WO2023136182A1 - Metasurface - Google Patents
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- WO2023136182A1 WO2023136182A1 PCT/JP2022/048663 JP2022048663W WO2023136182A1 WO 2023136182 A1 WO2023136182 A1 WO 2023136182A1 JP 2022048663 W JP2022048663 W JP 2022048663W WO 2023136182 A1 WO2023136182 A1 WO 2023136182A1
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- metasurface
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
Definitions
- the present invention relates to metasurfaces.
- Optical lenses are important parts in science and technology such as microscopes, displays, and optical lithography.
- Conventional refractive lenses are made of transparent convex or concave materials and are widely used, but their large size limits the miniaturization of optical components.
- complicated and time-consuming three-dimensional (3D) surface processing is required to create an aspheric refractive lens for correcting spherical aberration.
- Diffractive lenses with sawtooth profiles offer an alternative to achieve thin and compact lenses, but their focusing ability is inherently limited by shadowing effects, and diffractive lenses have low NA (numerical aperture). ) only.
- a metasurface a two-dimensional array of sub-wavelength antennas
- the transmitted and reflected waves can be arbitrarily modulated when light interacts with the metasurface, and many applications of ultra-thin lenses have already been demonstrated.
- a metalens can offer the opportunity to realize high-end, ultra-thin lenses without the limitations of shadowing effects.
- a metalens is composed of a plurality of structures having one nano-sized dielectric column or fin in a unit on a substrate. The structure of each unit brings about a phase shift of light depending on its shape and size. Since the light is confined in the dielectric in the unitary unit, there is little interference with adjacent units. Therefore, by controlling the shapes and positions of these structures, a metalens having a desired phase profile can be realized.
- To construct a lens we need cylindrical nanostructures of multiple diameters covering the phase shift induced by the nanostructures from 0° to 360°. That is, a metalens can be realized by arranging a plurality of cylinders having different diameters so as to realize a desired phase profile.
- the metasurface can be manufactured in one process by nanoimprinting, in which dielectric resin is molded using a fine pattern mold.
- resin containing nanofillers which are high refractive index materials
- the refractive index is 1.8 to 1.9 when titanium dioxide is applied, and the refractive index is about 2.2 even when amorphous silicon is applied. lower refractive index. Therefore, it is necessary to increase the height of the cylinder in order to cover a sufficient phase range.
- the transmittance varies greatly depending on the diameter of the cylinder, and there was a problem that the transmittance was 40% or less depending on the diameter. This is because it is necessary to increase the unit size in order to cover the phase with a cylinder having an aspect ratio that can be molded by nanoimprinting, and when the unit size increases, the effect of diffraction occurs and the transmittance fluctuates.
- an object of the present invention is to provide a metasurface with a low aspect ratio using a dielectric resin without increasing the unit size.
- the present invention provides a metasurface comprising a substrate that transmits light and a plurality of microstructures arranged on the substrate for controlling the phase distribution of the light. and wherein the plurality of microstructures have two or more heights.
- the maximum aspect ratio of the plurality of types of microstructures is preferably smaller than the maximum aspect ratio when the plurality of types of microstructures are designed to have the same height and the same phase difference.
- the aspect ratio of the fine structure is preferably 5 or less.
- the pitch of the microstructures is 3/4 or less of the wavelength of the light.
- the fine structure may be a resin.
- two or more layers of the microstructure may be laminated.
- the metasurface of the present invention can be provided without increasing the unit size.
- FIG. 1 is a cross-sectional view showing a metasurface of the present invention
- FIG. 1 is a cross-sectional view showing a metasurface having a two-layer structure according to the present invention
- FIG. FIG. 4 is a cross-sectional view showing a method of manufacturing a master mold for metasurface according to the present invention
- FIG. 4 is a cross-sectional view showing a method for manufacturing a hole replica mold for metasurface according to the present invention
- FIG. 4 is a cross-sectional view showing a method for manufacturing a metasurface according to the present invention
- FIG. 4 is a cross-sectional view showing a method for manufacturing a metasurface having a two-layer structure according to the present invention
- FIG. 3A is a sectional view and (b) a plan view showing a metasurface used in Simulation 1.
- FIG. FIG. 10 is a diagram showing the pitch P, the diameter D1, and the transmittance of the microstructure in Simulation 1;
- FIG. 11 is a cross-sectional view showing a microstructure in Simulation 2;
- FIG. 10 is a diagram showing the diameter and phase difference of a fine structure in Simulation 2;
- FIG. 11 is a cross-sectional view showing a microstructure in Simulation 3;
- FIG. 10 is a diagram showing the diameter and phase difference of a fine structure in Simulation 3;
- FIG. 11(a) is a cross-sectional view and (b) a plan view showing a microstructure in Simulation 4;
- FIG. 10 is a diagram showing the pitch P, the diameter D1, and the transmittance of the microstructure in Simulation 4;
- FIG. 11 is a cross-sectional view showing a microstructure in Simulation 5;
- FIG. 11 is a diagram showing the diameter and phase difference of a fine structure in Simulation 5;
- FIG. 11 is a cross-sectional view showing a microstructure in Simulation 6;
- FIG. 10 is a diagram showing the diameter and phase difference of a fine structure in Simulation 6;
- FIG. 12 is a diagram showing the electric field intensity distribution of the metalens in Simulation 7;
- FIG. 11 is a diagram showing an electric field intensity distribution of a metalens in Simulation 8;
- the metasurface of the present invention will be described below.
- the metasurface of the present invention is mainly composed of a substrate 1 and a plurality of microstructures 2 arranged on the substrate 1, as shown in FIG.
- the substrate 1 is for arranging a plurality of fine structures 2 .
- Any material may be used as long as it allows light to pass therethrough and a plurality of microstructures 2 can be arranged thereon.
- a glass substrate made of SiO 2 or the like may be used.
- the fine structure 2 is made of a dielectric with a size smaller than the wavelength of light used for the metasurface, and is used to control the phase of transmitted light. If the pitch of the microstructures 2 becomes large, a diffraction effect occurs, and the transmittance varies depending on the diameter of the microstructures 2. Therefore, the smaller the pitch, the better, preferably 3/4 or less of the light used. is good.
- the dielectric for example, a high refractive index resin containing a filler such as amorphous silicon ( ⁇ -Si) or titanium dioxide (TiO 2 ) can be used. In particular, resin is preferable in that the fine structure 2 can be directly molded by the nanoimprint method.
- the shape of the microstructure 2 may be any shape as long as the phase can be controlled, but it can be, for example, columnar, frustum, or conical.
- a truncated cone shape and a conical shape are preferable in that when the fine structure 2 is directly molded by the nanoimprint method, the shape can be easily released.
- the planar shape (cross-sectional shape viewed from the convex side) of the microstructure 2 is not limited as long as the phase can be controlled. can be done.
- the fine structure 2 is formed by the nanoimprint method, it is preferable because it is easy to form a cylindrical shape, a truncated cone shape, or a conical shape.
- the phase increases as the height and diameter of the microstructure 2 are increased.
- the diameter means the diameter of the circle of the cylinder.
- the microstructure 2 is other than a cylinder, it means the diameter of a circle when the volume of the microstructure 2 is converted into a cylinder having the same volume.
- the height of the microstructure 2 was kept constant, and the phase distribution of light was controlled only by the diameter of the microstructure 2.
- the aspect ratio of the fine structure 2 becomes large, so there is a problem that it is difficult to mold or release the fine structure 2 by the imprint method. Therefore, as a result of intensive research by the present inventors, it has been found that the phase distribution can be controlled and the aspect ratio can be reduced by changing the height. Specifically, it was found that when the phase difference to be designed is low, the height can be reduced and the aspect ratio can be reduced.
- the microstructure 2 has two or more different heights, and the diameter of each height is adjusted so that the aspect ratio of the microstructure 2 is 5 or less, 4.5 or less, It can be formed as small as 4 or less, 3.5 or less, 3 or less, or 2.5 or less.
- the thickness is preferably 1/4 or less of the wavelength of the light used.
- the fine structure 2 may be laminated with two or more layers.
- the phase difference provided by the microstructures 2 of the second and subsequent layers can be added to the phase difference provided by the microstructures 2 of the first layer. Therefore, by aligning the position of the microstructures 2 in the first layer with the positions of the microstructures 2 in the second and subsequent layers, the height and aspect ratio of the microstructures 2 can be further reduced.
- the space between the microstructures may be filled with a resin having a refractive index lower than that of the microstructures.
- a method for manufacturing a metasurface according to the present invention will be described below.
- a method of manufacturing the master mold 10 is shown in FIG.
- a hard mask 12 is deposited on a substrate 11 as shown in FIG. 3(a).
- a glass substrate such as SiO 2 may be used.
- metal such as Cr may be used.
- Film formation of the hard mask 12 may be performed by a well-known method such as a sputtering method.
- FIG. 3B a fine structure pattern 13 is formed on the hard mask 12.
- a well-known technique such as a photolithography technique or a nanoimprint technique may be used to create the pattern 13, for example.
- the pattern 13 is used to etch the hard mask 12 . Subsequently, the substrate 11 is etched. A well-known method such as RIE may be used for etching the hard mask 12 and the substrate 11 . The etching depth of the substrate 11 is set to the depth of the lowest height of the microstructures to be formed. The pattern 13 may be removed by ashing or the like after the hard mask 12 is etched and before the substrate 11 is etched. Next, as shown in FIG. 3(d), a pattern 14 is formed to cover the top of the lowest microstructure. A well-known technique such as photolithography technique or nanoimprint technique may be used to create the pattern 14, for example. Next, as shown in FIG.
- the substrate 1 is etched so as to form a fine structure having the second lowest height. Then pattern 14 is removed. When three or more heights are to be used, the third and subsequent microstructures may be produced in the same manner. Finally, as shown in FIG. 3(f), the master mold 10 can be manufactured by removing the pattern 13 and the hard mask 12. Next, as shown in FIG.
- a method for manufacturing the hole replica 25 will be described.
- a resin 21 is applied onto the master mold 10, and after the resin 21 is cured, the mold is released to form a pillar replica 22 as shown in FIG. 4(b).
- a resin 24 is applied onto the substrate 23 as shown in FIG. 4(b).
- the pillar replica 22 is pressed against the resin 24 as shown in FIG. 4(c).
- a glass substrate such as SiO 2 may be used for the substrate 23, for example.
- the resin 24 is cured, it is released from the mold to form a hole replica 25 as shown in FIG. 4(d).
- a high refractive index resin 31 is applied to the hole replica 25 as shown in FIG. 5(a).
- the high refractive index resin 31 for example, a resin containing a filler such as amorphous silicon ( ⁇ -Si) or titanium dioxide (TiO 2 ) may be used.
- the high refractive index resin 31 is pressure-bonded to the substrate 32 and then cured.
- the metasurface of the present invention can be manufactured by releasing the hole replica 25 from the mold.
- the master mold 10 is created by lowering the height of each pattern by the above-described manufacturing method (see FIG. 3).
- a pillar replica 22 and a hole replica 25 are produced with this master mold 10 in the same manner as in the manufacturing method described above (see FIG. 4).
- the resin 24 of the hole replica 25 a low refractive index resin is used.
- a resin 61 having a refractive index higher than that of the resin 24 is applied onto the hole replica 25 to fill the holes, and then flattened and cured with UV.
- the high refractive index resin 61 for example, a resin containing a filler such as amorphous silicon ( ⁇ -Si) or titanium dioxide (TiO 2 ) may be used.
- a low refractive index resin 62 is applied on the high refractive index resin 61.
- the pillar replica 22 is pressed against the low refractive index resin 62 and released to form a hole-like pattern.
- a high refractive index resin 63 is applied to fill the holes, then flattened and cured with UV.
- FIG. 8(a) shows simulation results of the pitch P and diameter D of the microstructure and the transmittance.
- FIG. 8(b) shows the relationship between the diameter D and the transmittance for five types of the pitch P of the fine structure, 520 nm, 600 nm, 680 nm, 760 nm, and 840 nm.
- the transmittance decreases depending on the diameter D of the microstructures when the pitch P of the microstructures is larger than 3/4 wavelength of the incident light. Therefore, it is preferable to set the pitch P of the fine structures to 3/4 or less of the wavelength of the light used.
- [Simulation 2] The relationship between the diameter of the microstructure and the phase difference of transmitted light was simulated.
- the wavelength of light incident on the metasurface was set to 940 nm.
- the fine structure was cylindrical with a pitch P of 0.65 ⁇ m.
- the refractive index was set to 1.85 assuming a resin containing titanium dioxide (TiO 2 ) filler.
- the heights H1 and H2 of the fine structure are of two types, 1.6 ⁇ m and 0.9 ⁇ m.
- the refractive index of the substrate was set to 1.5.
- FIG. 10 shows simulation results of the diameter D of the fine structure and the phase difference.
- the phase difference of transmitted light decreases as the height of the fine structure decreases. Further, as the diameter D of the fine structure increases, the phase difference of transmitted light increases. Therefore, when the height of the microstructure is reduced, the diameter D must be increased in order to keep the phase difference of the transmitted light the same. That is, since the height is low and the diameter is large, the aspect ratio can be reduced.
- microstructures two types are designed: a microstructure A that provides a phase difference of 45 degrees ( ⁇ /4 radians) and a microstructure B that provides a phase difference of 315 degrees (7 ⁇ /4 radians).
- the microstructure A should have a diameter of 0.5 ⁇ m and the microstructure B should have a diameter of 0.207 ⁇ m.
- the aspect ratio of the fine structure A is 3.2
- the aspect ratio of the fine structure B is 7.7.
- the height of the microstructure B is 0.9 ⁇ m
- the diameter of the microstructure B can be 0.27 ⁇ m.
- the aspect ratio is 3.3, and the aspect ratio of the entire fine structure can be made smaller by changing the heights of the fine structures A and B than by keeping the heights of the fine structures A and B constant. can be done.
- [Simulation 3] The relationship between the diameter of the microstructure and the phase difference of transmitted light was simulated.
- the wavelength of light incident on the metasurface was set to 940 nm.
- the fine structure was cylindrical with a pitch P1 of 0.68 ⁇ m.
- the refractive index was set to 2.2 assuming a resin containing amorphous silicon ( ⁇ -Si) filler.
- the heights H1 and H2 of the fine structure are of two types, 1.1 ⁇ m and 0.75 ⁇ m.
- the refractive index of the substrate was set to 1.5.
- FIG. 12 shows simulation results of the diameter of the fine structure and the phase difference.
- the phase difference of transmitted light decreases as the height of the fine structure decreases. Further, as the diameter of the fine structure increases, the phase difference of transmitted light increases. Therefore, if the height of the microstructure is reduced, the diameter must be increased in order to keep the phase difference of the transmitted light the same. That is, since the height is low and the diameter is large, the aspect ratio can be reduced.
- microstructures two types are designed: a microstructure A that provides a phase difference of 45 degrees ( ⁇ /4 radians) and a microstructure B that provides a phase difference of 315 degrees (7 ⁇ /4 radians).
- the microstructure A should have a diameter of 0.46 ⁇ m and the microstructure B should have a diameter of 0.214 ⁇ m.
- the aspect ratio of fine structure A is 2.4
- the aspect ratio of fine structure B is 5.14.
- the diameter of the microstructure B can be 0.245 ⁇ m.
- the aspect ratio is 3.06, and the aspect ratio of the entire fine structure can be made smaller by changing the heights of the fine structures A and B than by keeping the heights of the fine structures A and B constant. can be done.
- [Simulation 4] A simulation was performed of the relationship between the pitch of the microstructures and the transmittance when two layers of the same microstructures were laminated one above the other.
- the wavelength of light incident on the metasurface was set to 940 nm.
- the microstructures were cylindrical with a height H1 of 1.2 ⁇ m and a refractive index of 1.85, and arranged in a hexagonal arrangement.
- the pitch of the fine structures was set to 0.69 ⁇ m.
- the refractive index of the resin embedded between the fine structures was 1.35, and the refractive index of the substrate was 1.5.
- FIG. 14 shows simulation results of the pitch P and diameter D of the microstructure and the transmittance.
- the transmittance decreases depending on the diameter D of the microstructures when the pitch P of the microstructures is larger than 3/4 wavelength of the incident light. Therefore, it is preferable to set the pitch P of the fine structures to 3/4 or less of the wavelength of the light used. Also, even with two layers, there was no significant effect on the transmittance.
- [Simulation 5] A simulation was performed of the relationship between the diameter of the fine structure and the phase difference of the transmitted light when two layers of the same fine structure are laminated one above the other.
- the wavelength of light incident on the metasurface was set to 940 nm.
- the fine structure was cylindrical with a pitch P of 0.69 ⁇ m.
- the refractive index was set to 2.2 assuming a resin containing amorphous silicon ( ⁇ -Si) filler.
- the heights H1 and H2 of the microstructures were of two types, 1.2 ⁇ m and 0.65 ⁇ m.
- the refractive index of the resin embedded between the fine structures was 1.35, and the refractive index of the substrate was 1.5.
- FIG. 16 shows simulation results of the diameter D of the fine structure and the phase difference.
- the phase difference of transmitted light decreases as the height of the fine structure decreases. Further, as the diameter D of the fine structure increases, the phase difference of transmitted light increases. Therefore, when the height of the microstructure is reduced, the diameter D must be increased in order to keep the phase difference of the transmitted light the same. That is, since the height is low and the diameter is large, the aspect ratio can be reduced.
- microstructures two types are designed: a microstructure A that provides a phase difference of 45 degrees ( ⁇ /4 radians) and a microstructure B that provides a phase difference of 315 degrees (7 ⁇ /4 radians).
- a microstructure A that provides a phase difference of 45 degrees ( ⁇ /4 radians)
- a microstructure B that provides a phase difference of 315 degrees (7 ⁇ /4 radians).
- the microstructure A should have a diameter of 0.57 ⁇ m and the microstructure B should have a diameter of 0.22 ⁇ m.
- the aspect ratio of fine structure A is 2.1
- the aspect ratio of fine structure B is 5.45.
- the diameter of the microstructure B can be 0.287 ⁇ m.
- the aspect ratio is 2.26, and the aspect ratio of the entire fine structure can be made smaller by changing the heights of the fine structures A and B than by keeping the heights of the fine structures A and B constant. can be done.
- the aspect ratio could be made considerably smaller than in the case of one layer.
- [Simulation 6] A simulation was performed on the relationship between the diameter and the phase difference of transmitted light when the fine structure is cylindrical and when it is truncated cone.
- the wavelength of light incident on the metasurface was set to 940 nm.
- the shape of the microstructures as shown in FIG. 17, the microstructures A, C, D, and F were truncated conical, and the microstructures B and E were cylindrical.
- the angle of the side surfaces of the microstructures A, C, D, and F with respect to the substrate was set to 87 degrees.
- the height H1 of the microstructures A to C was set to 1.6 ⁇ m
- the height H2 of the microstructures D to F was set to 0.9 ⁇ m.
- the diameters of the microstructures A and D are the diameters of the top surface of the truncated cone, and the diameters of the microstructures C and F are the diameter of the bottom surface of the truncated cone.
- the refractive index was set to 1.85 assuming a resin containing titanium dioxide (TiO 2 ) filler. Also, the refractive index of the substrate was set to 1.5.
- FIG. 18 shows simulation results of the diameter D of the fine structure and the phase difference.
- the phase difference of the transmitted light is also reduced. Also, as the diameter of the truncated conical microstructure increases, the phase difference of the transmitted light also increases. Therefore, it was found that even if the shape of the fine structure is a truncated cone, the phase difference can be controlled by the height and diameter of the fine structure as in the case of the cylindrical shape.
- the diameters of the fine structures were D1: 470 nm, D2: 440 nm, D3: 395 nm, D4: 490 nm, D5: 410 nm, D6: 340 nm, and D7: 260 nm.
- the pitch U of the fine structures was set to 620 nm.
- the refractive index of the microstructure was set to 1.85, and the refractive index of the substrate was set to 1.5.
- These microstructures (a) to (g) were arranged as shown in FIG. 19(B).
- FIG. 20A shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens.
- FIG. 21A shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens A.
- FIG. 21(b) shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens B. As shown in FIG.
- the electric field strength distributions of metalens A and metalens B were almost the same.
- the light collection efficiency of the metalens A is 68.9%
- the light collection efficiency of the metalens B is 70.3%.
- the metalens A exhibits performance comparable to that of the conventional metalens B. I understand. Therefore, it was found that even a metalens made of a low-refractive-index material can exhibit performance comparable to that of a conventional metalens if microstructures with two different heights are used.
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Abstract
The purpose of the present invention is to provided a metasurface having a low aspect ratio, using a dielectric resin, without increasing the size of a unit. This metasurface comprises a substrate 1 that transmits light, and a plurality of microstructures 2 disposed on the substrate 1 to control the phase distribution of the light, and the plurality of microstructures 2 have two or more varieties of heights. The maximum aspect ratio of the plurality of varieties of microstructures 2 is smaller than the maximum aspect ratio if the plurality of varieties of microstructures 2 were designed so as to generate the same phase difference at the same height.
Description
本発明は、メタサーフェスに関するものである。
The present invention relates to metasurfaces.
光学レンズは,顕微鏡,ディスプレイ,光リソグラフィーなどの科学技術において重要な部品である。従来の屈折レンズは、透明な凸型または凹型の材料で構成されており、広く使用されているが、大型であるため、光学部品の小型化には限界がある。また球面収差を補正するための非球面屈折レンズを作るには、複雑で時間のかかる3次元(3D)の表面加工が必要である。鋸歯状のプロファイルを持つ回折レンズは、薄くてコンパクトなレンズを実現するための代替手段を提供するが、集束能力はシャドーイング効果によって本質的に制限されており、回折レンズは低NA(開口度)のみで利用可能である。
Optical lenses are important parts in science and technology such as microscopes, displays, and optical lithography. Conventional refractive lenses are made of transparent convex or concave materials and are widely used, but their large size limits the miniaturization of optical components. In addition, complicated and time-consuming three-dimensional (3D) surface processing is required to create an aspheric refractive lens for correcting spherical aberration. Diffractive lenses with sawtooth profiles offer an alternative to achieve thin and compact lenses, but their focusing ability is inherently limited by shadowing effects, and diffractive lenses have low NA (numerical aperture). ) only.
これに代わるものとして、サブ波長アンテナの2次元アレイであるメタサーフェスを超薄型光学デバイスとして利用することができる。光がメタサーフェスと相互作用するとき、アンテナの物理的な形状をエンジニアリングすることで、透過波と反射波を任意に変調することができ、すでに超薄型レンズの多くの応用例が実証されている。このようなメタレンズは、シャドーイング効果の制限を受けずにハイエンドの超薄型レンズを実現する機会を提供することができる。メタレンズは基板上の単位ユニット内に一つのナノサイズの誘電体の円柱やフィンを有する複数の構造体によって構成される。各ユニットの構造体はその形状やサイズにより光の位相シフトをもたらす。単位ユニットにおいて光は誘電体中に閉じ込められるので、隣接するユニットへの干渉はほとんどない。このためこれらの複数の構造体の形状と位置を制御することで所望の位相プロファイルを持ったメタレンズを実現することができる。
As an alternative, a metasurface, a two-dimensional array of sub-wavelength antennas, can be used as an ultra-thin optical device. By engineering the physical shape of the antenna, the transmitted and reflected waves can be arbitrarily modulated when light interacts with the metasurface, and many applications of ultra-thin lenses have already been demonstrated. there is Such metalens can offer the opportunity to realize high-end, ultra-thin lenses without the limitations of shadowing effects. A metalens is composed of a plurality of structures having one nano-sized dielectric column or fin in a unit on a substrate. The structure of each unit brings about a phase shift of light depending on its shape and size. Since the light is confined in the dielectric in the unitary unit, there is little interference with adjacent units. Therefore, by controlling the shapes and positions of these structures, a metalens having a desired phase profile can be realized.
単位ユニットの中に一つの誘電体の円柱が配置され、前記円柱が一定の高さであり、光の位相シフトを円柱の径で制御するタイプのメタレンズは、入射する光の偏光に依存せず広く光学レンズとして使用することができる。レンズを構成するためには、ナノ構造体によって生じる位相シフトが0°から360°までをカバーする複数の径の円柱のナノ構造体が必要となる。すなわち径の異なる複数の円柱を所望の位相プロファイルを実現するように配置することでメタレンズを実現することができる。
A metalens of the type in which one dielectric cylinder is arranged in a unit, the cylinder has a constant height, and the phase shift of light is controlled by the diameter of the cylinder does not depend on the polarization of incident light. Can be widely used as an optical lens. To construct a lens, we need cylindrical nanostructures of multiple diameters covering the phase shift induced by the nanostructures from 0° to 360°. That is, a metalens can be realized by arranging a plurality of cylinders having different diameters so as to realize a desired phase profile.
製造工程は、まずガラス上にプラズマCVDでアモルファスシリコン(α-Si)を成膜する。次に、当該アモルファスシリコン上にレジストパターンをリソグラフィーで形成する。そして、このレジストパターンをマスクにアモルファスシリコンをエッチングすることでパターンを形成している。また、可視光を対象にしたものとしては、屈折率約2.4である二酸化チタン(TiO2)の円柱を用いた構造が報告されている。(例えば、特許文献1)
In the manufacturing process, first, an amorphous silicon (α-Si) film is formed on glass by plasma CVD. Next, a resist pattern is formed on the amorphous silicon by lithography. A pattern is formed by etching amorphous silicon using this resist pattern as a mask. For visible light, a structure using titanium dioxide (TiO 2 ) cylinders with a refractive index of about 2.4 has been reported. (For example, Patent Document 1)
ここで、誘電体樹脂を微細パターンの金型で成型するナノインプリントによって、メタサーフェスを1工程で製造できれば製造コストを低減することができる。しかし、高屈折率材料のナノフィラーを含有する樹脂の場合、二酸化チタンを塗りこんだ場合で1.8~1.9、アモルファスシリコンを塗りこんだ場合でも屈折率2.2程度であり純粋な二酸化チタン、アモルファスシリコンに比べて屈折率が低くなる。このため十分な位相範囲をカバーするためには円柱の高さを高くする必要がある。
Here, manufacturing costs can be reduced if the metasurface can be manufactured in one process by nanoimprinting, in which dielectric resin is molded using a fine pattern mold. However, in the case of resin containing nanofillers, which are high refractive index materials, the refractive index is 1.8 to 1.9 when titanium dioxide is applied, and the refractive index is about 2.2 even when amorphous silicon is applied. lower refractive index. Therefore, it is necessary to increase the height of the cylinder in order to cover a sufficient phase range.
しかし、この構造では透過率は円柱の径よって大きく変動し、径によっては透過率が40%以下になってしまうという問題があった。これはナノインプリントで成型可能なアスペクト比の円柱で位相をカバーするためには単位ユニットを大きくする必要があり、当該単位ユニットが大きくなると回折の効果が発生し透過率が変動するためである。
However, in this structure, the transmittance varies greatly depending on the diameter of the cylinder, and there was a problem that the transmittance was 40% or less depending on the diameter. This is because it is necessary to increase the unit size in order to cover the phase with a cylinder having an aspect ratio that can be molded by nanoimprinting, and when the unit size increases, the effect of diffraction occurs and the transmittance fluctuates.
そこで本発明は、誘電体樹脂を用いて単位ユニットを大きくすることなくアスペクト比の低いメタサーフェスを提供することを目的とする。
Therefore, an object of the present invention is to provide a metasurface with a low aspect ratio using a dielectric resin without increasing the unit size.
上記目的を達成するために、本発明のメタサーフェスは、光を透過する基板と、前記光の位相分布を制御するために前記基板上に配置された複数の微細構造体とを具備するメタサーフェスであって、前記複数の微細構造体は、2種類以上の高さを有することを特徴とする。
To achieve the above objects, the present invention provides a metasurface comprising a substrate that transmits light and a plurality of microstructures arranged on the substrate for controlling the phase distribution of the light. and wherein the plurality of microstructures have two or more heights.
ここで、前記複数種類の微細構造体の最大アスペクト比は、複数種類の微細構造体を同じ高さで同じ位相差を生じるように設計した場合の最大アスペクト比より小さい方が好ましい。具体的には、前記微細構造体のアスペクト比が5以下である方が好ましい。
Here, the maximum aspect ratio of the plurality of types of microstructures is preferably smaller than the maximum aspect ratio when the plurality of types of microstructures are designed to have the same height and the same phase difference. Specifically, the aspect ratio of the fine structure is preferably 5 or less.
また、前記微細構造体のピッチは、前記光の波長の3/4以下である方が好ましい。
Further, it is preferable that the pitch of the microstructures is 3/4 or less of the wavelength of the light.
また、前記微細構造体は、樹脂であってもよい。
Also, the fine structure may be a resin.
また、前記微細構造体が2層以上積層されていてもよい。
In addition, two or more layers of the microstructure may be laminated.
本発明のメタサーフェスは、単位ユニットを大きくすることなく提供することができる。
The metasurface of the present invention can be provided without increasing the unit size.
以下に、本発明のメタサーフェスについて説明する。本発明のメタサーフェスは、図1に示すように、基板1と、基板1上に配置された複数の微細構造体2とで主に構成される。
The metasurface of the present invention will be described below. The metasurface of the present invention is mainly composed of a substrate 1 and a plurality of microstructures 2 arranged on the substrate 1, as shown in FIG.
ここで、基板1とは複数の微細構造体2を配置するためのものである。材質は光を透過し、複数の微細構造体2を配置できればどのようなものでもよいが、例えば、SiO2等からなるガラス基板を用いればよい。
Here, the substrate 1 is for arranging a plurality of fine structures 2 . Any material may be used as long as it allows light to pass therethrough and a plurality of microstructures 2 can be arranged thereon. For example, a glass substrate made of SiO 2 or the like may be used.
微細構造体2とは、メタサーフェスに使用する光の波長よりも小さいサイズの誘電体からなるもので、透過光の位相を制御するためのものである。微細構造体2のピッチが大きくなると回折の効果が発生し、微細構造体2の径によって透過率が変動するため、ピッチは小さい方がよく、好ましくは使用する光の3/4以下とする方がよい。誘電体としては、例えば、アモルファスシリコン(α-Si)や二酸化チタン(TiO2)等のフィラーを含有する高屈折率の樹脂を用いることができる。特に、樹脂は微細構造体2をナノインプリント法で直接成形することができる点で好ましい。
The fine structure 2 is made of a dielectric with a size smaller than the wavelength of light used for the metasurface, and is used to control the phase of transmitted light. If the pitch of the microstructures 2 becomes large, a diffraction effect occurs, and the transmittance varies depending on the diameter of the microstructures 2. Therefore, the smaller the pitch, the better, preferably 3/4 or less of the light used. is good. As the dielectric, for example, a high refractive index resin containing a filler such as amorphous silicon (α-Si) or titanium dioxide (TiO 2 ) can be used. In particular, resin is preferable in that the fine structure 2 can be directly molded by the nanoimprint method.
微細構造体2の形状は、位相を制御できればどのようなものでもよいが、例えば、柱状や錐台状、錐状にすることができる。特に、錐台状、錐状は微細構造体2をナノインプリント法で直接成形する場合、離形がし易い点で好ましい。また、微細構造体2の平面形状(凸部側から見た断面形状)は、位相を制御することができれば限定されるものではないが、例えば、楕円や三角形、四角形、六角形等にすることができる。ナノインプリント法で微細構造体2を成形する場合には、円柱状や円錐台状、円錐状が形成しやすい点で好ましい。
The shape of the microstructure 2 may be any shape as long as the phase can be controlled, but it can be, for example, columnar, frustum, or conical. In particular, a truncated cone shape and a conical shape are preferable in that when the fine structure 2 is directly molded by the nanoimprint method, the shape can be easily released. In addition, the planar shape (cross-sectional shape viewed from the convex side) of the microstructure 2 is not limited as long as the phase can be controlled. can be done. When the fine structure 2 is formed by the nanoimprint method, it is preferable because it is easy to form a cylindrical shape, a truncated cone shape, or a conical shape.
また、位相は、微細構造体2の高さや径を大きくすると高くなる。ここで径とは、微細構造体2が円柱の場合には、当該円柱の円の直径を意味する。また、微細構造体2が円柱以外の場合には、当該微細構造体2の体積を同じ体積の円柱に換算した場合の円の直径をいうものとする。
Also, the phase increases as the height and diameter of the microstructure 2 are increased. Here, when the fine structure 2 is a cylinder, the diameter means the diameter of the circle of the cylinder. In addition, when the microstructure 2 is other than a cylinder, it means the diameter of a circle when the volume of the microstructure 2 is converted into a cylinder having the same volume.
従来は、微細構造体2の高さを一定とし、光の位相分布を微細構造体2の径のみで制御していた。しかしながら、光の位相分布を径のみで制御しようとすると微細構造体2のアスペクト比が大きくなるため、インプリント法で成形や離形をすることが難しいという問題があった。そこで、本発明者等が鋭意研究した結果、高さを変更することでも位相分布を制御でき、またアスペクト比を小さくできることがわかった。具体的には、設計する位相差が低い場合は高さを低くすることができ、アスペクト比を小さくできることがわかった。そこで、本発明のメタサーフェスでは、微細構造体2を2種類以上の高さとし、それぞれの高さについて、径を調節することにより、微細構造体2のアスペクト比を5以下、4.5以下、4以下、3.5以下、3以下、2.5以下のように小さく形成することができる。
Conventionally, the height of the microstructure 2 was kept constant, and the phase distribution of light was controlled only by the diameter of the microstructure 2. However, when trying to control the phase distribution of light only by the diameter, the aspect ratio of the fine structure 2 becomes large, so there is a problem that it is difficult to mold or release the fine structure 2 by the imprint method. Therefore, as a result of intensive research by the present inventors, it has been found that the phase distribution can be controlled and the aspect ratio can be reduced by changing the height. Specifically, it was found that when the phase difference to be designed is low, the height can be reduced and the aspect ratio can be reduced. Therefore, in the metasurface of the present invention, the microstructure 2 has two or more different heights, and the diameter of each height is adjusted so that the aspect ratio of the microstructure 2 is 5 or less, 4.5 or less, It can be formed as small as 4 or less, 3.5 or less, 3 or less, or 2.5 or less.
また、微細構造体2の上面側又は底面側に、ナノインプリント技術等によって生じる残膜のようなパターンのない層があっても、位相分布には影響を与えない。しかしながら、光の透過率の観点からは、使用する光の波長の1/4以下の厚さである方が好ましい。
In addition, even if there is a pattern-free layer such as a residual film produced by nanoimprint technology or the like on the top side or the bottom side of the microstructure 2, it does not affect the phase distribution. However, from the viewpoint of light transmittance, the thickness is preferably 1/4 or less of the wavelength of the light used.
また、微細構造体2は、図2に示すように、2層以上が積層されていてもよい。これにより第1層目の微細構造体2によって付与された位相差に、第2層目以降の微細構造体2によって付与される位相差を加えていくことができる。したがって、第1層目の微細構造体2の位置と第2層目以降の微細構造体2の位置を合わせれば、微細構造体2の高さやアスペクト比を更に小さくすることができる。なお、微細構造体間は、微細構造体の屈折率より低い樹脂で埋めてもよい。
Further, as shown in FIG. 2, the fine structure 2 may be laminated with two or more layers. Thereby, the phase difference provided by the microstructures 2 of the second and subsequent layers can be added to the phase difference provided by the microstructures 2 of the first layer. Therefore, by aligning the position of the microstructures 2 in the first layer with the positions of the microstructures 2 in the second and subsequent layers, the height and aspect ratio of the microstructures 2 can be further reduced. Note that the space between the microstructures may be filled with a resin having a refractive index lower than that of the microstructures.
以下に、本発明のメタサーフェスの製造方法について説明する。まず、マスターモールド10の製造方法を図3に示す。最初に、図3(a)に示すように、基板11にハードマスク12を成膜する。基板11には例えば、SiO2等のガラス基板を用いればよい。また、ハードマスク12としては例えばCr等の金属を用いればよい。ハードマスク12の成膜にはスパッタリング法など、周知の方法で行えばよい。次に、図3(b)に示すように、ハードマスク12上に微細構造体のパターン13を作成する。このパターン13の作成には、例えば、フォトリソグラフィ技術やナノインプリント技術等の周知の技術を用いればよい。次に、図3(c)に示すように、パターン13を用いてハードマスク12をエッチングする。続けて、基板11のエッチングを行う。ハードマスク12、基板11のエッチングにはRIE等の周知の方法を用いればよい。基板11のエッチング深さは作成したい微細構造体のうち一番高さの低いものの深さになるようにする。なお、ハードマスク12のエッチング後であって基板11のエッチングの前にパターン13をアッシング等によって除去しておいてもよい。次に、図3(d)に示すように、一番高さの低い微細構造体の上部を覆うパターン14を作成する。パターン14の作成には、例えば、フォトリソグラフィ技術やナノインプリント技術等の周知の技術を用いればよい。次に、図3(e)に示すように、今度は二番目に高さの低い微細構造体ができるように、基板1のエッチングを行う。そしてパターン14を除去する。高さを3種類以上にする場合には、同様にして三番目以降の微細構造体を作成すればよい。最後に、図3(f)に示すように、パターン13やハードマスク12を除去すればマスターモールド10が製造できる。
A method for manufacturing a metasurface according to the present invention will be described below. First, a method of manufacturing the master mold 10 is shown in FIG. First, a hard mask 12 is deposited on a substrate 11 as shown in FIG. 3(a). For the substrate 11, for example, a glass substrate such as SiO 2 may be used. As the hard mask 12, metal such as Cr may be used. Film formation of the hard mask 12 may be performed by a well-known method such as a sputtering method. Next, as shown in FIG. 3B, a fine structure pattern 13 is formed on the hard mask 12. Next, as shown in FIG. A well-known technique such as a photolithography technique or a nanoimprint technique may be used to create the pattern 13, for example. Next, as shown in FIG. 3C, the pattern 13 is used to etch the hard mask 12 . Subsequently, the substrate 11 is etched. A well-known method such as RIE may be used for etching the hard mask 12 and the substrate 11 . The etching depth of the substrate 11 is set to the depth of the lowest height of the microstructures to be formed. The pattern 13 may be removed by ashing or the like after the hard mask 12 is etched and before the substrate 11 is etched. Next, as shown in FIG. 3(d), a pattern 14 is formed to cover the top of the lowest microstructure. A well-known technique such as photolithography technique or nanoimprint technique may be used to create the pattern 14, for example. Next, as shown in FIG. 3(e), the substrate 1 is etched so as to form a fine structure having the second lowest height. Then pattern 14 is removed. When three or more heights are to be used, the third and subsequent microstructures may be produced in the same manner. Finally, as shown in FIG. 3(f), the master mold 10 can be manufactured by removing the pattern 13 and the hard mask 12. Next, as shown in FIG.
次にホールレプリカ25の製造方法を説明する。図4(a)のように、マスターモールド10上に樹脂21を塗布し、当該樹脂21を硬化させた後に離型して、図4(b)のようなピラーレプリカ22を成形する。次に図4(b)のように基板23上に樹脂24を塗布する。そして、図4(c)のようにピラーレプリカ22を樹脂24に加圧する。基板23には、例えば、SiO2等のガラス基板を用いればよい。最後に、樹脂24を硬化させた後、離形し、図4(d)に示すようなホールレプリカ25を作成する。
Next, a method for manufacturing the hole replica 25 will be described. As shown in FIG. 4(a), a resin 21 is applied onto the master mold 10, and after the resin 21 is cured, the mold is released to form a pillar replica 22 as shown in FIG. 4(b). Next, a resin 24 is applied onto the substrate 23 as shown in FIG. 4(b). Then, the pillar replica 22 is pressed against the resin 24 as shown in FIG. 4(c). A glass substrate such as SiO 2 may be used for the substrate 23, for example. Finally, after the resin 24 is cured, it is released from the mold to form a hole replica 25 as shown in FIG. 4(d).
次に、本発明のメタサーフェスの製造方法を説明する。図5(a)のようにホールレプリカ25に高屈折率樹脂31を塗布する。高屈折率樹脂31としては、例えば、アモルファスシリコン(α-Si)や二酸化チタン(TiO2)等のフィラーを含有する樹脂を用いればよい。次に図5(b)に示すように、高屈折率樹脂31を基板32に圧着した後で硬化させる。最後に、図5(c)に示すように、ホールレプリカ25を離型すれば、本発明のメタサーフェスを製造することができる。
Next, a method for manufacturing a metasurface according to the present invention will be described. A high refractive index resin 31 is applied to the hole replica 25 as shown in FIG. 5(a). As the high refractive index resin 31, for example, a resin containing a filler such as amorphous silicon (α-Si) or titanium dioxide (TiO 2 ) may be used. Next, as shown in FIG. 5(b), the high refractive index resin 31 is pressure-bonded to the substrate 32 and then cured. Finally, as shown in FIG. 5(c), the metasurface of the present invention can be manufactured by releasing the hole replica 25 from the mold.
次に、本発明のメタサーフェスを積層する場合の製造方法について説明する。メタサーフェスの微細構造体は積層しても効果があることがわかっている。そこで、例えばn層に積層して作成したい場合は、上述した製造方法(図3参照)により、各パターンの高さを低くしてマスターモールド10を作成する。このマスターモールド10で上述した製造方法(図4参照)と同様にピラーレプリカ22及びホールレプリカ25を作成する。ここで、ホールレプリカ25の樹脂24としては、低屈折率樹脂を用いる。
Next, a manufacturing method for laminating the metasurface of the present invention will be described. Metasurface microstructures have been found to be effective even when stacked. Therefore, when it is desired to laminate n layers, for example, the master mold 10 is created by lowering the height of each pattern by the above-described manufacturing method (see FIG. 3). A pillar replica 22 and a hole replica 25 are produced with this master mold 10 in the same manner as in the manufacturing method described above (see FIG. 4). Here, as the resin 24 of the hole replica 25, a low refractive index resin is used.
次に、図6(a)に示すように、ホールレプリカ25上に、樹脂24よりも高屈折率である樹脂61を塗布してホールを埋めた後、平坦化してUVで硬化させる。高屈折率樹脂61としては、例えば、アモルファスシリコン(α-Si)や二酸化チタン(TiO2)等のフィラーを含有する樹脂を用いればよい。続いて、図6(b)に示すように、高屈折率樹脂61上に低屈折率樹脂62を塗布する。そして、図6(c)に示すように、ピラーレプリカ22を低屈折率樹脂62に加圧、離形して、ホール状のパターンを成形する。最後に、図6(d)に示すように、高屈折率樹脂63を塗布してホールを埋めた後、平たん化してUVで硬化させればよい。
Next, as shown in FIG. 6A, a resin 61 having a refractive index higher than that of the resin 24 is applied onto the hole replica 25 to fill the holes, and then flattened and cured with UV. As the high refractive index resin 61, for example, a resin containing a filler such as amorphous silicon (α-Si) or titanium dioxide (TiO 2 ) may be used. Subsequently, as shown in FIG. 6B, a low refractive index resin 62 is applied on the high refractive index resin 61. Then, as shown in FIG. Then, as shown in FIG. 6(c), the pillar replica 22 is pressed against the low refractive index resin 62 and released to form a hole-like pattern. Finally, as shown in FIG. 6(d), a high refractive index resin 63 is applied to fill the holes, then flattened and cured with UV.
次に、本発明のメタサーフェスの構造に関し、種々のシミュレーションをした結果を以下に示す。なお、シミュレーションには、RCWA法(Rigorous Coupled Wave Analysis)を用いた。
[シミュレーション1]
微細構造体のピッチ及び径と透過率の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図7(a)、(b)に示すように、高さH1が1.6μmで屈折率N1が1.85の円柱状とし、これを六方配列とした。また、基板の屈折率N0は1.5とした。図8(a)に微細構造体のピッチP及び径Dと透過率のシミュレーション結果を示す。また、微細構造体のピッチPのうち、520nm、600nm、680nm、760nm、840nmの5種類について径Dと透過率の関係を図8(b)に示す。 Next, the results of various simulations performed on the structure of the metasurface of the present invention are shown below. The RCWA method (Rigorous Coupled Wave Analysis) was used for the simulation.
[Simulation 1]
The relationship between the pitch and diameter of the microstructures and the transmittance was simulated. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIGS. 7(a) and 7(b), the microstructures were cylindrical with a height H1 of 1.6 μm and a refractive index N1 of 1.85, and arranged in a hexagonal arrangement. Also, the refractive index N0 of the substrate was set to 1.5. FIG. 8(a) shows simulation results of the pitch P and diameter D of the microstructure and the transmittance. FIG. 8(b) shows the relationship between the diameter D and the transmittance for five types of the pitch P of the fine structure, 520 nm, 600 nm, 680 nm, 760 nm, and 840 nm.
[シミュレーション1]
微細構造体のピッチ及び径と透過率の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図7(a)、(b)に示すように、高さH1が1.6μmで屈折率N1が1.85の円柱状とし、これを六方配列とした。また、基板の屈折率N0は1.5とした。図8(a)に微細構造体のピッチP及び径Dと透過率のシミュレーション結果を示す。また、微細構造体のピッチPのうち、520nm、600nm、680nm、760nm、840nmの5種類について径Dと透過率の関係を図8(b)に示す。 Next, the results of various simulations performed on the structure of the metasurface of the present invention are shown below. The RCWA method (Rigorous Coupled Wave Analysis) was used for the simulation.
[Simulation 1]
The relationship between the pitch and diameter of the microstructures and the transmittance was simulated. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIGS. 7(a) and 7(b), the microstructures were cylindrical with a height H1 of 1.6 μm and a refractive index N1 of 1.85, and arranged in a hexagonal arrangement. Also, the refractive index N0 of the substrate was set to 1.5. FIG. 8(a) shows simulation results of the pitch P and diameter D of the microstructure and the transmittance. FIG. 8(b) shows the relationship between the diameter D and the transmittance for five types of the pitch P of the fine structure, 520 nm, 600 nm, 680 nm, 760 nm, and 840 nm.
図8(a)(b)に示すように、微細構造体のピッチPが入射光の波長の3/4波長より大きくなると微細構造体の径Dによっては透過率が下がることがわかる。したがって、微細構造体のピッチPは、使用する光の波長の3/4以下とする方が好ましい。
As shown in FIGS. 8(a) and 8(b), it can be seen that the transmittance decreases depending on the diameter D of the microstructures when the pitch P of the microstructures is larger than 3/4 wavelength of the incident light. Therefore, it is preferable to set the pitch P of the fine structures to 3/4 or less of the wavelength of the light used.
[シミュレーション2]
微細構造体の径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図9に示すように、ピッチPが0.65μmの円柱状とした。屈折率は、二酸化チタン(TiO2)フィラーを含有する樹脂を想定して1.85とした。また、微細構造体の高さH1とH2は、1.6μmと0.9μmの2種類とした。また、基板の屈折率は1.5とした。図10に微細構造体の径Dと位相差のシミュレーション結果を示す。 [Simulation 2]
The relationship between the diameter of the microstructure and the phase difference of transmitted light was simulated. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIG. 9, the fine structure was cylindrical with a pitch P of 0.65 μm. The refractive index was set to 1.85 assuming a resin containing titanium dioxide (TiO 2 ) filler. Also, the heights H1 and H2 of the fine structure are of two types, 1.6 μm and 0.9 μm. Also, the refractive index of the substrate was set to 1.5. FIG. 10 shows simulation results of the diameter D of the fine structure and the phase difference.
微細構造体の径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図9に示すように、ピッチPが0.65μmの円柱状とした。屈折率は、二酸化チタン(TiO2)フィラーを含有する樹脂を想定して1.85とした。また、微細構造体の高さH1とH2は、1.6μmと0.9μmの2種類とした。また、基板の屈折率は1.5とした。図10に微細構造体の径Dと位相差のシミュレーション結果を示す。 [Simulation 2]
The relationship between the diameter of the microstructure and the phase difference of transmitted light was simulated. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIG. 9, the fine structure was cylindrical with a pitch P of 0.65 μm. The refractive index was set to 1.85 assuming a resin containing titanium dioxide (TiO 2 ) filler. Also, the heights H1 and H2 of the fine structure are of two types, 1.6 μm and 0.9 μm. Also, the refractive index of the substrate was set to 1.5. FIG. 10 shows simulation results of the diameter D of the fine structure and the phase difference.
図10に示すように、微細構造体の高さが低くなると透過光の位相差が小さくなる。また、微細構造体の径Dが大きくなると透過光の位相差は大きくなる。したがって、微細構造体の高さを低くすると、透過光の位相差を同じとするためには、径Dを大きくする必要がある。すなわち、高さが低く径が大きくなるため、アスペクト比を小さくすることができる。
As shown in FIG. 10, the phase difference of transmitted light decreases as the height of the fine structure decreases. Further, as the diameter D of the fine structure increases, the phase difference of transmitted light increases. Therefore, when the height of the microstructure is reduced, the diameter D must be increased in order to keep the phase difference of the transmitted light the same. That is, since the height is low and the diameter is large, the aspect ratio can be reduced.
具体的には、例えば、45度(π/4ラジアン)の位相差を付与する微細構造体Aと315度(7π/4ラジアン)の位相差を付与する微細構造体Bの2種類を設計する場合について検討する。どちらの微細構造体も円柱状で高さを1.6μmとすると、微細構造体Aは径を0.5μm、微細構造体Bは径を0.207μmとする必要がある。この場合、微細構造体Aのアスペクト比は3.2、微細構造体Bのアスペクト比は7.7となる。一方、微細構造体Bの高さを0.9μmとした場合、微細構造体Bの径は0.27μmとすることができる。この場合、アスペクト比は3.3となり、微細構造体A,Bの高さを一定にした場合より微細構造体A,Bの高さを変えた方が、微細構造体全体のアスペクト比を小さくすることができる。
Specifically, for example, two types of microstructures are designed: a microstructure A that provides a phase difference of 45 degrees (π/4 radians) and a microstructure B that provides a phase difference of 315 degrees (7π/4 radians). Consider the case. Assuming that both microstructures are cylindrical and have a height of 1.6 μm, the microstructure A should have a diameter of 0.5 μm and the microstructure B should have a diameter of 0.207 μm. In this case, the aspect ratio of the fine structure A is 3.2, and the aspect ratio of the fine structure B is 7.7. On the other hand, when the height of the microstructure B is 0.9 μm, the diameter of the microstructure B can be 0.27 μm. In this case, the aspect ratio is 3.3, and the aspect ratio of the entire fine structure can be made smaller by changing the heights of the fine structures A and B than by keeping the heights of the fine structures A and B constant. can be done.
[シミュレーション3]
微細構造体の径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図11に示すように、ピッチP1が0.68μmの円柱状とした。屈折率は、アモルファスシリコン(α-Si)フィラーを含有する樹脂を想定して2.2とした。また、微細構造体の高さH1とH2は、1.1μmと0.75μmの2種類とした。また、基板の屈折率は1.5とした。図12に微細構造体の径と位相差のシミュレーション結果を示す。 [Simulation 3]
The relationship between the diameter of the microstructure and the phase difference of transmitted light was simulated. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIG. 11, the fine structure was cylindrical with a pitch P1 of 0.68 μm. The refractive index was set to 2.2 assuming a resin containing amorphous silicon (α-Si) filler. Also, the heights H1 and H2 of the fine structure are of two types, 1.1 μm and 0.75 μm. Also, the refractive index of the substrate was set to 1.5. FIG. 12 shows simulation results of the diameter of the fine structure and the phase difference.
微細構造体の径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図11に示すように、ピッチP1が0.68μmの円柱状とした。屈折率は、アモルファスシリコン(α-Si)フィラーを含有する樹脂を想定して2.2とした。また、微細構造体の高さH1とH2は、1.1μmと0.75μmの2種類とした。また、基板の屈折率は1.5とした。図12に微細構造体の径と位相差のシミュレーション結果を示す。 [Simulation 3]
The relationship between the diameter of the microstructure and the phase difference of transmitted light was simulated. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIG. 11, the fine structure was cylindrical with a pitch P1 of 0.68 μm. The refractive index was set to 2.2 assuming a resin containing amorphous silicon (α-Si) filler. Also, the heights H1 and H2 of the fine structure are of two types, 1.1 μm and 0.75 μm. Also, the refractive index of the substrate was set to 1.5. FIG. 12 shows simulation results of the diameter of the fine structure and the phase difference.
図12に示すように、微細構造体の高さが低くなると透過光の位相差が小さくなる。また、微細構造体の径が大きくなると透過光の位相差は大きくなる。したがって、微細構造体の高さを低くすると、透過光の位相差を同じとするためには、径を大きくする必要がある。すなわち、高さが低く径が大きくなるため、アスペクト比を小さくすることができる。
As shown in FIG. 12, the phase difference of transmitted light decreases as the height of the fine structure decreases. Further, as the diameter of the fine structure increases, the phase difference of transmitted light increases. Therefore, if the height of the microstructure is reduced, the diameter must be increased in order to keep the phase difference of the transmitted light the same. That is, since the height is low and the diameter is large, the aspect ratio can be reduced.
具体的には、例えば、45度(π/4ラジアン)の位相差を付与する微細構造体Aと315度(7π/4ラジアン)の位相差を付与する微細構造体Bの2種類を設計する場合について検討する。どちらの微細構造体も円柱状で高さを1.1μmとすると、微細構造体Aは径を0.46μm、微細構造体Bは径を0.214μmとする必要がある。この場合、微細構造体Aのアスペクト比は2.4、微細構造体Bのアスペクト比は5.14となる。一方、微細構造体Bの高さを0.75μmとした場合、微細構造体Bの径は0.245μmとすることができる。この場合、アスペクト比は3.06となり、微細構造体A,Bの高さを一定にした場合より微細構造体A,Bの高さを変えた方が、微細構造体全体のアスペクト比を小さくすることができる。
Specifically, for example, two types of microstructures are designed: a microstructure A that provides a phase difference of 45 degrees (π/4 radians) and a microstructure B that provides a phase difference of 315 degrees (7π/4 radians). Consider the case. Assuming that both microstructures are cylindrical and have a height of 1.1 μm, the microstructure A should have a diameter of 0.46 μm and the microstructure B should have a diameter of 0.214 μm. In this case, the aspect ratio of fine structure A is 2.4, and the aspect ratio of fine structure B is 5.14. On the other hand, when the height of the microstructure B is 0.75 μm, the diameter of the microstructure B can be 0.245 μm. In this case, the aspect ratio is 3.06, and the aspect ratio of the entire fine structure can be made smaller by changing the heights of the fine structures A and B than by keeping the heights of the fine structures A and B constant. can be done.
[シミュレーション4]
同じ微細構造体を2層、上下に積層した場合の微細構造体のピッチと透過率の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図13(a)、(b)に示すように、高さH1が1.2μmで屈折率が1.85の円柱状とし、これを六方配列とした。また、微細構造体のピッチは、0.69μmとした。また、微細構造体間に埋め込んだ樹脂の屈折率を1.35、基板の屈折率を1.5とした。図14に微細構造体のピッチPおよび径Dと透過率のシミュレーション結果を示す。 [Simulation 4]
A simulation was performed of the relationship between the pitch of the microstructures and the transmittance when two layers of the same microstructures were laminated one above the other. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIGS. 13(a) and 13(b), the microstructures were cylindrical with a height H1 of 1.2 μm and a refractive index of 1.85, and arranged in a hexagonal arrangement. Also, the pitch of the fine structures was set to 0.69 μm. The refractive index of the resin embedded between the fine structures was 1.35, and the refractive index of the substrate was 1.5. FIG. 14 shows simulation results of the pitch P and diameter D of the microstructure and the transmittance.
同じ微細構造体を2層、上下に積層した場合の微細構造体のピッチと透過率の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図13(a)、(b)に示すように、高さH1が1.2μmで屈折率が1.85の円柱状とし、これを六方配列とした。また、微細構造体のピッチは、0.69μmとした。また、微細構造体間に埋め込んだ樹脂の屈折率を1.35、基板の屈折率を1.5とした。図14に微細構造体のピッチPおよび径Dと透過率のシミュレーション結果を示す。 [Simulation 4]
A simulation was performed of the relationship between the pitch of the microstructures and the transmittance when two layers of the same microstructures were laminated one above the other. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIGS. 13(a) and 13(b), the microstructures were cylindrical with a height H1 of 1.2 μm and a refractive index of 1.85, and arranged in a hexagonal arrangement. Also, the pitch of the fine structures was set to 0.69 μm. The refractive index of the resin embedded between the fine structures was 1.35, and the refractive index of the substrate was 1.5. FIG. 14 shows simulation results of the pitch P and diameter D of the microstructure and the transmittance.
図14に示すように、微細構造体のピッチPが入射光の波長の3/4波長より大きくなると微細構造体の径Dによっては透過率が下がることがわかる。したがって、微細構造体のピッチPは、使用する光の波長の3/4以下とする方が好ましい。また、2層にしても透過率に大きな影響はなかった。
As shown in FIG. 14, it can be seen that the transmittance decreases depending on the diameter D of the microstructures when the pitch P of the microstructures is larger than 3/4 wavelength of the incident light. Therefore, it is preferable to set the pitch P of the fine structures to 3/4 or less of the wavelength of the light used. Also, even with two layers, there was no significant effect on the transmittance.
[シミュレーション5]
同じ微細構造体を2層、上下に積層した場合の微細構造体の径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図15に示すように、ピッチPが0.69μmの円柱状とした。屈折率は、アモルファスシリコン(α-Si)フィラーを含有する樹脂を想定して2.2とした。また、微細構造体の高さH1とH2は、1.2μmと0.65μmの2種類とした。また、微細構造体間に埋め込んだ樹脂の屈折率を1.35、基板の屈折率を1.5とした。図16に微細構造体の径Dと位相差のシミュレーション結果を示す。 [Simulation 5]
A simulation was performed of the relationship between the diameter of the fine structure and the phase difference of the transmitted light when two layers of the same fine structure are laminated one above the other. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIG. 15, the fine structure was cylindrical with a pitch P of 0.69 μm. The refractive index was set to 2.2 assuming a resin containing amorphous silicon (α-Si) filler. Also, the heights H1 and H2 of the microstructures were of two types, 1.2 μm and 0.65 μm. The refractive index of the resin embedded between the fine structures was 1.35, and the refractive index of the substrate was 1.5. FIG. 16 shows simulation results of the diameter D of the fine structure and the phase difference.
同じ微細構造体を2層、上下に積層した場合の微細構造体の径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体は、図15に示すように、ピッチPが0.69μmの円柱状とした。屈折率は、アモルファスシリコン(α-Si)フィラーを含有する樹脂を想定して2.2とした。また、微細構造体の高さH1とH2は、1.2μmと0.65μmの2種類とした。また、微細構造体間に埋め込んだ樹脂の屈折率を1.35、基板の屈折率を1.5とした。図16に微細構造体の径Dと位相差のシミュレーション結果を示す。 [Simulation 5]
A simulation was performed of the relationship between the diameter of the fine structure and the phase difference of the transmitted light when two layers of the same fine structure are laminated one above the other. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As shown in FIG. 15, the fine structure was cylindrical with a pitch P of 0.69 μm. The refractive index was set to 2.2 assuming a resin containing amorphous silicon (α-Si) filler. Also, the heights H1 and H2 of the microstructures were of two types, 1.2 μm and 0.65 μm. The refractive index of the resin embedded between the fine structures was 1.35, and the refractive index of the substrate was 1.5. FIG. 16 shows simulation results of the diameter D of the fine structure and the phase difference.
図16に示すように、微細構造体の高さが低くなると透過光の位相差が小さくなる。また、微細構造体の径Dが大きくなると透過光の位相差は大きくなる。したがって、微細構造体の高さを低くすると、透過光の位相差を同じとするためには、径Dを大きくする必要がある。すなわち、高さが低く径が大きくなるため、アスペクト比を小さくすることができる。
As shown in FIG. 16, the phase difference of transmitted light decreases as the height of the fine structure decreases. Further, as the diameter D of the fine structure increases, the phase difference of transmitted light increases. Therefore, when the height of the microstructure is reduced, the diameter D must be increased in order to keep the phase difference of the transmitted light the same. That is, since the height is low and the diameter is large, the aspect ratio can be reduced.
具体的には、例えば、45度(π/4ラジアン)の位相差を付与する微細構造体Aと315度(7π/4ラジアン)の位相差を付与する微細構造体Bの2種類を設計する場合について検討する。どちらの微細構造体も円柱状で高さを1.2μmとすると、微細構造体Aは径を0.57μm、微細構造体Bは径を0.22μmとする必要がある。この場合、微細構造体Aのアスペクト比は2.1、微細構造体Bのアスペクト比は5.45となる。一方、微細構造体Bの高さを0.65μmとした場合、微細構造体Bの径は0.287μmとすることができる。この場合、アスペクト比は2.26となり、微細構造体A,Bの高さを一定にした場合より微細構造体A,Bの高さを変えた方が、微細構造体全体のアスペクト比を小さくすることができる。また、2層積層した場合には、1層で構成した場合よりも、アスペクト比かなり小さくすることができた。
Specifically, for example, two types of microstructures are designed: a microstructure A that provides a phase difference of 45 degrees (π/4 radians) and a microstructure B that provides a phase difference of 315 degrees (7π/4 radians). Consider the case. Assuming that both microstructures are cylindrical and have a height of 1.2 μm, the microstructure A should have a diameter of 0.57 μm and the microstructure B should have a diameter of 0.22 μm. In this case, the aspect ratio of fine structure A is 2.1, and the aspect ratio of fine structure B is 5.45. On the other hand, when the height of the microstructure B is 0.65 μm, the diameter of the microstructure B can be 0.287 μm. In this case, the aspect ratio is 2.26, and the aspect ratio of the entire fine structure can be made smaller by changing the heights of the fine structures A and B than by keeping the heights of the fine structures A and B constant. can be done. In addition, when two layers were laminated, the aspect ratio could be made considerably smaller than in the case of one layer.
[シミュレーション6]
微細構造体が円柱状である場合と円錐台状である場合における径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体の形状は、図17に示すように、微細構造体A,C,D,Fを円錐台状、微細構造体B,Eを円柱状とした。また、基板に対する微細構造体A,C,D,Fの側面の角度を87度とした。また、微細構造体A~Cの高さH1を1.6μm、微細構造体D~Fの高さH2を0.9μmとした。また、微細構造体A,Dの径は円錐台の上面の径とし、微細構造体C,Fの径は円錐台の底面の径とした。屈折率は、二酸化チタン(TiO2)フィラーを含有する樹脂を想定して1.85とした。また、基板の屈折率は1.5とした。図18に微細構造体の径Dと位相差のシミュレーション結果を示す。 [Simulation 6]
A simulation was performed on the relationship between the diameter and the phase difference of transmitted light when the fine structure is cylindrical and when it is truncated cone. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As for the shape of the microstructures, as shown in FIG. 17, the microstructures A, C, D, and F were truncated conical, and the microstructures B and E were cylindrical. Also, the angle of the side surfaces of the microstructures A, C, D, and F with respect to the substrate was set to 87 degrees. Also, the height H1 of the microstructures A to C was set to 1.6 μm, and the height H2 of the microstructures D to F was set to 0.9 μm. The diameters of the microstructures A and D are the diameters of the top surface of the truncated cone, and the diameters of the microstructures C and F are the diameter of the bottom surface of the truncated cone. The refractive index was set to 1.85 assuming a resin containing titanium dioxide (TiO 2 ) filler. Also, the refractive index of the substrate was set to 1.5. FIG. 18 shows simulation results of the diameter D of the fine structure and the phase difference.
微細構造体が円柱状である場合と円錐台状である場合における径と透過光の位相差の関係をシミュレーションした。シミュレーションでは、メタサーフェスに入射させる光の波長を940nmとした。微細構造体の形状は、図17に示すように、微細構造体A,C,D,Fを円錐台状、微細構造体B,Eを円柱状とした。また、基板に対する微細構造体A,C,D,Fの側面の角度を87度とした。また、微細構造体A~Cの高さH1を1.6μm、微細構造体D~Fの高さH2を0.9μmとした。また、微細構造体A,Dの径は円錐台の上面の径とし、微細構造体C,Fの径は円錐台の底面の径とした。屈折率は、二酸化チタン(TiO2)フィラーを含有する樹脂を想定して1.85とした。また、基板の屈折率は1.5とした。図18に微細構造体の径Dと位相差のシミュレーション結果を示す。 [Simulation 6]
A simulation was performed on the relationship between the diameter and the phase difference of transmitted light when the fine structure is cylindrical and when it is truncated cone. In the simulation, the wavelength of light incident on the metasurface was set to 940 nm. As for the shape of the microstructures, as shown in FIG. 17, the microstructures A, C, D, and F were truncated conical, and the microstructures B and E were cylindrical. Also, the angle of the side surfaces of the microstructures A, C, D, and F with respect to the substrate was set to 87 degrees. Also, the height H1 of the microstructures A to C was set to 1.6 μm, and the height H2 of the microstructures D to F was set to 0.9 μm. The diameters of the microstructures A and D are the diameters of the top surface of the truncated cone, and the diameters of the microstructures C and F are the diameter of the bottom surface of the truncated cone. The refractive index was set to 1.85 assuming a resin containing titanium dioxide (TiO 2 ) filler. Also, the refractive index of the substrate was set to 1.5. FIG. 18 shows simulation results of the diameter D of the fine structure and the phase difference.
図18に示すように、円錐台状の微細構造体も高さが低くなると透過光の位相差が小さくなる。また、円錐台状の微細構造体も径が大きくなると透過光の位相差は大きくなる。したがって、微細構造体の形状が円錐台状であったとしても、円柱状の場合と同様に微細構造体の高さと径によって位相差を制御できることがわかった。
As shown in FIG. 18, when the height of the truncated cone-shaped fine structure is lowered, the phase difference of the transmitted light is also reduced. Also, as the diameter of the truncated conical microstructure increases, the phase difference of the transmitted light also increases. Therefore, it was found that even if the shape of the fine structure is a truncated cone, the phase difference can be controlled by the height and diameter of the fine structure as in the case of the cylindrical shape.
[シミュレーション7]
2種類の高さを持つ2次元メタレンズの特性についてシミュレーションした。シミュレーションでは、図19(A)(a)~(g)のような微細構造体を用いた。これらはそれぞれ(a)315度(7π/4ラジアン)、(b)270度(3π/2ラジアン)、(c)225度(5π/4ラジアン)、(d)180度(πラジアン)、(e)135度(3π/4ラジアン)、(f)90度(π/2ラジアン)、(g)45度(π/4ラジアン)の位相差を付与するものである。微細構造体の高さH1とH2は、1600nmと900nmの2種類とした。また、微細構造体の径はD1:470nm、D2:440nm、D3:395nm、D4:490nm、D5:410nm、D6:340nm、D7:260nmとした。また、微細構造体のピッチUは620nmとした。また、微細構造体の屈折率を1.85、基板の屈折率を1.5とした。これらの微細構造体(a)~(g)を図19(B)のように並べた。図20(a)に、メタレンズからZ方向(高さ方向)の電界強度分布のシミュレーション結果を示す。また、図20(b)に、焦点付近(Z=32.6μm)におけるX-Y平面上の電界強度分布のシミュレーション結果を示す。 [Simulation 7]
We simulated the properties of two-dimensional metalens with two different heights. In the simulation, microstructures such as those shown in (a) to (g) of FIG. 19(A) were used. These are respectively (a) 315 degrees (7π/4 radians), (b) 270 degrees (3π/2 radians), (c) 225 degrees (5π/4 radians), (d) 180 degrees (π radians), ( A phase difference of e) 135 degrees (3π/4 radians), (f) 90 degrees (π/2 radians), and (g) 45 degrees (π/4 radians) is provided. The heights H1 and H2 of the microstructures were of two types, 1600 nm and 900 nm. The diameters of the fine structures were D1: 470 nm, D2: 440 nm, D3: 395 nm, D4: 490 nm, D5: 410 nm, D6: 340 nm, and D7: 260 nm. Also, the pitch U of the fine structures was set to 620 nm. Also, the refractive index of the microstructure was set to 1.85, and the refractive index of the substrate was set to 1.5. These microstructures (a) to (g) were arranged as shown in FIG. 19(B). FIG. 20A shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens. Also, FIG. 20(b) shows a simulation result of the electric field strength distribution on the XY plane in the vicinity of the focal point (Z=32.6 μm).
2種類の高さを持つ2次元メタレンズの特性についてシミュレーションした。シミュレーションでは、図19(A)(a)~(g)のような微細構造体を用いた。これらはそれぞれ(a)315度(7π/4ラジアン)、(b)270度(3π/2ラジアン)、(c)225度(5π/4ラジアン)、(d)180度(πラジアン)、(e)135度(3π/4ラジアン)、(f)90度(π/2ラジアン)、(g)45度(π/4ラジアン)の位相差を付与するものである。微細構造体の高さH1とH2は、1600nmと900nmの2種類とした。また、微細構造体の径はD1:470nm、D2:440nm、D3:395nm、D4:490nm、D5:410nm、D6:340nm、D7:260nmとした。また、微細構造体のピッチUは620nmとした。また、微細構造体の屈折率を1.85、基板の屈折率を1.5とした。これらの微細構造体(a)~(g)を図19(B)のように並べた。図20(a)に、メタレンズからZ方向(高さ方向)の電界強度分布のシミュレーション結果を示す。また、図20(b)に、焦点付近(Z=32.6μm)におけるX-Y平面上の電界強度分布のシミュレーション結果を示す。 [Simulation 7]
We simulated the properties of two-dimensional metalens with two different heights. In the simulation, microstructures such as those shown in (a) to (g) of FIG. 19(A) were used. These are respectively (a) 315 degrees (7π/4 radians), (b) 270 degrees (3π/2 radians), (c) 225 degrees (5π/4 radians), (d) 180 degrees (π radians), ( A phase difference of e) 135 degrees (3π/4 radians), (f) 90 degrees (π/2 radians), and (g) 45 degrees (π/4 radians) is provided. The heights H1 and H2 of the microstructures were of two types, 1600 nm and 900 nm. The diameters of the fine structures were D1: 470 nm, D2: 440 nm, D3: 395 nm, D4: 490 nm, D5: 410 nm, D6: 340 nm, and D7: 260 nm. Also, the pitch U of the fine structures was set to 620 nm. Also, the refractive index of the microstructure was set to 1.85, and the refractive index of the substrate was set to 1.5. These microstructures (a) to (g) were arranged as shown in FIG. 19(B). FIG. 20A shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens. Also, FIG. 20(b) shows a simulation result of the electric field strength distribution on the XY plane in the vicinity of the focal point (Z=32.6 μm).
図20に示すように、2つの高さをもつメタレンズでも、Z=32.6μm付近に焦点を有するレンズとして良好に機能していることがわかった。
As shown in FIG. 20, it was found that even a metalens having two heights functions well as a lens having a focal point near Z=32.6 μm.
[シミュレーション8]
屈折率1.8である2種類の高さの微細構造体(ピッチ620nm)をもつメタレンズAと、屈折率3.13である1種類の高さの微細構造体(ピッチ400nm)をもつ従来のメタレンズBについて、その特性を比較した。図21(a)に、メタレンズAからZ方向(高さ方向)の電界強度分布のシミュレーション結果を示す。また、図21(b)に、メタレンズBからZ方向(高さ方向)の電界強度分布のシミュレーション結果を示す。 [Simulation 8]
Metalens A, which has two types of height microstructures (pitch 620 nm) with a refractive index of 1.8, and conventional metalens A, which has one type of height microstructures (pitch 400 nm) with a refractive index of 3.13. The properties of metalens B were compared. FIG. 21A shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens A. FIG. FIG. 21(b) shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens B. As shown in FIG.
屈折率1.8である2種類の高さの微細構造体(ピッチ620nm)をもつメタレンズAと、屈折率3.13である1種類の高さの微細構造体(ピッチ400nm)をもつ従来のメタレンズBについて、その特性を比較した。図21(a)に、メタレンズAからZ方向(高さ方向)の電界強度分布のシミュレーション結果を示す。また、図21(b)に、メタレンズBからZ方向(高さ方向)の電界強度分布のシミュレーション結果を示す。 [Simulation 8]
Metalens A, which has two types of height microstructures (pitch 620 nm) with a refractive index of 1.8, and conventional metalens A, which has one type of height microstructures (pitch 400 nm) with a refractive index of 3.13. The properties of metalens B were compared. FIG. 21A shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens A. FIG. FIG. 21(b) shows a simulation result of the electric field strength distribution in the Z direction (height direction) from the metalens B. As shown in FIG.
図21に示すように、メタレンズAとメタレンズBの電界強度分布はほぼ同等であった。また、メタレンズAの集光効率は68.9%、メタレンズBの集光効率は、70.3%であり、集光効率においても、メタレンズAは、従来のメタレンズBと遜色のない性能を示すことがわかった。したがって、低屈折率材料を用いたメタレンズであっても、2種類の高さの微細構造体を用いれば、従来のメタレンズと遜色ない性能を示すことがわかった。
As shown in FIG. 21, the electric field strength distributions of metalens A and metalens B were almost the same. In addition, the light collection efficiency of the metalens A is 68.9%, and the light collection efficiency of the metalens B is 70.3%. In terms of light collection efficiency, the metalens A exhibits performance comparable to that of the conventional metalens B. I understand. Therefore, it was found that even a metalens made of a low-refractive-index material can exhibit performance comparable to that of a conventional metalens if microstructures with two different heights are used.
1 基板
2 微細構造体
10 マスターモールド
11 基板
12 ハードマスク
13 パターン
14 パターン
21 樹脂
22 ピラーレプリカ
23 基板
24 樹脂
25 ホールレプリカ
31 高屈折率樹脂
32 基板
61 高屈折率樹脂
62 低屈折率樹脂
63 高屈折率樹脂 1 substrate 2 fine structure 10 master mold 11 substrate 12 hard mask 13 pattern 14 pattern 21 resin 22 pillar replica 23 substrate 24 resin 25 hole replica 31 high refractive index resin 32 substrate 61 high refractive index resin 62 low refractive index resin 63 high refractive index rate resin
2 微細構造体
10 マスターモールド
11 基板
12 ハードマスク
13 パターン
14 パターン
21 樹脂
22 ピラーレプリカ
23 基板
24 樹脂
25 ホールレプリカ
31 高屈折率樹脂
32 基板
61 高屈折率樹脂
62 低屈折率樹脂
63 高屈折率樹脂 1 substrate 2 fine structure 10 master mold 11 substrate 12 hard mask 13 pattern 14 pattern 21 resin 22 pillar replica 23 substrate 24 resin 25 hole replica 31 high refractive index resin 32 substrate 61 high refractive index resin 62 low refractive index resin 63 high refractive index rate resin
Claims (6)
- 光を透過する基板と、前記光の位相分布を制御するために前記基板上に配置された複数種類の微細構造体と、を具備するメタサーフェスであって、
前記複数種類の微細構造体は、2種類以上の高さを有することを特徴とするメタサーフェス。 A metasurface comprising a substrate that transmits light and a plurality of types of microstructures arranged on the substrate for controlling the phase distribution of the light,
The metasurface, wherein the plurality of types of microstructures have two or more types of heights. - 前記複数種類の微細構造体の最大アスペクト比は、複数種類の微細構造体を同じ高さで同じ位相差を生じるように設計した場合の最大アスペクト比より小さいことを特徴とする請求項1記載のメタサーフェス。 2. The method according to claim 1, wherein the maximum aspect ratio of the plurality of types of microstructures is smaller than the maximum aspect ratio when the plurality of types of microstructures are designed to have the same height and produce the same phase difference. metasurface.
- 前記微細構造体のアスペクト比が、5以下であることを特徴とする請求項1記載のメタサーフェス。 The metasurface according to claim 1, wherein the aspect ratio of the fine structure is 5 or less.
- 前記微細構造体のピッチは、前記光の波長の3/4以下であることを特徴とする請求項1ないし3のいずれかに記載のメタサーフェス。 4. The metasurface according to any one of claims 1 to 3, wherein the pitch of the fine structures is 3/4 or less of the wavelength of the light.
- 前記微細構造体は、樹脂であることを特徴とする請求項1ないし3のいずれかに記載のメタサーフェス。 The metasurface according to any one of claims 1 to 3, wherein the fine structure is resin.
- 前記微細構造体が2層以上積層されていることを特徴とする請求項1ないし3のいずれかに記載のメタサーフェス。 4. The metasurface according to any one of claims 1 to 3, wherein the fine structures are laminated in two or more layers.
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US20200174163A1 (en) * | 2018-12-03 | 2020-06-04 | Samsung Electronics Co., Ltd. | Meta-lens and optical apparatus including the same |
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