Metasurface and manufacturing method for same

Abstract

A metasurface according to one aspect of the present invention is a metasurface comprising: a substrate; and a plurality of nanostructures formed on at least one surface of the substrate, wherein each of the nanostructures comprises: a structure portion made of a polymer; and a high-refractive material layer formed on a surface of at least a part of the structure portion, and the high-refractive material layer has a refractive index of 2.0 or greater with respect to light having a wavelength of 400 nm.

Description

Metasurface and its manufacturing method

[0001] The present invention relates to a metasurface and a method for manufacturing the same.

[0002] A metasurface generally refers to a surface patterned at or smaller than the wavelength of light. Metasurfaces can produce various electromagnetic or wave-dynamic effects by modulating the phase, intensity, and direction of light depending on the pattern arrangement. This allows them to be used in applications such as, but not limited to, lenses, holograms, antennas, other optical devices, and acoustic and vibration control.

[0003] Therefore, since metamaterials were proposed as a higher concept in the late 20th century, scientists have devoted much research to elucidating the properties of metamaterials or metasurfaces and developing their applications.

[0004] However, metasurfaces are difficult to manufacture because they require numerous nanostructures, micrometer-scale or smaller, to be arranged on the surface according to the designed geometry. For example, methods such as electron beam lithography can be used to form fine structures. However, in this case, the surrounding area must be removed one by one to reflect the shape of the nanostructure by irradiating the electron beam. This makes the process very slow and the possible area for implementation very limited, resulting in economical manufacturing problems.

[0005] As an alternative to solve these problems, a method of forming nanostructures using an imprint method has been proposed. The imprint method is a method of filling a reusable mold with a polymer material (e.g., resin) and transferring it to a substrate, and has the advantage of being able to manufacture metasurfaces at a high process speed.

[0006] However, due to the nature of the process, polymer materials such as resins must be used as materials for nanostructures. However, in the case of resins, the refractive index for light is not high, so there is a problem that the efficiency of the metasurface is very low.

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

[0008] In addition, according to another aspect of the present invention, a metasurface and a method for manufacturing the same can be provided that can prevent a decrease in refractive index and increase efficiency even when manufacturing a nanostructure by a method such as an imprint method.

[0009] The objectives of the present invention are not limited to those described above. Anyone with ordinary skill in the art will have no difficulty understanding the additional objectives of the present invention from the contents of the specification.

[0010] A metasurface according to one aspect of the present invention is a metasurface comprising a substrate and a plurality of nanostructures formed on at least one surface of the substrate, wherein the nanostructures include a structural portion made of a polymer and a high-refractive material layer formed on at least a portion of the surface of the structural portion, and the high-refractive material layer may have a refractive index of 2.0 or more for light having a wavelength of 400 nm.

[0011] At this time, the high refractive index material layer may have a refractive index of 3.0 or less for light having a wavelength of 400 nm.

[0012] Additionally, the thickness of the high refractive index material layer may be 5 to 30 nm.

[0013] And, the high refractive index material layer may include ZrO2.

[0014] Additionally, the high refractive index material layer may be coated on the surface of the structural portion by atomic layer deposition (ALD) or chemical vapor deposition (CVD).

[0015] And, the structural part of the above nano structure may be formed by imprinting.

[0016] And, the sum of the length, width, and height of the structural portion may be 500 to 1500 nm, and at this time, the length of the structural portion may be 180 to 300 nm, the width of the structural portion may be 30 to 100 nm, and the height of the structural portion may be 450 to 700 nm.

[0017] The above-described metasurface may have an average distance (period) between the center of one structural part and the center of a structural part adjacent to the structural part of 200 to 400 nm.

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

[0019] At this time, the high refractive index material layer may be obtained by coating the surface of the structural part using atomic layer deposition (ALD) or chemical vapor deposition (CVD).

[0020] In addition, when coating a high-refractive material layer on the surface of a structural part using the above-described atomic layer deposition (ALD) method, the time for injecting a precursor material into a vacuum chamber per cycle can be set to 2 to 4 seconds, and the time for performing plasma treatment can be set to 20 to 40 seconds.

[0021] Additionally, the thickness of the high refractive index material layer can be set to 10 to 20 nm.

[0022] And, in the step of forming the plurality of structural parts, the sum of the length, width, and height of the structural parts formed may be 500 to 1500 nm.

[0023] According to the present invention, by including a nanostructure including a structural portion and a high-refractive material layer formed on at least a portion of the surface of the structural portion, the effective refractive index of the nanostructure can be controlled, and as a result, the efficiency of the metasurface can be improved.

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

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

[0026] FIG. 3 is a graph measuring the energy band gap of a ZrO2 layer provided in one embodiment of the present invention.

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

[0028] Fig. 5 is a device for measuring the focus forming characteristics of a metasurface. In the drawing, LP represents a linear polarizer, QWP represents a quarter wave plate, ML represents a metalens (metasurface), and OL represents an objective lens.

[0029] FIG. 6 is a result of measuring the characteristics of a metasurface according to an embodiment of the present invention using the device of FIG. 5.

[0030] Figure 7 is a device for measuring the resolution of a metasurface. In the drawing, 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] Fig. 8 is a graph showing the image form (a) for measuring resolution using the device of Fig. 7 and the result of measuring resolution using the image form (b).

[0032] Fig. 9 is a graph showing the wavelength-specific conversion efficiency of a metalens obtained by an embodiment of the present invention.

[0033] Figure 10 is a graph (a) showing that the conversion efficiency changes according to the length and width of the structural part, and a graph (b) showing that the conversion efficiency changes according to the thickness of the high-refractive material layer.

[0034] Figure 11 is a graph comparing the change in refractive index of a high-refractive-index material layer depending on the injection time of the precursor material and the plasma treatment time when coating a high-refractive-index material layer on a structural part using an atomic layer deposition method.

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

[0036] For example, a person skilled in the art who understands the idea of ​​the present invention will be able to easily suggest other embodiments included within the scope of the idea of ​​the present invention through addition, change, or deletion of components, but this will also be considered to be included within the scope of the idea of ​​the present invention.

[0037] In addition, throughout the specification, the term "including" a component does not exclude other components unless specifically stated otherwise, but rather means that other components may be included. In addition, the distinction between "up and down", "front and back", or "left and right" in this specification does not imply an absolute physical positional relationship, and it should be noted that even if it is above, it can be implemented in a shape that exists below, unless it is contrary to natural phenomena or clearly impossible to implement. In addition, the directions illustrated in the specification are used to help understanding, and are not limited to the directions illustrated in the drawings.

[0038] Additionally, unless otherwise specified herein, the refractive index means the refractive index for light having a wavelength of 400 nm.

[0039] FIG. 1 illustrates an exemplary shape of a metasurface (1) according to one embodiment of the present invention. As can be seen in the drawing, the metasurface (1) of the present invention includes a substrate (10) and a plurality of nanostructures (20) formed on at least one surface of the substrate (10), wherein the nanostructures (20) include a structural portion (30) made of a polymer and a high-refractive material layer (40) formed on at least a portion of the surface of the structural portion (30).

[0040] That is, the present invention aims to increase the effective refractive index of the nanostructure (20) by forming a nanostructure (20) with a structural part (30) made of a polymer with a relatively low refractive index and a material layer (40) with a high refractive index formed on at least a portion of the surface of the structural part. The high refractive index material layer (high refractive index material layer) may be formed on the entire surface of the structural part. Although not limited thereto, the polymer included in the structural part (20) can be advantageously formed on the surface of a substrate by an imprint method, so that there is an advantage in that the nanostructure (20) can be manufactured economically. The type of polymer that can be used in the present invention is not limited as long as it is a polymer that can be utilized in the imprint method. However, non-limiting examples of the polymer that can be used in the present invention include a photocurable polymer or a thermocurable polymer, and in one embodiment of the present invention, MINS-311RM of Minutatech can be used. However, although not necessarily limited to this, since the refractive index of polymers is not high, typically at the level of 1.4 to 1.5, the polymers are not advantageous in terms of efficiency of metasurfaces that seek to obtain electromagnetic or optical effects by refracting electromagnetic waves such as light. In order to solve this problem, in the present invention, as described above, a high refractive index material layer having a high refractive index is formed on the surface of the structure substantially composed of the polymer.

[0041] According to one embodiment of the present invention, the high refractive index material layer (40) may have a refractive index of 2.0 or more for light having a wavelength of 400 nm. 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 having a wavelength of 400 nm can be adjusted to 1.9 or more. According to another embodiment of the present invention, the refractive index of the refractive index material layer (40) for light having a wavelength of 400 nm can be 2.0 or more, and more preferably, 2.1 or more. As the refractive index of the refractive index material layer (40) increases, the effective refractive index of the nanostructure (20) can also increase, and therefore, the upper limit of the refractive index of the refractive index material layer (40) is not particularly limited. However, when considering the type of material formed on the surface of the structural portion (30), etc., in one embodiment of the present invention, the upper limit of the refractive index of the high refractive material layer (40) for light having a wavelength of 400 nm may be set to 3.0, and in another embodiment, the upper limit of the refractive index of the high refractive material layer (40) may be set to 2.9.

[0042] In addition, in order to obtain a sufficient refractive index increase effect, the thickness of the high refractive material layer (40) may be 5 nm or more in one embodiment of the present invention. In another embodiment of the present invention, the thickness of the high refractive material layer (40) may be limited to 10 nm or more. However, the thickness of the high refractive material layer interacts with the shape of the nanostructure and also affects the efficiency of the metasurface. If the thickness is too thick, the efficiency of the metasurface may decrease. Therefore, in one embodiment of the present invention, the upper limit of the thickness may be set to 30 nm, in another embodiment, the upper limit may be set to 25 nm, and in another embodiment, the upper limit may be set to 20 nm. In one embodiment of the present invention, the thickness of the high refractive material layer (40) may mean the average thickness of the portion where the material layer is formed.

[0043] There is no limitation on the type of material forming the high refractive index material layer (40) as long as it satisfies the refractive index condition. However, considering that one embodiment of the present invention can provide a metasurface (1) operating in the ultraviolet region, the material forming the high refractive index material layer (40) may be ZrO2, HfO2, Nb2O5, Silicon Nitride, etc., and ZrO2 may be used in one embodiment of the present invention. For example, as can be seen in FIG. 2, ZrO2 provided in an embodiment of the present invention not only satisfies the refractive index (n, solid line) condition of the present invention, but also has low absorption (k, dotted line) in the ultraviolet region with a wavelength of 400 nm or less. In addition, as can be seen in FIG. 3, the band gap is also very high at 6.195 eV, so it has the advantage of being transparent in the ultraviolet region. Atomic layer deposition (ALD) or chemical vapor deposition (CVD) can be used as a method for forming the high refractive index material layer. ZrO2 can be formed on the surface of the structural portion (30) by atomic layer deposition (ALD). However, such a ZrO2 layer, when formed on the surface of the structural portion (30) which is usually a polymer material, exhibits a low refractive index of 1.8 or lower, so that the refractive index of the overall nanostructure (20) may not be sufficient. However, the inventors of the present invention discovered that a nanostructure with a high refractive index can be formed by forming a high refractive material layer with a refractive index of 2.0 or higher on the surface of the structural portion (30), and thus led to the present invention.

[0044] In one embodiment of the present invention, the structural portion (30) of the nanostructure (20) can be formed by imprinting. That is, in the past, nanostructures could be formed by photolithography methods such as electron beam lithography, but in this case, it was not possible to economically obtain a metasurface due to various limitations as described above. 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, a polymer material must be 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 present invention, since the nanostructure (20) is obtained by forming the high-refractive material layer (40) on at least a portion of the surface of the structural portion (30), the effective refractive index of the nanostructure (20) can be increased.

[0045] In addition, in one embodiment of the present invention, the sum of the length, width, and height of the structural portion (30) may be 500 to 1500 nm. The size of the nanostructure (20) may be determined depending 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 fact that ultraviolet rays having a wavelength of 400 nm or less are processed, the sum of the length, width, and height of the structural portion may be set within the above-described range. In another embodiment of the present invention, the sum of the length, width, and height may be set to 600 to 1400 nm.

[0046] More specifically, the length of the structural portion (30) may be 180 to 300 nm, preferably 210 to 280 nm. In addition, the width of the structural portion (30) may be 30 to 100 nm, preferably 50 to 85 nm. The height of the structural portion (30) may be 450 to 700 nm, preferably 470 to 620 nm. In the present invention, the length and width of the structural portion (30) may refer to the length and width of the lowest portion, that is, the portion in contact with the substrate. The structural portion (30) often has a rectangular shape, but even if not, after drawing a rectangle (30) with the smallest area that can accommodate the shape of the lower portion of the structural portion (30), the long side of the rectangle can be regarded as the length and the short side as the width. If the rectangle with the smallest area that can accommodate the lower part can have various shapes, the rectangle with the largest difference in length and width can be taken, and the length and width of that rectangle can be used as the length and width of the structural part (30).

[0047] In addition, according to the research results of the present inventors, the wavelength-specific 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 present invention, the period may be 200 to 400 nm, and in the case of another embodiment, the period may be 230 to 450 nm. In the present invention, the period may mean the average distance between the center of one structural part and the center of a structural part adjacent to the one structural part. That is, as shown in FIG. 1, the distance P between the center of one structural part and another structural part adjacent to another structural part may be referred to as the period. However, since there may be multiple structural parts adjacent to one structural part, in this case, the average of the distances to the adjacent structural parts may be referred to as the period. For example, when the structural parts are arranged in a lattice shape, there may be a total of four structural parts that are adjacent in the horizontal and vertical directions, and the average of the distances between them may be determined as the period. If the average distance between adjacent structural parts is different for each structural part, the average of all these average distances can be set as the period.

[0048] The metasurface (1) can be used for various purposes depending on the arrangement of the structural portion (30). The effects according to the arrangement are widely known in the technical field to which the present invention pertains, and anyone skilled in the art can change and apply the arrangement of the structural portion (30) of the metasurface (1) according to the desired purpose. Therefore, the arrangement form of the structural portion is not specifically mentioned in this specification.

[0049] In one embodiment of the present invention, the substrate (10) is not particularly limited as long as it can be commonly used in the technical field to which the present invention pertains. In some cases, the type of substrate may be applied differently depending on the purpose of the metasurface (1). In an exemplary embodiment, the substrate may be made of glass, plastic, or a flexible film. In one embodiment of the present invention, the substrate may be one having a low absorption rate in the ultraviolet (UV) region, and specifically, one having a band gap energy of 8 eV or more may be used as the substrate. In one embodiment of the present invention, the thickness of the substrate may be 0.1 mm or more. There is no need to specifically set an upper limit of the thickness, but considering practicality, it may be set to 10 cm or less, or 5 cm or less, or 3 cm or less, or 1 cm or less and 5 mm or less.

[0050] Hereinafter, one method for manufacturing the metasurface of the present invention will be described. However, the metasurface of the present invention need not be manufactured solely by the manufacturing method described below, and it is of course possible to manufacture it using various technologies applicable in the technical field to which the present invention pertains, with reference to the matters described herein.

[0051] A method for manufacturing a metasurface of the present invention may include the steps of preparing a substrate; forming a plurality of structural parts on the substrate by an imprint method; and forming a high-refractive material layer on at least a portion of the surfaces of the plurality of structural parts.

[0052] A substrate satisfying the above-described conditions can be used as the substrate. Multiple structural parts can be formed on the substrate using an imprinting method. The imprinting method is widely known in the technical field to which the present invention pertains, and those skilled in the art will have no particular difficulty implementing it even without a detailed description. However, for the sake of understanding, a brief description is provided with reference to Figure 4. The accompanying photographs next to each step in the drawing represent the results of that step.

[0053] First, a transparent plate coated with Cr or Al is prepared, although not necessarily limited thereto. The Cr or Al is for blocking light in the subsequent lithography process, and other materials may be used as long as they can achieve the same effect. An electron beam is irradiated on the transparent plate (a) to obtain a photomask having a desired pattern formed thereon (b). Due to the nature of the subsequent lithography process, the size of the photomask may be larger than the size of the final pattern obtained, and in one embodiment of the present invention, a photomask that is about 3 to 5 times larger in length can be manufactured. Thereafter, for example, a photoresist material is applied on a substrate made of a silicon wafer, and then unnecessary portions are etched (c) using the photomask by a photolithography method to obtain a master stamp (d).

[0054] Thereafter, a replica mold can be manufactured using the master stamp (e). The replica mold has a pattern opposite to the pattern formed on the master stamp. In other words, the master stamp and the replica mold are complementary. That is, by combining the material of the replica mold with the master stamp and then separating it, a replica mold having a pattern opposite to the pattern of the master stamp can be obtained. Thereafter, a curable polymer material, which is a raw material for the structural part (30) of the nanostructure (20) of the present invention, is filled into the replica mold (f), the polymer material is transferred onto a substrate (g), and the replica mold is removed (h) to form the structural part on the substrate. In the process of transferring the polymer material onto the substrate (10) (g), light such as ultraviolet rays can be irradiated to harden the polymer material, thereby forming the structural part (30). However, the above imprint process is just one example, and any imprint technology used in the technical field to which the present invention pertains can be applied to the present invention unless there is a reason why application to the present invention is significantly impossible. In particular, the dimensions illustrated in the drawings are dimensions used in one embodiment of the present invention, and it goes without saying that the present invention can be applied to metasurfaces of various dimensions. The overall process does not necessarily have to be performed in a manner of manufacturing one metasurface (a substrate with a structure formed on the surface) from one master stamp, and may also be performed as a mass process in which multiple metasurfaces are formed at once from multiple master stamps on a large-area substrate, as illustrated in FIG. 4.

[0055] Afterwards, a process of forming a high-refractive material layer (40) on at least a portion of the surface of the structural portion is performed (i). The high-refractive material layer (40) can be formed by coating the surface of the structural portion by atomic layer deposition (ALD) or chemical vapor deposition (CVD). The atomic layer deposition (ALD) is not necessarily limited thereto, but may include a process of loading the substrate (10) on which the structural portion (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 so that a metal component (e.g., Zr) among the precursor materials reacts with oxygen to form an oxide. In one embodiment of the present invention, the vacuum in the entire atomic layer deposition process is 10 -1 ~ can be adjusted to a range of 5 Torr. In addition, one embodiment of the present invention may include a step of purging with Ar gas after injecting the precursor material.

[0056] However, conventional plasma treatment is performed at a high temperature of 200°C or higher, in which case the structural part (30) made of a polymer material may be damaged by the heat. In order to prevent the structural part (30) from being damaged, the temperature of the plasma treatment needs to be lowered to 150°C or lower, preferably 100°C or lower. However, in this case, a large number of vacancies are formed in the high-refractive-index material layer (40) formed by atomic layer deposition, which causes a problem in that the refractive index is reduced. Therefore, it has been generally recognized that it is difficult to form a material layer having a high refractive index on a polymer by atomic layer deposition. However, the inventors of the present invention have discovered that a high-refractive-index material layer (40) having a refractive index of 2.0 or higher can be formed on the structural part (30) without damaging the structural part by controlling the injection time of the precursor material while lowering the temperature of the plasma. That is, in one embodiment of the present invention, when forming a high-refractive-index material layer (40) by atomic layer deposition, the time for injecting a precursor material into a vacuum chamber is set to about 2 to 4 seconds, and the plasma treatment time is set to 20 to 40 seconds. If the injection time of the precursor material is short, a sufficient refractive index is not obtained, and if the time is too long, not only is the effect no longer increased, but expensive precursor material is consumed unnecessarily. The amount of precursor material injected is not greatly affected by the size of the chamber as long as the amount can coat the entire substrate, and the injection time is important. However, according to one embodiment of the present invention, the precursor material may be supplied into the chamber by being added to Ar gas injected at a rate of 0.1 to 0.4 SCCM / cm3 per chamber unit volume (SCCM).

[0057] In addition, if the plasma treatment time is short, the thickness of the high-refractive-index material layer formed is insufficient, and if it is long, the problem occurs that the high-refractive-index material layer is formed beyond the appropriate thickness range. A more preferable plasma treatment time may be 25 to 35 seconds. In one embodiment of the present invention, the temperature of the plasma treatment may be 150°C or less, preferably 100°C or less, and more preferably 80 to 100°C.

[0058] In this way, the process from precursor material injection to plasma treatment can be called one cycle, and a thin atomic layer of 10 angstroms (Å) or less is formed through one cycle coating process, and by repeating this cycle several times, the thickness of the formed high-refractive material layer (40) can be controlled to a desired degree.

[0059] Among the specific details including the material, shape, arrangement of the structural part, and the material, thickness, and refractive index of the high-refractive material layer, any parts that overlap with those described above are omitted here.

[0060] Hereinafter, the present invention will be described in detail through examples. However, it should be noted that the following examples are intended only to illustrate and concretize the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0061] (Example)

[0062] Example 1

[0063] A structure (30) was formed by performing imprinting according to the procedure shown in Fig. 4. A photomask pattern was formed on a circular transparent plate with a diameter of 4 cm to correspond to the length, width, and period of the structure, thereby producing a photomask. The photomask pattern is designed to be four times the pattern size of the target metasurface (1), and a master stamp with a size of 1 / 4 of the photomask pattern can be obtained by an electron beam lithography process. Therefore, the master stamp is circular and has a diameter of 1 cm, and a replica mold can be manufactured using the master stamp. By installing a plurality of the master stamps on a silicon wafer with a diameter of 8 inches (approximately 20 cm), a plurality of corresponding replica molds can also be installed, thus enabling mass production. After filling the replica mold with an ultraviolet-curable polymer material (MINS-311RM, Minutatech product), the structure (30) was obtained by curing it with ultraviolet rays while applying pressure. The structural member (30) is arranged so that the metasurface (1) can act as a metalens.

[0064] As a substrate (10) forming a structural portion during imprinting, a SiO2 substrate having a diameter of 1 cm and a thickness of 0.5 mm (500 μm) was used. The structural portion (30) was designed to have a shape of 240 nm in length, 60 nm in width, and 550 nm in height, and the structural portion (30) was arranged in a regular lattice shape with a period of 280 nm in both the horizontal and vertical directions.

[0065] After that, the substrate was loaded into a chamber with an internal volume of 30 cm * 30 cm * 1 cm, and the entire surface of the substrate (10) on which the structure (30) was formed was coated with ZrO2 as a high-refractive material layer (40) using the atomic layer deposition method. As a specific coating method, TEMAZr was used as a precursor material during the coating, and the precursor material was added to argon gas supplied at a flow rate of 200 SCCM and injected into the chamber for 3 seconds, followed by a cycle of treating with O2 plasma for 30 seconds, which was performed several times. The pressure in the chamber from precursor injection to plasma treatment was set to 1 Torr. It was confirmed that an atomic layer of a high-refractive material of approximately 2.8 Å was formed by one cycle, and the cycle was repeated until the desired thickness was obtained. The formed ZrO2 coating had a uniform thickness without significant deviation, and the average thickness was 15 nm.

[0066] A performance measurement experiment was conducted by installing the device in the form shown in Fig. 5 using the obtained metalens, and as a result, as can be seen in Fig. 6, it was confirmed that the focus was formed at the targeted focal distance and that it had an ideal Airy disk.

[0067] In addition, by installing the device in the form shown in Fig. 7 and measuring the resolution by imaging the USAF 1951 target shown in Fig. 8 (a), it was confirmed that a high resolution was obtained, as can be seen in Fig. 8 (b). Each graph in Fig. 8 (b) corresponds to the parts indicated by the red and blue lines in Fig. 8 (a), respectively.

[0068] The wavelength-specific conversion efficiency of the metalens obtained in this example was confirmed and the results are shown in Fig. 9. As can be seen in the figure, it exhibited a high conversion efficiency of over 60% in the 300-400 nm band, which is a commonly used wavelength range. The conversion efficiency was determined by the ratio of light whose phase was adjusted when converted to left-circular polarization (LCP) when right-circular polarization (RCP) was incident.

[0069] Example 2

[0070] In order to confirm the optimal thickness of the high refractive index material layer, the metasurface was manufactured in the same manner as in Example 1 except that the wavelength of light was fixed at 325 nm and the length and width of the structural portion (30) were changed. Then, the conversion efficiency was confirmed, and the result is shown in Fig. 10 (a). As can be seen in the drawing, it was found that the conversion efficiency rapidly decreased as the width of the structural portion (30) exceeded 100 nm. Although not shown in the drawing, it was confirmed that good conversion efficiency was exhibited until the width of the structural portion (30) reached 30 nm. In addition, it can be seen from the drawing that the conversion efficiency is high in the region where the length of the structural portion (30) is 180 nm or more. Although not shown in the drawing, high conversion efficiency could be obtained until the length of the structural portion (30) became 300 nm.

[0071] Example 3

[0072] The same structure as the structure (30) obtained in the above Example 1 was formed, but the wavelength was fixed to 325 nm, and only the thickness of the ZrO2, which is a high refractive material layer (40), was changed to examine the change in conversion efficiency. The thickness could be adjusted by changing the number of cycles of the above-described process. The result is shown in Fig. 10 (b). As can be seen in the drawing, a high conversion efficiency of 60% or more is obtained in the region where the thickness is 5 nm or more. As the thickness increases, the conversion efficiency increases, but when the value exceeds 15 nm, the conversion efficiency decreases, and when the thickness exceeds about 30 nm, the conversion efficiency becomes insufficient.

[0073] Example 4 (Comparison of Comparative Example and Example 1)

[0074] Nanostructures were manufactured in the same manner as in Example 1, except that the injection time of the precursor material was limited to 0.5 seconds and the plasma treatment time was limited to 10 seconds. The refractive index of the manufactured nanostructures according to the wavelength is shown in Fig. 11. As shown in Fig. 2, the refractive index of the nanostructure manufactured by Example 1 was a high value of 2.0 or more, whereas in the case of the comparative example shown in Fig. 11, the refractive index value was less than 1.8, which was not sufficient to form a metasurface.

[0075] Therefore, the advantageous effects of the present invention could be confirmed.

Claims

1. A metasurface comprising a substrate and a plurality of nanostructures formed on at least one surface of the substrate, The above nanostructure comprises a structural part made of a polymer and a high refractive material layer formed on at least a portion of the surface of the structural part, The above high refractive material layer is a metasurface having a refractive index of 2.0 or more for light having a wavelength of 400 nm.

2. In the first paragraph, the high refractive index material layer is a metasurface having a refractive index of 3.0 or less for light having a wavelength of 400 nm.

3. A metasurface in the first paragraph, wherein the thickness of the high refractive material layer is 5 to 30 nm.

4. In the first paragraph, the high refractive index material layer is a metasurface including ZrO2.

5. A metasurface in the first paragraph, wherein the high-refractive material layer is coated on the surface of the structure by atomic layer deposition (ALD) or chemical vapor deposition (CVD).

6. In the first paragraph, the structural part of the nanostructure is a metasurface formed by imprinting.

7. A metasurface in the first paragraph, wherein the sum of the length, width, and height of the structural portion is 500 to 1,500 nm.

8. A metasurface in clause 7, wherein the length of the structural part is 180 to 300 nm.

9. A metasurface in clause 7, wherein the width of the structural portion is 30 to 100 nm.

10. A metasurface in clause 7, wherein the height of the structural portion is 450 to 700 nm.

11. A metasurface according to any one of claims 7 to 10, wherein the average distance (period) between the center of one structural part and the center of a structural part adjacent to the structural part is 200 to 400 nm.

12. Step of preparing the substrate; A step of forming a plurality of structural parts made of a polymer by an imprint method on the substrate; and Comprising a step of forming a high refractive material layer on at least a portion of the surface of the plurality of structural parts, The above high refractive material layer is a method for manufacturing a metasurface having a refractive index of 2.0 or more for light having a wavelength of 400 nm.

13. A method for manufacturing a metasurface in claim 12, wherein the high-refractive material layer is formed by coating the surface of the structural part by atomic layer deposition (ALD) or chemical vapor deposition (CVD).

14. A method for manufacturing a meta surface in claim 13, wherein when coating a high-refractive material layer on the surface of a structural part by the atomic layer deposition (ALD) method, the time for injecting a precursor material into a vacuum chamber per cycle is 2 to 4 seconds, and the time for performing plasma treatment is 20 to 40 seconds.

15. A method for manufacturing a metasurface in accordance with claim 12, wherein the thickness of the high refractive material layer is set to 10 to 20 nm.

16. A method for manufacturing a metasurface in which the sum of the length, width and height of the structural parts formed in the step of forming the plurality of structural parts in the 12th paragraph is 500 to 1,500 nm.

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