CN113504585A - Polarization-independent superlens - Google Patents
Polarization-independent superlens Download PDFInfo
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- CN113504585A CN113504585A CN202110861902.4A CN202110861902A CN113504585A CN 113504585 A CN113504585 A CN 113504585A CN 202110861902 A CN202110861902 A CN 202110861902A CN 113504585 A CN113504585 A CN 113504585A
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- 230000010287 polarization Effects 0.000 title claims abstract description 31
- 230000004075 alteration Effects 0.000 claims abstract description 14
- 239000000758 substrate Substances 0.000 claims abstract description 13
- 239000002086 nanomaterial Substances 0.000 claims description 12
- 238000009826 distribution Methods 0.000 claims description 6
- 230000005540 biological transmission Effects 0.000 claims description 5
- 230000000694 effects Effects 0.000 claims description 5
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical group [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 4
- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 abstract description 3
- 239000010703 silicon Substances 0.000 abstract description 3
- 238000000034 method Methods 0.000 abstract description 2
- 238000002834 transmittance Methods 0.000 abstract description 2
- 238000013461 design Methods 0.000 description 8
- 230000003287 optical effect Effects 0.000 description 8
- 239000006185 dispersion Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
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- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
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- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/002—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B3/00—Simple or compound lenses
- G02B3/02—Simple or compound lenses with non-spherical faces
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Abstract
The invention discloses a polarization-independent super lens, which comprises a substrate layer and a super unit for constructing a super surface array on the substrate layer, wherein the super unit comprises a single cylinder, an annular column and a concentric column, and the polarization-independent super lens controls the wave front of incident linearly polarized light and eliminates chromatic aberration by combining a propagation phase and a compensation phase. The incident linear polarized light vertically irradiates the super-surface structure, the structural parameters of the dielectric column are scanned and optimized according to the selected incident central wavelength, the required compensation phase can be obtained by changing the size of the cylindrical silicon, high transmittance is realized, and the method of combining the structure selection and the propagation phase is ensured to control the wave front of the incident light and eliminate chromatic aberration.
Description
Technical Field
The invention belongs to the technical field of composite material super surfaces, and particularly relates to a polarization-independent super lens.
Background
Wavelength dispersion is an important property of optical materials and has been an important role in the design of optical components and systems, in most media like glass, where the refractive index decreases with increasing wavelength, called normal dispersion, with which the refractive lens will have a larger focal length at longer wavelengths than at short wavelengths, while the prism will be deflected at smaller angles, which chromatic aberration severely degrades the performance of full-color optical applications, such as communication, detection, imaging, display, etc. At present, superlenses use multilayer structures to eliminate chromatic aberration of two wavelengths and three wavelengths, and although this strategy is successful, the weight, complexity and cost of optical systems are increased, and the use of the superlenses is greatly limited; and these superlenses are limited to polarization dependence and can only focus circularly polarized light.
Therefore, recent research has focused on the design of polarization insensitive achromatic superlenses for visible and near infrared, however, it remains a great challenge to design an achromatic superlens that is not affected by polarization to eliminate chromatic aberration effect in the mid-infrared band.
Disclosure of Invention
It is an object of the present invention to provide a polarization independent superlens that overcomes the above-mentioned problems.
The technical purpose of the invention is realized by the following technical scheme:
a polarization-independent superlens comprises a substrate layer and superunits for constructing a super-surface array on the substrate layer, wherein each superunit comprises a single cylinder, an annular column and a concentric column;
the polarization-independent super lens controls the wave front of incident linearly polarized light and eliminates chromatic aberration by combining a propagation phase and a compensation phase;
the transmission phase is used as a focusing phase, incident linearly polarized light vertically irradiates the superunit, the incident wavelength range is 3.7-4.7 mu m, the superunit is selected through the principle of the transmission phase to control the wave front of the incident linearly polarized light, and the focusing is carried out at the selected central wavelength;
the required different compensation phase values are obtained through three different types of structures in the superunit, and the linear relation between the compensation phase and the reciprocal of the incident wavelength is ensured in the selected incident wavelength range, so that the chromatic aberration effect at the incident wavelength outside the central wavelength is eliminated.
Further, the single cylinder, the annular column and the concentric column are all of Si nanostructures, and the height H of the single cylinder, the annular column and the concentric column is 4.5 μm.
Further, the material of the substrate layer adopts CaF2。
Further, the outer diameters of the single cylinder, annular cylinder and concentric cylinder in the superunit remain uniform.
Further, the formula phi (x, lambda) of the phase distribution of the polarization-independent superlens is (2 pi lambda) neffH, wherein neffRepresenting the effective refractive index of the nanostructure and H represents the height of each structure in the superunit.
Further, the distance between the superunits constructing the super surface array is 1.8 μm.
Has the advantages that:
the achromatization realized by the super surface designed by the invention is in the range of continuous bandwidth, the achromatization can be realized by the super surface alone, and the achromatization can be combined with the traditional optical device, thereby improving the performance and the size of the super surface achromatization device and expanding the application range;
according to the invention, the adopted incident linear polarized light vertically irradiates a super-surface structure, structural parameter scanning and optimization are carried out on the dielectric column according to the selected incident central wavelength, the required compensation phase can be obtained by changing the size of the cylindrical silicon, high transmittance is realized, and the method of combining structure selection and transmission phase is ensured to control the wave front of incident light and eliminate chromatic aberration;
the polarization-independent broadband achromatic device based on the dielectric super surface realizes achromatization in a continuous bandwidth range, and greatly reduces the volume and the cost compared with the traditional device.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic of the dispersion of the present invention;
FIG. 3 is a phase distribution diagram of the present invention;
FIGS. 4 and 5 are physical analyses of three prototype structures according to the invention;
FIG. 6 is a phase profile of a polarization insensitive BAML in accordance with the present invention;
in the figure: 1. a base layer; 2. a single cylinder; 3. an annular column; 4. a concentric cylinder.
Detailed Description
In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "front", "rear", and the like, indicate orientations or positional relationships only for the purpose of describing the present invention and simplifying the description, but do not indicate or imply that the designated device or structure must have a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
As shown in FIG. 1, the polarization-independent superlens of the present invention includes a substrate layer and a superunit configured as a super-surface array on the substrate layer, wherein the superunit includes a single cylinder, an annular column and a concentric column, and the substrate layer is made of CaF2The single cylinder, the annular column and the concentric column are all of Si nano structures, the height H of the single cylinder, the height H of the annular column and the height H of the concentric column are 4.5 mu m, the outer diameters of the single cylinder, the annular column and the concentric column in the super unit are kept consistent, and the distance between the super units for constructing the super surface array is 1.8 mu m.
The polarization-independent super lens controls the wave front of incident linearly polarized light and eliminates chromatic aberration by combining a propagation phase and a compensation phase, firstly, the propagation phase is used as a focusing phase, the incident linearly polarized light vertically irradiates a super unit, the incident wavelength range is 3.7-4.7 mu m, and the super unit is selected to control the wave front of the incident linearly polarized light by the principle of the propagation phase so as to focus at the selected central wavelength; secondly, different compensation phase values are obtained through three different types of structures in the superunit, and the linear relation between the compensation phase and the reciprocal of the incident wavelength is ensured in the selected incident wavelength range, so that the chromatic aberration effect at the incident wavelength outside the central wavelength is eliminated; further, the offsetEquation phi (x, lambda) of phase distribution of vibration independent superlens (2 pi lambda) neffH, wherein neffRepresenting the effective refractive index of the nanostructure, is closely related to the radius of the nanostructure, and H represents the height of each structure in the superunit.
Description of the principle:
first, as shown in fig. 3, to realize a broadband achromatic superlens, the formula of the phase distribution is:
wherein,
wherein in the formulae (1) and (2) < lambda >0Is a defined center wavelength, in this example λ0Is chosen to be 4.2 μm, so that the broadband achromatic superlens is only when
And
can be realized when the requirements are met; first item
At a reference wavelength λ0A non-dispersive phase, i.e. as shown in fig. 2; second item
Is a function of the operating wavelength and is linearly related to 1/lambda, called the compensation phase.
Briefly, according to
And
two phase design edgesThe superunit of the broadband achromatic superlens arranged along the x-axis is feasible only for the superlens with polarization dependence, and the development of the achromatic super surface device is limited.
Therefore, the superunit in this embodiment uses a new nanostructure to implement a polarization insensitive broadband achromatic superlens, specifically: is prepared from calcium fluoride (CaF)2) Placing a dielectric super-surface platform of silicon (Si) nano structures on a substrate, wherein the height of each Si nano structure is H ═ 4.5 mu m; wherein CaF is selected2As a substrate due to its low refractive index (n ═ 1.4) and low absorption loss at the design wavelength; for the designed structure, the phase at a given spatial coordinate x is phi (x, lambda) n (2 pi lambda)effH, wherein neffRepresents the effective refractive index of the nanostructure, and is closely related to the radius of the nanostructure; in the above, a sub-class of superunits consists of three prototype shapes, namely a single cylinder, a circular column and a concentric column, the plane geometry of each prototype is variable, and the distance between each superunit is 1.8 μm, and in this embodiment, the optical response of each prototype can be controlled by changing its associated radius, ensuring that the achromatic superlens is polarization insensitive due to the symmetry of the structures.
Wherein a single cylinder provides the most compensated phase for each phase value, since it has the highest effective index compared to the other two prototypes with the same outer radius; however, a single cylinder only enables each phase to obtain a single compensated phase value, i.e. it is difficult to find a single cylinder that satisfies both of the two conditions
And
all superunits of the achromatic superlens of (1); compared with a single cylinder, the annular column and the concentric column both have relatively low effective refractive indexes, so that more compensation phases can be realized; therefore, the above three prototypes are simultaneously selected in this application to design a superlens.
Further, for three superunits at xThe optical properties for both (colored dots) and y (black dots) polarized light incidence were calculated as shown in fig. 4, from which it can be seen that the optical responses for x-polarized and y-polarized light incidence are identical; and FIG. 4 demonstrates phase
And a linear relationship of frequency (1/lambda) between the design wavelength range.
Further analysis of the polarization insensitivity of the three prototypes, calculations were performed on the near field distributions of the electric fields in the three prototypes, and the results are shown in FIG. 5, with selected wavelengths of 4.3 μm, 3.9 μm and 4.0 μm, as shown by the dashed lines in FIG. 4, corresponding to the three prototypes, respectively, top and bottom views being top and side views, respectively, and these same near field results for the above x and y polarization incidence indicate that the selected prototypes are polarization insensitive.
Thus, in this embodiment, the proposed superlens has a diameter of 77.4 μm and a focal length f of 25 μm (NA ≈ 0.84), and fig. 6 plots the phases respectively
Function of spatial position and compensating phase
The design wavelength of each superunit is 4.2 μm; the results show that the phase and the compensation phase achieved by the selected superunit are in good agreement with the desired values.
In summary, based on the principle of compensating dispersion accumulated phase by propagation phase, three different prototype structures are selected, and the achromatic superlens is realized within a bandwidth of 3.7-4.7 μm, the compensation phase ranges realized by the three prototype structures are different, wherein the compensation phase realized by the cylinder is the largest and the coaxial is the smallest, the conclusion can be deduced by the equivalent medium theory, as the adopted unit structures are all centrosymmetric structures, the geometric phase cannot be used, the focusing phase is satisfied by the propagation phase at the central wavelength of 4.2 μm, so that the key of realizing polarization-independent achromatic supersurface is realized, and the achromatic superlens can obviously inhibit chromatic aberration effect by comparing with the chromatic aberration lens.
In order to make the objects, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the above specific embodiments, which are only used for describing the present invention, and should not be construed as limiting the scope of the present invention. It should be understood that any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (6)
1. A polarization-independent superlens is characterized by comprising a substrate layer (1) and superunits for constructing a super-surface array on the substrate layer, wherein the superunits comprise single cylinders (2), annular cylinders (3) and concentric cylinders (4);
the polarization-independent super lens controls the wave front of incident linearly polarized light and eliminates chromatic aberration by combining a propagation phase and a compensation phase;
the transmission phase is used as a focusing phase, incident linearly polarized light vertically irradiates the superunit, the incident wavelength range is 3.7-4.7 mu m, the superunit is selected through the principle of the transmission phase to control the wave front of the incident linearly polarized light, and the focusing is carried out at the selected central wavelength;
the required different compensation phase values are obtained through three different types of structures in the superunit, and the linear relation between the compensation phase and the reciprocal of the incident wavelength is ensured in the selected incident wavelength range, so that the chromatic aberration effect at the incident wavelength outside the central wavelength is eliminated.
2. The polarization-independent superlens of claim 1, wherein the single cylinder, annular cylinder, and concentric cylinder are all Si nanostructures, and the height H of the single cylinder, annular cylinder, and concentric cylinder is 4.5 μ ι η.
3. The polarization-independent superlens of claim 1, wherein the substrate layer is CaF2。
4. The polarization-independent superlens of claim 1, wherein the outer diameters of the single, annular, and concentric cylinders in the superunit remain uniform.
5. The polarization-independent superlens of claim 1, wherein the formula of the phase distribution of the polarization-independent superlens is phi (x, lambda) ne (2 pi lambda)ffH, wherein neffRepresenting the effective refractive index of the nanostructure and H represents the height of each structure in the superunit.
6. The polarization-independent superlens of claim 1, wherein a distance between superunits constructing the supersurface array is 1.8 μm.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115421227A (en) * | 2022-10-08 | 2022-12-02 | 桂林电子科技大学 | Novel bionic antireflection film structure |
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|---|---|---|---|---|
| US20190196068A1 (en) * | 2017-12-26 | 2019-06-27 | Academia Sinica | Broadband achromatic metalens in the visible spectrum |
| CN110333560A (en) * | 2019-07-09 | 2019-10-15 | 合肥工业大学 | A kind of broadband Achromatic device surpassing surface based on medium |
| CN112394429A (en) * | 2020-11-27 | 2021-02-23 | 南京大学 | Mid-infrared polarization-independent broadband achromatic superlens and construction method thereof |
| CN112946793A (en) * | 2021-02-08 | 2021-06-11 | 合肥工业大学 | Polarization-independent broadband achromatic device based on dielectric super-surface |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20190196068A1 (en) * | 2017-12-26 | 2019-06-27 | Academia Sinica | Broadband achromatic metalens in the visible spectrum |
| CN110333560A (en) * | 2019-07-09 | 2019-10-15 | 合肥工业大学 | A kind of broadband Achromatic device surpassing surface based on medium |
| CN112394429A (en) * | 2020-11-27 | 2021-02-23 | 南京大学 | Mid-infrared polarization-independent broadband achromatic superlens and construction method thereof |
| CN112946793A (en) * | 2021-02-08 | 2021-06-11 | 合肥工业大学 | Polarization-independent broadband achromatic device based on dielectric super-surface |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115421227A (en) * | 2022-10-08 | 2022-12-02 | 桂林电子科技大学 | Novel bionic antireflection film structure |
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