Cascaded achromatic superlens

Abstract

The application discloses a kind of cascaded achromatic superlenses, basic unit structure is substrate and nanopillar (including first nanopillar and second nanopillar), convenient processing, while the corresponding relationship of each part in simple structure is limited, and the corresponding relationship formula can be met to produce cascade effect to eliminate chromatic aberration, obtain corresponding achromatic superlens, without large-scale complex calculation, can adapt to any wavelength range, and can well eliminate chromatic aberration in design range.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of super surface lens, and particularly relates to a cascaded achromatic super lens. BACKGROUND

[0002] In today's life, people are increasingly pursuing convenience, and the requirements for devices are developing towards miniaturization and integration. The super lens designed by the super surface not only has a much smaller volume than the traditional glass lens, but also can realize multiple focal points, abnormal refraction, reflection and other special functions, so the super lens shows broad application prospects.

[0003] The super surface is formed by arranging basic units on a substrate according to a certain rule. The super surface realizes focusing by controlling the phase of a light beam. The phase control method of the super surface includes transmission phase control and geometric phase control, and the geometric phase control method is more popular due to its simple design and ability to realize focusing of a wide-band light beam.

[0004] Although the geometric phase super lens can focus a wide-band light beam, it has a serious chromatic aberration problem because the phase distribution required for focusing light beams of different wavelengths is not the same. According to the design principle of the super lens, the super lens does not have spherical aberration, so chromatic aberration is the main source of axial aberration of the super lens, which seriously restricts the practical application ability of the super lens.

[0005] At present, the design of achromatic super lenses is basically based on structure and material. In terms of structure, the solution depends on detecting super surface basic units of multiple different structures, selecting appropriate structures and verifying their combination methods to find a super lens structure that meets the achromatic phase requirements of each working wavelength. This inevitably leads to a large amount of design verification work, and this method needs to be verified and calculated once for each new working wavelength of the super lens, which is not universal, and the complex structure also brings great difficulty to processing. In terms of materials, most of them use special phase change materials to eliminate chromatic aberration, and use the different phase change amounts of the phase change materials at different wavelengths to compensate for the phase distribution requirements of focusing light beams of different wavelengths. This method requires special phase change materials to construct the super surface, and the wavelength range that can eliminate chromatic aberration can only be determined according to the characteristics of the material, and the working wavelength range cannot be freely designed.

[0006] The information disclosed in this BACKGROUND section is only intended to increase an understanding of the general background of the application and is not intended to be a recognition or any form of admission that this information constitutes prior art. SUMMARY

[0007] The application aims to provide a kind of cascade achromatic superlens, simple structure, can well eliminate the chromatic aberration in the required wavelength range.

[0008] In order to achieve the above-mentioned purpose, a specific embodiment of the present application provides a kind of cascade achromatic superlens, comprising:

[0009] The substrate has opposite first surface and second surface;

[0010] The object plane side superlens is formed on the first surface of the substrate, and the object plane side superlens is arranged by a plurality of first nanometer columns;

[0011] The image plane side superlens is formed on the second surface of the substrate, and the image plane side superlens is arranged by a plurality of second nanometer columns;

[0012] The focal length of the object plane side superlens and wavelength satisfy:

[0013]

[0014] The focal length of the image plane side superlens and wavelength satisfy:

[0015]

[0016] The focal length of the object plane side superlens and the image plane side superlens satisfy:

[0017]

[0018] The focal length f of the cascade achromatic superlens satisfies:

[0019]

[0020] Wherein, λ1 is the starting wavelength of the working wavelength range of the cascade achromatic superlens, λ2 is the ending wavelength of the working wavelength range of the cascade achromatic superlens, f1 is the focal length of the object plane side superlens at the starting wavelength, f'1 is the focal length of the object plane side superlens at the ending wavelength, x is the x-axis coordinate of different first nanometer columns in the coordinate system with the geometric center of the substrate as the origin; f2 is the focal length of the image plane side superlens at the starting wavelength, f'2 is the focal length of the image plane side superlens at the ending wavelength, x' is the x-axis coordinate of different second nanometer columns in the coordinate system with the geometric center of the substrate as the origin; l is the vertical distance between the first surface and the second surface of the substrate.

[0021] In one or more embodiments of the present application, the starting wavelength λ1 and the ending wavelength λ2 of the working wavelength range of the cascade achromatic superlens satisfy: 0.3um < λ1 < λ2 < 3um.

[0022] In one or more embodiments of the present application, the object-side superlens has a focal length f1 at a starting working wavelength, the image-side superlens has a focal length f2 at the starting working wavelength, and a straight-line distance between the first surface and the second surface of the substrate is l, and a relationship between f1, f2 and l satisfies: f1 > f2 and l < f1.

[0023] In one or more embodiments of the present application, the object-side superlens and the image-side superlens are both geometric phase superlenses.

[0024] In one or more embodiments of the present application, the object-side superlens is formed by periodically arranging first nanocolumns with different directional angles on the first surface of the substrate;

[0025] The image-side superlens is formed by periodically arranging second nanocolumns with different directional angles on the second surface of the substrate.

[0026] In one or more embodiments of the present application, the directional angle θ1(x) of each first nanocolumn of the object-side superlens satisfies:

[0027]

[0028] wherein λ1 is a starting wavelength in a chromatic-aberration-corrected wavelength range of the cascaded chromatic-aberration-corrected superlens, f1 is a focal length of the object-side superlens at the starting working wavelength, and x is an x-axis coordinate of different first nanocolumns in a coordinate system with a geometric center of the substrate as an origin.

[0029] In one or more embodiments of the present application, the directional angle θ2(x') of each second nanocolumn of the image-side superlens satisfies:

[0030]

[0031] wherein λ1 is a starting wavelength in a chromatic-aberration-corrected wavelength range of the cascaded chromatic-aberration-corrected superlens, f2 is a focal length of the image-side superlens at the starting working wavelength, and x' is an x-axis coordinate of different second nanocolumns in a coordinate system with a geometric center of the substrate as an origin.

[0032] In one or more embodiments of the present application, the first nanocolumn is a rectangular column, and a length L, a width W and a height H of the first nanocolumn respectively satisfy: 0.2um < L < 0.3um, 0.08um < W < 0.1um, and 0.5um < H < 0.7um.

[0033] The second nanocolumn is a rectangular column, and a length L', a width W' and a height H' of the second nanocolumn respectively satisfy: 0.2um < L' < 0.3um, 0.08um < W' < 0.1um, and 0.5um < H' < 0.7um.

[0034] In one or more embodiments of the present application, the material of the first nanorod and the second nanorod is a dielectric material.

[0035] In one or more embodiments of the present application, the material of the substrate comprises glass or silicon oxide.

[0036] Compared with the prior art, the cascaded achromatic superlens of the present application has a simple structure, the basic unit structure is a substrate and a nanorod (including a first nanorod and a second nanorod), is convenient to process, and satisfies the above corresponding relationship to generate a cascaded effect to eliminate chromatic aberration, to obtain a corresponding achromatic superlens, without large-scale complex calculation.

[0037] The cascaded achromatic superlens of the present application satisfies the structure of the present application, can design a cascaded achromatic superlens of any wavelength range, and is suitable for any wavelength range, and can well eliminate chromatic aberration in the design range. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0039] Figure 1 FIG. 1 is a schematic diagram of a cascaded achromatic superlens in an embodiment of the present application;

[0040] Figure 2 FIG. 2 is a first nanorod / second nanorod structure diagram of the cascaded achromatic superlens in an embodiment of the present application;

[0041] Figure 3 FIG. 3 is a light intensity diagram along the light beam incident direction under different wavelengths of the cascaded achromatic superlens in an embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the person skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0043] As described in the background, the current design of achromatic superlens is basically based on structure and material. In terms of structure, the solution relies on detecting a variety of different structures of super surface basic units, selecting appropriate structures and verifying their combination methods, so as to find superlens structures that meet the achromatic phase requirements at each working wavelength. This inevitably leads to a large amount of design verification work, and this method needs to be verified and calculated once for each new working wavelength of superlens, which is not universal, and the complex structure also brings great difficulty to processing. In terms of materials, most of them are through special phase change materials to eliminate chromatic aberration, and use the different phase change amounts of phase change materials at different wavelengths to compensate for the phase distribution requirements of focusing light beams at different wavebands. This method requires special phase change materials to construct super surface, and the wavelength range that can eliminate chromatic aberration can only be determined according to the characteristics of the material, and the working wavelength range cannot be freely designed.

[0044] Based on this, the application provides a kind of cascade achromatic superlens, simple structure, basic unit structure is base and nano column (including first nano column and second nano column), convenient processing, meet corresponding relationship formula can produce cascade effect to eliminate chromatic aberration, obtain corresponding achromatic superlens, without large-scale complex calculation, it can adapt to any wavelength range, and can eliminate chromatic aberration in design range well.

[0045] In the cascade achromatic superlens of the application, by constructing super surface structures (object plane side superlens 20 and image plane side superlens 30) on the first surface and the second surface of the base, and limiting various corresponding relationships between the two super surface structures (object plane side superlens 20 and image plane side superlens 30), the cascade effect between the two super surface structures (object plane side superlens 20 and image plane side superlens 30) is generated, and different phase compensation is provided for light of different wavelengths to eliminate chromatic aberration.

[0046] As shown in Figure 1 The cascade achromatic superlens in an embodiment of the application includes a base 10, an object plane side superlens 20 and an image plane side superlens 30.

[0047] The material of the base 10 is silicon dioxide or glass. The base 10 has opposite first and second surfaces. The material of the base 10 is selected with reference to the working wavelength range to ensure as high transmittance as possible.

[0048] The object plane side superlens 20 is formed on the first surface of the base 10. The object plane side superlens 20 is a geometric phase superlens, which is arranged by a plurality of first nano columns 21 of dielectric material. Preferably, the dielectric material is titanium dioxide. The dielectric material is selected with reference to the working wavelength range to ensure as high transmittance as possible.

[0049] The object-side superlens 20 is formed by periodically arranging the first titanium dioxide nanorods 21 with different direction angles on the first surface of the substrate 10. The first nanorods 21 are rectangular rods, and the length L, width W and height H of the first nanorods 21 satisfy: 0.2um < L < 0.3um, 0.08um < W < 0.1um, 0.5um < H < 0.7um, respectively.

[0050] Reference Figure 2 In a specific embodiment, L = 0.2um, W = 0.085um, H = 0.6um are satisfied, as shown. Wherein, L, W, H represent the length, width and height of the first nanorods, respectively.

[0051] The direction angle θ1(x) of each first nanorod 21 of the object-side superlens 20 of the cascaded achromatic superlens satisfies:

[0052]

[0053] Wherein, λ1 is the starting wavelength in the achromatic wavelength range of the cascaded achromatic superlens, f1 is the focal length of the object-side superlens at the starting working wavelength, and x is the x-axis coordinate of the different first nanorods in the coordinate system with the geometric center of the substrate as the origin.

[0054] The focal length and wavelength of the object-side superlens 20 of the cascaded achromatic superlens satisfy:

[0055]

[0056] Wherein, λ1 is the starting wavelength in the working wavelength range of the cascaded achromatic superlens, λ2 is the ending wavelength in the working wavelength range of the cascaded achromatic superlens, f1 is the focal length of the object-side superlens at the starting wavelength, f'1 is the focal length of the object-side superlens at the ending wavelength, and x is the x-axis coordinate of the different first nanorods in the coordinate system with the geometric center of the substrate as the origin.

[0057] The starting wavelength λ1 and the ending wavelength λ2 in the working wavelength range of the cascaded achromatic superlens satisfy: 0.3um < λ1 < λ2 < 3um.

[0058] In a specific embodiment, the starting wavelength λ1 = 0.48um and the ending wavelength λ2 = 0.6um.

[0059] The image-side superlens 30 is formed on the second surface of the substrate 10. The image-side superlens 30 is a geometric phase superlens formed by arranging a plurality of second nanorods 31 of dielectric material. Preferably, the dielectric material is titanium dioxide. The selection of the dielectric material is based on the working wavelength range to ensure the highest possible transmittance.

[0060] The image-side superlens 30 is formed by the second titanium dioxide nanorods 31 with different directional angles arranged periodically on the second surface of the substrate 10. The second nanorods 31 are rectangular rods, and the length L', width W' and height H' of the second nanorods 31 satisfy: 0.2um < L' < 0.3um, 0.08um < W' < 0.1um, 0.5um < H' < 0.7um, respectively.

[0061] In a specific embodiment, L' = 0.2um, W' = 0.085um, and H' = 0.6um are satisfied. Wherein, L', W' and H' represent the length, width and height of the second nanorods, respectively.

[0062] The directional angle θ2(x') of each second nanorod 31 of the image-side superlens 30 of the cascaded achromatic superlens satisfies:

[0063]

[0064] Wherein, λ1 is the starting wavelength in the achromatic wavelength range of the cascaded achromatic superlens, f2 is the focal length of the image-side superlens at the starting working wavelength, and x' is the x-axis coordinate of the different second nanorods in the coordinate system with the geometric center of the substrate as the origin.

[0065] The focal length and wavelength of the image-side superlens of the cascaded achromatic superlens satisfy:

[0066]

[0067] Wherein, λ1 is the starting wavelength in the working wavelength range of the cascaded achromatic superlens, λ2 is the ending wavelength in the working wavelength range of the cascaded achromatic superlens, f2 is the focal length of the image-side superlens at the starting wavelength, f'2 is the focal length of the image-side superlens at the ending wavelength, and x' is the x-axis coordinate of the different second nanorods in the coordinate system with the geometric center of the substrate as the origin.

[0068] The starting wavelength λ1 and the ending wavelength λ2 in the working wavelength range of the cascaded achromatic superlens satisfy: 0.3um < λ1 < λ2 < 3um.

[0069] In a specific embodiment, the starting wavelength λ1 = 0.48um and the ending wavelength λ2 = 0.6um.

[0070] The focal length of the object-side superlens 20 at the starting working wavelength is f1, the focal length of the image-side superlens 30 at the starting working wavelength is f2, and the straight-line distance between the first surface and the second surface of the substrate 10 is l, and the relationship between f1, f2 and l satisfies: f1 > f2 and l < f1.

[0071] The focal lengths of the object-side superlens 20 and the image-side superlens 30 of the cascaded achromatic superlens satisfy:

[0072]

[0073] The focal length f of the cascaded achromatic superlens satisfies:

[0074]

[0075] Where f1 is the focal length of the object-side superlens at the starting wavelength, f'1 is the focal length of the object-side superlens at the ending wavelength; f2 is the focal length of the image-side superlens at the starting wavelength, f'2 is the focal length of the image-side superlens at the ending wavelength; and l is the vertical distance between the first and second surfaces of the substrate.

[0076] Example 1:

[0077] In this embodiment, the relevant parameters of the cascaded achromatic superlens are shown in Table 1: (Table 1, unit: μm)

[0078] Table 1

[0079] f1 f'1 f2 f'2 f l L W H L’ W’ H’ ​ ​ 32 25.6 23 18.4 24 24 0.21 0.085 0.6 0.21 0.085 0.6 0.48 0.6

[0080] In this embodiment, the intensity diagrams of light beams of different wavelengths along the incident direction in the wavelength range of 480nm to 600nm are as follows. Figure 3 As shown.

[0081] from Figure 3 As can be seen in the diagram, beams of different wavelengths are focused at the same focal length, as shown in the intensity diagram highlighting the focal point. Figure 3 The feasibility of the cascaded achromatic superlens proposed in this application is particularly evident in the image below.

[0082] Compared with the prior art, the cascaded achromatic superlens of the present invention has a simple structure. The basic unit structure is a substrate and nanopillars (including the first nanopillar and the second nanopillar), which is convenient to process. By satisfying the above-mentioned corresponding relationship, a cascade effect can be generated to eliminate chromatic aberration and obtain the corresponding achromatic superlens, without the need for large-scale complex calculations.

[0083] The cascaded achromatic superlens of the present invention satisfies the structure of this application, and can be designed with cascaded achromatic superlenses in any wavelength range, and is adaptable to any wavelength range, and can effectively eliminate chromatic aberration within the design range.

[0084] It will be obvious to a person skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments and can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference signs in the claims should not be construed as limiting the claims concerned.

[0085] Furthermore, it should be understood that although the description is made on the basis of the embodiments, not every embodiment contains only one independent technical solution, and the description is made in this way only for the sake of clarity, and a person skilled in the art should consider the description as a whole, and the technical solutions in each embodiment can also be combined appropriately to form other embodiments that can be understood by a person skilled in the art.

Claims

1. A cascaded achromatic superlens, characterized in that, include: A substrate having opposing first and second surfaces; An object-side superlens is formed on the first surface of the substrate, and the object-side superlens is composed of a plurality of first nanopillars arranged in a manner. An image-side superlens is formed on the second surface of the substrate, and the image-side superlens is composed of a plurality of second nanopillars arranged in a manner. The focal length and wavelength of the object-side superlens satisfy the following: ； The focal length and wavelength of the image-side superlens satisfy the following: ； The focal lengths of the object-side superlens and the image-side superlens satisfy the following: ； The focal length f of the cascaded achromatic superlens satisfies: ； The orientation angle θ1(x) of each of the first nanopillars of the object-side superlens satisfies: ； The orientation angle θ2(x') of each of the second nanopillars of the image-side superlens satisfies: ； Wherein, λ1 is the starting wavelength of the cascaded achromatic superlens's operating wavelength range, λ2 is the ending wavelength of the cascaded achromatic superlens's operating wavelength range, f1 is the focal length of the object-side superlens at the starting wavelength, f'1 is the focal length of the object-side superlens at the ending wavelength, x is the x-axis coordinate of different first nanopillars in a coordinate system with the geometric center of the substrate as the origin; f2 is the focal length of the image-side superlens at the starting wavelength, f'2 is the focal length of the image-side superlens at the ending wavelength, x' is the x-axis coordinate of different second nanopillars in a coordinate system with the geometric center of the substrate as the origin; l is the vertical distance between the first and second surfaces of the substrate.

2. The cascaded achromatic superlens according to claim 1, characterized in that, The starting wavelength λ1 and ending wavelength λ2 of the working wavelength range of the cascaded achromatic superlens satisfy the following: 0.3um < λ1 < λ2 < 3um.

3. The cascaded achromatic superlens according to claim 1, characterized in that, The focal length of the object-side superlens at the initial working wavelength is f1, the focal length of the image-side superlens at the initial working wavelength is f2, and the linear distance between the first and second surfaces of the substrate is l. The relationship between f1, f2 and l satisfies: f1>f2 and l<f1.

4. The cascaded achromatic superlens according to claim 1, characterized in that, Both the object-side superlens and the image-side superlens are geometric phase superlenses.

5. The cascaded achromatic superlens according to claim 1, characterized in that, The object-side superlens is formed by periodically arranging first nanopillars with different directional angles on the first surface of the substrate; The image-side superlens is formed by periodically arranging second nanopillars at different directional angles on the second surface of the substrate.

6. The cascaded achromatic superlens according to claim 1, characterized in that, The first nanopillar is a rectangular pillar, and the length L, width W, and height H of the first nanopillar satisfy the following conditions: 0.2um < L < 0.3um, 0.08um < W < 0.1um, and 0.5um < H < 0.7um, respectively. The second nanopillar is a rectangular pillar, and the length L', width W', and height H' of the second nanopillar satisfy the following conditions: 0.2um < L' < 0.3um, 0.08um < W' < 0.1um, and 0.5um < H' < 0.7um, respectively.

7. The cascaded achromatic superlens according to claim 1, characterized in that, Both the first nanoparticle and the second nanopillar are made of dielectric materials.

8. The cascaded achromatic superlens according to claim 1, characterized in that, The substrate material includes glass or silicon oxide.

Images