An adjustable polarization converter based on a chiral nanoarray with a MIM structure

Abstract

The present invention provides an adjustable polarization converter based on a chiral nanoarray with a MIM structure. The chiral metal nanostructure array includes a plurality of MIM tetramer nano-units arranged periodically; the MIM tetramer nano-unit includes two metal layer tetramers with the same thickness and a dielectric layer tetramer disposed between the two metal layer tetramers; each single-layer tetramer includes four rectangular nano-structures with chiral response arranged at intervals. The present invention uses three metal / dielectric nano-rectangular bodies with the same size and one metal / dielectric nano-rectangular body with a different size to form a planar tetramer arranged with a certain gap and longitudinally stacked into a MIM tetramer chiral structure. Under the irradiation of left- and right-handed circularly polarized light, due to the difference in the refractive index of the structure for different polarized lights, optical activity is generated, thereby realizing the tuning conversion of polarization and rotation direction. A Fabry–Pérot cavity is formed between the upper and lower metal layers of the MIM structure, which has strong adjustable chiral response and can perform periodic modulation on the polarization and chirality of light.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano optical technologies, and more particularly, to an adjustable polarization converter based on a chiral nanoarray with a MIM structure. Background Art

[0002] With the improvement of the level of nano-processing technology, metal nanostructures with different shapes and sizes can be fabricated. Therefore, people have shown great research interest in the optical response characteristics exhibited by metal nanostructures and the corresponding optical physics mechanisms. One of the most important research topics is local surface plasmons, that is, under the action of an incident light field, free electrons on the surface of a metal nanostructure resonate with the incident light field, resulting in strong absorption and scattering at the resonance frequency and a large field enhancement within a very small volume near the surface of the metal nanostructure. Local surface plasmon resonance can enhance optical physical effects, making metal nanostructures one of the research hotspots in the fields of micro-nano optical device design and optical modulation.

[0003] Chirality refers to the fact that an object in three-dimensional space cannot be made to coincide with its mirror image by translation or rotation, just like our hands, which are mirror-symmetric but cannot coincide. As a common phenomenon existing in the universe, chirality has important applications in the fields of chiral optical devices, chiral substance detection, and chiral optical modulation. Therefore, the research on chirality has great potential and important application value.

[0004] Chiral molecules have different refractive indices for different polarized lights, which can rotate the direction of the polarization plane of the incident light by an angle. This property of being able to rotate the polarization plane is called optical activity, and this optical activity makes it possible to design polarization conversion optical devices. Therefore, in order to study the chiral polarization conversion technology with high optical activity, there have been many theoretical analyses and experimental studies dedicated to chiral phenomena based on surface plasmons, especially the enhanced optical response of local surface plasmons based on chiral metal nanostructures. Existing polarization converters based on metal nanostructures can modulate the polarization angle of linearly polarized light or convert linearly polarized light into elliptically polarized light. However, the existing polarization converters do not have good flexible adjustable properties due to the single modulation effect. Based on the Fabry–Pérot (FP) cavity effect of the MIM nanostructure, for the first time, circularly polarized light is converted into linearly polarized light and elliptically polarized light with the opposite sense of rotation, which can not only change the polarization of light, but also change the rotation of light, and can even achieve periodic modulation of light, thereby obtaining more different optical properties. Summary of the Invention

[0005] In view of the technical problem that the optical polarization modulation effect proposed above is single and lacks good flexibility and adjustability, a tunable polarization converter based on a chiral nanoarray with an MIM structure is provided. In the present invention, the polarization and rotation direction of light are modulated and converted by the optical rotation property of the chiral plasmonic nanostructure. The present invention mainly uses three metal / dielectric nano-cuboids of the same size and one metal / dielectric nano-cuboid of a different size to form a planar tetramer arranged with a certain gap and longitudinally stacked into an MIM tetramer chiral structure. Under the irradiation of left-handed circularly polarized light and right-handed circularly polarized light, due to the difference in the refractive index of the structure for different polarized lights, optical rotation is generated, thereby realizing the tuning and conversion of polarization and rotation direction. An FP cavity is formed between the upper and lower metal layers of the MIM structure, which has strong tunability of chiral response and can modulate the optical rotation property of the structure periodically.

[0006] The technical means adopted in the present invention are as follows:

[0007] A tunable polarization converter based on a chiral nanoarray with an MIM structure, comprising: a transparent substrate, and a chiral metal nanostructure array disposed on the transparent substrate, wherein:

[0008] The chiral metal nanostructure array includes a plurality of periodically arranged MIM tetramer nano-units;

[0009] Each MIM tetramer nano-unit includes three stacked single-layer tetramer nano-units, namely two metal-layer tetramer nano-units with the same thickness and a dielectric-layer tetramer nano-unit disposed between the two metal-layer tetramer nano-units;

[0010] Each single-layer tetramer includes four spaced-apart cuboid nanostructures with chiral response, that is, each single-layer tetramer includes a first horizontal cuboid, a first vertical cuboid, a second vertical cuboid, and a second horizontal cuboid arranged at intervals.

[0011] Further, it includes: a transparent substrate, and a chiral metal nanostructure array disposed on the transparent substrate, wherein:

[0012] The chiral metal nanostructure array includes a plurality of periodically arranged MIM tetramer nano-units;

[0013] Each MIM tetramer nano-unit includes three stacked single-layer tetramer nano-units, namely two metal-layer tetramer nano-units with the same thickness and a dielectric-layer tetramer nano-unit disposed between the two metal-layer tetramer nano-units;

[0014] Each single-layer tetramer includes four nanostructured rectangular parallelepipeds with chiral responses arranged at intervals, that is, each single-layer tetramer includes a first horizontal rectangular parallelepiped (1), a first vertical rectangular parallelepiped (2), a second vertical rectangular parallelepiped (3), and a second horizontal rectangular parallelepiped (4) arranged at intervals.

[0015] Furthermore, the metal layers in the metal-layer tetramer nano-units are all made of noble metal materials, and the dielectric layers in the dielectric-layer tetramer nano-units are made of dielectric materials.

[0016] Furthermore, the period of the chiral metal nanostructure array can be arbitrarily selected, and the selected period is P x = 380 - 620 nm, P y = 240 - 480 nm.

[0017] Furthermore, the long axis of the first horizontal rectangular parallelepiped is perpendicular to the long axes of the first vertical rectangular parallelepiped and the second vertical rectangular parallelepiped, the long axis of the second horizontal rectangular parallelepiped is perpendicular to the long axes of the first vertical rectangular parallelepiped and the second vertical rectangular parallelepiped, and the long axis of the first horizontal rectangular parallelepiped is parallel to the long axis of the second horizontal rectangular parallelepiped.

[0018] Furthermore, the distances between the first horizontal rectangular parallelepiped and the first vertical rectangular parallelepiped, between the first horizontal rectangular parallelepiped and the second vertical rectangular parallelepiped, between the first vertical rectangular parallelepiped and the second horizontal rectangular parallelepiped, between the second vertical rectangular parallelepiped and the second horizontal rectangular parallelepiped, and between the first vertical rectangular parallelepiped and the second vertical rectangular parallelepiped are all the same, and the distance is 10 - 40 nm.

[0019] Furthermore, the length of the first horizontal rectangular parallelepiped is 160 - 240 nm, and the width is 40 - 80 nm; the first vertical rectangular parallelepiped, the second vertical rectangular parallelepiped, and the second horizontal rectangular parallelepiped have the same dimensions, with a length of 110 - 190 nm and a width of 40 - 80 nm.

[0020] Furthermore, the right side line of the first horizontal rectangular parallelepiped is collinear with the right side line of the second vertical rectangular parallelepiped in the y-axis direction; the left side line of the first vertical rectangular parallelepiped is collinear with the left side line of the second horizontal rectangular parallelepiped in the y-axis direction; the upper side line of the first horizontal rectangular parallelepiped is collinear with the upper side line of the first vertical rectangular parallelepiped in the x-axis direction; the lower side line of the second vertical rectangular parallelepiped is collinear with the lower side line of the second horizontal rectangular parallelepiped in the x-axis direction.

[0021] Furthermore, the transparent substrate includes a glass substrate.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The tunable polarization converter based on the chiral nanoarray with the MIM structure provided by the present invention utilizes the periodic modulation characteristic of the FP cavity formed by the upper and lower metal layers of the MIM structure on the properties of light, and converts the polarization of light through the optical rotation characteristic generated by the difference in the refractive index of different polarized lights by the structure, and has strong tuning ability.

[0024] 2. The tunable polarization converter based on the chiral nanoarray with the MIM structure provided by the present invention can convert circularly polarized light into elliptically polarized light, linearly polarized light, and polarized light with the opposite sense of rotation, realizing the modulation of light.

[0025] 3. When the tunable polarization converter based on the chiral nanoarray with the MIM structure provided by the present invention is in use, under the irradiation of left-handed circularly polarized light and right-handed circularly polarized light, due to the difference in the real part of the refractive index of different polarized lights by the structure, optical rotation is generated, thereby realizing the tuning conversion of polarization.

[0026] For the above reasons, the present invention can be widely promoted in the fields of micro-nano optics and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a three-dimensional schematic diagram of a single nano-structural unit in the tunable polarization converter based on the chiral nanoarray with the MIM structure of the present invention.

[0029] Figure 2 It is a three-dimensional structural schematic diagram of the tunable polarization converter based on the chiral nanoarray with the MIM structure of the present invention.

[0030] Figure 3 It is a planar structural schematic diagram of the tunable polarization converter based on the chiral nanoarray with the MIM structure of the present invention.

[0031] Figure 4 It is an ellipticity spectrogram of the tunable polarization converter based on the chiral nanoarray with the MIM structure provided by the embodiment of the present invention under the condition that the thickness of the dielectric layer is 140 nm.

[0032] Figure 5 It is for the tunable polarization converter based on the chiral nanoarray with the MIM structure provided by the embodiment of the present invention Figure 4 The polarization angle change diagram at the wavelength λ = 825 nm marked by the circle shown.

[0033] Figure 6 This is a graph showing the variation of the ellipticity spectrum of the tunable polarization converter based on the chiral nanoarray with the MIM structure provided by the embodiments of the present invention modulated by the thickness of the dielectric layer.

[0034] In the figure: 1. The first horizontal cuboid; 2. The first vertical cuboid; 3. The second vertical cuboid; 4. The second horizontal cuboid. Detailed implementation manners

[0035] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0036] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0037] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0038] Unless otherwise specifically stated, the relative arrangements of the components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods and devices should be regarded as part of the authorized specification. In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0039] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by orientation terms such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. is usually based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description. Without contrary explanation, these orientation terms do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the protection scope of the present invention: the orientation terms "inner, outer" refer to the inside and outside relative to the contour of each component itself.

[0040] For the sake of convenience in description, spatial relative terms such as "above...", "over...", "on the upper surface of...", "upper...", etc. can be used here to describe the spatial positional relationship between a device or feature shown in the drawings and other devices or features. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation described in the drawings for the device. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "over other devices or structures" will then be positioned as "below other devices or structures" or "under other devices or structures". Thus, the exemplary term "above..." can include both the orientations of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations should be made for the spatial relative descriptions used here.

[0041] In addition, it should be noted that using words such as "first", "second", etc. to limit components is only for the convenience of distinguishing the corresponding components. Without additional declaration, the above words have no special meaning. Therefore, it should not be construed as a limitation on the protection scope of the present invention.

[0042] As Figures 1-3 shown, the present invention provides an adjustable polarization converter based on a chiral nanoarray of a MIM (Metal-Insulator-Metal) structure, including: a transparent substrate, and a chiral metal nanostructure array disposed on the transparent substrate, wherein:

[0043] The chiral metal nanostructure array includes a plurality of MIM tetramer nano-units arranged periodically;

[0044] Each MIM tetramer nano-unit includes three stacked monolayer tetramer nano-units, namely two metal-layer tetramer nano-units with the same thickness and a dielectric-layer tetramer nano-unit disposed between the two metal-layer tetramer nano-units;

[0045] Each single-layer tetramer includes four chiral-responsive rectangular nanostructures arranged at intervals, that is, each single-layer tetramer includes a first horizontal rectangular body 1, a first vertical rectangular body 2, a second vertical rectangular body 3, and a second horizontal rectangular body 4 arranged at intervals.

[0046] In specific implementation, as a preferred implementation manner of the present invention, such as Figure 1 shown, the thickness of the metal layer in the metal layer tetramer nano-unit is h1 = h3 = 10 - 120 nm; the thickness of the dielectric layer in the dielectric layer tetramer nano-unit is h2 = 0 - 2900 nm, which is used to determine the chiral optical response of the structure and has a periodic modulation effect. The metal layer in the metal layer tetramer nano-unit is made of noble metal materials (including but not limited to gold, silver, copper, etc.), and the dielectric layer in the dielectric layer tetramer nano-unit is made of dielectric materials (including but not limited to silicon dioxide (SiO2), indium tin oxide (ITO), or polydimethylsiloxane (PDMS), etc.).

[0047] In specific implementation, as a preferred implementation manner of the present invention, the period of the chiral metal nanostructure array can be arbitrarily selected, and the selected period is P x = 380 - 620 nm, P y = 240 - 480 nm.

[0048] In specific implementation, as a preferred implementation manner of the present invention, continue to refer to Figures 1-3 , the long axis of the first horizontal rectangular body 1 is perpendicular to the long axes of the first vertical rectangular body 2 and the second vertical rectangular body 3, the long axis of the second horizontal rectangular body 4 is perpendicular to the long axes of the first vertical rectangular body 2 and the second vertical rectangular body 3, and the long axis of the first horizontal rectangular body 1 is parallel to the long axis of the second horizontal rectangular body 4. The distances between the first horizontal rectangular body 1 and the first vertical rectangular body 2, between the first horizontal rectangular body 1 and the second vertical rectangular body 3, between the first vertical rectangular body 2 and the second horizontal rectangular body 4, between the second vertical rectangular body 3 and the second horizontal rectangular body 4, and between the first vertical rectangular body 2 and the second vertical rectangular body 3 are the same, and the distance is g = 10 - 40 nm.

[0049] In specific implementation, as a preferred implementation manner of the present invention, the length of the first horizontal rectangular body 1 is all l1 = 160 - 240 nm, and the width is all w = 40 - 80 nm. The sizes of the first vertical rectangular body 2, the second vertical rectangular body 3, and the second horizontal rectangular body 4 are the same, the length is all l = 110 - 190 nm, and the width is all w = 40 - 80 nm.

[0050] In specific implementation, as a preferred implementation manner of the present invention, continue to refer to Figure 1, the right side line of the first horizontal cuboid 1 and the right side line of the second vertical cuboid 3 are collinear in the y-axis direction. The left side line of the first vertical cuboid 2 and the left side line of the second horizontal cuboid 4 are collinear in the y-axis direction. The upper side line of the first horizontal cuboid 1 and the upper side line of the first vertical cuboid 2 are collinear in the x-axis direction. The lower side line of the second vertical cuboid 3 and the lower side line of the second horizontal cuboid 4 are collinear in the x-axis direction.

[0051] In specific implementation, as a preferred implementation manner of the present invention, the transparent substrate includes a glass substrate.

[0052] Example 1

[0053] In this embodiment, based on the characteristic that the refractive indices of the chiral nanoarray based on the MIM structure are different for different polarized lights, optical activity is generated, which is manifested as the conversion of the original polarization state of light. When circularly polarized light passes through this structure, due to the optical rotation effect, the circularly polarized light is converted into elliptically polarized light, and when at the characteristic wavelength, the phenomenon that the circularly polarized light can be converted into linearly polarized light is observed, showing a strong modulation ability for light.

[0054] Based on the finite-difference time-domain method, simulation experiments are carried out using FDTD Solutions simulation software. The specific parameters are preferably as follows:

[0055] The chiral metal nanostructure array is placed on a glass substrate, and the length of the array period is P x = 470 nm, P y = 330 nm. The nanostructure is divided into three layers. The upper and lower metal layers are made of gold, with a height of h1 = h3 = 30 nm. The middle dielectric layer is made of silicon dioxide, with a height of h2 = 140 nm. The length of the first horizontal cuboid 1 is l1 = 200 nm, and the width is w = 60 nm. The lengths of the first vertical cuboid 2, the second vertical cuboid 3, and the second horizontal cuboid 4 are l = 150 nm, and the width is w = 60 nm. The distances between the first horizontal cuboid 1 and the first vertical cuboid 2, between the first horizontal cuboid 1 and the second vertical cuboid 3, between the first vertical cuboid 2 and the second horizontal cuboid 4, between the second vertical cuboid 3 and the second horizontal cuboid 4, and between the first vertical cuboid 2 and the second vertical cuboid 3 are the same and equal to g = 20 nm. As Figure 3 shown, the right side line of the first horizontal cuboid 1 and the right side line of the second vertical cuboid 3 are collinear in the y-axis direction, the left side line of the first vertical cuboid 2 and the left side line of the second horizontal cuboid 4 are collinear in the y-axis direction, the upper side line of the first horizontal cuboid 1 and the upper side line of the first vertical cuboid 2 are collinear in the x-axis direction, and the lower side line of the second vertical cuboid 3 and the lower side line of the second horizontal cuboid 4 are collinear in the x-axis direction.

[0056] The ellipticity response in this embodiment is calculated by ε = ±u / v, where u represents the minor axis of the polarization ellipse, v represents the major axis of the polarization ellipse, and the symbols "-" and "+" represent the left-handed and right-handed directions of light, respectively. As Figure 4 shown, in this embodiment, the chiral tetramer MIM structure generates an optical rotation effect under the incidence of left-handed circularly polarized light. It can be observed from the figure that in the wavelength ranges of 700 - 825 nm, 883 - 943 nm, and 961 - 1100 nm, -1 < ε < 0, and the structure modulates the left-handed circularly polarized light into left-handed elliptically polarized light. Therefore, the structure in this embodiment can change the polarization state of the transmitted light. In the wavelength ranges of 825 - 883 nm and 943 - 961 nm, 0 < ε < 1, and the structure modulates the left-handed circularly polarized light into right-handed elliptically polarized light. Therefore, the structure in this embodiment can not only change the polarization state of the transmitted light, but also change the rotation direction of the polarization ellipse to obtain different optical properties.

[0057] As Figure 5 shown, at the wavelength λ = 825 nm marked by the circle in Figure 4 shown, the curve of the polarization angle of the outgoing light changing with the coordinate on the negative half-axis of the z-axis. It can be seen from the figure that the polarization angle of the outgoing light shows an oscillation mode similar to a square wave as the coordinate on the negative half-axis of the z-axis increases, which matches the characteristics of linearly polarized light. Further confirmed that in the wavelength ranges of 825, 883, 943, and 961 nm where ε = 0 shown in Figure 4 shown, the structure modulates the left-handed circularly polarized light into linearly polarized light.

[0058] In this embodiment, when circularly polarized light is incident, due to the different refractive indices of the structure for different polarized lights, optical rotation is generated, causing the circularly polarized light to be converted into elliptically polarized light. And when at the characteristic wavelength, the phenomenon that the circularly polarized light can be converted into linearly polarized light is observed, showing a strong modulation ability for light.

[0059] Embodiment 2

[0060] Based on Embodiment 1, this embodiment can also achieve periodic modulation of polarization. As Figure 6As shown, the grayscale map of the ellipticity spectrum varying with the thickness of the intermediate dielectric layer. The white dashed line in the figure is 2πN = 2π×(2h2·n / λ), where N is a positive integer representing the order of the FP mode, h2 represents the height of the dielectric layer of the MIM structure, n represents the effective refractive index, and λ represents the wavelength. It can be seen from the figure that the periodic variation of the ellipticity spectrum matches the FP order. This is because an FP cavity is formed between the upper and lower metal layers of the MIM, and the generated FP mode causes constructive and destructive interferences to alternate under the influence of the height of the MIM dielectric layer, forming a periodicity related to the FP order. Therefore, the structure of this embodiment can not only change the polarization state of the transmitted light and the rotation direction of the polarization ellipse, but also perform periodic modulation on the polarization to obtain different optical characteristics.

[0061] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adjustable polarization converter based on a chiral nanoarray with an MIM structure, characterized in that, Comprising: A transparent substrate, and a chiral metal nanostructure array disposed on the transparent substrate, wherein: The chiral metal nanostructure array includes a plurality of periodically arranged MIM tetramer nano-units; Each MIM tetramer nano-unit includes three stacked single-layer tetramer nano-units, namely, two metal-layer tetramer nano-units with the same thickness and a dielectric-layer tetramer nano-unit disposed between the two metal-layer tetramer nano-units; Each single-layer tetramer includes four spaced-apart rectangular nano-structures with chiral response, that is, each single-layer tetramer includes a first horizontal rectangular body (1), a first vertical rectangular body (2), a second vertical rectangular body (3), and a second horizontal rectangular body (4) arranged at intervals; The major axis of the first horizontal rectangular body (1) is perpendicular to the major axes of the first vertical rectangular body (2) and the second vertical rectangular body (3), the major axis of the second horizontal rectangular body (4) is perpendicular to the major axes of the first vertical rectangular body (2) and the second vertical rectangular body (3), and the major axis of the first horizontal rectangular body (1) is parallel to the major axis of the second horizontal rectangular body (4); The spacing between the first horizontal rectangular body (1) and the first vertical rectangular body (2), the spacing between the first horizontal rectangular body (1) and the second vertical rectangular body (3), the spacing between the first vertical rectangular body (2) and the second horizontal rectangular body (4), the spacing between the second vertical rectangular body (3) and the second horizontal rectangular body (4), and the spacing between the first vertical rectangular body (2) and the second vertical rectangular body (3) are all the same.

2. The adjustable polarization converter based on the chiral nanoarray with an MIM structure according to claim 1, characterized in that, The thickness of the metal layer in the metal-layer tetramer nano-unit is 10 - 120 nm; the thickness of the dielectric layer in the dielectric-layer tetramer nano-unit is 0 - 2900 nm, which is used to determine the chiral optical response of the structure and has a periodic modulation effect.

3. The adjustable polarization converter based on the chiral nanoarray with an MIM structure according to claim 2, characterized in that, The metal layer in the metal-layer tetramer nano-unit is made of a noble metal material, and the dielectric layer in the dielectric-layer tetramer nano-unit is made of a dielectric material.

4. The adjustable polarization converter based on the chiral nanoarray with an MIM structure according to claim 1, characterized in that, The period of the chiral metal nanostructure array is P x = 380 - 620 nm, P y = 240 - 480 nm.

5. The adjustable polarization converter based on the chiral nanoarray with an MIM structure according to claim 1, characterized in that, The spacing between the first horizontal rectangular body (1) and the first vertical rectangular body (2), the spacing between the first horizontal rectangular body (1) and the second vertical rectangular body (3), the spacing between the first vertical rectangular body (2) and the second horizontal rectangular body (4), the spacing between the second vertical rectangular body (3) and the second horizontal rectangular body (4), and the spacing between the first vertical rectangular body (2) and the second vertical rectangular body (3) are all 10 - 40 nm.

6. The adjustable polarization converter based on the chiral nanoarray with an MIM structure according to claim 5, characterized in that, The length of the first horizontal rectangular body (1) is 160 - 240 nm, and the width is 40 - 80 nm; the first vertical rectangular body (2), the second vertical rectangular body (3), and the second horizontal rectangular body (4) have the same dimensions, with the length being 110 - 190 nm and the width being 40 - 80 nm.

7. The adjustable polarization converter based on the chiral nanoarray with an MIM structure according to claim 6, characterized in that, The right side line of the first horizontal cuboid (1) is collinear with the right side line of the second vertical cuboid (3) in the y-axis direction; the left side line of the first vertical cuboid (2) is collinear with the left side line of the second horizontal cuboid (4) in the y-axis direction; the upper side line of the first horizontal cuboid (1) is collinear with the upper side line of the first vertical cuboid (2) in the x-axis direction; The lower side line of the second vertical cuboid (3) is collinear with the lower side line of the second horizontal cuboid (4) in the x-axis direction.

8. The adjustable polarization converter based on the chiral nanoarray with an MIM structure according to claim 1, characterized in that, The transparent substrate includes a glass substrate.

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