meta-atom group 310 and the second meta-atom group 320, and is preferably a low refractive index medium with a lower refractive index for the target light than the material composition constituting the first meta-atom 310a and the second meta-atom 320a.

[0040] The metasurface 300 can be designed, by combination of the first and second metaatom groups 310 and 320 and the third medium, to exhibit a refraction effect due to propagation phase delay, geometric phase delay, etc., for light in a desired wavelength range that is the target light of the optical element 100.

[0041] The first meta-atom 310a is an artificial structure having a pillar structure and constitutes the first meta-atom group 310. The cross-sectional shape and height of the first meta-atom 310a, as well as the distance between the first meta-atoms 310a, can be appropriately selected according to the wavelength of the target light that the optical element 100 is targeting. In principle, the size of the first meta-atom 310a is sufficiently small compared to the wavelength of the target light that the optical element 100 is targeting.

[0042] The first meta-atom 310a constituting the first meta-atom group 310 preferably has the same material composition as the base material 2. Furthermore, it is more preferable that the first meta-atom 310a does not have an interface with the base material 2, is integral with the base material 2, and is part of the surface shape of the base material 2. In other words, it is more preferable that the first meta-atom 310a is a structure formed by processing the surface of the base material 2.

[0043] The second meta-atom 320a is an artificial structure having a pillar structure and constitutes the second meta-atom group 320. The cross-sectional shape and height of the second meta-atom 320a, as well as the distance between the second meta-atoms 320a, can be appropriately selected according to the wavelength of the target light that the optical element 100 is targeting. In principle, the size of the second meta-atom 320a is sufficiently small compared to the wavelength of the target light that the optical element 100 is targeting.

[0044] The second meta-atom 320a, which constitutes the second meta-atom group 320, is a structure formed on the substrate 2 with a material composition that has a different refractive index from the first meta-atom 310a, which constitutes the first meta-atom group 310, i.e., a material composition that has a different refractive index from the substrate 2. As the material for the second meta-atom 320a, materials that can be deposited by dry deposition methods such as chemical vapor deposition (CVD) and atomic layer deposition (ALD), or by wet coating methods such as dipping and spin coating, can be used.

[0045] Furthermore, the first metaatom 310a and the second metaatom 320a are not limited to structures having a pillar structure, but may be other structures having a convex structure.

[0046] Next, the method for manufacturing the optical element 100 according to this embodiment will be described with reference to Figures 2 to 3I. Figure 2 is a flowchart showing the manufacturing process in the method for manufacturing the optical element 100 according to this embodiment. Figures 3A to 3I are cross-sectional views showing an example of the method for manufacturing the optical element 100 according to this embodiment.

[0047] First, as shown in Figure 3A, a substrate 2 to be used for forming the optical element 100 is prepared (step S11). The substrate 2 can be a plate, a sheet, or any other predetermined shape.

[0048] Next, by processing the surface of the substrate 2, the first metaatom group 310 is formed on the surface of the substrate 2, and at the same time, a base surface for forming the second metaatom group 320 is formed on the surface of the substrate 2. In this processing step, it is preferable to process the substrate 2 using etching removal. Specifically, the processing step for processing the substrate 2 using etching removal is as follows.

[0049] First, as shown in Figure 3B, a positive-type photoresist 400 is applied to the surface of the prepared substrate 2 (step S12).

[0050] Next, the photoresist 400 on the surrounding area of ​​the portion that will become the first meta-atom 310a constituting the first meta-atom group 310 on the substrate 2, and on the portion that will become the base surface of the second meta-atom group 320 on the substrate 2, is exposed with an exposure apparatus. This increases the solubility of the photoresist 400 on these portions. Next, the exposed and increasedly solubility portions of the photoresist 400 are removed with a solvent and developed. In this way, the pattern is transferred to the photoresist 400 by photolithography and developed (step S13). The photoresist 400 on which the pattern has been transferred has a coating pattern corresponding to the first meta-atom 310a constituting the first meta-atom group 310. Note that the pattern formation step on the photoresist 400 is not limited to a photolithography method, but may also be a step in which the pattern is formed on the photoresist 400 by other methods such as imprinting. In this way, a photoresist 400 with a pattern formed on it is created using a photolithography method, an imprint method, or the like, to be used as a mask for the next etching process.

[0051] Subsequently, the patterned photoresist 400 is used as a mask, and the substrate 2 is engraved using processing methods such as ion beam etching and reactive ion etching. As a result, as shown in Figure 3C, the first metaatom group 310 is formed on the surface of the substrate 2, and a base surface for forming the second metaatom group 320 in a later step is also formed on the surface of the substrate 2 (step S14). Then, as shown in Figure 3D, the remaining photoresist 400 is removed (step S15).

[0052] Next, as shown in Figure 3E, a positive-type photoresist 401 is applied again to cover the processed surface of the substrate 2 (step S16).

[0053] Next, the photoresist 401 on the portion of the substrate 2 that forms the second meta-atom 320a, which is included in the base surface for forming the second meta-atom group 320, is exposed with an exposure apparatus. This increases the solubility of the photoresist 401 on this portion. Then, the exposed portion of the photoresist 401 with increased solubility is removed with a solvent and developed. Thus, as shown in Figure 3F, the pattern is transferred to the photoresist 401 by photolithography and developed (step S17). The photoresist 401 on which the pattern has been transferred has an aperture pattern including an aperture 4011 corresponding to the second meta-atom 320a that constitutes the second meta-atom group 320. Note that the pattern formation step on the photoresist 401 is not limited to a step by photolithography, but may also be a step in which the pattern is formed on the photoresist 401 by other methods such as imprinting. Thus, the photoresist 401 with the pattern formed is formed by photolithography, imprinting, etc., to be used as a mask for film formation in the next step.

[0054] Next, as shown in Figure 3G, a film 3201 of the material that will become the second meta-atom 320a of the second meta-atom group 320 is deposited and filled into the opening 4011 developed on the patterned photoresist 401 (step S18). Methods such as CVD, ALD, dipping, and spin coating can be used to deposit the film 3201.

[0055] Next, as shown in Figure 3H, the film 3201 and photoresist 401 are polished to the first metaatom 310a using a method such as CMP (Chemical Mechanical Polishing) to prepare the metasurface 300. As a result, a second metaatom 320a, consisting of the film 3201 filling the opening 4011, is formed on the substrate 2.

[0056] Next, as shown in Figure 3I, the photoresist 401 remaining on the substrate 2 is removed with a solvent (step S19). After that, a functional film such as a protective film or an anti-reflective film may be appropriately applied to the metasurface 300. Alternatively, the substrate 2 may be cut to match the size of the optical element 100. In this way, the optical element 100 according to this embodiment can be manufactured.

[0057] Thus, according to this embodiment, since the first metaatom group 310 having the same material composition as the base material 2 is formed using the base material 2, the number of materials that can be selected to form the first metaatom group 310 can be increased. Therefore, according to this embodiment, the design freedom of the metasurface 300 can be improved. By improving the design freedom of the metasurface 300, it becomes possible to develop optical elements 100 having the metasurface 300 in a wide range of applications and products.

[0058] In this embodiment, the example described is that the metasurface 300 has two types of metaatom groups, a first metaatom group 310 and a second metaatom group 320, but it is not limited to this. The metasurface 300 may have three or more types of metaatom groups. In this case, other metaatom groups with different refractive indices from the first metaatom group 310 and the second metaatom group 320 can be further formed on the substrate 2 in the same manner as the second metaatom group 320.

[0059] [Second Embodiment] An optical element according to a second embodiment of this disclosure will be described with reference to Figures 4A to 4B. Components similar to those in the optical element according to the first embodiment will be given the same reference numerals, and their descriptions will be omitted or simplified.

[0060] First, the configuration of the optical element according to this embodiment will be described using Figures 4A and 4B. Figure 4A is a perspective view showing the optical element 100 according to this embodiment. Figure 4B is a cross-sectional view showing the optical element 100 according to this embodiment.

[0061] As shown in Figures 4A and 4B, the optical element 100 according to this embodiment is composed of a metasurface 300. The metasurface 300 is composed of a plurality of metaatom groups, specifically having at least a first metaatom group 330, a second metaatom group 340, and a metaatom 350. The first metaatom group 330 and the second metaatom group 340 are distinct from each other. The first metaatom group 330 is a group of first metaatoms 330a. The second metaatom group 340 is a group of second metaatoms 340a. The metaatom 350 is a structure filled between the first metaatoms 330a and the first metaatoms 330a, between the second metaatoms 340a and the second metaatoms 340a, and between the first metaatoms 330a and the second metaatoms 340a.

[0062] The first meta-atom 330a constituting the first meta-atom group 330, the second meta-atom 340a constituting the second meta-atom group 340, and the meta-atom 350 have material compositions with different refractive indices. Furthermore, the materials of the first meta-atom 330a, the second meta-atom 340a, and the third meta-atom 350 are all solid media capable of transmitting and propagating the target light of the optical element 100. In this embodiment, the meta-surface 300 has three types of solid media: the first meta-atom group 330 as the first medium, the second meta-atom group 340 as the second medium, and the meta-atom 350 as the third medium.

[0063] In the optical element 100 according to this embodiment, as shown in Figures 4A and 4B, the metasurface 300 is not provided on the substrate. In this case, the optical element 100 can be formed by the first metaatom 330a, the second metaatom 340a, and the metaatom 350 being in close contact with each other.

[0064] Thus, in this embodiment, the metasurface 300 is not provided on the substrate. For this reason, in this embodiment, from the viewpoint of the rigidity and ease of manufacture of the optical element 100, it is preferable that the material composition of the first metaatom group 330 is a glass containing silicon oxide or a metal oxide, or a plastic resin. In particular, it is preferable that the oxide contained in the glass is at least one of Si, La, Nb, W, Ti, K, Na, and Li. Furthermore, it is preferable that the plastic resin is a resin containing cycloolefin or a resin containing polyolefin.

[0065] The first metaatom group 330 can be formed by processing the temporary base material 3, as described later. Since the temporary base material 3 can be made of the same material as the base material 2 in the first embodiment, the first metaatom group 330 can also be made of the same material as the base material 2 in the first embodiment.

[0066] Furthermore, it is preferable that the material compositions of the second metaatom group 340 and metaatom 350 are the same as those of the second metaatom group 320 in the first embodiment, but with different refractive indices.

[0067] Thus, in this embodiment, since the metasurface 300 is not provided on the substrate, the thickness of the optical element 100 can be reduced while improving the design flexibility of the metasurface 300.

[0068] In this embodiment as well, a metasurface 300 may be provided on the substrate 2, similar to the first embodiment. In this case, the first metaatom group 330 is preferably made of the same material as the substrate 2, and more preferably formed continuously with the substrate 2.

[0069] Next, the method for manufacturing the optical element 100 according to this embodiment will be described with reference to Figures 5A to 5L. Figures 5A to 5L are cross-sectional views showing the process for manufacturing the optical element 100 according to this embodiment.

[0070] First, as shown in Figure 5A, a temporary substrate 3 is prepared for use in forming the optical element 100. The temporary substrate 3 can have a predetermined shape, such as a plate or a sheet. Alternatively, the temporary substrate 3 can be made of the same material as the substrate 2 in the first embodiment.

[0071] Next, by processing the surface of the temporary substrate 3, the first metaatom group 330 is formed on the surface of the temporary substrate 3, and at the same time, a temporary base surface for forming the second metaatom group 340 and metaatom 350 is formed on the surface of the temporary substrate 3. In this processing step, it is preferable to process the temporary substrate 3 using etching removal. Specifically, the processing step for processing the temporary substrate 3 using etching removal is as follows.

[0072] First, as shown in Figure 5B, a positive-type photoresist 402 is applied to the surface of the prepared temporary substrate 3.

[0073] Next, the photoresist 402 on the surrounding area of ​​the portion that will become the first meta-atom 330a constituting the first meta-atom group 330 on the temporary substrate 3 is exposed using an exposure apparatus. Simultaneously with this exposure, the photoresist 402 on the portion that will become the temporary base surface of the second meta-atom group 340 and the meta-atom 350 on the temporary substrate 3 is also exposed. This increases the solubility of the photoresist 402 on these portions. Next, the exposed and increasedly solubility portions of the photoresist 402 are removed with a solvent and developed. In this way, the pattern is transferred to the photoresist 402 by photolithography and developed. The photoresist 402 on which the pattern has been transferred has a coating pattern corresponding to the first meta-atom 330a constituting the first meta-atom group 330. Note that the pattern formation step on the photoresist 402 is not limited to a photolithography method, but may also be a step in which the pattern on the photoresist 402 is formed by other methods such as the imprint method. In this way, a photoresist 402 with a pattern formed on it is created using a photolithography method, an imprint method, or the like, to be used as a mask for etching in the next step.

[0074] Subsequently, the patterned photoresist 402 is used as a mask, and the temporary substrate 3 is engraved using processing methods such as ion beam etching and reactive ion etching. As a result, as shown in Figure 5C, the first meta-atom group 330 is formed on the surface of the temporary substrate 3, and a temporary base surface for forming the second meta-atom group 340 and meta-atom 350 is also formed on the surface of the temporary substrate 3. After that, as shown in Figure 5D, the remaining photoresist 402 is removed.

[0075] Next, as shown in Figure 5E, a positive-type photoresist 403 is applied again to cover the processed surface of the temporary substrate 3.

[0076] Next, the photoresist 403 on the portion that forms the second meta-atom 340a, which is included in the temporary base surface for forming the second meta-atom group 340 on the temporary substrate 3, is exposed with an exposure apparatus. This increases the solubility of the photoresist 403 on this portion. Then, the exposed and increasedly solubility portion of the photoresist 403 is removed with a solvent and developed. Thus, as shown in Figure 5F, the pattern is transferred to the photoresist 403 by photolithography and developed. The photoresist 403 on which the pattern has been transferred has an aperture pattern including an aperture 4031 corresponding to the second meta-atom 340a that constitutes the second meta-atom group 340. Note that the pattern formation step on the photoresist 403 is not limited to a step by photolithography, but may also be a step in which the pattern is formed on the photoresist 403 by other methods such as imprinting. Thus, the photoresist 403 with the pattern formed is formed by photolithography, imprinting, or the like to be used as a mask for film formation in the next step.

[0077] Next, as shown in Figure 5G, a film 3401 of the material that will become the second meta-atom 304a of the second meta-atom group 340 is deposited and filled into the opening 4031 developed on the patterned photoresist 403. Methods such as CVD, ALD, dipping, and spin coating can be used to deposit the film 3401.

[0078] Next, as shown in Figure 5H, the film 3401 and photoresist 403 are polished by CMP or the like until they reach the first metaatom 330a, thereby preparing the metasurface 300. This forms a second metaatom 340a consisting of the film 3401 filling the opening 4031.

[0079] Next, as shown in Figure 5I, the photoresist 403 remaining on the temporary substrate 3 is removed with a solvent.

[0080] Next, as shown in Figure 5J, a film 3501 of the material that will become the metaatom 350 is deposited. This fills the spaces between the first metaatoms 330a, between the second metaatoms 340a, and between the first metaatoms 330a and the second metaatoms 340a with film 3501. Similar to the case of film 3401, methods such as CVD, ALD, dipping, and spin coating can be used to deposit film 3501. Here again, since the film is deposited and filled into the openings, similar to the case of film 3401, methods such as CVD, ALD, dipping, and spin coating can be used to deposit film 3501.

[0081] Next, as shown in Figure 5K, the film 3501 is polished by the CMP method or the like until it reaches the first metaatom 330a, thereby preparing the metasurface 300. This forms a metaatom 350 made of film 3501.

[0082] Next, the photoresist remaining on the temporary substrate 3 is removed with a solvent. After that, a functional film such as a protective film or an anti-reflective film may be appropriately applied to the metasurface 300.

[0083] Next, as shown in Figure 5L, the temporary substrate 3 is polished from the side opposite to the surface on which the metasurface 300, which includes the first and second metaatom groups 330, 340 and the metaatom 350, is formed. The temporary substrate 3 can be polished until the material of the metaatoms provided in the previous step is exposed.

[0084] Subsequently, the optical element 100 obtained as described above may be cut to the desired size. In this way, the optical element 100 according to this embodiment can be manufactured.

[0085] Thus, according to this embodiment, since a first metaatom group 330 having the same material composition as the base material 3 is formed using a temporary base material 3, the number of materials that can be selected to form the first metaatom group 330 can be increased. Therefore, according to this embodiment, the design freedom of the metasurface 300 can be improved. By improving the design freedom of the metasurface 300, it becomes possible to develop optical elements 100 having a metasurface 300 in a wide range of applications and products.

[0086] [Examples] Next, the optical elements according to this disclosure will be described in detail using examples. Examples 1 to 4 are examples of the optical element 100 according to the first embodiment. In Examples 1 to 4, a substrate 2 was prepared according to the manufacturing method shown in Figures 3A to 3I, and the substrate 2 was processed to produce an optical element 100 having a metasurface 300. In Examples 1 and 3, the material of the substrate 2 was optical glass S-TIH57 (OHARA). In Examples 2 and 4, the material of the substrate 2 was optical glass S-LAL61Q (OHARA). S-TIH57 was a high refractive index glass containing Ti. S-LAL61Q was a high refractive index glass containing La.

[0087] In Examples 1 to 4, a positive-type photoresist 400 was applied to the prepared substrate 2 by spin coating, the photoresist 400 was patterned using photolithography, and the patterned portion of the photoresist 400 was removed using a solvent. Subsequently, the substrate 2 was etched by ion beam etching, processing a portion of the substrate 2 into numerous columnar portions and recesses surrounding the columnar portions. This formed a first meta-atom group 310 containing multiple first meta-atoms 310a composed of columnar portions. At the same time, flat portions were formed in the etched recesses of the substrate 2 for the provision of a second meta-atom group 320 in a later process. Next, the photoresist 400 was removed with a stripping solution, and a positive-type photoresist 401 was applied again to the processed surface of the substrate 2. Then, the photoresist 401 was patterned using photolithography, and the patterned portion of the photoresist 401 was removed using a solvent. In the process described above, a silicon nitride film (Si3N4 film) was deposited as a film 3201 into the opening 4011 corresponding to the second metaatom group 320 provided in the photoresist 401, and filled in by ALD (Advanced Laser Development). This formed a second metaatom group 320 containing multiple second metaatoms 320a composed of the Si3N4 film. Subsequently, the surface covered with the Si3N4 film was polished by CMP (Chemical Polishing) until the first metaatom group 310 and the photoresist 401 remaining on the substrate 2 were exposed. Then, the exposed photoresist 401 was removed with a stripping solution. In this way, the optical elements 100 of Examples 1 to 4 were fabricated.

[0088] In Examples 1 to 4, the first and second metaatoms 310a and 320a constituting the first and second metaatom groups 310 and 320 were cylindrical in shape. In Examples 1 and 2, the diameter of the cylindrical first and second metaatoms 310a and 320a was 300 nm. In Examples 3 and 4, the diameter of the cylindrical first and second metaatoms 310a and 320a was 400 nm.

[0089] In the optical elements 100 of Examples 1 to 4, a first meta-atom group 310 made of the material of the substrate 2 and a second meta-atom group 320 made of a Si3N4 film 3201 deposited on the substrate 2 were provided. By combining the first and second meta-atom groups 310 and 320 with air in the atmosphere, which is a medium with a relatively low refractive index compared to the materials constituting them, a propagation phase delay effect was exhibited at the meta-surface 300 in the optical elements 100 of Examples 1 to 4.

[0090] Table 1 shows the refractive index ratios for Examples 1 to 4 for light wavelengths of 435.83 nm, 587.56 nm, and 706.52 nm, respectively. Here, the refractive index ratio refers to the ratio n2 / n1 of the relative refractive index n2 of the second metaatom 320a with respect to air to the relative refractive index n1 of the first metaatom 310a with respect to air.

[0091] [Table 1]

[0092] Examples 1 and 3 demonstrate that using S-TIH57 as the material for the first meta-atom 310a increases the design flexibility in optical designs where a slightly lower refractive index is required over a wide wavelength range compared to the second meta-atom 320a made of Si3N4.

[0093] Example 2 demonstrates that using S-LAL61Q as the material for the first meta-atom 310a increases the design flexibility in optical designs where aberration correction on the relatively short wavelength side is required compared to the second meta-atom 320a made of Si3N4.

[0094] Example 4 demonstrates that using S-LAL61Q as the material for the first meta-atom 310a increases the design flexibility in optical designs where a refractive index approximately 10% lower over a wide wavelength range is required compared to the second meta-atom 320a made of Si3N4.

[0095] In the optical design required for the final product, the ability to select from a wide variety of effects is extremely important. In Examples 1 to 4, it was confirmed that the design freedom of the metasurface 300 in the optical element 100 was improved, and that a wide variety of effects could be selected.

[0096] [Third Embodiment] An optical element and a method for manufacturing an optical element according to a third embodiment of this disclosure will be described with reference to Figures 6 to 8. Components similar to those in the optical elements of the first and second embodiments described above are denoted by the same reference numerals, and their descriptions are omitted or simplified.

[0097] First, the configuration of the optical element according to this embodiment will be described with reference to Figures 6 to 8. Figure 6 is a cross-sectional view showing the optical element 100 according to this embodiment. Figure 7 is a cross-sectional view showing another example of the configuration of the metaatom in the optical element 100 according to this embodiment. Figure 8 is a cross-sectional view showing an example in which the peripheral region 361 of the optical element 100 according to this embodiment is filled with solid material.

[0098] As shown in Figure 6, the optical element 100 according to this embodiment has a first substrate 21 and a second substrate 22. The second substrate 22 is positioned opposite the first substrate 21. Furthermore, the optical element 100 according to this embodiment has a metasurface 300 formed between the first substrate 21 and the second substrate 22. The first substrate 21 and the second substrate 22 are joined together such that the metasurface 300 is interposed between them.

[0099] The metasurface 300 is composed of multiple metaatom groups, specifically, at least a first metaatom group 310 and a second metaatom group 320 that is different from the first metaatom group 310. Here, a metaatom group is a collection of metaatoms. A metaatom is an artificially created structure that has a size sufficiently small with respect to the wavelength of the target light that the optical element 100 targets. The first metaatom group 310 is a collection of first metaatoms 310a. The second metaatom group 320 is a collection of second metaatoms 320a. The first substrate 21 refers to the portion directly below each of the multiple first metaatoms 310a and the portion connecting these portions. The second substrate 22 refers to the portion directly below each of the multiple second metaatoms 320a and the portion connecting these portions.

[0100] The first meta-atom group 310 is formed on the surface of the first substrate 21 facing the second substrate 22. The top surface of the first meta-atom 310a constituting the first meta-atom group 310 may be facing the surface of the second substrate 22 facing the first substrate 21 with a gap between them, or it may be joined to the surface of the second substrate 22 facing the first substrate 21. The second meta-atom group 320 is formed on the surface of the second substrate 22 facing the first substrate 21. The top surface of the second meta-atom 320a constituting the second meta-atom group 320 may be facing the surface of the first substrate 21 facing the second substrate 22 with a gap between them, or it may be joined to the surface of the first substrate 21 facing the second substrate 22.

[0101] The metasurface 300 includes peripheral regions 361. That is, the areas between the first metaatoms 310a and the first metaatoms 310a, between the first metaatoms 310a and the second metaatoms 320a, and between the second metaatoms 320a each form peripheral regions 361. The peripheral regions 361 are filled with, for example, air. The air filling the peripheral regions 361 is a medium that can transmit the target light of the optical element 100 and is a low refractive index medium with a lower refractive index with respect to the target light of the optical element 100 than the first metaatoms 310a and the second metaatoms 320a. Note that the metasurface 300 may also include, instead of air, a medium that can transmit the target light of the optical element 100 and is a low refractive index medium with a lower refractive index with respect to the target light than the first metaatoms 310a and the second metaatoms 320a in the peripheral regions 361.

[0102] The configuration of the metaatoms in the optical element 100 according to this embodiment, including the positional relationship between the first metaatom group 310 and the second metaatom group 320, and the arrangement of the first metaatom 310a and the second metaatom 320a, is not limited to the example shown in Figure 6. The configuration of the metaatoms in the optical element 100 according to this embodiment may differ from the configuration shown in Figure 6, as shown in the example in Figure 7.

[0103] The multiple meta-atom groups in the optical element 100 are distinguished by the material composition of each meta-atom. Specifically, the first meta-atom 310a constituting the first meta-atom group 310 and the second meta-atom 320a constituting the second meta-atom group 320 are composed of materials with different refractive indices with respect to the target light that the optical element 100 is targeting. As a result, the first meta-atom group 310 and the second meta-atom group 320 are composed of materials with different refractive indices with respect to the target light of the optical element 100. For example, with respect to target light in a certain wavelength range, the refractive index due to the material composition of the first meta-atom group 310 is smaller than the refractive index due to the material composition of the second meta-atom group 320.

[0104] Furthermore, the material composition of the first metaatom group 310 is the same as the material composition of the first substrate 21. Furthermore, the material composition of the second metaatom group 320 is the same as the material composition of the second substrate 22. Here, having the same material composition means that the majority or main parts of the material composition that govern the optical properties of the two objects of interest are the same. Differences in surface or internal alteration of the objects due to processing or other treatments do not prevent the material composition from being the same.

[0105] The effect of metasurfaces on light changes with wavelength, angle of incidence, and polarization. Therefore, while it is possible to optimize them for specific incidence conditions, it is difficult to accommodate a wide range of incidence conditions. For this reason, most optical elements with metasurfaces currently on the market are limited to specific incidence conditions, such as sensors using monochromatic lasers.

[0106] One reason why it is difficult to accommodate a wide range of incidence conditions is that there are few methods for forming metasurfaces and few materials that can be selected as metasurface materials, resulting in a low degree of design freedom for metasurfaces. There is a wide range of needs for optical elements with metasurfaces, such as achromatic lenses that can accommodate a wide spectral range and wide-field-of-view lenses that can accommodate a wide angle of incidence, and there is a need to improve the design freedom of metasurfaces.

[0107] In this embodiment, the material composition of the first meta-atom group 310, which is at least one of the multiple meta-atom groups in the optical element 100, is the same as the material composition of the first substrate 21. Furthermore, in this embodiment, the material composition of the second meta-atom group 320, which is at least one of the multiple meta-atom groups, is the same as the material composition of the second substrate 22. There are many materials that can be selected for the first substrate 21 and the second substrate 22. Therefore, there are many materials that can be selected as the material for the first meta-atom group 310, which has the same material composition as the first substrate 21. Moreover, there are many materials that can be selected as the material for the second meta-atom group 320, which has the same material composition as the second substrate 22. Accordingly, according to this embodiment, the design freedom of the meta-surface 300 can be improved.

[0108] Furthermore, it is more preferable that the first meta-atom group 310, which has the same material composition as the first substrate 21, is formed continuously with the first substrate 21. Similarly, it is more preferable that the second meta-atom group 320, which has the same material composition as the second substrate 22, is formed continuously with the second substrate 22. In these cases, the first meta-atom group 310 and the second meta-atom group 320 can be formed by processing the first substrate 21 and the second substrate 22, respectively. This makes it possible to select the material composition of the first meta-atom group 310 and the second meta-atom group 320 without being restricted by the film formation method. As a result, the material composition of the first meta-atom group 310 and the second meta-atom group 310 can be selected from a wider range, thereby improving the design freedom of the meta-surface 300. In this context, "continuously formed" means that, for the first metaatom group 310 and the second metaatom group 310, the metaatom group and the substrate have no interface and form an integral structure, and the metaatom group is composed of a part of the surface shape of the substrate.

[0109] The first substrate 21 and the second substrate 22, the metasurface 300, and the first and second metaatoms 310a and 320a of the optical element 100 according to this embodiment will be described in detail below.

[0110] The first substrate 21 and the second substrate 22 are materials such as substrates that are transparent to light of a desired wavelength, which is the target wavelength of the optical element 100, and serve as the basis for forming the first metaatom group 310 and the second metaatom group 320 on their surfaces. The material, size, and thickness of the first substrate 21 and the second substrate 22 can be appropriately selected according to the application of the optical element 100.

[0111] For example, if the optical element 100 targets visible light between 400 nm and 800 nm, it is preferable that the materials for the first substrate 21 and the second substrate 22 include a metal oxide. Specifically, it is preferable that at least one of the materials for the first substrate 21 and the second substrate 22 includes an oxide containing at least one of La, Nb, W, Ti, K, Na, and Li. Alternatively, it is preferable that at least one of the materials for the first substrate 21 and the second substrate 22 is a resin containing a cycloolefin or a resin containing a polyolefin. Considering the performance of the optical element 100, it is preferable that the first substrate 21 and the second substrate 22 have a transmittance of at least 60% or more to the target light of the optical element 100.

[0112] On the other hand, when the wavelength of the target light of the optical element 100 is longer than visible light, it is preferable that at least one of the materials of the first substrate 21 and the second substrate 22 is selected to include at least one of polycrystalline silicon, Ge, ZnSe, SeS, ZnS, CaF2, sapphire, and chalcogenide glass.

[0113] Furthermore, when the wavelength of the light targeted by the optical element 100 is shorter than visible light, it is preferable that at least one of the materials of the first substrate 21 and the second substrate 22 is a material containing at least one fluoride from among Al, Mg, Ca, Ba, and Sr. Specifically, when the wavelength of the light targeted is shorter than visible light, it refers to ultraviolet light with a wavelength of 257 nm to 360 nm.

[0114] In addition, at least one of the materials for the first substrate 21 and the second substrate 22 may be selected from any one of Si, Al, Ti, Hf, Ta, and Nb, such as an oxide, nitride, or oxynitride.

[0115] Furthermore, depending on the application of the optical element 100, it is possible to target visible light and light with wavelengths longer than visible light, or visible light and light with wavelengths shorter than visible light. For example, the material of the first substrate 21 can be a material optimized for visible light, and the material of the second substrate 22 can be a material optimized for light with wavelengths shorter than visible light.

[0116] The first substrate 21 may have a functional film on the side opposite to the metasurface 300. Similarly, the second substrate 22 may also have a functional film on the side opposite to the metasurface 300. These functional films are, for example, protective films, anti-reflective films, etc.

[0117] The metasurface 300 is an optical surface provided on the surfaces of the first substrate 21 and the second substrate 22, which face each other. The surface of the first substrate 21 has a first metaatom group 310, and the surface of the second substrate 22 has a second metaatom group 320. The first metaatom group 310 and the second metaatom group 320 are composed of materials with different refractive indices with respect to the target light of the optical element 100.

[0118] The first metaatom group 310 is a colony of multiple first metaatoms 310a. The second metaatom group 320 is a colony of multiple second metaatoms 320a.

[0119] Furthermore, the metasurface 300 has three or more types of media that can transmit and propagate the target light of the optical element 100. In this embodiment, the metasurface 300 has three types of media: a first metaatom group 310 as the first medium, a second metaatom group 320 as the second medium, and air or the like that filling the surrounding region 361 as the third medium.

[0120] The first meta-atom group 310 and the second meta-atom group 320 have the same material composition as the first substrate 21 and the second substrate 22, respectively, and the materials can be appropriately selected depending on the wavelength of the target light of the optical element 100, similar to the first substrate 21 and the second substrate 22. That is, when the optical element 100 targets visible light between 400 nm and 800 nm, it is preferable that at least one of the materials in the first meta-atom group 310 and the second meta-atom group 320 is a material containing a metal oxide. In this case, specifically, it is preferable that at least one of the materials in the first meta-atom group 310 and the second meta-atom group 320 is a material containing at least one oxide from among La, Nb, W, Ti, K, Na, and Li. Alternatively, in this case, at least one of the materials in the first meta-atom group 310 and the second meta-atom group 320 may be a material containing either a resin containing a cycloolefin or a resin containing a polyolefin.

[0121] On the other hand, when the wavelength of the target light for the optical element 100 is longer than visible light, it is preferable that at least one of the materials for the first metaatom group 310 and the second metaatom group 320 is selected to be a material containing at least one of polycrystalline silicon, Ge, ZnSe, SeS, ZnS, CaF2, sapphire, and chalcogenide glass.

[0122] Furthermore, if the wavelength of the light targeted by the optical element 100 is shorter than visible light, at least one of the materials of the first metaatom group 310 and the second metaatom group 320 may be selected from materials containing at least one fluoride from among Al, Mg, Ca, Ba, and Sr.

[0123] In addition, at least one of the materials in the first metaatom group 310 and the second metaatom group 320 may be selected from any one of Si, Al, Ti, Hf, Ta, and Nb, including oxides, nitrides, or oxynitrides.

[0124] As a third medium that can transmit the target light and fills the peripheral region 361 of the metasurface 300, air, water, vacuum, etc., can be selected. Also, when the peripheral region 361 is filled with a solid as shown in Figure 8, a plastic resin such as a thermoplastic resin, Si oxide, MgF2, etc., can be selected as a third medium that can transmit the target light. The third medium has a different refractive index from the first metaatom group 310 and the second metaatom group 320, and it is preferable that the third medium is a low refractive index medium with a lower refractive index with respect to the target light than the material composition constituting the first metaatom 310a and the second metaatom 320a.

[0125] The metasurface 300 can be designed, by combination of the first and second metaatom groups 310 and 320 and the third medium, to exhibit a refraction effect due to propagation phase delay, geometric phase delay, etc., for light in a desired wavelength range that is the target light of the optical element 100.

[0126] The first meta-atom 310a is an artificial structure having a pillar structure and constitutes the first meta-atom group 310. The cross-sectional shape and height of the first meta-atom 310a, as well as the distance between the first meta-atoms 310a, can be appropriately selected according to the wavelength of the target light that the optical element 100 is targeting. In principle, the size of the first meta-atom 310a is sufficiently small compared to the wavelength of the target light that the optical element 100 is targeting.

[0127] The first meta-atom 310a constituting the first meta-atom group 310 preferably has the same material composition as the first substrate 21. Furthermore, it is more preferable that the first meta-atom 310a does not have an interface with the first substrate 21, is integral with the first substrate 21, and is part of the surface shape of the first substrate 21. In other words, it is more preferable that the first meta-atom 310a is formed by processing the surface of the first substrate 21.

[0128] The second meta-atom 320a is an artificial structure having a pillar structure and constitutes the second meta-atom group 320. The cross-sectional shape and height of the second meta-atom 320a, as well as the distance between the second meta-atoms 320a, can be appropriately selected according to the wavelength of the target light that the optical element 100 is targeting. In principle, the size of the second meta-atom 320a is sufficiently small compared to the wavelength of the target light that the optical element 100 is targeting.

[0129] The second meta-atom 320a, which constitutes the second meta-atom group 320, is a structure formed on the second substrate 22 with a material composition that has a different refractive index from the first meta-atom 310a, which constitutes the first meta-atom group 310. In other words, the second meta-atom 320a is a structure formed on the second substrate 22 with a material composition that has a different refractive index from the first substrate 21. It is preferable that the second meta-atom 320a has the same material composition as the second substrate 22. Furthermore, it is more preferable that the second meta-atom 320a does not have an interface with the second substrate 22, is an integral structure with the second substrate 22, and is part of the surface shape of the second substrate 22. That is, it is more preferable that the second meta-atom 320a is a structure formed by processing the surface of the second substrate 22.

[0130] Furthermore, the first metaatom 310a and the second metaatom 320a are not limited to structures having a pillar structure, but may be other structures having a convex structure.

[0131] Next, the method for manufacturing the optical element 100 according to this embodiment will be described with reference to Figures 9 to 10E. Figure 9 is a flowchart showing an example of the manufacturing process in the method for manufacturing the optical element 100 according to this embodiment. Figures 10A to 10E are cross-sectional views showing an example of the manufacturing process for the optical element 100 according to this embodiment.

[0132] First, as shown in Figure 10A, a first substrate 21 and a second substrate 22 to be used for forming the optical element 100 are prepared (step S21). The first substrate 21 and the second substrate 22 can be prepared having predetermined shapes such as plates or sheets.

[0133] Next, the first metaatom group 310 and the second metaatom group 320 are formed on the surfaces of the first substrate 21 and the second substrate 22, respectively, by processing the surfaces of the first substrate 21 and the second substrate 22. In these processing steps, it is preferable to process the first substrate 21 and the second substrate 22 using etching removal. Specifically, the processing steps for processing the first substrate 21 and the second substrate 22 using etching removal are as follows. Note that the processing steps including steps S22 to S26 described below can be performed at any time for the first substrate 21 and the second substrate 22. In other words, the processing steps including steps S22 to S26 for the first substrate 21 and the processing steps including steps S22 to S26 for the second substrate 22 can be performed in any order and may be performed simultaneously.

[0134] First, as shown in Figure 10B, positive-type photoresists 501 and 502 are applied to the surfaces of the prepared first substrate 21 and second substrate 22, respectively (step S22).

[0135] Next, the photoresist 501 surrounding the portion that will become the first meta-atom 310a constituting the first meta-atom group 310 on the first substrate 21 is exposed using an exposure apparatus. The photoresist 502 surrounding the portion that will become the second meta-atom 320a constituting the second meta-atom group 320 on the second substrate 22 is also exposed using an exposure apparatus. This increases the solubility of the photoresists 501 and 502 in these portions. Next, the exposed and increasedly soluble portions of the photoresist 501 are removed with a solvent and developed. Similarly, the exposed and increasedly soluble portions of the photoresist 502 are removed with a solvent and developed. In this way, the pattern is transferred to the photoresists 501 and 502 by photolithography and developed (step S23). The photoresist 501 on which the pattern has been transferred now has a coating pattern corresponding to the first meta-atom 310a constituting the first meta-atom group 310. Furthermore, the photoresist 502 on which the pattern has been transferred has a coating pattern corresponding to the second meta-atom 320a that constitutes the second meta-atom group 320. Note that the pattern formation process on the photoresists 501 and 502 is not limited to a process by photolithography, but may also be a process in which patterns are formed on the photoresists 501 and 502 by other methods such as the imprint method. In this way, the photoresists 501 and 502 with patterns formed on them are formed by photolithography, imprint method, etc., to be used as masks for etching in the next process.

[0136] Subsequently, the first substrate 21 is engraved using the patterned photoresist 501 as a mask and processing methods such as ion beam etching and reactive ion etching. The second substrate 22 is then engraved using the patterned photoresist 502 as a mask and processing methods such as ion beam etching and reactive ion etching. This creates a first metaatom group 310 on the surface of the first substrate 21 and a second metaatom group 320 on the surface of the second substrate 22, as shown in Figure 10C (step S24). Afterward, the remaining photoresists 501 and 502 are removed, as shown in Figure 10D (step S25).

[0137] Next, the vertex surfaces of the first metaatom group 310 formed by the CMP method or the like are polished to adjust their height. Then, the vertex surfaces of the second metaatom group 320 formed by the CMP method or the like are polished to adjust their height (step S26).

[0138] Thus, by processing steps applied to the first substrate 21 and the second substrate 22 respectively, a first substrate 21 having the first metaatom group 310 on its surface is prepared, and a second substrate 22 having the second metaatom group 320 on its surface is prepared.

[0139] Next, the surface of the first substrate 21 having the first metaatom group 310 and the surface of the second substrate 22 having the second metaatom group 320 are brought into contact, and the first substrate 21 and the second substrate 22 are joined together as shown in Figure 10E (step S27). This joins the first substrate 21 and the second substrate 22 such that a metasurface 300 containing the first metaatom group 310 and the second metaatom group 320 is interposed between the first substrate 21 and the second substrate 22. For joining the first substrate 21 and the second substrate 22, for example, the SAB (Surface Activated Bonding) method can be used.

[0140] In this way, the optical element 100 according to this embodiment can be manufactured. The manufactured optical element 100 may be cut into pieces according to the required application.

[0141] Thus, in this embodiment, the first metaatom group 310 and the second metaatom group 320 are formed by processing a first substrate 21 and a second substrate 22 having two different material compositions. Therefore, according to this embodiment, the number of materials that can be selected when forming the metasurface 300 can be increased, and the design freedom of the metasurface 300 can be improved. By improving the design freedom of the metasurface 300, it becomes possible to develop optical elements 100 having the metasurface 300 in a wide range of applications and products.

[0142] [Fourth Embodiment] An optical element and a method for manufacturing an optical element according to the fourth embodiment of this disclosure will be described with reference to Figure 11. Components similar to those in the optical elements according to the first to third embodiments will be denoted by the same reference numerals, and their descriptions will be omitted or simplified.

[0143] The basic configuration of the optical element 100 according to this embodiment is the same as that of the optical element 100 according to the third embodiment. The optical element 100 according to this embodiment differs from the optical element 100 according to the third embodiment in that it further has a third meta-atom group 370. The configuration of the optical element 100 according to this embodiment will be described below with reference to Figure 11. Figure 11 is a cross-sectional view showing the optical element 100 according to this embodiment.

[0144] As shown in Figure 11, the optical element 100 according to this embodiment has a first substrate 21 and a second substrate 22. The second substrate 22 is positioned opposite the first substrate 21. Furthermore, the optical element 100 according to this embodiment has a metasurface 300 formed between the first substrate 21 and the second substrate 22. The first substrate 21 and the second substrate 22 are joined together such that the metasurface 300 is interposed between them.

[0145] The metasurface 300 is composed of a plurality of metaatom groups. Specifically, in this embodiment, the metasurface 300 has at least a first metaatom group 310 and a second metaatom group 320 that is different from the first metaatom group 310. Furthermore, in this embodiment, the metasurface 300 has a third metaatom group 370 that is different from the first metaatom group 310 and the second metaatom group 320. The first metaatom group 310 is a group of first metaatoms 310a. The second metaatom group 320 is a group of second metaatoms 320a. The third metaatom group 370 is a group of third metaatoms 370a.

[0146] The first metaatom group 310 is formed on the surface of the first substrate 21 facing the second substrate 22. The second metaatom group 320 is formed on the surface of the second substrate 22 facing the first substrate 21. The third metaatom group 370 is formed on the surface of the first substrate 21 on the same side as the first metaatom group 310, but where the first metaatom group 310 is not formed. The third metaatom group 370 may also be formed on the surface of the second substrate 22 on the same side as the second metaatom group 320, but where the second metaatom group 320 is not formed.

[0147] In this embodiment as well, the multiple meta-atom groups in the optical element 100 are distinguished by the material composition of each meta-atom. Specifically, the first meta-atom 310a constituting the first meta-atom group 310, the second meta-atom 320a constituting the second meta-atom group 320, and the third meta-atom 370a constituting the third meta-atom group 370 are composed of the following material compositions: The first meta-atom 310a, the second meta-atom 320a, and the third meta-atom 370a are composed of materials having different refractive indices with respect to the target light that the optical element 100 is targeting.

[0148] Furthermore, the material composition of the first metaatom group 310 is the same as that of the first substrate 21, as in the third embodiment. Furthermore, the material composition of the second metaatom group 320 is the same as that of the second substrate 22, as in the third embodiment.

[0149] Furthermore, it is more preferable that the first meta-atom group 310, which has the same material composition as the first substrate 21, is formed continuously with the first substrate 21, similar to the third embodiment. Similarly, it is more preferable that the second meta-atom group 320, which has the same material composition as the second substrate 22, is formed continuously with the second substrate 22, similar to the third embodiment. In these cases, the first meta-atom group 310 and the second meta-atom group 320 can be formed by processing the first substrate 21 and the second substrate 22, respectively. Therefore, it becomes possible to select the material compositions of the first meta-atom group 310 and the second meta-atom group 320 without being restricted by the film formation method.

[0150] Furthermore, in this embodiment, the third metaatom group 370 can be formed, for example, by processing a film obtained by a film deposition method. Specifically, in the manufacturing method shown in Figure 9, after step S26 and before step S27, the third metaatom group 370 can be formed on the surface of the first substrate 21 on the same side as the first metaatom group 310, where the first metaatom group 310 is not formed. The third metaatom group 370 can be formed, for example, using a film deposition method in the same manner as the method used to form the second metaatom group 320 in the manufacturing method of the optical element 100 according to the first embodiment. The third metaatom group 370 may also be formed on the surface of the second substrate 22 on the same side as the second metaatom group 320, where the second metaatom group 320 is not formed.

[0151] The third metaatom group 370 has a different material composition from the first metaatom group 310 and the second metaatom group 320, that is, a different material composition from the first substrate 21 and the second substrate 22.

[0152] In this embodiment, similar to the third embodiment, the material composition of the first meta-atom group 310, which is at least one of the multiple meta-atom groups in the optical element 100, is the same as the material composition of the first substrate 21. Furthermore, in this embodiment, similar to the third embodiment, the material composition of the second meta-atom group 320, which is at least one of the multiple meta-atom groups, is the same as the material composition of the second substrate 22.

[0153] The first substrate 21 and the second substrate 22 can be made from a wide variety of materials. Therefore, there are many materials that can be selected as the material for the first metaatom group 310, which has the same material composition as the first substrate 21 and the second substrate 22. Furthermore, there are many materials that can be selected as the material for the second metaatom group 320, which has the same material composition as the second substrate 22. In addition, in this embodiment, a third metaatom group 370 obtained by a film deposition method is added, which increases the number of combinations of material compositions of the metaatom groups included in the metasurface 300.

[0154] Thus, in this embodiment, a first metaatom group 310 and a second metaatom group 320 are formed by processing a first substrate 21 and a second substrate 22 having two different material compositions. Furthermore, in this embodiment, a third metaatom group 370, formed by a film deposition method, is combined with the first metaatom group 310 and the second metaatom group 320. Therefore, according to this embodiment, the number of materials that can be selected when forming the metasurface 300 can be further increased, and the design freedom of the metasurface 300 can be further improved. By improving the design freedom of the metasurface 300, it becomes possible to develop optical elements 100 having the metasurface 300 for a wide range of applications and products.

[0155] This embodiment includes the following configurations and methods. (Composition 1) Substrate and Having a metasurface formed on the aforementioned substrate, The metasurface has a first metaatom capable of transmitting light, and a second metaatom capable of transmitting light and having a different refractive index from the first metaatom. The material composition of the first metaatom is the same as the material composition of the substrate. An optical element characterized by the following features. (Configuration 2) The first metaatom is formed continuously with the substrate. The optical element according to configuration 1, characterized by the features described above. (Composition 3) The first metaatom is obtained by processing the substrate. The optical element according to configuration 2, characterized by the features described above. (Composition 4) The metasurface has a medium capable of transmitting the light, The medium has a different refractive index from the first metaatom and the second metaatom. An optical element according to any one of configurations 1 to 3, characterized in that it is an optical element. (Composition 5) The metasurface includes voids, The medium is the air filling the void. The optical element according to configuration 4, characterized by the features described above. (Composition 6) The first metaatom and the second metaatom each have a pillar structure. An optical element according to any one of configurations 1 to 5, characterized in that it is an optical element. (Composition 7) The substrate contains at least one oxide of La, Nb, W, Ti, K, Na, and Li. An optical element according to any one of configurations 1 to 6, characterized by the above. (Composition 8) The substrate is a resin containing a cycloolefin or a resin containing a polyolefin. An optical element according to any one of configurations 1 to 6, characterized by the above. (Composition 9) The substrate has a transmittance of 60% or more to the light with a wavelength of 400 nm to 800 nm. An optical element according to any one of configurations 1 to 8, characterized by the above. (Composition 10) The substrate includes at least one of the following: polycrystalline silicon, Ge, ZnSe, SeS, ZnS, CaF2, sapphire, and chalcogenide glass. An optical element according to any one of configurations 1 to 6, characterized by the above. (Composition 11) The substrate contains at least one fluoride of Al, Mg, Ca, Ba, and Sr. An optical element according to any one of configurations 1 to 6, characterized by the above. (Composition 12) The substrate contains one of the following oxides, nitrides, or oxynitrides: Si, Al, Ti, Hf, Ta, and Nb. An optical element according to any one of configurations 1 to 6, characterized by the above. (Composition 13) The aforementioned substrate is The first substrate and A second substrate is positioned opposite the first substrate, It has, The metasurface is formed between the first substrate and the second substrate, The first metaatom is formed on the surface of the first substrate facing the second substrate, The first metaatom is formed on the surface of the second substrate facing the first substrate, The first metaatom has the same material composition as the first substrate. The optical element according to any one of configurations 1 to 12, characterized in that the second meta-atom has the same material composition as the second substrate. (Composition 14) The optical element according to configuration 13, characterized in that the first metaatom is formed continuously with the first substrate. (Composition 15) The optical element according to configuration 13 or 14, characterized in that the second metaatom is formed continuously with the second substrate. (Composition 16) The metasurface has a third metaatom formed on the surface of the first substrate or the second substrate, The optical element according to any one of configurations 13 to 15, characterized in that the third meta-atom has a different material composition from the first substrate and the second substrate. (Composition 17) The metasurface includes a low refractive index medium capable of propagating the light, The optical element according to any one of the configurations 13 to 16, characterized in that the low refractive index medium has a lower refractive index with respect to light than the first meta-atom and the second meta-atom. (Composition 18) The optical element according to any one of configurations 13 to 17, characterized in that at least one of the first substrate and the second substrate has a functional film on the surface opposite to the metasurface. (Composition 19) An optical element having a metasurface, The metasurface has a solid medium capable of transmitting light, The medium comprises at least a first metaatom, a second metaatom, and a third metaatom. The first metaatom, the second metaatom, and the third metaatom have different refractive indices. The first metaatom is a silicon oxide or metal oxide, or a plastic resin. An optical element characterized by the following features. (Composition 20) The first metaatom is a resin containing a cycloolefin or a polyolefin, which contains at least one oxide of Si, La, Nb, W, Ti, K, Na, and Li. The optical element according to configuration 19, characterized by the features described above. (Method 1) A step of forming a first metaatom on the surface of a substrate by processing the surface of the substrate, A step of forming a second metaatom having a different refractive index from the first metaatom on the substrate on which the first metaatom is formed. A method for manufacturing an optical element, characterized by having the following features. (Method 2) The first step in forming the metaatom involves processing the surface by etching. A method for manufacturing an optical element according to Method 1, characterized by the features described above. (Method 3) The step of forming the first metaatom involves forming a first mask by photolithography or imprinting, and processing the surface by etching using the first mask. A method for manufacturing an optical element according to method 2, characterized by the features described above. (Method 4) The step of forming the second metaatom involves forming the second metaatom by film deposition using a second mask. A method for manufacturing an optical element according to any one of methods 1 to 3. (Method 5) The step of forming the second metaatom involves forming the second mask by photolithography or imprinting. A method for manufacturing an optical element according to method 4, characterized by the features described above. (Method 6) The step of forming the first metaatom is a step of forming the first metaatom on the first substrate by processing the first substrate, The step of forming the aforementioned second metaatom is a step of forming the aforementioned second metaatom on the aforementioned second substrate by processing the aforementioned second substrate, A step of joining a first substrate and a second substrate such that a metasurface containing the first metaatom and the second metaatom is interposed between the first substrate and the second substrate. A method for manufacturing an optical element according to any one of methods 1 to 5, characterized by having the following: (Method 7) The method for manufacturing an optical element according to method 26, characterized in that the step of forming the second metaatom involves processing the second substrate by etching. (Method 8) The method for manufacturing an optical element according to method 7, characterized in that the step of forming the second metaatom involves processing the second substrate by etching using a mask formed by photolithography or imprinting. (Method 9) A method for manufacturing an optical element according to any one of methods 6 to 8, characterized in that, after the step of forming the first metaatom and the second metaatom, and before the step of joining the first substrate and the second substrate, a third metaatom is formed using a film-forming method on the same side of the first substrate as the first metaatom or on the same side of the second substrate as the second metaatom. (Method 10) A method for manufacturing an optical element according to any one of methods 6 to 9, characterized in that the step of joining the first substrate and the second substrate is to join the first substrate and the second substrate by a surface activation bonding method. (Method 11) A method for manufacturing an optical element, characterized in that it includes the step of forming a third meta-atom having a different refractive index from the first meta-atom and the second meta-atom on the surface on which the first meta-atom and the second meta-atom are formed. (Method 12) The step of forming the second metaatom involves forming the second metaatom by film deposition. The step of forming the third metaatom involves forming the third metaatom by film deposition. A method for manufacturing an optical element according to method 11, characterized by the features described above. (Method 13) The process includes polishing the substrate from the side opposite to the surface on which the first metaatom, second metaatom, and third metaatom are formed, thereby removing the substrate. A method for manufacturing an optical element according to method 11 or 12, characterized by the features described above. [Explanation of Symbols]

[0156] 2: Base material 3: Temporary base material 21: First substrate 22: Second base material 100: Optical element 300: Metasurface 310: The first meta-atom group 310a: First metaatom 320: The second meta-atom group 320a: Second meta-atom 330: The first metaatom group 330a: First metaatom 340: The second meta-atom group 340a: Second meta-atom 350: Metaatom 370: The third meta-atom group 370a: The third meta-atom

Claims

1. Substrate and Having a metasurface formed on the aforementioned substrate, The metasurface has a first metaatom capable of transmitting light, and a second metaatom capable of transmitting light and having a different refractive index from the first metaatom. The material composition of the first metaatom is the same as the material composition of the substrate. An optical element characterized by the following features.

2. The first metaatom is formed continuously with the substrate. The optical element according to feature 1.

3. The first metaatom is obtained by processing the substrate. The optical element according to feature 2.

4. The metasurface has a medium capable of transmitting the light, The medium has a different refractive index from the first metaatom and the second metaatom. The optical element according to feature 1.

5. The metasurface includes voids, The medium is the air filling the void. The optical element according to feature 4.

6. The first metaatom and the second metaatom each have a pillar structure. The optical element according to feature 1.

7. The substrate contains at least one oxide of La, Nb, W, Ti, K, Na, and Li. The optical element according to feature 1.

8. The substrate is a resin containing a cycloolefin or a resin containing a polyolefin. The optical element according to feature 1.

9. The substrate has a transmittance of 60% or more to the light with a wavelength of 400 nm to 800 nm. The optical element according to feature 1.

10. The aforementioned substrates are polycrystalline silicon, Ge, ZnSe, SeS, ZnS, and CaF ２ , including at least one of sapphire and chalcogenide glass The optical element according to feature 1.

11. The substrate contains at least one fluoride of Al, Mg, Ca, Ba, and Sr. The optical element according to feature 1.

12. The substrate comprises one of the following oxides, nitrides, or oxynitrides: Si, Al, Ti, Hf, Ta, and Nb. The optical element according to feature 1.

13. The aforementioned substrate is The first substrate and A second substrate is positioned opposite the first substrate, It has, The metasurface is formed between the first substrate and the second substrate, The first metaatom is formed on the surface of the first substrate facing the second substrate, The first metaatom is formed on the surface of the second substrate facing the first substrate, The first metaatom has the same material composition as the first substrate. The optical element according to claim 1, characterized in that the second meta-atom has the same material composition as the second substrate.

14. The optical element according to claim 13, characterized in that the first metaatom is formed continuously with the first substrate.

15. The optical element according to claim 13, characterized in that the second metaatom is formed continuously with the second substrate.

16. The metasurface has a third metaatom formed on the surface of the first substrate or the second substrate, The optical element according to claim 13, characterized in that the third meta-atom has a different material composition from the first substrate and the second substrate.

17. The metasurface includes a low refractive index medium capable of propagating the light, The optical element according to claim 13, characterized in that the low refractive index medium has a lower refractive index with respect to light than the first meta-atom and the second meta-atom.

18. The optical element according to claim 13, characterized in that at least one of the first substrate and the second substrate has a functional film on the surface opposite to the metasurface.

19. An optical element having a metasurface, The metasurface has a solid medium capable of transmitting light, The medium comprises at least a first metaatom, a second metaatom, and a third metaatom. The first metaatom, the second metaatom, and the third metaatom have different refractive indices. The first metaatom is a silicon oxide or metal oxide, or a plastic resin. An optical element characterized by the following features.

20. The first metaatom is a resin containing a cycloolefin or a polyolefin, comprising at least one oxide of Si, La, Nb, W, Ti, K, Na, and Li. The optical element according to feature 19.

21. A step of forming a first metaatom on the surface of a substrate by processing the surface of the substrate, A step of forming a second metaatom having a different refractive index from the first metaatom on the substrate on which the first metaatom is formed. A method for manufacturing an optical element, characterized by having the following features.

22. The first step in forming the metaatom involves processing the surface by etching. A method for manufacturing an optical element according to claim 21.

23. The step of forming the first metaatom involves forming a first mask by photolithography or imprinting, and processing the surface by etching using the first mask. A method for manufacturing an optical element according to claim 22, characterized in that it is a method for manufacturing an optical element.

24. The step of forming the second metaatom involves forming the second metaatom by film deposition using a second mask. A method for manufacturing an optical element according to claim 21.

25. The step of forming the second metaatom involves forming the second mask by photolithography or imprinting. A method for manufacturing an optical element according to the feature described in 24.

26. The step of forming the first metaatom is a step of forming the first metaatom on the first substrate by processing the first substrate, The step of forming the second metaatom is a step of forming the second metaatom on the second substrate by processing the second substrate, A step of joining the first substrate and the second substrate such that a metasurface containing the first metaatom and the second metaatom is interposed between the first substrate and the second substrate. A method for manufacturing an optical element according to any one of claims 21 to 25, characterized by having the following features.

27. The method for manufacturing an optical element according to claim 26, characterized in that the step of forming the second metaatom involves processing the second substrate by etching.

28. The method for manufacturing an optical element according to claim 27, characterized in that the step of forming the second metaatom involves processing the second substrate by etching using a mask formed by photolithography or imprinting.

29. The method for manufacturing an optical element according to claim 26, characterized in that, after the step of forming the first metaatom and the second metaatom, and before the step of joining the first substrate and the second substrate, a third metaatom is formed using a film-forming method on the same side of the first substrate as the first metaatom or on the same side of the second substrate as the second metaatom.

30. The method for manufacturing an optical element according to claim 26, characterized in that the step of joining the first substrate and the second substrate is to join the first substrate and the second substrate by a surface activation bonding method.

31. A method for manufacturing an optical element according to any one of claims 21 to 25, characterized by comprising the step of forming a third meta-atom having a refractive index different from that of the first meta-atom and the second meta-atom on the surface on which the first meta-atom and the second meta-atom are formed.

32. The step of forming the second metaatom involves forming the second metaatom by film deposition. The step of forming the third metaatom involves forming the third metaatom by film deposition. The method for manufacturing an optical element according to claim 31.

33. The process includes polishing the substrate from the side opposite to the surface on which the first metaatom, second metaatom, and third metaatom are formed, thereby removing the substrate. The method for manufacturing an optical element according to claim 31.

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