CN117706665A - Zoom superlens based on reconfigurable sparse aperture and preparation method thereof - Google Patents

Abstract

The invention discloses a zoom superlens based on reconfigurable sparse aperture and a preparation method thereof, wherein the zoom superlens comprises a stretchable substrate and a plurality of sparse apertures; wherein the number of sparse apertures is greater than one; symmetry exists among the plurality of sparse apertures and the sparse apertures are uniformly distributed; the sparse aperture comprises a plurality of phase structures; a stretchable substrate for supporting the sparse apertures and for changing a distance between a center of the plurality of sparse apertures and a center of the stretchable substrate by deformation; sparse aperture for adjusting focal length of zoom superlens; and the phase structure is used for carrying out wave front regulation and control on the incident light. The embodiment of the invention reduces the preparation difficulty and the preparation cost, can realize the focusing performance of active regulation and control, and can be widely applied to the field of optical devices.

Description

A zoom metalens based on reconfigurable sparse aperture and its preparation method

Technical field

The invention relates to the field of optical devices, and in particular to a zoom hyperlens based on reconfigurable sparse apertures and a preparation method thereof.

Background technique

Metalenses play an important role in display imaging, wireless communications, information encryption and other fields. Among them, optical imaging has continuously increasing requirements for imaging resolution. The angular resolution of a hyperlens is proportional to the ratio of the operating wavelength to the entrance pupil diameter. Increasing the aperture of the hyperlens is a traditional method to improve resolution. However, the structural units of metalenses are usually sub-wavelength scale, and the patterning in the production process relies on the photolithography process. The difficulty, cost, and time-consuming of the photolithography process increase sharply as the aperture increases, greatly increasing the It is difficult to prepare, is not conducive to production and manufacturing, and limits the wide application of large-aperture metalens.

Moreover, in related technologies, the focal length of a metalens based on reconfigurable sparse apertures is fixed, and the focal length needs to be adjusted by regulating the electromagnetic characteristics or background parameters of the incident light.

Contents of the invention

In view of this, the purpose of embodiments of the present invention is to provide a zoom metalens based on reconfigurable sparse apertures and a preparation method thereof, which reduces the difficulty and cost of preparation and can achieve actively regulated focusing performance.

In a first aspect, embodiments of the present invention provide a zoom metalens based on reconfigurable sparse apertures, including a stretchable substrate and several sparse apertures; wherein the number of sparse apertures is greater than one; between the several sparse apertures There is symmetry and uniform distribution; the sparse aperture includes several phase structures;

A stretchable substrate is used to support sparse apertures and to change the distance between the centers of several sparse apertures and the center of the stretchable substrate through deformation;

Sparse aperture, used to adjust the focal length of the zoom metalens;

Phase structure is used to control the wavefront of incident light.

Optionally, the stretchable substrate includes any one of a flexible substrate, an elastic substrate, or a malleable substrate.

Optionally, the stretchable substrate includes a central electrode, several spring structures, several comb electrodes and several peripheral electrodes; the central electrode is arranged at the center of the stretchable substrate; from the central electrode to the stretchable substrate In the direction of the edge of the bottom, there are several spring structures, several sparse apertures, several comb-shaped electrodes and several peripheral electrodes; among them,

The center electrode is used to provide a first voltage to one end of the comb electrode;

a peripheral electrode for providing a second voltage to the other end of the comb electrode;

A spring structure used to generate deformation to change the distance between the center of several sparse apertures and the center of the stretchable substrate;

Comb-shaped electrodes are used to generate electrostatic force to deform the spring structure.

Optionally, the spring structure, sparse apertures and comb electrodes are suspended in the air through the tensile force between the spring structure and the central electrode, and the tensile force between the comb electrode and the peripheral electrode.

Optionally, the shape of the sparse apertures includes a first regular shape, and the first regular shape includes any one or more of a sector, a circle, or a rectangle.

Optionally, several sparse apertures are symmetrical to each other about the center of the stretchable substrate, or about a straight line passing through the center of the stretchable substrate.

Optionally, several sparse apertures constitute several focusing units; the sparse apertures in the same focusing unit are symmetrical.

Optionally, the sparse aperture further includes a rigid substrate, and etching is performed on the rigid substrate to form a phase structure; the cross-sectional shape of the phase structure includes a second regular pattern, and the second regular pattern includes a T-shape or a circle.

In a second aspect, embodiments of the present invention also provide a method for preparing a zoom hyperlens based on reconfigurable sparse apertures, which can be applied to the zoom hyperlens as described above, including:

Pretreat the substrate;

Preparing several layer bonding layers and a stretchable substrate on the pretreated substrate;

Prepare a sparse aperture layer at a preset position, and prepare a sparse aperture layer in the sparse aperture layer;

Remove the substrate and the bonding layer corresponding to the substrate.

Optionally, when the stretchable substrate includes a central electrode, several spring structures, several comb electrodes and several peripheral electrodes, the preparation method includes:

Preparing a protective layer, a bonding layer and a sparse aperture layer on the substrate in sequence;

Prepare sparse apertures, spring structures and comb structures in the sparse aperture layer;

Prepare comb-shaped electrodes on the comb-teeth structure;

Part of the substrate and part of the bonding layer are removed to allow the sparse apertures, spring structures, and comb electrodes to float.

Implementing embodiments of the present invention includes the following beneficial effects: Embodiments of the present invention provide a zoom hyperlens based on reconfigurable sparse apertures and a preparation method thereof. The zoom hyperlens includes a stretchable substrate and several sparse apertures; wherein, The number of sparse apertures is greater than one; there is symmetry between several sparse apertures and they are evenly distributed; the sparse apertures include several phase structures; the stretchable substrate is used to support the sparse apertures and make several sparse apertures through deformation The distance between the center of the lens and the center of the stretchable substrate changes; the sparse aperture is used to adjust the focal length of the zoom metalens; the phase structure is used to control the wavefront of the incident light. By stretching the stretchable substrate, the focal length of the hyperlens is actively controlled, and the focal length is linearly related to the amount of substrate stretching, making it easy to regulate; the number and arrangement of sparse apertures can be freely designed according to actual needs, and it has a relatively large High flexibility; several sparse apertures in the same zoom metalens can form multiple focusing units, achieving spatial multiplexing of sparse apertures; making the center of the sparse apertures in different focusing units consistent with the center of the stretchable substrate The distances between them produce different changes, achieving independent control of multiple focusing units. The preparation method of the embodiment of the present invention involves photolithography, ion etching, bonding and ion beam evaporation technology, and the structure in the zoom hyperlens is prepared layer by layer. The process flow is simple, the preparation difficulty and preparation cost are reduced, and it is conducive to widespread production. and applications.

Description of the drawings

Figure 1 is a schematic structural diagram of a zoom metalens based on reconfigurable sparse aperture provided by an embodiment of the present invention;

Figure 2 is a schematic diagram of the structure and electric field of a zoom metalens based on reconfigurable sparse apertures provided by an embodiment of the present invention;

Figure 3 is a schematic three-dimensional structural diagram of a zoom hyperlens based on reconfigurable sparse apertures provided by an embodiment of the present invention;

Figure 4 is a schematic three-dimensional structural diagram of another zoom hyperlens based on reconfigurable sparse apertures provided by an embodiment of the present invention;

Figure 5 is a schematic diagram of the structure, electric field and focusing performance of a zoom metalens based on biaxial stretching and reconfigurable sparse aperture provided by an embodiment of the present invention;

Figure 6 is a schematic diagram of the structure, electric field and focusing performance of a zoom hyperlens based on four-axis stretching and reconfigurable sparse aperture provided by an embodiment of the present invention;

Figure 7 is a schematic diagram of the structure, electric field and focusing performance of a zoom metalens based on uniaxial stretching and reconfigurable sparse aperture provided by an embodiment of the present invention;

Figure 8 is a schematic diagram of the structure, electric field and focusing performance of another zoom metalens based on biaxial stretching and reconfigurable sparse apertures provided by an embodiment of the present invention;

Figure 9 is a schematic diagram of the structure, electric field and focusing performance of another zoom metalens based on four-axis stretching and reconfigurable sparse aperture provided by an embodiment of the present invention;

Figure 10 is a schematic flow chart of a method for preparing a zoom metalens based on reconfigurable sparse apertures provided by an embodiment of the present invention;

Figure 11 is a schematic flow chart of another method for preparing a zoom hyperlens based on reconfigurable sparse apertures provided by an embodiment of the present invention;

FIG. 12 is a schematic flowchart of another method for preparing a zoom hyperlens based on reconfigurable sparse apertures provided by an embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only set for the convenience of explanation. The order between the steps is not limited in any way. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art. sexual adjustment.

In the following description, reference is made to "some embodiments" which describe a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or a different subset of all possible embodiments, and Can be combined with each other without conflict.

In the following description, the terms "first\second\third" are only used to distinguish similar objects and do not represent a specific ordering of objects. It is understandable that "first\second\third" Where permitted, the specific order or sequence may be interchanged so that the embodiments of the invention described herein may be practiced in other sequences than illustrated or described herein.

Unless otherwise defined, all technical and scientific terms used in the embodiments of the present invention have the same meanings as commonly understood by those skilled in the technical field of the present invention. The terms used in the embodiments of the present invention are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

As shown in Figure 1, the embodiment of the present invention provides a zoom metalens based on reconfigurable sparse apertures 2, including a stretchable substrate 1 and several sparse apertures 2; wherein the number of sparse apertures 2 is greater than one; There is symmetry between several sparse apertures 2 and they are evenly distributed; the sparse apertures 2 include several phase structures 21;

The stretchable substrate 1 is used to support sparse apertures 2 and to change the distance between the centers of several sparse apertures 2 and the center of the stretchable substrate 1 through deformation;

Sparse aperture 2, used to adjust the focal length of the zoom metalens;

The phase structure 21 is used to control the wavefront of the incident light.

Specifically, the sparse aperture 2 is provided on the stretchable substrate 1, or the stretchable substrate 1 includes several parts. The stretchable substrate 1 is connected to both sides of the sparse aperture 2, and the sparse aperture 2 is connected to the stretchable substrate 1. suspended; the number of sparse apertures 2 is greater than one, so that a symmetrical structure can be formed between several sparse apertures 2; a sufficient number of phase structures 21 are provided in the sparse apertures 2 to achieve wavefront control of the incident light through the phase structures 21, Combined with the fact that the distance between the centers of several sparse apertures 2 and the center of the stretchable substrate 1 changes by stretching or compressing the stretchable substrate 1, the focusing of the zoom hyperlens is achieved.

Specifically, the incident light may be incident from the direction from the sparse aperture 2 to the stretchable substrate 1 , or from the direction from the stretchable substrate 1 to the sparse aperture 2 .

Specifically, the center of a sparse aperture 2 and the center of the stretchable substrate 1 are connected to an axis. By stretching or compressing the stretchable substrate 1, each sparse aperture 2 moves on the axis, thereby making the sparse apertures The distance between the center of 2 and the center of stretchable substrate 1 increases or decreases.

In a specific embodiment, as shown in (a) in Figure 2, the size of the sparse aperture is 3mm×4.5mm; as shown in (a)-(c) in Figure 2, when the sparse aperture moves in the transverse direction respectively 3mm, 4.5mm and 9mm; the normalized electric field distribution of the emitted light moved by 3mm is shown in Figure 2(d), and the normalized electric field distribution of the emitted light moved by 4.5mm is shown in Figure 2(e) As shown, the normalized electric field distribution of the emitted light moved by 9mm is shown in (f) in Figure 2; where the electric field intensity is black when the electric field intensity is 0, and the electric field intensity is 1 when it is white. It can be seen from (d)-(f) in Figure 2 that the electric field energy distribution at the focus is tilted, where the focus is the maximum value of the electric field along the central axis of the zoom metalens; as the sparse aperture moves, a single sparse The focal length of the aperture will change, but the electric field distribution will be off-center. Therefore, it is necessary to maintain the central distribution of the electric field and change the focal length by increasing the number of sparse apertures and creating symmetry between several sparse apertures; the electric field synthesis of the zoom metalens based on two centrally symmetric sparse apertures is shown in Figure 2 As shown in (g), the positional relationship between the two sparse apertures from left to right is close, original position and far away respectively; when the two sparse apertures are close to each other, the focal points of the two sparse apertures no longer overlap and the focal length decreases; The sparse apertures are far away from each other, the focus of the two sparse apertures no longer coincides, and the focal length increases. By moving two sparse apertures closer or farther away from each other, the distribution of the synthetic electric field can be changed accordingly, and the position of the maximum electric field along the central axis of the zoom metalens will also change, thereby achieving effective control of the focal length of the metalens.

Optionally, the stretchable substrate includes any one of a flexible substrate, an elastic substrate, or a malleable substrate.

Specifically, when the stretchable substrate is any one of a flexible substrate, an elastic substrate, or a stretchable substrate, sparse apertures are provided on the stretchable substrate, and the stretchable substrate is Applying an external force on the axis connecting the center and the center of the stretchable substrate causes the distance between the center of the sparse aperture and the center of the stretchable substrate to change.

Specifically, when the stretchable substrate is a flexible substrate, the zoom metalens shown in (a) in Figure 3 is uniaxially stretched, and the number of sparse apertures is 2; as shown in (b) in Figure 3 The zoom metalens is biaxial stretching, and the number of sparse apertures is 4; the zoom metalens shown in (c) in Figure 3 is four-axis stretching, and the number of sparse apertures is 8.

Specifically, a flexible substrate refers to a base material with high flexibility and bendability that can withstand multiple bends and deformations without cracking or damage. The material of the flexible substrate includes any one of polymer film, thin metal foil, plastic film, etc. The specific flexible substrate material is determined according to the actual situation. There is no limitation in the embodiments of the present invention, and only examples are provided for reference. For reference, the material of the flexible substrate may be polydimethylsiloxane (PDMS).

Specifically, an elastic substrate refers to a base material with high elasticity and restorability, which can be deformed under the action of external force, but can quickly return to its original shape after the external force is removed. The material of the elastic substrate includes elastomer material or elastic film. The specific elastic substrate material is determined according to the actual situation and is not limited in the embodiment of the present invention.

Specifically, a malleable substrate refers to a base material that is highly malleable and stretchable and can be stretched and deformed significantly under the action of external forces without cracking or losing functionality. The material of the stretchable substrate includes elastomer material or elastic polymer film. The specific elastic stretchable substrate material is determined according to the actual situation and is not limited in the embodiments of the present invention.

As shown in Figure 4, the stretchable substrate 1 includes a central electrode 11, several spring structures 12, several comb electrodes 13 and several peripheral electrodes 14; the central electrode 11 is disposed at the center of the stretchable substrate 1 ; In the direction from the center electrode 11 to the edge of the stretchable substrate 1, several spring structures 12, several sparse apertures 2, several comb electrodes 13 and several peripheral electrodes 14 are arranged in sequence; wherein,

The center electrode 11 is used to provide a first voltage to one end of the comb electrode 13;

The peripheral electrode 14 is used to provide the second voltage to the other end of the comb electrode 13;

The spring structure 12 is used to generate deformation so that the distance between the centers of several sparse apertures 2 and the center of the stretchable substrate 1 changes;

The comb electrode 13 is used to generate electrostatic force to deform the spring structure 12 .

Specifically, the stretchable substrate 1 is composed of a central electrode 11, several spring structures 12, several comb-shaped electrodes 13, and several peripheral electrodes 14; with the central electrode 11 as the center, several spring structures are connected outward in sequence. 12. Several sparse apertures 2, several comb electrodes 13 and several peripheral electrodes 14; wherein the number of spring structures 12, comb electrodes 13 and peripheral electrodes 14 is the same as the number of sparse apertures 2.

Specifically, the comb-shaped electrode 13, also called an interdigital electrode, is composed of metal electrodes arranged alternately to form comb-shaped motor teeth. The spacing between electrode teeth is usually very close, forming several small gaps.

Specifically, when the stretchable substrate 1 includes a central electrode 11, a plurality of spring structures 12, a plurality of comb electrodes 13 and a plurality of peripheral electrodes 14, the stretchable substrate 1 is implemented through Micro Electro Mechanical Systems (MEMS). Stretching of substrate 1.

Specifically, two different voltages, such as a positive voltage and a negative voltage, are applied to the central electrode 11 and the peripheral electrode 14 respectively, so that mutually attractive electrostatic forces are generated between the intersecting electrode teeth in the comb-shaped electrode 13. are close to each other, so that the spring structure 12 is stretched, so that the distance between the center of the sparse aperture 2 and the center of the stretchable substrate 1 increases; when the potential difference between the first voltage and the second voltage is reduced , the stretch degree of the spring structure 12 decreases, so that the distance between the center of the sparse aperture 2 and the center of the stretchable substrate 1 decreases.

Specifically, when the stretchable substrate 1 includes a central electrode 11, a plurality of spring structures 12, a plurality of comb electrodes 13 and a plurality of peripheral electrodes 14, the zoom metalens shown in (a) in Figure 4 is single-axis. Stretching, the number of sparse apertures 2 is 2; the zoom metalens shown in (b) in Figure 4 is biaxial stretching, and the number of sparse apertures 2 is 4; as shown in (c) in Figure 4 The zoom metalens is a four-axis stretch, and the number of sparse apertures 2 is 8.

Optionally, the spring structure, sparse apertures and comb electrodes are suspended in the air through the tensile force between the spring structure and the central electrode, and the tensile force between the comb electrode and the peripheral electrode.

Specifically, the sparse aperture, the spring structure and the comb electrode are in a suspended state, so that when electrostatic force is generated between the intersecting electrode teeth in the comb electrode, the spring structure can deform, causing the sparse aperture to move.

Specifically, a protective layer and a substrate are connected to the bottom of the central electrode, peripheral electrodes and/or part of the comb-shaped electrodes to support the central electrode, spring structure, sparse apertures, comb-shaped electrodes and peripheral electrodes, so that the sparse apertures, spring structures and The comb-shaped electrode is suspended in the air through the pulling force between the spring structure and the central electrode, and the pulling force between the comb-shaped electrode and the peripheral electrode; among them, the bottom of some comb-shaped electrodes is connected with a protective layer and a substrate, making the comb-shaped electrode When an electrostatic force is generated between the intersecting electrode teeth in the electrode, the electrode teeth can move without being fixed by the protective layer or substrate, and the electrode teeth cannot move.

Optionally, the shape of the sparse apertures includes a first regular shape, and the first regular shape includes any one or more of a sector, a circle, or a rectangle.

Specifically, the first regular shape includes any one or more of a sector, a circle, or a rectangle. The specific shape is determined according to the actual situation. There is no limitation in the embodiments of the present invention, and the embodiments are only provided for reference, such as, The first regular shape may be a rectangle.

Optionally, several sparse apertures are symmetrical to each other about the center of the stretchable substrate, or about a straight line passing through the center of the stretchable substrate.

Specifically, when the shape of the sparse aperture itself is an axially symmetric figure, the symmetry of several sparse apertures about the center of the stretchable substrate is equivalent to the symmetry about the axis passing through the center of the stretchable substrate; when the shape of the sparse aperture itself is non-symmetrical. Axis-symmetrical figures, such as non-equilateral triangles or non-isosceles triangles, have two different symmetry modes: symmetry of several sparse apertures about the center of the stretchable substrate and symmetry about the axis passing through the center of the stretchable substrate.

Optionally, several sparse apertures constitute several focusing units; the sparse apertures in the same focusing unit are symmetrical.

Specifically, a zoom metalens can include one or more focusing units; the number of sparse apertures in one focusing unit is greater than one, and there is symmetry in the sparse apertures in the same focusing unit.

In a specific embodiment, the structure of the zoom metalens is shown in Figure 5 (a), including four sparse apertures 201-204; among them, the sparse aperture 201 and the sparse aperture 203 constitute a focusing unit, and the sparse apertures 202 and 203 constitute a focusing unit. Sparse aperture 204 constitutes another focusing unit. The stretchable substrate is compressed or stretched along the long side direction of the sparse aperture, and the normalized electric field energy of the emitted light is shown in (b) in Figure 5, where the stretchable substrate is compressed toward the center to Negative travel distances are represented; stretching away from the center of the stretchable substrate is represented by positive travel distances. The changes in focusing characteristics of the emitted light in the transverse magnetic mode and the transverse electric mode with movement are shown in (c)-(f) in Figure 5, where (c)-(d) are two focusing units in the transverse magnetic mode. The focusing characteristic diagrams of Focusing quality can achieve linear changes in focal length; among them, in the transverse magnetic mode, the linear correlation coefficients of the focal lengths of the two focusing units are 0.99772 and 0.99908 respectively; in the transverse electric mode, the linear correlation coefficients of the focal lengths of the two focusing units They are 0.99877 and 0.99705 respectively.

In another specific embodiment, the structure of the zoom metalens is shown in Figure 6 (a), including eight sparse apertures; where sparse apertures 205, 207, 209, and 212 constitute a focusing unit, and sparse apertures 206 and 208 , 210, and 213 constitute another focusing unit. The stretchable substrate is compressed or stretched along the long side direction of the sparse aperture, and the normalized electric field energy of the emitted light is shown in Figure 6 (b). The focusing characteristics of the transverse magnetic mode and transverse electric mode of the emitted light change with movement as shown in (c)-(d) in Figure 6. The full width at half maximum of the emitted light can exceed or approach the diffraction limit, indicating that the zoom metalens has excellent The focusing quality can achieve linear changes in focal length; among them, in the transverse magnetic mode, the linear correlation coefficients of the focal lengths of the two focusing units are 0.99416 and 0.99955 respectively; in the transverse electric mode, the linear correlation coefficients of the focal lengths of the two focusing units The coefficients are 0.99967 and 0.99866 respectively.

Optionally, the sparse aperture further includes a rigid substrate, and etching is performed on the rigid substrate to form a phase structure; the cross-sectional shape of the phase structure includes a second regular pattern, and the second regular pattern includes a T-shape or a circle.

Specifically, the specific second regular pattern is determined according to the actual situation, and is not limited in the embodiment of the invention. The embodiment is only provided for reference. For example, the second regular pattern may be T-shaped.

Specifically, the sparse pore material includes a rigid material, and the rigid material includes silicon. The specific sparse pore material is determined according to the actual situation, and is not limited in the embodiment of the present invention.

Specifically, the sparse aperture also includes a rigid substrate, which is etched to form a phase structure, that is, there is a layer of rigid material between the phase structure and the stretchable substrate, causing the stretchable substrate to deform. When , the deformation of the sparse aperture has a negligible effect on the focusing and focusing effects of the zoom metalens.

Specifically, the phase structure includes a polarization-dependent phase structure, so that the emergent light passing through the zoom metalens realizes a transverse magnetic mode and a transverse electric mode.

In a specific embodiment, the cross-sectional shape of the phase structure is T-shaped. The T-shaped phase structure has polarization-dependent characteristics and can achieve focusing in two polarization directions.

In a specific embodiment, a zoom hyperlens based on uniaxial stretching of sparse apertures is shown in Figure 1. The stretchable substrate is a flexible substrate; the number of sparse apertures is 2. Regarding the stretchable substrate Central symmetry; the shape of the sparse aperture is rectangular, and the phase structure is a T-shaped phase structure in cross-section. By stretching the flexible substrate along the long side of the sparse aperture, the focal length of the metalens is changed.

In a specific embodiment, the structure of a uniaxially stretched reconfigurable sparse aperture-based zoom metalens (stretchable single-axis metalens, SSM) is shown in Figure 7 (a), including two rectangular sparse apertures. ; The stretchable substrate stretches along the long side of the rectangle, and the normalized electric field energy of the emitted light is shown in (b) in Figure 7. It can be seen from the figure that the SSM maintains good focusing characteristics in the axial direction. And the focal length increases as the amount of movement increases; compression toward the center of the stretchable substrate is represented by a negative movement distance; stretching in a direction away from the center of the stretchable substrate is represented by a positive movement distance. Movement distance expressed. The focusing characteristics of the emitted light in the transverse magnetic mode change with movement as shown in Figure 7(c). The focusing characteristics of the emitted light in the transverse electric mode change with movement as shown in Figure 7(d). The movement of the sparse aperture When the distance increases from -500 μm to 500 μm in steps of 250 μm, the focal length maintains a linear increase in both the transverse magnetic mode and the transverse electric mode. The linear correlation coefficient of the transverse magnetic mode is 0.99804, and the linear correlation coefficient of the transverse electric mode is 0.99855. The full width at half maximum represents the focusing performance of the zoom metalens. The longitudinal and lateral full width at half maximum are shown in Figures (c)-(d), which are very close to or even exceed the diffraction limit.

In another specific embodiment, the structure of a biaxially stretched zoom metalens (stretchable dual-axis metalens, SDM) based on reconfigurable sparse apertures is shown in Figure 8 (a), including four rectangular sparse Aperture, four rectangular sparse apertures are the same focusing unit; the stretchable substrate expands and contracts along the long side of the rectangle, and the normalized electric field energy of the emitted light is shown in (b) in Figure 8. It can be seen from the figure that SDM Good focusing characteristics are maintained in the axial direction, and the focal length increases as the amount of movement increases. The focusing characteristics of the emitted light in the transverse magnetic mode change with movement as shown in Figure 8(c), and the focusing characteristics of the emitted light in the transverse electric mode change with movement as shown in Figure 8(d). It can be seen from the figure , the longitudinal and transverse full width at half maximum are very close to the diffraction limit. The focal length of SDM shows a good linear change trend with the moving distance of the sparse aperture. The linear correlation coefficient of the transverse magnetic mode is 0.99852, and the linear correlation coefficient of the transverse electric mode is 0.99858. .

In another specific embodiment, the structure of a four-axis stretched zoom metalens (stretchable quad-axis metalens, SQM) based on reconfigurable sparse apertures is shown in Figure 9 (a), including eight rectangular sparse Aperture, eight rectangular sparse apertures are the same focusing unit; the stretchable substrate stretches along the long side of the rectangle, and the normalized electric field energy of the emitted light is shown in Figure 9(b). It can be seen from the figure that SQM Good focusing characteristics are maintained in the axial direction, and the focal length increases with the increase in movement. The focusing characteristics of the emitted light in the transverse magnetic mode change with movement as shown in Figure 9 (c), and the focusing characteristics of the emitted light in the transverse electric mode change with movement as shown in Figure 9 (d). It can be seen from the figure It can be seen that the longitudinal and transverse full width at half maximum are very close to the diffraction limit. The focal length of the SDM shows a good linear change trend with the moving distance of the sparse aperture. The linear correlation coefficient of the transverse magnetic mode is 0.99655, and the linear correlation coefficient of the transverse electric mode is 0.99862.

As shown in Figure 10, an embodiment of the present invention also provides a method for preparing a zoom hyperlens based on reconfigurable sparse apertures, which can be applied to the zoom hyperlens as described above, including:

S100. Preprocess the substrate 3.

Specifically, the material of the substrate includes silicon or silicon dioxide. The specific substrate material is determined according to the actual situation. It is not limited in the embodiments of the invention and is only provided for reference. For example, the substrate as shown in the figure The material is silicon.

Specifically, the pretreatment includes cleaning the substrate 3 .

Specifically, the substrate 3 serves as a temporary substrate so that the vacuum adsorption process involved will not affect the flexible substrate during the photolithography process.

S200. Prepare several bonding layers and a stretchable substrate on the pretreated substrate 3; the stretchable substrate includes a flexible substrate, a center electrode, several spring structures, several comb electrodes and several any one or more of the peripheral electrodes.

Specifically, when the stretchable substrate is a flexible substrate, several bonding layers and the stretchable substrate are prepared on the pretreated substrate, including:

S201. As shown in (a) of Figure 11, the first bonding layer 4 and the flexible substrate 5 are sequentially prepared on the pretreated substrate 3.

Specifically, the material of the flexible substrate 5 includes any one of polydimethylsiloxane (PDMS), polyester (PET) or polyimide (PI). Specifically, the flexible substrate 5 The material of the substrate 5 is determined according to the actual situation, and is not limited in the embodiments of the invention. The embodiments are only provided for reference. For example, the flexible substrate 5 as shown in the figure is PDMS.

S300. Prepare a sparse aperture layer 6 at a preset position, and prepare sparse apertures in the sparse aperture layer 6.

S301. As shown in (b)-(c) in Figure 11, clean the sparse aperture layer 6, partially pattern the sparse aperture layer 6 through photolithography and deep reactive ion etching, and then use the second bonding layer 7 to The partially patterned sparse aperture layer 6 is bonded to a preset position on the flexible substrate 5 so that the partially patterned sparse aperture layer 6 is evenly distributed on the flexible substrate and has symmetry;

S302. As shown in (d) of Figure 11, perform secondary alignment photolithography and deep reactive ion etching on the partially patterned sparse aperture layer 6 to etch the phase structure 21 to obtain the sparse aperture 2.

Specifically, the material of the sparse pores 2 includes silicon. The specific sparse pore material is determined according to the actual situation. There is no limitation in the embodiments of the invention. The examples are only provided for reference. For example, the material of the sparse pores as shown in the figure is silicon. .

Specifically, the material of the first bonding layer 4 or the second bonding layer 7 includes organic glue. The specific bonding layer material is determined according to the actual situation. There is no limitation in the embodiments of the invention, and the examples are only provided for reference, such as , as shown in the figure, the first bonding layer 4 and the second bonding layer 7 respectively use two different organic glues.

S400. Remove the substrate 3 and the bonding layer corresponding to the substrate 3.

Specifically, as shown in (e) of Figure 11 , the substrate 3 and the first bonding layer 4 are removed to obtain a stretchable substrate based on a flexible substrate and a zoom metalens with reconfigurable sparse apertures.

In a specific embodiment, a solution that can dissolve the first bonding layer 4 but cannot dissolve the second bonding layer 7 is used to remove the substrate and the first bonding layer 4 .

Optionally, when the stretchable substrate includes a central electrode, several spring structures 12, several comb-shaped electrodes 13, and several peripheral electrodes, the preparation method of a zoom metalens based on reconfigurable sparse apertures includes:

S500: Prepare a protective layer 8, a bonding layer and a sparse aperture layer 6 on the substrate 3 in sequence.

S501. As shown in (a) of Figure 12, a protective layer 8 is prepared on the substrate 3. The material of the protective layer 8 includes silicon dioxide. The specific protective layer material is determined according to the actual situation and is not limited in the embodiments of the invention. Examples are only provided for reference. For example, the material of the protective layer 8 shown in (a) in Figure 12 is silicon dioxide;

S502. As shown in (b) of Figure 12, the third bonding layer 9 and the sparse aperture layer 6 are sequentially prepared on the protective layer 8, and through photolithography and deep reactive ion etching, as shown in (b) of Figure 12 The structure shown has alignment marks etched through the entire structure.

S600. Prepare sparse apertures, a spring structure 12 and a comb structure 15 in the sparse aperture layer 6 .

Specifically, as shown in (d)-(e) in Figure 12, the sparse aperture layer 6 is partially patterned by photolithography and deep reactive ion etching, and the partially patterned sparse aperture layer 6 is subjected to secondary processing. Quasi-photolithography and deep reactive ion etching are used to etch the phase structure 21, the spring structure 12 and the comb structure 15 to obtain a sparse aperture 2.

S700. Prepare the comb electrode 13 on the comb structure 15.

Specifically, as shown in (f) of FIG. 12 , electron beam evaporation is performed on the comb structure 15 to obtain a metal electrode, and the metal electrode is patterned through a liftoff process to obtain the comb electrode 13 .

S800. Remove part of the substrate and part of the bonding layer so that the sparse apertures, spring structures 12 and comb electrodes 13 are suspended.

Specifically, as shown in (g)-(h) in FIG. 12 , part of the substrate 3 and the protective layer 8 are removed by photolithography and deep reactive ion etching, so that the sparse apertures, spring structures 12 and part of the comb electrodes 13 Hanging.

Implementing embodiments of the present invention includes the following beneficial effects: Embodiments of the present invention provide a zoom hyperlens based on reconfigurable sparse apertures and a preparation method thereof. The zoom hyperlens includes a stretchable substrate and several sparse apertures; wherein, The number of sparse apertures is greater than one; there is symmetry between several sparse apertures and they are evenly distributed; the sparse apertures include several phase structures; the stretchable substrate is used to support the sparse apertures and make several sparse apertures through deformation The distance between the center of the lens and the center of the stretchable substrate changes; the sparse aperture is used to adjust the focal length of the zoom metalens; the phase structure is used to control the wavefront of the incident light. By stretching the stretchable substrate, the focal length of the hyperlens is actively controlled, and the focal length is linearly related to the amount of substrate stretching, making it easy to regulate; the number and arrangement of sparse apertures can be freely designed according to actual needs, and it has a relatively large High flexibility; several sparse apertures in the same zoom metalens can form multiple focusing units, achieving spatial multiplexing of sparse apertures; by using stretchable substrates based on microelectromechanical systems (MEMS), different The distance between the center of the sparse aperture in the focusing unit and the center of the stretchable substrate changes differently, achieving independent regulation of multiple focusing units. The preparation method of the embodiment of the present invention involves photolithography, ion etching, bonding and ion beam evaporation technology, and the structure in the zoom hyperlens is prepared layer by layer. The process flow is simple, the preparation difficulty and preparation cost are reduced, and it is conducive to widespread production. and applications.

The above is a detailed description of the preferred implementation of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art can also make various equivalent modifications or substitutions without violating the spirit of the present invention. , these equivalent modifications or substitutions are included in the scope defined by the claims of this application.

Claims (10)

1. The zoom superlens based on the reconfigurable sparse aperture is characterized by comprising a stretchable substrate and a plurality of sparse apertures; wherein the number of sparse apertures is greater than one; symmetry exists among the plurality of sparse apertures, and the sparse apertures are uniformly distributed; the sparse aperture comprises a plurality of phase structures;

the stretchable substrate is used for supporting the sparse apertures and changing the distances between the centers of the sparse apertures and the centers of the stretchable substrate through deformation;

the sparse aperture is used for adjusting the focal length of the zoom super lens;

the phase structure is used for carrying out wave front regulation and control on incident light.

2. The reconfigurable sparse aperture based zoom superlens of claim 1, wherein the stretchable substrate comprises any one of a flexible substrate, an elastic substrate, or a malleable substrate.

3. The reconfigurable sparse aperture based zoom superlens of claim 1, wherein the stretchable substrate comprises a central electrode, a number of spring structures, a number of comb electrodes, and a number of peripheral electrodes; the center electrode is arranged at the center of the stretchable substrate; a plurality of spring structures, a plurality of sparse apertures, a plurality of comb-shaped electrodes and a plurality of peripheral electrodes are sequentially arranged in the direction from the central electrode to the edge of the stretchable substrate; wherein,

the center electrode is used for providing a first voltage for one end of the comb-shaped electrode;

the peripheral electrode is used for providing a second voltage for the other end of the comb-shaped electrode;

the spring structure is used for generating deformation so as to change the distances between the centers of the sparse apertures and the centers of the stretchable substrates;

the comb-shaped electrode is used for generating electrostatic force so as to deform the spring structure.

4. A reconfigurable sparse aperture based zoom superlens according to claim 3, wherein the spring structure, the sparse aperture and the comb electrode are suspended by a pulling force between the spring structure and the central electrode, and a pulling force between the comb electrode and the peripheral electrode.

5. The reconfigurable sparse aperture based zoom superlens of claim 1, wherein the shape of the sparse aperture comprises a first regular shape comprising any one or more of a sector, a circle, or a rectangle.

6. The reconfigurable sparse aperture based zoom superlens of claim 1, wherein a number of the sparse apertures are symmetrical about a center of the stretchable substrate or about a line passing through a center of the stretchable substrate.

7. The reconfigurable sparse aperture based zoom superlens of claim 1, wherein a number of the sparse apertures comprise a number of focusing elements; symmetry exists for sparse apertures in the same focusing element.

8. The reconfigurable sparse aperture based zoom superlens of claim 1, wherein the sparse aperture further comprises a rigid substrate on which etching is performed to form the phase structure; the cross-sectional shape of the phase structure includes a second regular pattern including a T-shape or a circle shape.

9. A method for preparing a zoom superlens based on reconfigurable sparse aperture, which is applied to the zoom superlens as claimed in claim 1, comprising:

pretreating a substrate;

preparing a plurality of layer bonding layers and the stretchable substrate on the pretreated substrate; the method comprises the steps of carrying out a first treatment on the surface of the

Preparing the sparse aperture layer at a preset position, and preparing the sparse aperture in the sparse aperture layer;

and removing the substrate and the bonding layer corresponding to the substrate.

10. The method of manufacturing a reconfigurable sparse aperture based zoom superlens of claim 9, wherein when the stretchable substrate comprises the center electrode, the number of spring structures, the number of comb electrodes, and the number of peripheral electrodes, the method of manufacturing comprises:

preparing a protective layer, the bonding layer and the sparse aperture layer on the substrate in sequence;

preparing the sparse aperture, the spring structure and the comb structure in the sparse aperture layer;

preparing the comb-shaped electrode on the comb-tooth structure;

and removing part of the substrate and part of the bonding layer so as to suspend the sparse aperture, the spring structure and the comb-shaped electrode.