Metasurface and method of manufacturing the same

Abstract

The metasurface according to one aspect of the present application is a metasurface including a substrate and a plurality of nanostructures formed on at least one surface of the substrate, the nanostructures can include a structure portion composed of a polymer and a high refractive substance layer formed on at least a portion of a surface of the structure portion, the high refractive substance layer can have a refractive index of 2.0 or more for light having a wavelength of 400 nm.

Description

Technical Field

[0001] This invention relates to a metasurface and a method for manufacturing the same. Background Technology

[0002] Metasurfaces are generally defined as surfaces with patterns at or below the wavelength of light. By configuring these patterns, metasurfaces can modulate the phase, intensity, and direction of light, thereby achieving a variety of electromagnetic or wave effects. Therefore, while not limited to these applications, they can be used in lenses, holograms, antennas, other optical devices, audio equipment, and vibration control.

[0003] Therefore, since metamaterials were proposed as a higher-level concept in the late 20th century, scientists have devoted a great deal of research to revealing the properties of metamaterials or metasurfaces and exploring their applications.

[0004] However, metasurfaces require the arrangement of multiple micrometer-sized or smaller nanostructures on the surface according to a designed geometry, which presents numerous manufacturing challenges. For example, to form microstructures, methods such as electron beam lithography can be used. This involves irradiating the surface with an electron beam and removing surrounding areas one by one to reveal the shape of the nanostructure. Consequently, the process is very slow, and the achievable area is extremely limited, making it uneconomical to manufacture.

[0005] As a solution to this problem, a method for forming nanostructures by imprinting is proposed. Imprinting is a method of filling a polymer material (e.g., resin) into a reusable mold and transferring it onto a substrate. It has the advantage of being able to fabricate metasurfaces at high process speeds.

[0006] However, due to the characteristics of the process, polymer materials such as resins are required as materials for nanostructures. However, resins have a low refractive index to light, resulting in very low efficiency of metasurfaces. Summary of the Invention

[0007] (a) Technical problems to be solved According to one aspect of the present invention, a highly efficient metasurface and a method for manufacturing the same can be provided.

[0008] Furthermore, according to another aspect of the present invention, a metasurface and a method thereof can be provided that can prevent the reduction of refractive index and improve efficiency even when nanostructures are manufactured by means of imprinting.

[0009] The technical problems addressed by this invention are not limited to those described above. Those skilled in the art will readily understand the additional technical problems addressed by this invention from the contents of this specification.

[0010] (II) Technical Solution According to one aspect of the present invention, a metasurface may be a metasurface comprising a substrate and a plurality of nanostructures formed on at least one side of the substrate, wherein the nanostructures may include a structural portion made of a polymer and a high-refractive-index material layer formed on at least a portion of the surface of the structural portion, wherein the high-refractive-index material layer may have a refractive index of 2.0 or higher for light with a wavelength of 400 nm.

[0011] At this time, the refractive index of the high-refractive material layer for light with a wavelength of 400nm can be below 3.0.

[0012] Furthermore, the thickness of the high-refractive material layer can be 5-30 nm.

[0013] Furthermore, the high-refractive-index material layer may contain ZrO2.

[0014] Furthermore, the high-refractive-index material layer can be coated onto the surface of the structure using atomic layer deposition (ALD) or chemical vapor deposition (CVD).

[0015] Furthermore, the structural portion of the nanostructure can be formed by imprinting.

[0016] Furthermore, the sum of the length, width, and height of the structural part can be 500-1500nm. In this case, the length of the structural part can be 180-300nm, the width of the structural part can be 30-100nm, and the height of the structural part can be 450-700nm.

[0017] In the above metasurface, the average distance (period) between the center of a structural part and the center of the adjacent structural part can be 200-400 nm.

[0018] A method for manufacturing a metasurface according to another aspect of the present invention may include the following steps: preparing a substrate; forming a plurality of structural portions made of a polymer on the substrate by an imprinting method; and forming a high-refractive-index material layer on the surface of at least a portion of the plurality of structural portions, wherein the high-refractive-index material layer may have a refractive index of 2.0 or higher for light with a wavelength of 400 nm.

[0019] At this time, the high-refractive-index material layer can be formed by coating the surface of the structure using atomic layer deposition (ALD) or chemical vapor deposition (CVD).

[0020] Furthermore, when coating the surface of the structure with a high-refractive-index material layer by the atomic layer deposition (ALD) method, the time for injecting the precursor material into the vacuum chamber in each cycle can be 2-4 seconds, and the time for plasma treatment can be 20-40 seconds.

[0021] Furthermore, the thickness of the high-refractive-index material layer can be 10-20 nm.

[0022] Furthermore, the sum of the length, width, and height of the structural portions formed in the step of forming the plurality of structural portions can be 500-1500 nm.

[0023] (III) Beneficial Effects According to the present invention, by including a structural portion and a layer of highly refractive material formed on at least a portion of the surface of the structural portion, the effective refractive index of the nanostructure can be adjusted, resulting in an effect that can improve the efficiency of the metasurface. Attached Figure Description

[0024] Figure 1 This is an exemplary shape of metasurface 1 according to one embodiment of the present invention.

[0025] Figure 2 This is a graph showing the refractive index (n) and absorption coefficient (k) of a ZrO2 layer provided in one embodiment of the invention, according to wavelength.

[0026] Figure 3 This is a measurement diagram of the band gap of a ZrO2 layer provided in one embodiment of the present invention.

[0027] Figure 4 This is a process flow diagram illustrating an exemplary method for manufacturing a metasurface according to an embodiment of the present invention by imprinting.

[0028] Figure 5 It is a device used to measure the focal point formation characteristics of metasurfaces. In the figure, LP represents a linear polarizer, QWP represents a quarter wave plate, ML represents a metalens, and OL represents an objective lens.

[0029] Figure 6 It is Figure 5 The apparatus measures the properties of the metasurface according to an embodiment of the present invention.

[0030] Figure 7 It is a device used to measure the resolution of metasurfaces. In the figure, LP represents a linear polarizer, QWP represents a quarter wave plate, OL represents an objective lens, RT represents a resolution target (USAF 1951 target), and ML represents a metalens (metasurface).

[0031] Figure 8 It is shown that... Figure 7The image morphology (a) of the device for measuring resolution and the result of measuring resolution using the image morphology (b).

[0032] Figure 9 This is a graph showing the wavelength conversion efficiency of a superlens obtained according to an embodiment of the present invention.

[0033] Figure 10 Figure (a) shows the conversion efficiency as a function of the length and width of the structure, and Figure (b) shows the conversion efficiency as a function of the thickness of the high-refractive-index material layer.

[0034] Figure 11 This is a graph comparing the refractive index of a high-refractive-index material layer coated on a structural part using atomic layer deposition (ALD) with the injection time of the precursor material and the plasma treatment time. Best practice

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the concept of the present invention is not limited to the illustrated embodiments.

[0036] For example, those skilled in the art who understand the spirit of the present invention can easily propose other embodiments within the scope of the spirit of the present invention by adding, changing or deleting constituent elements, which can also be regarded as included within the scope of the spirit of the present invention.

[0037] Furthermore, throughout this specification, unless otherwise stated specifically to the contrary, "comprising" or "including" a constituent element means that it may further include other constituent elements, not exclude other constituent elements. It should also be noted that the distinctions made in this specification as "upper and lower," "front and back," or "left and right" mean that even a shape at the top can be realized as a shape at the bottom, unless it violates natural phenomena or is clearly impossible to achieve, and are not based on absolute physical positional relationships. Furthermore, the directions illustrated in this specification are for illustrative purposes and are not limited to the directions illustrated in the accompanying drawings.

[0038] Furthermore, unless otherwise specified in this specification, the refractive index refers to the refractive index for light with a wavelength of 400 nm.

[0039] Figure 1 An exemplary shape of a metasurface 1 according to one embodiment of the present invention is shown. As shown, the metasurface 1 of the present invention includes a substrate 10 and a plurality of nanostructures 20 formed on at least one side of the substrate 10. The nanostructures 20 include structural portions 30 made of polymer and a high-refractive-index material layer 40 formed on at least a portion of the surface of the structural portions 30.

[0040] That is, the object of the present invention is to improve the effective refractive index of the nanostructure 20 by forming a nanostructure 20 by means of a structural portion 30 composed of a polymer with a relatively low refractive index and a layer 40 of a material with a high refractive index formed on at least a portion of the surface of the structural portion. The layer of the material with a high refractive index (high refractive index material layer) can be formed on the entire surface of the structural portion. While not limited thereto, the polymer included in the structural portion 20 can be advantageously formed on the surface of a substrate by imprinting, thus having the advantage of being able to economically manufacture the nanostructure 20. The polymers that can be used in the present invention are not limited in type, as long as they are polymers that can be utilized by imprinting. However, as non-limiting examples of polymers that can be used in the present invention, photocurable polymers or thermocurable polymers can be listed, and in one embodiment of the present invention, Minuta Technology's MINS-311RM can be used. However, while not limited thereto, the refractive index of the polymer is typically in the 1.4-1.5 range, which is not high, and therefore, from the perspective of the efficiency of metasurfaces that are expected to obtain electromagnetic or optical effects by refracting electromagnetic waves such as light, the polymer is not advantageous. To address this problem, as described above, the present invention forms a high-refractive-index material layer on the surface of a structure substantially composed of a polymer.

[0041] According to one embodiment of the present invention, the refractive index of the high-refractive-index material layer 40 for light with a wavelength of 400 nm can be 2.0 or higher. By forming the high-refractive-index material layer 40 on the surface of the structural portion 30, the effective refractive index of the nanostructure 20 for light with a wavelength of 400 nm can be adjusted to 1.9 or higher. According to another embodiment of the present invention, the refractive index of the refractive index material layer 40 for light with a wavelength of 400 nm can be 2.0 or higher, more preferably 2.1 or higher. The higher the refractive index of the refractive index material layer 40, the higher the effective refractive index of the nanostructure 20 can be; therefore, there is no particular upper limit to the refractive index of the refractive index material layer 40. However, considering the type of material formed on the surface of the structural portion 30, in one embodiment of the present invention, the upper limit of the refractive index of the high-refractive-index material layer 40 for light with a wavelength of 400 nm can be set to 3.0, and in another embodiment, the upper limit of the refractive index of the high-refractive-index material layer 40 can be set to 2.9.

[0042] Furthermore, to achieve a sufficient increase in refractive index, in one embodiment of the invention, the thickness of the high-refractive-index material layer 40 can be 5 nm or more. In another embodiment of the invention, the thickness of the high-refractive-index material layer 40 can also be limited to 10 nm or more. However, the thickness of the high-refractive-index material layer interacts with the shape of the nanostructure and can also affect the efficiency of the metasurface. When the thickness is too thick, the efficiency of the metasurface may decrease. Therefore, in one embodiment of the invention, the upper limit of the thickness can be 30 nm, in another embodiment it can be 25 nm, and in yet another embodiment it can be 20 nm. In one embodiment of the invention, the thickness of the high-refractive-index material layer 40 can refer to the average thickness of the portion on which the material layer is formed.

[0043] There are no restrictions on the type of material constituting the high-refractive-index layer 40, provided the refractive index condition is met. However, considering that a metasurface 1 operating in the ultraviolet region can be provided in one embodiment of the present invention, the material constituting the high-refractive-index layer 40 can be ZrO2, HfO2, Nb2O5, silicon nitride, etc., and ZrO2 can be used in one embodiment of the present invention. For example, as... Figure 2 As shown, the ZrO2 provided in the embodiments of the present invention not only satisfies the refractive index (n, solid line) condition of the present invention, but also has a low absorption rate (k, dashed line) in the ultraviolet region with wavelengths below 400 nm. Furthermore, as... Figure 3 It can be confirmed that the band gap is as high as 6.195 eV, and it has the advantage of being transparent in the ultraviolet region. As a method for forming the high-refractive-index material layer, atomic layer deposition (ALD) or chemical vapor deposition (CVD) can be used. ZrO2 can be formed on the surface of the structure 30 by atomic layer deposition (ALD). However, when the ZrO2 layer is typically formed on the surface of the structure 30, which is a polymer material, as described above, it exhibits a low refractive index of 1.8 or less, so the overall refractive index of the nanostructure 20 may be insufficient. However, the inventors of this invention have discovered that by forming a high-refractive-index material layer with a refractive index of 2.0 or higher on the surface of the structure 30, a nanostructure with a high refractive index can be formed, thus completing this invention.

[0044] In one embodiment of the present invention, the structural portion 30 of the nanostructure 20 can be formed by imprinting. That is, nanostructures can conventionally be formed by photolithography such as electron beam lithography, but in this case, due to various limitations as described above, it is not economical to obtain a metasurface. Therefore, in the present invention, the structural portion 30 of the nanostructure 20 is formed on the surface of the substrate 10 by imprinting. When the structural portion 30 is formed by imprinting, the polymer material is necessarily included in the structural portion 30, and in this case, the efficiency of the metasurface 1 is reduced due to the low refractive index. However, in the case of the present invention, the nanostructure 20 is obtained by forming the high-refractive-index material layer 40 on at least a portion of the surface of the structural portion 30, thus improving the effective refractive index of the nanostructure 20.

[0045] Furthermore, in one embodiment of the invention, the sum of the length, width, and height of the structural portion 30 can be 500-1500 nm. The size of the nanostructure 20 can be determined based on the constituent material and the wavelength of the light being processed. Therefore, considering the properties of the structural portion 30 and the high-refractive-index material layer 40 used in the present invention, and the aspect of processing ultraviolet light with wavelengths below 400 nm, the sum of the length, width, and height of the structural portion can be set within the aforementioned range. In another embodiment of the invention, the sum of the length, width, and height can also be set to 600-1400 nm.

[0046] More specifically, the length of the structural portion 30 can be 180-300 nm, preferably 210-280 nm. Furthermore, the width of the structural portion 30 can be 30-100 nm, preferably 50-85 nm. The height of the structural portion 30 can be 450-700 nm, preferably 470-620 nm. In this invention, the length and width of the structural portion 30 can refer to the length and width of the lowermost part, i.e., the part in contact with the substrate. The structural portion 30 often has a rectangular shape, but even if this is not the case, after drawing a rectangle 30 with the smallest area that can accommodate the lower end of the structural portion 30, the longer side of the rectangle can be considered the length, and the shorter side the width. When the rectangle with the smallest area that can accommodate the lower end can have multiple shapes, the rectangle with the largest difference in length and width is selected, and the length and width of this rectangle are used as the length and width of the structural portion 30.

[0047] Furthermore, according to the inventors' research, the wavelength-dependent resonance phenomenon of the metasurface 1 may be affected by the period of the nanostructure 20. In the case of the nanostructure 20 according to one embodiment of the invention, the period can be 200-400 nm, and according to another embodiment, the period can be 230-450 nm. In this invention, the period can refer to the average distance between the center of a structural portion and the center of a structural portion adjacent to the structural portion. That is, as... Figure 1 As shown, the distance P between the center of one structural part and the center of another adjacent structural part can be called the period. However, a structural part may have multiple adjacent structural parts, so in this case, the average distance to adjacent structural parts can be called the period. For example, when structural parts are arranged in a lattice pattern, there are a total of 4 adjacent structural parts in both the horizontal and vertical directions, and the average distance between them can be defined as the period. When the average distance between each structural part and its adjacent structural parts is different, the overall average of these average distances can be defined as the period.

[0048] Depending on the arrangement of the structural parts 30, the metasurface 1 can be used for a variety of purposes. The effects of the arrangement are well known in the technical field to which this invention pertains. Therefore, those skilled in the art can change the arrangement of the structural parts 30 of the metasurface 1 according to the required application. Thus, the arrangement of the structural parts is not specifically described in this specification.

[0049] In one embodiment of the present invention, the substrate 10 is not particularly limited as long as it is commonly used in the technical field to which the present invention pertains. Depending on the application of the metasurface 1, different types of substrates may be used. In an exemplary embodiment, a substrate made of glass, plastic, or a flexible film may be used as the substrate. In one embodiment of the present invention, a substrate with low absorption in the ultraviolet (UV) region may be used as the substrate; specifically, a substrate with a bandgap energy of 8 eV or higher may be used. In one embodiment of the present invention, the thickness of the substrate may be 0.1 mm or more. The upper limit of the thickness is not particularly limited, but for practical purposes, it may be set to 10 cm or less, 5 cm or less, 3 cm or less, 1 cm or less, or 5 mm or less.

[0050] The following describes one method for manufacturing the metasurface of the present invention. However, the metasurface of the present invention does not necessarily need to be manufactured solely by the manufacturing method described later; it can also be manufactured using various techniques available in the technical field to which this invention pertains, with reference to the description herein.

[0051] The method for manufacturing the metasurface of the present invention may include the following steps: preparing a substrate; forming a plurality of structural portions on the substrate by imprinting; and forming a high-refractive-index material layer on the surface of at least a portion of the plurality of structural portions.

[0052] As the substrate, a substrate meeting the above conditions can be used. Multiple structural portions can be formed on the substrate by an imprinting method. The imprinting method is a well-known method in the technical field to which this invention pertains, and can be implemented by those skilled in the art without particular difficulty, even without specific description. However, for the purpose of further understanding, refer to... Figure 4 A brief explanation is provided. The photos attached next to each step in the diagram show the result of that step.

[0053] First, although not necessarily limited to this, a transparent plate coated with Cr or Al is prepared. The Cr or Al is used to block light in subsequent photolithography processes; other materials can be used as long as they achieve the same effect. An electron beam is irradiated onto the transparent plate (a) to obtain a photomask with the desired pattern (b). Considering the characteristics of subsequent photolithography processes, the size of the photomask can be larger than the size of the final pattern obtained. In one embodiment of the invention, a photomask approximately 3 to 5 times larger than the length can be fabricated. Then, for example, after coating a photoresist material onto a substrate made of silicon wafer, unwanted portions are etched using photolithography (c) using the photomask to obtain a master mold (d).

[0054] Subsequently, a replica mold (e) can be manufactured using the master mold. The replica mold has a pattern in the opposite direction to the pattern formed on the master mold; in other words, the master mold and the replica mold are complementary. That is, by bonding the material of the replica mold to the master mold and then separating it, a replica mold with a pattern opposite to that of the master mold can be obtained. Then, a curable polymer material (f), which serves as the raw material for the structural portion 30 of the nanostructure 20 of the present invention, is filled into the replica mold, and the polymer material is transferred onto a substrate (g). The replica mold (h) is then removed, thereby forming the structural portion on the substrate. During the process of transferring the polymer material onto the substrate 10 (g), the polymer material can be cured by irradiating it with light such as ultraviolet light, thereby forming the structural portion 30. However, the above-described imprinting process is an example; any imprinting technique used in the technical field to which this invention pertains can be applied to the present invention without obvious reasons why it is not applicable. In particular, the dimensions illustrated in the figures are dimensions used in one embodiment of the present invention, and it is self-evident that the present invention can be applied to metasurfaces of various sizes. The entire process does not necessarily have to be carried out by manufacturing a metasurface (a substrate with structural parts formed on its surface) from a master mold; it can also be done as follows: Figure 4The example illustrates a mass production method in which multiple metasurfaces are formed simultaneously from multiple master molds on a large-area substrate.

[0055] Next, a process (i) is performed to form a high-refractive-index material layer 40 on the surface of at least a portion of the structure. The high-refractive-index material layer 40 can be formed by coating the surface of the structure using atomic layer deposition (ALD) or chemical vapor deposition (CVD). While not limited to this method, ALD can include placing a substrate 10 on which the structure 30 is formed into a chamber, applying a vacuum, injecting a precursor material (e.g., TEMAZr) into the chamber through a nozzle, and then applying O2 plasma into the chamber to cause the metallic component (e.g., Zr) in the precursor material to react with oxygen to form an oxide. In one embodiment of the invention, the vacuum throughout the atomic layer deposition process can be adjusted to 10. -1 -5 Torr range. Furthermore, in one embodiment of the invention, a step of purging with Ar gas after injecting the precursor material may be included.

[0056] However, conventional plasma treatment is performed at temperatures above 200°C, which can cause the polymer structure 30 to collapse due to heat. To prevent this collapse, the plasma treatment temperature needs to be lowered to below 150°C, preferably below 100°C. However, in this case, a large number of vacancy forms within the high-refractive-index material layer 40 formed by atomic layer deposition, resulting in a reduction in refractive index. Therefore, it has been generally considered difficult to form a high-refractive-index material layer on a polymer using atomic layer deposition. However, the inventors of this invention have discovered that by lowering the plasma temperature while adjusting the precursor material injection time, a high-refractive-index material layer 40 with a refractive index of 2.0 or higher can be formed on the structure 30 without damaging it. Specifically, in one embodiment of this invention, when forming the high-refractive-index material layer 40 by atomic layer deposition, the time for injecting the precursor material into the vacuum chamber is set to approximately 2-4 seconds, and the plasma treatment time is set to 20-40 seconds. When the injection time of the precursor material is too short, a sufficient refractive index cannot be obtained; when the injection time is too long, not only does the effect no longer increase, but it also unnecessarily consumes expensive precursor material. The amount of precursor material injected is not greatly affected by the chamber size, as long as it can be completely coated onto the substrate; the injection time is crucial. However, according to one embodiment of the present invention, the precursor material can be injected at a rate of [missing information - likely referring to a specific quantity per chamber unit volume (cm²)]. 3 The flow rate (standard milliliters per minute (SCCM)) is 0.1-0.4 SCCM / cm. 3 The ratio is added to the supplied Ar gas, thereby supplying it into the chamber.

[0057] Furthermore, when the plasma treatment time is short, the thickness of the formed high-refractive-index layer is insufficient; when the plasma treatment time is long, the high-refractive-index layer may exceed the appropriate thickness range. A more preferred plasma treatment time is 25-35 seconds. In one embodiment of the invention, the plasma treatment temperature can be below 150°C, preferably below 100°C, and more preferably 80-100°C.

[0058] The process of injecting precursor material into plasma treatment as described above can be considered as one cycle. A thin atomic layer of less than 10 angstroms (Å) can be formed through one cycle of coating process. By repeating the cycle as described above several times, the thickness of the formed high refractive material layer 40 can be adjusted to the desired level.

[0059] Details regarding the material, shape, and configuration of structural components, as well as the material, thickness, and refractive index of the high-refractive material layer, which overlap with the previously described parts, are omitted here. Detailed Implementation

[0060] The present invention will now be described in detail through specific embodiments. However, it should be noted that the following embodiments are merely illustrative and specific examples of the invention and are not intended to limit the scope of the invention. The scope of the invention is determined by the contents of the claims and the contents reasonably deduced therefrom.

[0061] (Example) Example 1 according to Figure 4 The steps shown are used to imprint and form the structure 30. A photomask pattern corresponding to the length, width, and period of the structure is formed on a circular transparent plate with a diameter of 4 cm, thereby fabricating a photomask. The photomask pattern is four times the size of the pattern on the target metasurface 1, and a master mold of 1 / 4 the size of the photomask pattern can be obtained by electron beam lithography. Therefore, the master mold is a circle with a diameter of 1 cm, and a replication mold can be manufactured using the master mold. By setting multiple master molds on a silicon wafer with a diameter of 8 inches (approximately 20 cm), multiple corresponding replication molds can also be set, thus enabling mass production. After filling the replication mold with a UV-curable polymer material (MINS-311RM, a product of Minuta Technology), pressure is applied while curing with UV light to obtain the structure 30. The structure 30 is arranged so that the metasurface 1 can function as a superlens.

[0062] During the imprinting process, a SiO2 substrate with a diameter of 1 cm and a thickness of 0.5 mm (500 μm) was used as the substrate 10 for forming the structural portion. The structural portion 30 was made to have a shape with a length of 240 nm, a width of 60 nm, and a height of 550 nm, and the structural portion 30 was arranged in a lattice pattern with the same period of 280 nm in both the transverse and longitudinal directions.

[0063] Next, the substrate is installed in an internal volume of 30cm³. 30cm In a 1 cm cavity, ZrO2, serving as a high-refractive-index material layer 40, was coated onto the entire surface of the substrate 10 on which the structure 30 was formed using atomic layer deposition. Specifically, TEMAZr was used as a precursor material. The precursor material was added to argon gas supplied at a flow rate of 200 SCCM and injected into the cavity for 3 seconds, followed by multiple cycles of O2 plasma treatment for 30 seconds. The pressure within the cavity was set to 1 Torr during the period from precursor injection to plasma treatment. It was confirmed that an atomic layer of approximately 2.8 Å of high-refractive-index material was formed in one cycle, and the cycle was repeated until the desired thickness was obtained. The resulting ZrO2 coating exhibited a uniform thickness with no significant deviations, with an average thickness of 15 nm.

[0064] Using the obtained superlens Figure 5 The device was set up in the form shown, and a performance measurement experiment was conducted. The results are as follows: Figure 6 As shown, it can be confirmed that a focal point is formed at the target focal length, and an ideal Airy disk is formed.

[0065] In addition, with Figure 7 The device shown is configured to... Figure 8 Image of the USAF 1951 target shown in (a) was performed, and the imaging resolution was measured. Figure 8 (b) confirms that a high resolution was obtained. Figure 8 The figures in (b) correspond to respectively Figure 8 The part indicated by red and blue lines in (a).

[0066] The wavelength-dependent conversion efficiency of the superlens obtained through this embodiment was confirmed, and the results are shown below. Figure 9 As shown in the figure, it exhibits a high conversion efficiency of over 60% in the commonly used 300-400nm wavelength range. Conversion efficiency is determined by the proportion of incident right-hand circularly polarized light (RCP) that is converted to left-hand circularly polarized light (LCP) while its phase is adjusted.

[0067] Example 2 To determine the optimal thickness of the high-refractive-index material layer, in addition to fixing the wavelength of light at 325 nm and varying the length and width of the structural portion 30, a metasurface was fabricated in the same manner as in Example 1. The conversion efficiency was then confirmed, and the results are presented below. Figure 10 In (a), it can be confirmed from the figure that the conversion efficiency decreases sharply when the width of the structure 30 is greater than 100 nm. Although not shown in the figure, it can be confirmed that good conversion efficiency is observed up to 30 nm in width of the structure 30. Furthermore, it can also be seen from the figure that the conversion efficiency is high in the region where the length of the structure 30 is 180 nm or more. Although not shown in the figure, high conversion efficiency can be obtained up to 300 nm in length of the structure 30.

[0068] Example 3 A structure identical to the structure 30 obtained in Example 1 was formed, but the wavelength was fixed at 325 nm, the thickness of the ZrO2 layer 40 (a high-refractive-index material) was varied, and the change in conversion efficiency was observed. The thickness can be adjusted by varying the number of cycles in the above process. The results are shown in... Figure 10 In (b), it can be confirmed from the figure that a high conversion efficiency of over 60% is achieved in the region with a thickness of 5 nm or more. The conversion efficiency increases with increasing thickness, but decreases when the value is greater than 15 nm, and becomes insufficient when the thickness is greater than approximately 30 nm.

[0069] Example 4 (Comparison between Comparative Example and Example 1) The nanostructures were fabricated in the same manner as in Example 1, except that the precursor material injection time was limited to 0.5 seconds and the plasma treatment time was limited to 10 seconds. The refractive index of the fabricated nanostructures according to wavelength is shown in [insert graph here]. Figure 11 In the middle. For example Figure 2 As shown, the refractive index of the nanostructure manufactured according to Example 1 exhibits a high value of 2.0 or higher. On the other hand, Figure 11 In the comparative example shown, the refractive index value is less than 1.8, which is insufficient to form a metasurface.

[0070] Therefore, the advantageous effects of the present invention can be confirmed.

Claims

1. A metasurface comprising a substrate and a plurality of nanostructures formed on at least one side of the substrate, The nanostructure includes a structural portion made of a polymer and a layer of highly refractive material formed on at least a portion of the surface of the structural portion. The high-refractive-index material layer has a refractive index of 2.0 or higher for light with a wavelength of 400 nm.

2. The metasurface according to claim 1, wherein, The high-refractive-index material layer has a refractive index of less than 3.0 for light with a wavelength of 400 nm.

3. The metasurface according to claim 1, wherein, The thickness of the high-refractive material layer is 5-30 nm.

4. The metasurface according to claim 1, wherein, The high-refractive-index material layer contains ZrO2.

5. The metasurface according to claim 1, wherein, The high-refractive-index material layer is formed by coating the surface of the structure using atomic layer deposition (ALD) or chemical vapor deposition (CVD).

6. The metasurface according to claim 1, wherein, The structural parts of the nanostructure are formed by imprinting.

7. The metasurface according to claim 1, wherein, The sum of the length, width, and height of the structure is 500-1500 nm.

8. The metasurface according to claim 7, wherein, The length of the structure is 180-300 nm.

9. The metasurface according to claim 7, wherein, The width of the structure is 30-100 nm.

10. The metasurface according to claim 7, wherein, The height of the structure is 450-700 nm.

11. The metasurface according to any one of claims 7 to 10, wherein, The average distance, i.e. the period, between the center of a structural part and the center of an adjacent structural part is 200-400 nm.

12. A method for manufacturing a metasurface, comprising the following steps: Prepare the substrate; Multiple structural portions made of polymer are formed on the substrate by an imprinting method; as well as A high-refractive-index material layer is formed on the surface of at least a portion of the plurality of structural parts. The high-refractive-index material layer has a refractive index of 2.0 or higher for light with a wavelength of 400 nm.

13. The method for manufacturing a metasurface according to claim 12, wherein, The high-refractive-index material layer is formed by coating the surface of the structure using atomic layer deposition (ALD) or chemical vapor deposition (CVD).

14. The method for manufacturing a metasurface according to claim 13, wherein, When coating the surface of the structure with a high-refractive-index material layer by atomic layer deposition (ALD), the time for injecting the precursor material into the vacuum chamber in each cycle is 2-4 seconds, and the time for plasma treatment is 20-40 seconds.

15. The method for manufacturing a metasurface according to claim 12, wherein, The thickness of the high-refractive material layer is 10-20 nm.

16. The method for manufacturing a metasurface according to claim 12, wherein, The sum of the length, width, and height of the structural parts formed in the step of forming the plurality of structural parts is 500-1500 nm.

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