PEDOT: PSS-based large-numerical-aperture electronic control zoom super-structure lens and design method

Abstract

The invention relates to the technical field of nano optics, and discloses a PEDOT: PSS-based large-numerical-aperture electric control zoom super-structure lens and a design method thereof, and the super-structure lens comprises a substrate, an electrode layer, a PEDOT: PSS polymer layer, a super-structure lens array layer, an electrolyte solution, ITO glass and a voltage regulation part. The PEDOT: PSS polymer layer is composed of fixed negative PSS-charges, the voltage adjusting part applies negative voltage to the PEDOT: PSS polymer layer to generate a first driving force, in order to compensate the fixed PSS-charges, large-size positive ions in the electrolyte solution are embedded into the PEDOT: PSS polymer layer under the action of the first driving force, so that the PEDOT: PSS polymer layer swells, and the thickness is increased. And the voltage adjusting part applies positive voltage to the PEDOT: PSS polymer layer to generate a second driving force, the PEDOT: PSS is doped by holes again, and large-size positive electrons in the PEDOT: PSS polymer layer are repelled by the second driving force, so that the PEDOT: PSS polymer layer is shrunk and the thickness of the PEDOT: PSS polymer layer is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nano-optics, in particular to a large numerical aperture electrically controlled zooming superlens based on PEDOT:PSS and a design method. BACKGROUND

[0002] Zooming function and high resolution imaging are the core performance indicators of modern optical lenses, and both of them are indispensable in biomedical observation, machine vision recognition and fine detection. As a kind of subwavelength artificial structural material, super surface can realize flexible regulation and control of light field in multiple dimensions such as wavefront phase, amplitude and polarization by accurately designing the geometric parameters of its nano-structure unit, which provides a new technical path for the miniaturization, integration and function reconstruction of optical lenses.

[0003] However, the existing superlenses mostly adopt static structure design, and their optical characteristics are fixed after preparation, so they cannot realize dynamic adjustment of focal length. Although preliminary progress has been made in reconfigurable schemes based on phase change materials and liquid crystal regulation, there are still some bottleneck problems in the visible light band, such as insufficient modulation depth and limited numerical aperture (NA), which restrict the realization of high-resolution dynamic imaging. SUMMARY

[0004] In view of the above technical bottlenecks, the present application proposes a superlens solution based on electrochemical regulation mechanism. By integrating the super surface structure with the poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonic acid) (PEDOT:PSS) functional layer with electrochromic deformation characteristics, a composite optical system immersed in an electrolyte solution is constructed. This scheme uses the ion intercalation / deintercalation effect induced by electrochemistry to accurately regulate the thickness change of the PEDOT:PSS polymer layer, and then realizes the dynamic reconfiguration of the focal length.

[0005] To achieve the above purpose, the large numerical aperture electrically controlled zooming superlens based on PEDOT:PSS designed by the present application comprises: a substrate, an electrode layer, a PEDOT:PSS polymer layer, a superlens array layer, an electrolyte solution, an ITO glass and a voltage adjustment part. One side of the substrate is provided with the electrode layer, the other side of the electrode layer is provided with the PEDOT:PSS polymer layer, the other side of the PEDOT:PSS polymer layer is provided with the superlens array layer, the superlens array layer is immersed in the electrolyte solution, the electrolyte solution is arranged in the interlayer between the PEDOT:PSS polymer layer and the ITO glass, and the output end of the voltage adjustment part is electrically connected with the PEDOT:PSS polymer layer.

[0006] The PEDOT:PSS polymer layer is composed of fixed negative PSS -Charge composition, the voltage adjusting part applies a negative voltage to the PEDOT:PSS polymer layer, which will generate a first driving force to compensate for the fixed PSS - Charge, large-size positive ions in the electrolyte solution are embedded in the PEDOT:PSS polymer layer under the action of the first driving force, causing the PEDOT:PSS polymer layer to swell and increase in thickness.

[0007] The voltage adjusting part applies a positive voltage to the PEDOT:PSS polymer layer, which will generate a second driving force, and the PEDOT:PSS is again hole-doped, and the large-size positive electrons in the PEDOT:PSS polymer layer are driven away by the second driving force, causing the PEDOT:PSS polymer layer to shrink and decrease in thickness.

[0008] Preferably, the superlens array layer is composed of a plurality of nanostructures, and the shapes of the nanostructures include five shapes: cuboid, cylinder, circular ring, rectangular ring, and cross.

[0009] Preferably, the electrolyte solution is tetrabutylammonium hexafluorophosphate solution with a concentration of 0.1 mol / L in acetonitrile solution, the electrolyte solution is transparent in the working waveband, and the refractive index of the electrolyte solution is 1.339±0.005.

[0010] Preferably, the relationship between the electrolyte solution and the object numerical aperture is: Where NA is the object numerical aperture, n is the refractive index of the object medium, and θ is half of the aperture angle of the optical system. The imaging resolution of the optical system is: Where λ represents the working wavelength.

[0011] When the numerical aperture increases, the minimum resolution distance decreases, and the superlens can distinguish finer structures, i.e., higher resolution. The electrolyte solution simultaneously meets the requirements of electrochemical regulation and optical gain, serving as an ion conduction medium for electrically controlled zooming and improving NA through refractive index, avoiding the complex design of additional optical medium.

[0012] Preferably, the material of the substrate is silicon dioxide.

[0013] Preferably, the materials of the electrode layer and the superlens array layer are both titanium dioxide, the thickness of the electrode layer is 200 nm, the height H of the nanostructure in the superlens array layer is 700 nm, and when titanium dioxide is used as the material of the superlens nano-unit, 0-2π full-phase coverage can be achieved through subwavelength size design (such as height 700 nm, period 360 nm), meeting the phase regulation requirements of high-resolution imaging.

[0014] A design method of a large numerical aperture electrically controlled zoom superlens based on PEDOT:PSS, the steps are as follows: S1, calculate the phase / amplitude regulation amount of different structure / size nanostructures under different PEDOT:PSS thicknesses through electromagnetic simulation software, calculate the corresponding phase and amplitude values of each combination through simulation, establish a one-to-one mapping relationship between structure parameters and electromagnetic response, and form an electromagnetic response library; S2, determine the working wavelength of the superlens, the maximum radius of the superlens, the focal length f1 and the focal length f2 in the zoom range of the superlens; S3, bring each focal length into the following formula to obtain the theoretical phase distribution of the superlens zoom: Wherein: represents the theoretical phase distribution of the superlens zoom to each focal length in the focal length set; x and y are the distance coordinates between any point on the surface of the superlens and the center, and the value range of x and y is (0, R); n is the refractive index of acetonitrile; R represents the maximum radius of the superlens; is the focal length of the superlens; c is a constant; It shifts the entire phase while keeping the phase distribution gradient (i.e. focusing ability) unchanged, so that the target phase distribution can better match the discrete phase values that can be actually realized in the electromagnetic response database, thereby effectively compensating for the mismatch between ideal design and physical implementation, and ultimately improving the focusing efficiency.

[0015] S4, adopt particle swarm algorithm, constantly optimize c for different focal lengths (f1, f2), and select unit structure morphology, size and PEDOT:PSS layer thickness from the electromagnetic response library to generate corresponding obtained phase, and the matching degree of ideal phase and obtained phase is represented by ϕ, the smaller the ϕ, the closer the obtained phase to the ideal phase: Wherein, represents the difference between the theoretical phase and the obtained phase of all nanostructures of the superlens at focal length 1; represents the theoretical phase at x, y; represents the obtained phase at x, y; Wherein, represents the difference between the theoretical phase and the obtained phase of all nanostructures of the superlens at focal length 2; denotes the theoretical phase at x, y; denotes the obtained phase at x, y; S5, selecting the nanostructure that satisfies the phase gradient at the focal length f1 and the focal length f2 in the solution space to obtain a phase distribution; with the increase of the number of iterations, the F is continuously optimized to be the minimum, and the best phase distribution matrix and the corresponding PEDOT:PSS layer thickness are obtained: wherein, aims to minimize the total phase deviation at two focal lengths, and ensure the overall imaging performance.

[0016] Preferably, the electromagnetic simulation software in the S1 step is Comsol Multiphysics.

[0017] Preferably, the phase / amplitude regulation amount of the nanostructure of different structures / sizes under different PEDOT:PSS thicknesses in the S1 step needs to traverse the combination of 5 kinds of nano-unit geometric shapes x 17 kinds of PEDOT:PSS thicknesses.

[0018] Preferably, the PEDOT:PSS thickness is in the range of 160nm-320nm. The initial thickness of PEDOT:PSS is 160nm, and can be reversibly changed between 160nm and 320nm under the regulation of an electric field.

[0019] Compared with the prior art, the present application has the following advantages: 1. The present application adopts PEDOT:PSS polymer as the electro-deformation layer, and realizes millisecond-level response through the ion intercalation / deintercalation mechanism under the driving of low voltage ±3V. Compared with the traditional liquid crystal lens (>20V driving voltage) or the MEMS lens (>50V driving voltage), the working voltage is reduced by more than 90%. The present application adopts a global common electrode architecture, and all superstructure units share the same working electrode and counter electrode, which omits the addressing electrode independently configured for each unit in the traditional scheme. This design improves the transmittance of the device (visible light band), reduces the process steps, and avoids the structural mismatch problem caused by microelectrode processing.

[0020] 2. By completely immersing the superstructure lens array in a specific ratio of electrolyte environment (0.1mol / L TBAPF6 acetonitrile solution, refractive index n=1.339), the high refractive index medium is creatively used to replace the traditional air environment (n=1.0). Under the same phase gradient condition, the numerical aperture of the object side is improved. This innovative design makes the system resolution reach 455nm (λ=589nm), which meets the observation requirements of biological organelles.

[0021] 3、This technical solution successfully solves the contradiction between "zooming ability", "imaging resolution" and "system power consumption" of dynamic superlens by low-voltage driving and the synergistic effect of high refractive index medium environment (n=1.339). This brings significant advantages: 1) No need to configure separate addressing electrodes, not only reduces material cost, but also improves the process yield and overall manufacturing efficiency of electron beam lithography; 2) This efficient zoom design realizes global high-definition imaging in the cavity of medical endoscopes and other instruments, greatly expanding its clinical application boundaries. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The schematic diagram of the large numerical aperture electrically controlled zooming superlens based on PEDOT:PSS and the design method of the application; Figure 2 Five structural forms of nanostructures in the application; Figure 3 The optical zooming schematic diagram of the application, the superlens will be focused at F1 and F2 respectively by PEDOT:PSS swelling or deintercalation, realizing the zooming of lens focal length from f1 to f2; Figure 4 The electromagnetic response library obtained by simulation of the application; Figure 5 The light intensity distribution diagram of the two focal lengths calculated based on Kirchhoff diffraction in the application. DETAILED DESCRIPTION

[0023] The technical solutions of the application will be described clearly and completely in combination with the drawings and examples. Obviously, the described examples are part of the examples of the application, not all examples. Based on the examples in the application, all other examples obtained by those skilled in the art without creative labor belong to the scope of the application.

[0024] As shown in Figures 1 to 5 A large numerical aperture electrically controlled zooming superlens based on PEDOT:PSS, the nanostructure of the super surface is silica as the substrate, titanium dioxide high H1=200nm as the electrode layer; immersed in the electrolyte solution, the periodic nanoarray structure optimized by particle swarm algorithm, and the PEDOT:PSS polymer layer constitute the superlens. By applying an external excitation voltage, ions undergo reversible processes of embedding or detaching from PEDOT:PSS, changing the thickness H2 of the PEDOT:PSS polymer layer, and then changing the phase of the superlens. Its structure is shown in Figure 1 .

[0025] 1、Based on electromagnetic simulation software to establish electromagnetic response library As shown in Figure 2As shown, the length, width and height of the nano brick unit structure are all sub-wavelength scale. After determining the working wavelength λ = 589 nm, the phase and amplitude modulation of the nano structure are calculated by means of electromagnetic simulation software, and a phase and amplitude database is established. Among them, the shape of the nano structure includes cuboid, cylinder, circular ring, cross and rectangular ring. The height H of the nano structure is 700 nm, and the period interval of the nano structure is 360 nm, and the optimized size parameters are as follows: (1) For circular ring, including outer diameter D, inner diameter D2, as shown in Figure 2 a; (2) For cross, including length L1 and width W1, length L2, width W2, as shown in Figure 2 b; (3) For cylinder, as shown in Figure 2 c; (4) For rectangular ring, including length L1, width L2, length W1, width W2, as shown in Figure 2 d; (5) For cuboid, including length L, width W, as shown in Figure 2 e; At the same time, by changing the thickness of the PEDOT:PSS polymer layer from 160-320 nm, nano structures of different sizes and shapes are obtained, and the amplitude and phase modulation under different voltages are obtained, and an electromagnetic response library of unit structure is established. (It contains 2344 groups of structure phase modulation under 17 PEDOT:PSS thicknesses, 39848 groups of data) as shown in Figure 4 .

[0026] 2, Determine the focal length of super lens Based on the Fresnel diffraction theory, the maximum radius of the super lens, the focal length f1 = 30 μm and the focal length f2 = 40 μm in the zoom range of the super lens are determined as shown in Figure 3 ; Taking 200 steps as an example, the maximum radius of the super lens is 36 μm. The theoretical phase distribution of the super lens zoom is obtained by bringing each focal length into the following formula, and the related parameters satisfy: 3, Phase distribution design By constantly iterating, the F converges to 39.49 by using simulated annealing algorithm and particle swarm optimization algorithm, so that the error of each nano unit structure is reduced to 0.62, which indicates that the designed phase is highly consistent with the theoretical target. Thus, the best array structure arrangement mode is obtained, and the relationship between the thickness of PEDOT:PSS and the corresponding designed focal length is obtained. Under f1 = 30 μm, the thickness of PEDOT:PSS layer is 190 nm, and under f2 = 40 μm, the thickness of PEDOT:PSS layer is 310 nm, and the optical response and dynamic focusing process is simulated.

[0027] 4. Periodic array Based on the Kirchhoff diffraction theory, the obtained super surface array is simulated for light field propagation: first, the parameter initialization is performed, and the two-dimensional grid of the incident surface and the three-dimensional grid of the detection surface are constructed respectively. The core calculation adopts the Kirchhoff diffraction integral method, and the light field complex amplitude is calculated point by point. This process fully considers the contribution of all points on the incident surface to the detection point, and accurately captures the physical process of light field propagation. The focal length 1 is 30 μm, and the numerical aperture is 0.7882. The focal length is 40 μm, and the numerical aperture is 0.6690. Finally, the light intensity distribution is obtained as shown in Figure 4 The figure clearly shows the light intensity distribution characteristics in the XY plane. When the PEDOT:PSS layer thickness is 190 nm, the lens focuses at 30 μm; when the thickness changes to 310 nm, the focal point moves to 40 μm. This result fully verifies the feasibility and excellent performance of the electrically controlled zooming of the super lens described in the application under the condition of large numerical aperture.

[0028] It should be noted that the above technical solutions are exemplary, and the present specification can be embodied in different forms, and should not be interpreted as being limited to the technical solutions described herein. On the contrary, providing these descriptions will make the present disclosure thorough and complete, and will fully convey the scope disclosed by the present specification to those skilled in the art. In addition, the technical solutions of the present application are limited only by the scope of the claims.

[0029] The aspects disclosed for describing the present specification and claims are only examples, and therefore, the present specification and claims are not limited to the details shown. In the above description, when the detailed description of the related known functions or configurations is determined to be unnecessary to obscure the focus of the present specification and claims, the detailed description will be omitted.

[0030] Finally, it should be noted that the above content is a further detailed description of the application in combination with the specific embodiments, and the specific embodiments of the application cannot be considered as being limited to these descriptions. For those skilled in the art, simple substitutions can be made without departing from the concept of the present application, and all such substitutions should be considered as falling within the protection scope of the present application. The above examples are only more representative examples of the present application. Obviously, the present application is not limited to the above examples, and there are many variations. Any simple modification, equivalent change and modification made according to the technical essence of the present application to the above examples should be considered as falling within the protection scope of the present application.

Claims

1. A large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS, characterized in that, include: Substrate, electrode layer, PEDOT:PSS polymer layer, metalens array layer, electrolyte solution, ITO glass, and voltage regulation unit; The electrode layer is disposed on one side of the substrate, and the PEDOT:PSS polymer layer is disposed on the other side of the electrode layer. The other side of the PEDOT:PSS polymer layer is connected to the meta-lens array layer. The meta-lens array layer is immersed in the electrolyte solution. The electrolyte solution is disposed in the interlayer between the PEDOT:PSS polymer layer and the ITO glass. The output terminal of the voltage regulation unit is electrically connected to the PEDOT:PSS polymer layer. The PEDOT:PSS polymer layer consists of a fixed negative PSS. - The charge composition, wherein the voltage regulation unit applies a negative voltage to the PEDOT:PSS polymer layer, will generate a first driving force to compensate for the fixed PSS. - The large positive ions in the electrolyte solution are embedded in the PEDOT:PSS polymer layer under the action of the first driving force, causing the PEDOT:PSS polymer layer to swell and increase in thickness. The voltage regulation unit applies a positive voltage to the PEDOT:PSS polymer layer, which generates a second driving force. PEDOT is doped with holes again, and the large-sized positrons in the PEDOT:PSS polymer layer are driven away by the second driving force, causing the PEDOT:PSS polymer layer to shrink and its thickness to decrease.

2. The large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 1, characterized in that, The meta-lens array layer is composed of several nanostructures, and the shapes of the nanostructures include five types: cuboid, cylinder, toroidal, rectangular toroidal, and cross.

3. The large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 1, characterized in that, The electrolyte solution is 0.1 mol / L tetrabutylammonium hexafluorophosphate dissolved in acetonitrile solution. The electrolyte solution is transparent in the working wavelength range and has a refractive index of 1.339 ± 0.

005.

4. The large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 3, characterized in that, The electrolyte solution possesses a stable electrochemical window and a refractive index n=1.339; when used as the object-side medium of a metalens, it can effectively increase the numerical aperture of the zoom metalens. The specific numerical relationship is as follows: Where NA is the object-side numerical aperture, n is the refractive index of the object-side medium, and θ is half of the aperture angle of the optical system; The imaging resolution of the optical system is: Where λ represents the operating wavelength.

5. The large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 1, characterized in that, The substrate is made of silicon dioxide.

6. The large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 1, characterized in that, Both the electrode layer and the meta-lens array layer are made of titanium dioxide.

7. A design method for a large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS, characterized in that, The steps are as follows: S1. Calculate the phase / amplitude modulation of nanostructures of different structures / sizes under different PEDOT:PSS thicknesses using electromagnetic simulation software. Calculate the phase and amplitude values ​​corresponding to each combination through simulation, establish a one-to-one mapping relationship between structural parameters and electromagnetic response, and form an electromagnetic response library. S2. Determine the working wavelength of the superlens, the maximum radius of the superlens, and the focal lengths f1 and f2 within the zoom range of the superlens; S3. For each target focal length fᵢ (i=1,2) determined in step S2, calculate its theoretical phase distribution: in: This represents the theoretical phase distribution when the superlens is zoomed to each focal length in this set of focal lengths; x and y are the distance coordinates between any point on the surface of the metalens and the center, respectively, and the range of x and y is (0, R). R represents the maximum radius of the superlens; n is the refractive index of acetonitrile; Let be the focal length of the superlens; c is a constant; S4. Using the particle swarm optimization algorithm, c is continuously optimized for different focal lengths (f1, f2). The unit structure morphology, size, and PEDOT:PSS layer thickness are selected from the electromagnetic response library to generate the corresponding obtained phase. ϕ represents the degree of matching between the ideal phase and the obtained phase. The smaller ϕ is, the closer the obtained phase is to the ideal phase. in, This represents the difference between the theoretical phase and the obtained phase of all nanostructures in the superlens at a focal length of 1. This represents the theoretical phase at x and y. This indicates the phase acquired at x and y. in, This represents the difference between the theoretical phase and the obtained phase of all nanostructures in the superlens at a focal length of 2; This represents the theoretical phase at x and y. This indicates the phase acquired at x and y. S5. Select nanostructures that satisfy the phase gradient at both focal lengths f1 and f2 in the solution space to obtain the phase arrangement; as the number of iterations increases, continuously optimize F to minimize it, thereby obtaining the optimal phase distribution matrix and the corresponding PEDOT:PSS layer thickness. in, The aim is to minimize the total phase deviation at both focal lengths to ensure overall imaging performance.

8. The design method for a large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 7, characterized in that, The electromagnetic simulation software used in step S1 is Comsol Multiphysics.

9. The design method for a large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 7, characterized in that, In step S1, calculating the phase / amplitude modulation of nanostructures of different structures / sizes under different PEDOT:PSS thicknesses requires traversing 5 combinations of nanounit geometries × 17 combinations of PEDOT:PSS thicknesses.

10. The design method of a large numerical aperture electrically controlled zoom meta-lens based on PEDOT:PSS according to claim 9, characterized in that, PEDOT: PSS thickness ranges from 160nm to 320nm.

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