Multifunctional achromatic superlens, design method and fabrication method

Abstract

This application discloses a multifunctional achromatic superlens, its design method, and its fabrication method. The design method includes setting a target operating wavelength and a target magnification; determining the substrate material based on the target operating wavelength; determining the lens diameter and target focal length of the first and second metasurfaces of the substrate based on the target magnification; determining target phase information based on the target operating wavelength and target focal length; and constructing superlenses on the first and second metasurfaces based on the target phase information to obtain a multifunctional achromatic superlens model. This application simultaneously achieves achromatic and magnification functions, meeting the lens requirements of small imaging devices. It can achieve magnification while ensuring the same NA numerical aperture, and the first and second metasurfaces determine the target phase information based on phase modulation functions, ensuring that light of different wavelengths can be focused to a single point after passing through the lens, thus achieving the achromatic function.

Description

Technical Field

[0001] This application belongs to the field of superlens technology, specifically relating to a multifunctional achromatic superlens, its design method, and its fabrication method. Background Technology

[0002] Superlenses are characterized by miniaturization and low profile, and their size is usually at the nanometer level. They have dynamic control functions of optical properties (such as amplitude, phase, polarization, spatial / spectral / temporal response) and early device functions (such as beam steering, tunable focusing, tunable filters / absorbers, dynamic holograms, etc.), basically achieving full coverage of traditional optical applications.

[0003] Current technologies for superlenses focus on achieving a single function, which is not conducive to the future development trend of optics. In some application scenarios, in order to achieve multifunctional lens functions, multiple superlenses need to be cascaded, which is not conducive to the miniaturization and integrated design of lenses. Summary of the Invention

[0004] The purpose of this application is to provide a multifunctional achromatic superlens, its design method, and its fabrication method, in order to solve the technical problem that existing superlenses focus on achieving a single function, which is not conducive to the future development trend of optics.

[0005] To achieve the above objectives, one technical solution adopted in this application is:

[0006] A design method for a multifunctional achromatic superlens is provided, including:

[0007] A design method for a multifunctional achromatic superlens includes:

[0008] Set the target operating wavelength and target magnification;

[0009] The substrate material is determined based on the target operating wavelength;

[0010] Based on the target magnification, the lens diameter and target focal length of the first metasurface and the second metasurface of the substrate are determined;

[0011] Based on the target operating wavelength and target focal length, the target phase information of the first metasurface and the second metasurface of the substrate is determined, and the target phase information includes the target phase of the subwavelength structure at different positions;

[0012] Based on the target phase information, superlenses are constructed on the first and second metasurfaces respectively to obtain a multifunctional achromatic superlens model.

[0013] In one or more embodiments, the target operating wavelength is in the visible light band, and the substrate material is gallium nitride.

[0014] In one or more embodiments, the step of determining the lens diameter and target focal length of the first metasurface and the second metasurface of the substrate based on the target magnification includes:

[0015] Based on the target magnification, the target focal length ratio of the first metasurface and the second metasurface is obtained;

[0016] Based on the target focal length ratio, the lens diameter and target focal length of the first metasurface and the second metasurface are determined, and the ratio of the target focal length to the lens diameter of the first metasurface is the same as the ratio of the target focal length to the lens diameter of the second metasurface.

[0017] In one or more embodiments, the step of determining the target phase information of the first metasurface and the second metasurface of the substrate based on the target operating wavelength and the target focal length includes:

[0018] Based on the phase modulation function, the target phase of the subwavelength structure at different locations is calculated. The expression for the phase modulation function is as follows:

[0019]

[0020] In the formula, Let f be the target phase, f be the target focal length, and λ be the target operating wavelength.

[0021] In one or more embodiments, the step of constructing a superlens on the first metasurface and the second metasurface respectively based on the target phase information to obtain a multifunctional achromatic superlens model includes:

[0022] Based on the target phase information, target rotation information is obtained, including the rotation angle of subwavelength structures at different positions;

[0023] Based on the target rotation information, superlenses are constructed on the first metasurface and the second metasurface, respectively.

[0024] In one or more embodiments, the step of obtaining target rotation information based on the target phase information includes:

[0025] Based on the PB control function, the rotation angle of the subwavelength structure at different positions is calculated. The expression for the PB control function is as follows:

[0026]

[0027] In the formula, Let θ be the target phase and θ be the rotation angle.

[0028] In one or more embodiments, the step of constructing a superlens on the first metasurface and the second metasurface based on the target rotation information includes:

[0029] Determine the subwavelength structural arrangement of the first metasurface and the second metasurface;

[0030] Determine the size and period of the subwavelength structure;

[0031] Based on the target rotation information, subwavelength structures are rotated at different positions on the first metasurface and the second metasurface, respectively.

[0032] In one or more embodiments, the step of determining the size and period of the subwavelength structure includes:

[0033] The height and period of the subwavelength structure are set to be consistent, and the length and width of the subwavelength structure are determined by parametric scanning.

[0034] To achieve the above objectives, another technical solution adopted in this application is:

[0035] A multifunctional achromatic superlens is provided, which is designed by the design method of the multifunctional achromatic superlens described in any of the above embodiments.

[0036] To achieve the above objectives, another technical solution adopted in this application is:

[0037] A method for fabricating the multifunctional achromatic superlens according to any of the above embodiments includes:

[0038] The first superlens is obtained by sequentially coating the first metasurface of the substrate with adhesive, exposing it, developing it, and etching it.

[0039] The substrate is rotated, and the second metasurface of the substrate is sequentially coated with adhesive, exposed, developed, and etched to obtain the second superlens.

[0040] The advantages of this application, which differ from existing technologies, are:

[0041] The multifunctional achromatic superlens of this application can simultaneously achieve achromatic and magnification functions, which can meet the lens requirements of small imaging devices and achieve color imaging and magnification functions under the limited lens size.

[0042] The design method of this application can achieve magnification by setting the target focal length and lens diameter of the first metasurface and the second metasurface of the substrate respectively, while ensuring that their NA numerical aperture is the same; at the same time, the first metasurface and the second metasurface determine the target phase information based on the phase modulation function respectively, ensuring that light of different wavelengths can be focused into a point after passing through the lens, thereby achieving the achromatic function.

[0043] The multifunctional achromatic superlens of this application can be fabricated using semiconductor photolithography, effectively avoiding the steps required for fabricating metal or dielectric materials on the surface of a substrate, thus simplifying the fabrication complexity. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating one embodiment of the design method for the multifunctional achromatic superlens of this application;

[0045] Figure 2 yes Figure 1 A flowchart of one embodiment corresponding to step S300;

[0046] Figure 3 yes Figure 1 A flowchart of one embodiment corresponding to step S500;

[0047] Figure 4 yes Figure 3 A flowchart of one embodiment corresponding to step S502;

[0048] Figure 5 This is a schematic diagram of the subwavelength structure arrangement of one embodiment of the multifunctional achromatic superlens of this application;

[0049] Figure 6 This is a schematic diagram of one embodiment of the multifunctional achromatic superlens of this application;

[0050] Figure 7 This is a schematic diagram of the working state of one embodiment of the multifunctional achromatic superlens of this application;

[0051] Figure 8 This is a schematic flowchart of one embodiment of the preparation method of the multifunctional achromatic superlens of this application. Detailed Implementation

[0052] The present application will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the protection scope of the present application.

[0053] Over the past 20 years, optical metasurfaces with subwavelength thickness have demonstrated enormous application potential in both fundamental and emerging optics. They exhibit powerful and flexible manipulation capabilities for various types of transmitted, reflected, and diffracted light. These metasurfaces possess dynamic control functions for optical properties (such as amplitude, phase, polarization, and spatial / spectral / temporal response) and early device functions (such as beam steering, tunable focusing, tunable filters / absorbers, and dynamic holograms), essentially achieving full coverage of traditional optical applications.

[0054] Lenses fabricated using optical metasurface technology are typically called superlenses. Early superlenses were generally focused on achieving a single function, which was not conducive to the future development of optics. Due to their miniaturization, low profile, and nanometer-scale size, recent research has adopted the combination of multiple superlenses to achieve multifunctional requirements, such as large field-of-view imaging, wide-band achromatic imaging, AR displays, zoom imaging, and so on.

[0055] In traditional optics, achromatic light is eliminated by combining multiple lenses into a lens group. This limits the miniaturization and integration of devices, posing a significant challenge, especially for applications such as portable and wearable devices. Superlenses, however, can easily solve this problem. Achromatic superlens design typically utilizes the resonance effect of materials with different refractive indices to modulate the phase at different spatial locations. However, when additional functions are required, current technologies can only achieve this by integrating multiple superlenses, which is detrimental to the miniaturization and integration of superlenses.

[0056] To address the aforementioned issues, the applicant has developed a design method for a multifunctional achromatic superlens. This design scheme can create a superlens that simultaneously possesses magnification and achromatic functions based on scenario requirements, thereby meeting the lens needs of small imaging devices.

[0057] Specifically, please refer to Figure 1 , Figure 1 This is a flowchart illustrating one embodiment of the design method for the multifunctional achromatic superlens of this application. The design method includes:

[0058] S100, set the target operating wavelength and target magnification.

[0059] First, it is necessary to have a target specification for the designed superlens, namely, to set the target operating wavelength and the magnification of the entire superlens system.

[0060] S200. Determine the substrate material based on the target operating wavelength.

[0061] Once the target operating wavelength is determined, the substrate material can be determined. The selection of this material should follow the principle of matching the operating wavelength, and it should have high transmittance when operating at the target wavelength.

[0062] In one application scenario, when the target operating wavelength is in the visible light band, gallium nitride self-supporting sheets can be selected as the substrate material. Therefore, semiconductor processing technology can be well applied when fabricating superlenses, avoiding the steps required in traditional superlens fabrication to fabricate metal or dielectric materials on the surface of the substrate, further simplifying the fabrication complexity.

[0063] S300. Based on the target magnification, determine the lens diameter and target focal length of the first and second metasurfaces of the substrate.

[0064] Once the target magnification is determined, the focal length relationship between the first and second metasurfaces of the substrate can be determined, thereby determining the lens diameter and the target focal length.

[0065] Specifically, please refer to Figure 2 , Figure 2 yes Figure 1 A flowchart of one embodiment corresponding to step S300.

[0066] In one embodiment, the method for determining the lens diameter and target focal length of the first metasurface and the second metasurface of the substrate includes:

[0067] S301. Based on the target magnification, obtain the target focal length ratio of the first metasurface and the second metasurface.

[0068] Understandably, in order to achieve the magnification function of the superlens, the target focal lengths of the first and second metasurfaces should be different, and the ratio of the target focal lengths of the first and second metasurfaces is the magnification.

[0069] S302. Based on the target focal length ratio, determine the lens diameter and target focal length of the first metasurface and the second metasurface.

[0070] Since the first metasurface and the second metasurface are located on opposite sides of the substrate, it is required that the NA numerical aperture of the lenses of the first metasurface and the second metasurface be consistent, that is, to keep the ratio of focal length to lens diameter the same.

[0071] After obtaining the target focal length ratio of the first metasurface and the second metasurface, the ratio of the lens diameter of the first metasurface and the second metasurface can be obtained. The lens diameter and target focal length of the first metasurface and the second metasurface can be set according to the application scenario to ensure that the magnification function is achieved.

[0072] S400: Based on the target operating wavelength and target focal length, determine the target phase information of the first metasurface and the second metasurface of the substrate.

[0073] After setting the target focal lengths of the first and second metasurfaces respectively, the target phase of the subwavelength structure at different positions of the metasurface can be calculated based on the target focal length and target operating wavelength of each metasurface, thus determining the target phase information.

[0074] Specifically, in one application scenario, the target phase information can be determined based on the phase modulation function, the expression of which is:

[0075]

[0076] In the formula, Let f be the target phase, f be the target focal length, and λ be the target operating wavelength.

[0077] By substituting the target operating wavelength and target focal length of the first and second metasurfaces into the above formula, the target phase of the subwavelength structure at different (x, y) coordinate positions of the first and second metasurfaces can be calculated.

[0078] S500: Based on the target phase information, superlenses are constructed on the first and second metasurfaces respectively to obtain a multifunctional achromatic superlens model.

[0079] Specifically, please refer to Figure 3 , Figure 3 yes Figure 1 A flowchart of one embodiment corresponding to step S500.

[0080] Methods for obtaining multifunctional achromatic superlens models include:

[0081] S501. Based on the target phase information, obtain the target rotation information.

[0082] Once the target phase information is obtained, the rotation angle of the subwavelength structure at different positions can be calculated based on the PB-phase modulation principle, thereby obtaining the target rotation information.

[0083] The PB-phase modulation principle is based on the simple linear relationship between changing the rotation angle of a superlens and the phase abrupt change it provides, when the subwavelength structure geometry of the superlens is fixed and the incident light is circularly polarized. In the formula, Let θ be the target phase and θ be the rotation angle.

[0084] S502. Based on the target rotation information, construct a superlens on the first metasurface and the second metasurface respectively.

[0085] Based on the target rotation information, it is possible to design the rotation of subwavelength structures at different positions by corresponding angles, thereby completing the construction.

[0086] Specifically, please refer to Figure 4 , Figure 4 yes Figure 3 A flowchart of one embodiment corresponding to step S502.

[0087] Methods for constructing superlenses include:

[0088] S5021. Determine the subwavelength structural arrangement of the first metasurface and the second metasurface.

[0089] In one application scenario, a subwavelength structure arrangement with alternating row spacing can be selected, such as... Figure 5 As shown, Figure 5 This is a schematic diagram of the subwavelength structure arrangement of one embodiment of the multifunctional achromatic superlens of this application. The subwavelength structure can be divided into three types, corresponding to red, green and blue respectively. Each type of subwavelength structure is arranged in a row, and the three types of subwavelength structures are arranged alternately to ensure that light of different wavelengths can be focused at a point after passing through the superlens to achieve the achromatic function.

[0090] In other application scenarios, subwavelength structures can also be arranged in other ways, such as in a ring arrangement.

[0091] S5022. Determine the size and period of the subwavelength structure.

[0092] After determining the arrangement of the subwavelength structures, the size and period of the subwavelength structures can be set.

[0093] To facilitate processing, a cuboid subwavelength structure can be selected, and the height and period of all subwavelength structures can be set to be the same. Then, a parametric scanning method can be used to determine the optimal length and width dimensions of the subwavelength structure.

[0094] In other application scenarios, the subwavelength structure can also be of other shapes, and its size can be set by preset or other means, all of which can achieve the effect of this embodiment.

[0095] S5023. Based on the target rotation information, subwavelength structures are rotated at different positions on the first metasurface and the second metasurface, respectively.

[0096] After determining the arrangement and size of the subwavelength structures, the subwavelength structures at different positions can be rotated based on the target rotation information to complete the construction of the superlens.

[0097] Specifically, before rotating the subwavelength structure, all subwavelength structures can be set in parallel along the same direction, so that after performing corresponding rotation operations on the subwavelength structures at different positions, the target phase can be obtained to achieve the achromatic function.

[0098] This application also provides a multifunctional achromatic superlens designed using the above-described design method. Please refer to [link / reference]. Figure 6 and Figure 7 , Figure 6 This is a schematic diagram of one embodiment of the multifunctional achromatic superlens of this application; Figure 7 This is a schematic diagram of the working state of one embodiment of the multifunctional achromatic superlens of this application.

[0099] This multifunctional achromatic superlens can achieve both achromatic aberration and magnification at the target magnification, such as... Figure 6 As shown, the focal length f1 of the superlens MF1 on one side is greater than the focal length f2 of the superlens MF2 on the other side, and the magnification is f1 / f2.

[0100] Meanwhile, the NA numerical aperture of the superlenses on both sides is the same, and the superlenses on both sides can ensure that light of different wavelengths can be focused at a point after passing through the superlenses, thus achieving the achromatic function.

[0101] The multifunctional achromatic superlens of this embodiment is ultra-thin, ultra-compact, achromatic, and magnifying. When applied to the lens of a small imaging device, it can achieve color imaging and magnification within the constraints of limited lens size.

[0102] This application also provides a method for fabricating a multifunctional achromatic superlens according to the above-described embodiment. When the multifunctional achromatic superlens uses a gallium nitride support sheet as the substrate material, the superlens can be constructed on both sides of the substrate by means of a semiconductor support.

[0103] To ensure that there are no errors in the alignment of the double-sided manufactured superlens, a first mark can be set on the first metasurface of the substrate and a second mark can be set on the second metasurface. The etching operation is then performed with the first mark and the second mark as references.

[0104] Specifically, the preparation process can be as follows: Figure 8 As shown, Figure 8 This is a schematic flowchart of one embodiment of the fabrication method of the multifunctional achromatic superlens of this application. The fabrication process includes:

[0105] Using the first mark as a reference, electron beam exposure resist is sequentially spin-coated on the first metasurface of the substrate, a metal mask layer is fabricated, electron beam exposure is performed, development is carried out, and etching is performed to obtain the first superlens; the substrate is rotated, and using the second mark as a reference, electron beam exposure resist is sequentially spin-coated on the second metasurface of the substrate, a metal mask layer is fabricated, electron beam exposure is performed, development is carried out, and etching is performed to obtain the second superlens.

[0106] By directly constructing superlenses on the substrate surface using photolithography, the traditional superlens process of fabricating metal or dielectric materials on the substrate surface is effectively avoided, simplifying the fabrication complexity.

[0107] The foregoing description of this disclosure is provided to enable any person skilled in the art to implement or use this disclosure. Various modifications to this disclosure will be apparent to those skilled in the art, and the general principles applicable herein can be applied to other variations without departing from the scope of this disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but is consistent with the widest scope of the principles and novel features disclosed herein.

Claims

1. A design method of a multifunctional achromatic superlens, characterized by, The method comprises the following steps: setting a target working wavelength and a target magnification; determining a material of a substrate based on the target working wavelength; determining lens diameters and target focal lengths of first and second super surfaces of the substrate based on the target magnification; determining target phase information of the first and second super surfaces of the substrate based on the target working wavelength and the target focal length, the target phase information comprising target phases of subwavelength structures at different positions; constructing super lenses on the first and second super surfaces respectively based on the target phase information to obtain a multifunctional achromatic super lens model; wherein the step of determining the lens diameters and the target focal lengths of the first and second super surfaces of the substrate based on the target magnification comprises: obtaining a target focal length ratio of the first and second super surfaces based on the target magnification; determining the lens diameters and the target focal lengths of the first and second super surfaces based on the target focal length ratio, the ratio of the target focal length to the lens diameter of the first super surface being the same as the ratio of the target focal length to the lens diameter of the second super surface.

2. The design method of claim 1, wherein The target working wavelength is in a visible light wavelength band, and the material of the substrate is gallium nitride.

3. The method of claim 1, wherein, The step of determining the target phase information of the first and second super surfaces of the substrate based on the target working wavelength and the target focal length comprises: calculating the target phases of the subwavelength structures at different positions based on a phase modulation function, the phase modulation function having an expression as follows: ； wherein φ is the target phase, f is the target focal length, and λ is the target working wavelength.

4. The method of claim 1, wherein The step of constructing the super lenses on the first and second super surfaces respectively based on the target phase information to obtain the multifunctional achromatic super lens model comprises: obtaining target rotation information comprising rotation angles of the subwavelength structures at different positions based on the target phase information; constructing the super lenses on the first and second super surfaces respectively based on the target rotation information.

5. The method of designing according to claim 4, wherein, The step of obtaining the target rotation information based on the target phase information comprises: calculating the rotation angles of the subwavelength structures at different positions based on a PB control function, the PB control function having an expression as follows: ； In the formula, φ is a target phase, is a rotation angle.

6. The method of designing according to claim 4, wherein, The step of constructing the super lenses on the first and second super surfaces respectively based on the target rotation information comprises: determining arrangement modes of the subwavelength structures of the first and second super surfaces; determining sizes and periods of the subwavelength structures; rotating the subwavelength structures at different positions on the first and second super surfaces respectively based on the target rotation information.

7. The method of designing according to claim 6, wherein, The step of determining the sizes and periods of the subwavelength structures comprises: setting the height and the period of the subwavelength structures to be consistent, and determining the length and the width of the subwavelength structures by parameterized scanning.

8. A multifunctional achromatic superlens, characterized by, The multifunctional achromatic super lens is designed by the design method of any one of claims 1 to 7.

9. A method of manufacturing the multifunctional achromatic superlens according to claim 8, characterized by, The method comprises the following steps: setting a first mark on a first super surface of a substrate and setting a second mark on a second super surface of the substrate; coating glue, exposing, developing and etching on the first super surface of the substrate in sequence based on the first mark to obtain a first super lens; The substrate is rotated, and the second superlens is obtained by gluing, exposing, developing and etching the second super surface of the substrate in turn with the second mark as the reference.

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