Optical superlens with high focusing efficiency and preparation method thereof

Abstract

This invention relates to a high-focusing-efficiency optical superlens and its fabrication method. The optical superlens includes a pair of optical substrates, an antireflective coating disposed on one side surface of the optical substrates, a moth-eye membrane protruding from the other side surface of the optical substrates, and a plurality of nanodielectric pillars composed of a high-refractive-index material disposed between the pair of moth-eye membranes. At least one structural parameter of the plurality of nanodielectric pillars along the length direction of the optical substrates is modulated to satisfy a 2π phase distribution. At least one structural parameter of the moth-eye membrane along the thickness direction of the optical substrates is modulated to complete the refractive index transition from the plurality of nanodielectric pillars to the optical substrates. This invention solves the problem of reduced transmittance caused by refractive index mismatch in traditional optical superlenses, and effectively improves the focusing efficiency of the optical superlens without affecting the original phase distribution.

Description

Technical Field

[0001] This invention relates to the technical field of optical elements, and in particular to a high-focusing-efficiency optical superlens and its fabrication method. Background Technology

[0002] Optical superlenses are lenses used to focus the entire visible light spectrum. They can precisely control the phase of light, allowing light to be focused or defocused within a very thin structure, and even achieving a negative refractive index effect under certain conditions. The design of optical superlenses must consider the phase changes of light waves, which often depend on the microstructure of optical materials. Traditional lens designs are based on large-scale optical components, while optical superlenses require micrometer- or even nanometer-scale fine structures, posing significant challenges to computation and manufacturing. For example, in the field of optical superlenses, to meet the needs of phase modulation, the structure in the optical superlens needs to have a high refractive index, such as TiO2 or Si3N4. These materials are often amorphous or polycrystalline thin film materials, and due to their high cost and mechanical brittleness, they cannot be directly fabricated into independent self-supporting wafers. Therefore, the material structure commonly used in optical superlenses is a high-refractive-index dielectric thin film grown on quartz glass to achieve phase modulation.

[0003] High-refractive-index optical superlenses can be approximated as composite thin layers formed by nanopillars of high-refractive-index material and air. This composite thin layer exhibits an equivalent refractive index that differs significantly from that of the air medium and the substrate material. Consequently, Fresnel reflection occurs at both interfaces, which is detrimental to the focusing efficiency of transmissive optical superlenses. Furthermore, the fabrication and processing of high-refractive-index thin films are complex and costly, and the films themselves have poor durability. These factors collectively limit the widespread application of optical superlens technology. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the first objective of the present invention is to provide an optical superlens with high focusing efficiency, which solves the problem of reduced transmittance caused by refractive index mismatch in traditional optical superlenses, and effectively improves the focusing efficiency of optical superlenses without affecting the original phase distribution.

[0005] The second objective of this invention is to provide a method for fabricating a high-focusing-efficiency optical superlens, which realizes the micro-nano fabrication of a sandwich structure, broadens the design freedom, and has the advantages of simple fabrication, low cost, and high yield.

[0006] To achieve the first objective mentioned above, the present invention provides the following technical solution:

[0007] A high-focusing-efficiency optical superlens includes a pair of optical substrates, an antireflective coating disposed on one side surface of the optical substrates, a moth-eye membrane protruding from the other side surface of the optical substrates, and a plurality of nanodielectric pillars disposed between the pair of moth-eye membranes and composed of a high refractive index material. At least one structural parameter of the plurality of nanodielectric pillars along the length direction of the optical substrates is modulated to satisfy a 2π phase distribution, and at least one structural parameter of the moth-eye membrane along the thickness direction of the optical substrates is modulated to complete the refractive index transition from the plurality of nanodielectric pillars to the optical substrates.

[0008] Furthermore, the plurality of nanodielectric pillars are arranged in a one-dimensional or two-dimensional array;

[0009] And / or, the nanodielectric pillars are mirror-symmetrical in a central plane parallel to the length direction of the optical substrate;

[0010] And / or, the plurality of nanomedium pillars have the same height and period, and the duty cycle increases along at least two array directions, wherein the at least two array directions (+X, -X, +Y, -Y) are array directions that are opposite, intersecting and / or perpendicular.

[0011] Furthermore, the high refractive index material of the nano-dielectric pillar is one or a combination of several of amorphous silicon, TiO2, SiC and diamond with a refractive index exceeding 1.7;

[0012] And / or, the cross-section of the nanomedium column is circular, elliptical, or polygonal;

[0013] And / or, the height of the nanomedium column is 100~1500 nm;

[0014] And / or, the period of the nanomedium column is 200~1000nm;

[0015] And / or, the duty cycle of the nanomedium column is in the range of 20-85%.

[0016] Furthermore, the moth eye membrane is composed of multiple frustum columns arranged in a two-dimensional array;

[0017] And / or, the frustum is mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate;

[0018] And / or, the plurality of frustum pillars have the same height and period, and their diameters increase in the direction from the nanomedium pillar to the optical substrate.

[0019] Furthermore, the material of the frustum column is one or a combination of several of the following: quartz, optical resin, SiC, and diamond.

[0020] And / or, the height of the frustum is 50~500nm;

[0021] And / or, the period of the frustum column is 100~600nm;

[0022] And / or, the diameter of the frustum is in the range of 30~600nm.

[0023] Furthermore, the optical substrate and the moth-eye membrane are integrally formed;

[0024] And / or, the optical substrate is made of one or a combination of several of the following: quartz, optical resin, SiC, and diamond;

[0025] And / or, the thickness of the optical substrate is 100~5000μm.

[0026] Furthermore, the antireflective coating is composed of alternating layers of low-refractive-index film layers with a refractive index not exceeding 1.7 and high-refractive-index film layers with a refractive index exceeding 2.1;

[0027] And / or, therefore the low refractive index film is a composite film of one or more of SiO2 and Al2O3;

[0028] And / or, the high refractive index film is a composite film of one or more of TiO2 and HfO2;

[0029] And / or, the thickness of the antireflective membrane is 0.5~50.0 μm.

[0030] To achieve the second objective mentioned above, the present invention provides the following technical solution:

[0031] A method for fabricating a high-focusing-efficiency optical superlens includes the following steps:

[0032] S1 deposits a thin film on one side surface of the optical substrate to obtain an antireflective film;

[0033] S2 performs a patterning process on the other side surface of the optical substrate obtained in S1 to obtain a moth eye membrane;

[0034] S3 first spin-coats photoresist onto the moth eye membrane obtained in S2, so that the photoresist fills the gaps on the moth eye membrane and extends beyond the surface of the moth eye membrane to the predetermined height of the nano-dielectric pillars, then performs patterning processing, and deposits multiple nano-dielectric pillars in the patterned area;

[0035] S4 directly bonds the moth eye membrane obtained in S2 onto the multiple nanomaterial pillars obtained in S3;

[0036] Alternatively, photoresist can be spin-coated onto the multiple nanodielectric pillars obtained in S3, so that the photoresist extends beyond the surface of the nanodielectric pillars to the predetermined height of the moth-eye film. Then, patterning is performed, and another moth-eye film is deposited in the patterned area. Thin film deposition is continued to obtain another optical substrate, and then S1 is repeated.

[0037] S5 removes the photoresist on the moth-eye membrane and nano-dielectric pillars obtained in S3 and S4 by wet stripping to obtain an optical superlens.

[0038] Furthermore, in S1, in the electron beam evaporation coating equipment, after setting the deposition parameters and target deposition values ​​for two types of film materials with refractive indices of no more than 1.7 and refractive indices of more than 2.1, several low refractive index film layers with refractive indices of no more than 1.7 and high refractive index film layers with refractive indices of more than 2.1 are deposited alternately to obtain an antireflective film.

[0039] Furthermore, in S2 and S4, the equivalent refractive index distribution curve of the optical superlens structure formed by multiple nano-dielectric pillars is obtained in advance to determine the range of refractive index variation from the optical superlens structure to the optical substrate in the optical superlens plane. Then, the structural parameters of the moth eye membrane are determined by the transition from the equivalent refractive index of the optical superlens to the refractive index of the optical substrate.

[0040] Further, in S2, the other side surface of the optical substrate is first exposed and developed, then a metal mask is deposited and the metal mask of the non-patterned area is peeled off, and then the optical substrate of the non-patterned area is etched to obtain the moth-eye film; wherein, the exposure dose and development time are controlled to obtain a complete patterned area, and the thickness of the metal mask is controlled to ensure successful peeling.

[0041] Furthermore, in step S3, photoresist (AZ1518) is first spin-coated onto the moth-eye film, and the photoresist above the surface of the moth-eye film is removed by dry etching. Then, photoresist (zep520) is spin-coated to the predetermined height of the nano-dielectric pillars. The photoresist surface is then exposed and developed, and a high-refractive-index material is deposited in the patterned area. Finally, the high-refractive-index material above the predetermined height of the nano-dielectric pillars is removed by dry etching to obtain multiple nano-dielectric pillars. The etching time of the photoresist is controlled, and a low deposition temperature is maintained to ensure the integrity of the photoresist.

[0042] Furthermore, in S4, the bonding pressure is controlled to a moderate value to ensure bonding strength without damaging the material structure.

[0043] Further, in S4, photoresist (AZ1518) is first spin-coated onto the surface of multiple nano-dielectric pillars and photoresist (zep520) to a predetermined height of the moth-eye film. Then, the photoresist surface is exposed and developed, and after material is deposited in the patterned area, the high refractive index material above the predetermined optical substrate thickness is removed by dry etching to obtain another moth-eye film and optical substrate. In this process, the exposure dose and development time are controlled to ensure the integrity of the micro-nano structure. In addition, the dry etching time is controlled so that the material above the thickness is just removed.

[0044] Furthermore, in S5, the concentration of the wet degumming solution and the wet degumming time are controlled.

[0045] In summary, the beneficial technical effects of the present invention are as follows:

[0046] 1. This invention proposes to fabricate a moth-eye membrane structure on a substrate of any material, then prepare a thin layer of high-refractive-index material on top of the moth-eye membrane, fabricate an optical superlens structure on the thin layer, and finally cover it with a substrate of any material that also has a moth-eye membrane structure, thus achieving a sandwich structure. The so-called moth-eye membrane structure mimics the special microstructure of a moth's eye surface. According to the equivalent medium theory, the refractive index of this structure is equivalent to that of a graded multilayer film, and it avoids the difficulties in fabricating multilayer films and the low durability of such films. Therefore, it can serve as a refractive index transition layer between the substrate and the optical superlens structure, and the same applies to the relationship between the optical superlens structure and air. This invention effectively solves the problem of reduced transmittance caused by refractive index mismatch in traditional optical superlenses, and effectively improves the focusing efficiency of optical superlenses without affecting the original phase distribution.

[0047] 2. To achieve 2π phase modulation, the nanopillars in optical superlenses often have high refractive indices, leading to strong interfacial reflections between them and both the air and the substrate, thus reducing propagation efficiency. This invention, without altering the phase distribution design of the optical superlens, utilizes a special micro-nano fabrication method to stack a microstructure layer on each side, increasing the transmittance at the interfaces between the nanopillars and the air and substrate, thereby further improving the efficiency of the optical superlens. For optical superlenses, this method significantly improves propagation efficiency without affecting the design of the optical superlens itself, thus enhancing the utilization rate of light energy in practical applications.

[0048] 3. The present invention can effectively improve the low efficiency of traditional optical superlenses caused by refractive index mismatch, without affecting the structural design of the optical superlens itself. The bulk material of the optical superlens can be any material, regardless of the refractive index, which broadens the selection of optical superlens materials and is beneficial to cost control and functional expansion. Attached Figure Description

[0049] Figure 1This is a schematic diagram of the structure of the optical superlens of Embodiment 1 of the present invention.

[0050] Figure 2 This is a flowchart of the method provided in Embodiment 6 of the present invention.

[0051] Figure 3 This is the equivalent refractive index distribution curve of Embodiment 9 of the present invention.

[0052] Figure 4 This is the transmittance curve of Embodiment 9 of the present invention.

[0053] In the figure, 1 is the optical substrate; 2 is the antireflective coating; 3 is the moth-eye membrane; 31 is the frustum column; and 4 is the nano-dielectric column. Detailed Implementation

[0054] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0055] Example 1: Refer to Figure 1 This invention discloses a high-focusing-efficiency optical superlens, comprising a pair of optical substrates 1, an antireflective coating 2 disposed on one side surface of the optical substrates 1, a moth-eye membrane 3 protruding from the other side surface of the optical substrates 1, and a plurality of nanodielectric pillars 4 disposed between the pair of moth-eye membranes 3 and composed of a high-refractive-index material. At least one structural parameter of the plurality of nanodielectric pillars 4 along the length direction of the optical substrates 1 is modulated to satisfy a 2π phase distribution, and at least one structural parameter of the moth-eye membrane 3 along the thickness direction of the optical substrates 1 is modulated to complete the refractive index transition from the plurality of nanodielectric pillars 4 to the optical substrates 1.

[0056] Example 2: This invention discloses a high-focusing-efficiency optical superlens. The difference from Example 1 is that, firstly, the nano-dielectric pillars 4 are arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The nano-dielectric pillars 4 are mirror-symmetrical on a central plane parallel to the length direction of the optical substrate 1. The height and period of these nano-dielectric pillars 4 are the same, and the duty cycle increases along the two array directions (+X, -X). Specifically, the high-refractive-index material of the nano-dielectric pillars 4 is amorphous silicon, with a circular cross-section, a height of 600 nm, a period of 500 nm, and a duty cycle ranging from 30% to 80%.

[0057] Secondly, the moth-eye membrane 3 consists of multiple frustum pillars 31 arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The frustum pillars 31 are mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate 1. These frustum pillars 31 have the same height and period, and their diameter increases from the nano-dielectric pillars 4 to the optical substrate 1. Specifically, the frustum pillars 31 are made of quartz, have a height of 200 nm, a period of 250 nm, and a diameter ranging from 70 to 160 nm.

[0058] Furthermore, the optical substrate 1 and the moth-eye membrane 3 are integrally formed. The optical substrate 1 is also made of quartz and has a thickness of 500μm.

[0059] Finally, the antireflective coating 2 is composed of ten alternating layers of low-refractive-index film (SiO2 film) and high-refractive-index film (TiO2 film). The thickness of the antireflective coating 2 is 0.811 μm. Starting from the air interface, the first layer is SiO2, the second layer is TiO2, and they are stacked sequentially with thicknesses of 170.9 nm, 114.8 nm, 2.5 nm, 79.9 nm, 7.9 nm, 91.8 nm, 87.9 nm, 92.2 nm, 88.3 nm, and 75.6 nm, respectively, achieving high transmittance in the near-infrared band of 1000~1550 nm.

[0060] Example 3: This invention discloses a high-focusing-efficiency optical superlens. The difference from Example 1 is that, firstly, the nano-dielectric pillars 4 are arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The nano-dielectric pillars 4 are mirror-symmetrical on a central plane parallel to the length direction of the optical substrate 1. The height and period of these nano-dielectric pillars 4 are the same, and the duty cycle increases along the two array directions (+X, -X). Specifically, the high-refractive-index material of the nano-dielectric pillars 4 is SiC, with a circular cross-section, a height of 900 nm, a period of 500 nm, and a duty cycle ranging from 30% to 80%.

[0061] Secondly, the moth-eye membrane 3 consists of multiple frustum pillars 31 arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The frustum pillars 31 are mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate 1. These frustum pillars 31 have the same height and period, and their diameter increases from the nano-dielectric pillars 4 to the optical substrate 1. Specifically, the frustum pillars 31 are made of quartz, have a height of 200 nm, a period of 250 nm, and a diameter ranging from 70 to 160 nm.

[0062] Furthermore, the optical substrate 1 and the moth-eye film 3 are integrally formed. The optical substrate 1 is also made of SiC and has a thickness of 500μm.

[0063] Finally, the antireflective coating 2 is composed of ten alternating layers of low-refractive-index film (SiO2 film) and high-refractive-index film (TiO2 film). The thickness of the antireflective coating 2 is 0.900 μm. Starting from the air interface, the first layer is silicon oxide, the second layer is titanium oxide, and they are stacked sequentially with thicknesses of 232.8 nm, 125.7 nm, 13.45 nm, 90.9 nm, 18.8 nm, 102.7 nm, 98.9 nm, 84.6 nm, 48.3 nm, and 86.6 nm, respectively, achieving high transmittance in the near-infrared band of 1000~1550 nm.

[0064] Example 4: This invention discloses a high-focusing-efficiency optical superlens. The difference from Example 1 is that, firstly, the nano-dielectric pillars 4 are arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The nano-dielectric pillars 4 are mirror-symmetrical on a central plane parallel to the length direction of the optical substrate 1. The height and period of these nano-dielectric pillars 4 are the same, and the duty cycle increases along the two array directions (+X, -X). Specifically, the high-refractive-index material of the nano-dielectric pillars 4 is TiO2, with a circular cross-section, a height of 100 nm, a period of 200 nm, and a duty cycle ranging from 20% to 40%.

[0065] Secondly, the moth-eye membrane 3 consists of multiple frustum pillars 31 arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The frustum pillars 31 are mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate 1. These frustum pillars 31 have the same height and period, and their diameter increases from the nano-dielectric pillars 4 to the optical substrate 1. Specifically, the frustum pillars 31 are made of optical resin, have a height of 50 nm, a period of 100 nm, and a diameter ranging from 30 to 100 nm.

[0066] Furthermore, the optical substrate 1 and the moth-eye film 3 are integrally formed. The optical substrate 1 is also made of TiO2 and has a thickness of 100μm.

[0067] Finally, the antireflective coating 2 is composed of ten alternating layers of low-refractive-index film (Al2O3 film) and high-refractive-index film (TiO2 film). The thickness of the antireflective coating 2 is 0.500 μm, achieving high transmittance in the near-infrared band of 1000~1550 nm.

[0068] Example 5: This invention discloses a high-focusing-efficiency optical superlens. The difference from Example 1 is that, firstly, the nano-dielectric pillars 4 are arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The nano-dielectric pillars 4 are mirror-symmetrical on a central plane parallel to the length direction of the optical substrate 1. The height and period of these nano-dielectric pillars 4 are the same, and the duty cycle increases along the two array directions (+X, -X). Specifically, the high-refractive-index material of the nano-dielectric pillars 4 is diamond, with a circular cross-section, a height of 1500 nm, a period of 1000 nm, and a duty cycle ranging from 60% to 85%.

[0069] Secondly, the moth-eye membrane 3 consists of multiple frustum pillars 31 arranged in a two-dimensional array along two mutually perpendicular directions (X, Y). The frustum pillars 31 are mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate 1. These frustum pillars 31 have the same height and period, and their diameter increases from the nano-dielectric pillars 4 to the optical substrate 1. Specifically, the frustum pillars 31 are made of quartz, have a height of 500 nm, a period of 600 nm, and a diameter ranging from 200 to 600 nm.

[0070] Furthermore, the optical substrate 1 and the moth-eye membrane 3 are integrally formed. The optical substrate 1 is also made of diamond and has a thickness of 5000μm.

[0071] Finally, the antireflective coating 2 is composed of ten alternating layers of low refractive index film (SiO2 film) and high refractive index film (HfO2 film), with a thickness of 50.000 μm, achieving high transmittance in the near-infrared band of 1000~1550 nm.

[0072] Example 6: Refer to Figure 2 This invention discloses a method for fabricating a high-focusing-efficiency optical superlens, which differs from Example 1 in that it includes the following steps:

[0073] S1 deposits a thin film on one side surface of the optical substrate 1 to obtain an antireflection film 2;

[0074] S2 performs a patterning process on the other side surface of the optical substrate 1 obtained in S1 to obtain a moth eye membrane 3;

[0075] S3 first spin-coats photoresist onto the moth eye membrane 3 obtained in S2, so that the photoresist fills the gaps on the moth eye membrane 3 and extends beyond the surface of the moth eye membrane 3 to the predetermined height of the nano-dielectric pillar 4, and then performs patterning processing, and deposits multiple nano-dielectric pillars 4 in the patterned area.

[0076] S4 directly bonds the moth eye membrane 3 obtained in S2 to the multiple nano-medium pillars 4 obtained in S3.

[0077] Alternatively, photoresist can be spin-coated onto the multiple nano-dielectric pillars 4 obtained in S3, so that the photoresist extends beyond the surface of the nano-dielectric pillars 4 to the predetermined height of the moth-eye film 3, then patterning is performed, and another moth-eye film 3 is deposited in the patterned area. Thin film deposition is then performed to obtain another optical substrate 1, and then S1 is repeated.

[0078] S5 removes the photoresist on the moth-eye membrane 3 and the nano-dielectric pillar 4 obtained in S3 and S4 by wet stripping to obtain an optical superlens.

[0079] Example 7: This is a method for fabricating a high-focusing-efficiency optical superlens disclosed in this invention. The difference from Example 6 is that it includes the following steps:

[0080] In S1, in an electron beam evaporation coating apparatus, the deposition parameters for two film materials, silicon oxide and titanium oxide, are set. At room temperature, the deposition rate of silicon oxide is 1.5 nm / s and the deposition rate of titanium oxide is 3 nm / s. The deposition time for each layer is set, and several silicon oxide film layers and titanium oxide film layers are deposited alternately to obtain antireflection film 2.

[0081] S2 first exposes and develops the other side of the optical substrate 1, then deposits a metal mask, and peels off the metal mask in the unpatterned area. Then, it etches the optical substrate 1 in the unpatterned area to obtain the moth-eye film 3. The exposure dose is selected as 20 nA, the development time is 1 min, a complete patterned area is obtained, and the thickness of the metal mask is controlled to be less than 80 nm in order to successfully peel off.

[0082] S3 first spin-coats photoresist (AZ1518) onto the moth-eye film 3, and then removes the photoresist above the surface of the moth-eye film 3 by dry etching. Next, spin-coats photoresist (zep520) up to the predetermined height of the nano-dielectric pillars 4. Then, the photoresist surface is exposed and developed, and a high refractive index material is deposited in the patterned area. After that, the high refractive index material above the predetermined height of the nano-dielectric pillars 4 is removed by dry etching to obtain multiple nano-dielectric pillars 4. The exposure dose is controlled at 10 nA, the development time is 1 min, the spin-coating speed of the photoresist is 200 rps / min, and the etching time of the photoresist is 10 min. In addition, the deposition is carried out at room temperature to ensure the integrity of the photoresist.

[0083] S4 controls the bonding pressure to a moderate value, ensuring bonding strength without damaging the material structure.

[0084] S5 removes the photoresist on the moth-eye film 3 and nano-dielectric pillar 4 obtained in S3 and S4 by wet stripping, controlling the wet stripping time using acetone solution to be 1 hour, to obtain the optical superlens shown in Example 2.

[0085] Example 8: This invention discloses a method for fabricating a high-focusing-efficiency optical superlens. The difference from Example 7 is that in S4, photoresist (AZ1518) is first spin-coated onto the surface of the multiple nano-dielectric pillars 4 and photoresist (zep520) obtained in S3 to the predetermined height of the moth-eye film 3. Then, the photoresist surface is exposed and developed. After material deposition in the patterned area, high-refractive-index material above the predetermined thickness of the optical substrate 1 is removed by dry etching to obtain another moth-eye film 3 and optical substrate 1. Then, S1 is repeated. The exposure dose is controlled at 10 nA, the development time at 1 min, the photoresist spin-coating speed at 200 rps / min, and the photoresist etching time at 10 min. Deposition is performed at room temperature to ensure the integrity of the photoresist. Finally, the optical superlens shown in Example 3 is obtained.

[0086] Example 9: This is a method for fabricating a high-focusing-efficiency optical superlens disclosed in this invention. The difference from Example 6 is that in S2 and S4, reference is made to... Figure 3 The equivalent refractive index distribution curves of an optical superlens structure formed by multiple nano-dielectric pillars 4 are obtained in advance to determine the range of refractive index variation from the optical superlens structure to the optical substrate 1 within the optical superlens plane. Then, by observing the transition from the equivalent refractive index of the optical superlens to the refractive index of the optical substrate 1, the structural parameters of the moth-eye membrane 3 are determined, ultimately achieving enhanced transmittance. Without an equivalent refractive index transition, the transmittance of the optical superlens is [missing value]. Figure 4 The curve containing the hollow circle in the image shows that, after calculating and matching the equivalent refractive index, the transmittance of the optical superlens is... Figure 4 As can be seen from the curve containing the solid circle, the transmittance of the optical superlens is effectively improved, thereby increasing the focusing efficiency.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An optical superlens with high focusing efficiency, characterized in that: The application relates to an optical substrate (1) and a moth-eye film (3) arranged on the optical substrate (1), wherein the moth-eye film (3) is composed of a plurality of nano medium columns (4) made of a high refractive index material, and the moth-eye film (3) is arranged on one side of the optical substrate (1) and protrudes from the other side of the optical substrate (1).

2. The optical superlens with high focusing efficiency according to claim 1, characterized in that: The plurality of nano medium columns (4) are arranged in one-dimensional or two-dimensional arrays. The nano medium columns (4) are mirror-symmetrical on a central plane parallel to the length direction of the optical substrate (1). The height and period of the plurality of nano medium columns (4) are the same, and the duty cycle increases along at least two array directions.

3. The optical superlens with high focusing efficiency according to claim 2, characterized in that: The refractive index of the high refractive index material of the nano medium column (4) is greater than 1.

7. The cross section of the nano medium column (4) is circular, elliptical or polygonal. The height of the nano medium column (4) is 100-1500 nm. The period of the nano medium column (4) is 200-1000 nm. The duty cycle of the nano medium column (4) ranges from 20 to 85%.

4. The optical superlens with high focusing efficiency according to claim 1, characterized in that: The moth-eye film (3) is composed of a plurality of circular truncated cone columns (31) arranged in two-dimensional arrays. The circular truncated cone columns (31) are mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate (1). The height and period of the plurality of circular truncated cone columns (31) are the same, and the diameter of the plurality of circular truncated cone columns (31) increases from the nano medium column (4) to the optical substrate (1).

5. The optical superlens with high focusing efficiency according to claim 4, characterized in that: The height of the circular truncated cone column (31) is 50-500 nm. The period of the circular truncated cone column (31) is 100-600 nm. The diameter of the circular truncated cone column (31) ranges from 30 to 600 nm.

6. The optical superlens with high focusing efficiency according to claim 1, characterized in that: The optical substrate (1) and the moth-eye film (3) are integrally formed. The optical substrate (1) is a transparent flat plate material. The thickness of the optical substrate (1) is 100-5000 mu m.

7. The optical superlens with high focusing efficiency according to claim 1, characterized in that: The antireflection film (2) is formed by alternately stacking a plurality of low refractive index film layers with a refractive index not greater than 1.7 and high refractive index film layers with a refractive index greater than 2.

1. The low refractive index film layer is a composite film of one or more of SiO2 and Al2O3. The high refractive index film layer is a composite film of one or more of TiO2 and HfO2. The thickness of the antireflection film (2) is 0.5-50.0 mu m.

8. The method of claim 1-7, wherein the method of preparing an optical superlens with high focusing efficiency is characterized in that: The application further discloses a preparation method of the optical substrate (1) and the moth-eye film (3). S1: thin film deposition is performed on one side surface of the optical substrate (1) to obtain the antireflection film (2). S2 patterning the other side surface of the optical substrate (1) obtained in S1 to obtain a moth-eye film (3); S3 coating photoresist on the moth-eye film (3) obtained in S2 to fill the gaps on the moth-eye film (3) and to exceed the surface of the moth-eye film (3) to a predetermined height of the nano-medium column (4), then patterning and depositing a plurality of nano-medium columns (4) in the patterned area; S4 directly bonding the moth-eye film (3) obtained by repeating S1-S2 on the plurality of nano-medium columns (4) obtained in S3; Or, coating photoresist on the plurality of nano-medium columns (4) obtained in S3 to exceed the surface of the nano-medium column (4) to a predetermined height of the moth-eye film (3), then patterning and depositing another moth-eye film (3) in the patterned area to continue thin film deposition to obtain another optical substrate (1), and then repeating S1; S5 removing the photoresist on the moth-eye film (3) and nano-medium column (4) obtained in S3 and S4 by wet stripping to obtain an optical superlens.

9. The method of claim 8, wherein the method further comprises: depositing a plurality of metal nanostructures on the substrate; and depositing a plurality of dielectric nanostructures on the substrate. In S2 and S4, the equivalent refractive index distribution curve of the optical superlens structure formed by the plurality of nano-medium columns (4) is obtained in advance, the refractive index variation range from the optical superlens structure to the optical substrate (1) in the plane of the optical superlens is determined, and then the structure parameters of the moth-eye film (3) are determined by the transition of the equivalent refractive index of the optical superlens to the refractive index of the optical substrate (1).

10. The method of claim 8, wherein the method further comprises: depositing a plurality of metal nanostructures on the substrate; and depositing a plurality of dielectric nanostructures on the substrate. In S4, photoresist is first coated on the surface of the plurality of nano-medium columns (4) and the photoresist to a predetermined height of the moth-eye film (3), then the photoresist surface is exposed and developed, and after depositing a material in the patterned area, the high refractive index material above the predetermined thickness of the optical substrate (1) is removed by dry etching to obtain another moth-eye film (3) and optical substrate (1).

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