Terahertz vortex generator based on conductive film spiral slit on flexible substrate

Abstract

The invention discloses a terahertz vortex generator based on a conductive film spiral slit on a flexible substrate, and belongs to the technical field of terahertz, the terahertz vortex generator comprises a flexible substrate, and one end face of the flexible substrate is coated with a layer of conductive film; the conductive film is provided with a first slit group and a second slit group. The first slit group and the second slit group are spirally arranged by taking the axis of the conductive film as the center, and the spiral directions of the first slit group and the second slit group are the same; wherein the first slit group comprises N first slits; the second slit group comprises N second slits; and the N first slits and the N second slit groups are respectively and sequentially arranged at intervals along two spiral directions. According to the terahertz vortex generator based on the conductive film spiral slit on the flexible substrate, the substrate is the stretchable flexible substrate, the flexible substrate is integrally stretched through the stretching clamp, equal-proportion expansion of the substrate is achieved, the width and radius of the slit are accurately adjusted and controlled, and effective control over emergent vortex waves is achieved.

Description

Technical Field

[0001] The invention belongs to the field of terahertz technology, and in particular relates to a terahertz vortex generator based on spiral slits of a conductive film on a flexible substrate. Background Art

[0002] Terahertz band (0.1-10THz, 1THz=10 12 Hz) is located between microwave and infrared spectrum, and has a wide range of application prospects due to its unique penetration ability and low energy characteristics. Compared with millimeter waves, terahertz waves have more concentrated beams and higher frequencies, so they have the characteristics of stable and confidential high-speed transmission. These characteristics make terahertz waves show great potential in security detection, biomedicine, communication technology and other fields. Terahertz waves can penetrate non-conductive materials without causing damage, which makes them particularly useful in the field of security detection. For example, terahertz waves can be used to detect prohibited items hidden in clothing or other non-metallic objects without causing harm to the human body or the detected objects; in the field of biomedicine, terahertz waves can be imaged through the skin, providing high-resolution tissue structure images, which helps to diagnose diseases at an early stage. In addition, in the field of communication technology, the high-frequency characteristics of terahertz waves enable high-speed data transmission to meet the bandwidth and speed requirements of future wireless communications. In particular, terahertz waves can carry orbital angular momentum, also known as vortex beams. At present, vortex beams have been applied to fields such as high-capacity communications, super-resolution imaging and imaging of rotating objects. Therefore, how to effectively generate terahertz vortex electromagnetic wave beams is one of the key technologies in the related field.

[0003] At present, the main methods for generating vortex beams include reflective and transmissive spiral phase plates, array antennas, metasurfaces, etc. Among them, the spiral phase plate is relatively thick, which is not conducive to integration and miniaturization. Although the theory of array antennas is very mature, it requires a complex feeding network, which is difficult to achieve in the terahertz band. Metasurface is a two-dimensional artificial structure composed of sub-wavelength unit structures, which has the advantages of thin thickness, light weight, and flexible control of electromagnetic waves. Metasurfaces can be divided into reflective and transmissive types. Compared with transmissive metasurfaces, reflective metasurfaces have simpler structures. However, metasurface structures are generally complex, and low-cost PCB and CNC processing technologies cannot be used in terahertz. It is necessary to use lithography technology with higher processing accuracy and higher costs. Moreover, after the metasurface is processed, the structure cannot be changed, and only a fixed vortex beam can be generated. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a terahertz vortex generator based on a spiral slit of a conductive film on a flexible substrate and a winding method, and adopts the following technical solutions:

[0005] A terahertz vortex generator based on a spiral slit of a conductive film on a flexible substrate, comprising:

[0006] A flexible substrate, wherein one end surface of the flexible substrate is coated with a conductive film; a first slit group and a second slit group are arranged on the conductive film; the first slit group and the second slit group are respectively arranged in a spiral with the axis of the conductive film as the center, and the spiral directions of the first slit group and the second slit group are the same;

[0007] The first slit group includes N first slits; the second slit group includes N second slits; the N first slits and the N second slit groups are arranged in sequence along two spiral directions.

[0008] Furthermore, a plurality of stretching fixtures are connected to the flexible substrate; the plurality of stretching fixtures are evenly arranged along the circumference of the edge of the flexible substrate to stretch the flexible substrate and change the size of the first slit and the size of the second slit.

[0009] Furthermore, the first slit is a convex arc-shaped structure; the circumferential angle covered by the first slit on the conductive film is N / 180 degrees;

[0010] The second slit is a concave arc-shaped structure; the circumferential angle covered by the second slit on the conductive film is N / 180 degrees.

[0011] Further, the first end of the second first slit overlaps with the second end of the first first slit, and so on, until the second end of the Nth first slit overlaps with the first end of the N-1th first slit; the first end of the second second slit overlaps with the second end of the first second slit, and so on, until the second end of the Nth second slit overlaps with the first end of the N-1th second slit.

[0012] Further, the first slits located at the first end of the first slit group are arranged at a certain distance from the first edge of the conductive film; the lengths of the plurality of first slits gradually increase from the first end of the first slit group to the second end of the first slit group;

[0013] The second slits located at the second end of the second slit group are arranged at a certain distance from the second edge of the conductive film and are arranged between the first end of the first slit group and the second end of the first slit group; the lengths of the plurality of second slits gradually increase from the first end of the second slit group to the second end of the second slit group;

[0014] The first edge of the conductive film and the second edge of the conductive film are two edges arranged opposite to each other on one end surface of the conductive film.

[0015] Further, the radius of the plurality of first slits gradually increases from the first end of the first slit group to the second end of the first slit group; the radius of the first slit is a line between an inner arc of the first slit and the center of the conductive film;

[0016] The radius of the plurality of second slits gradually increases from the first end of the first slit group to the second end of the first slit group; the radius of the second slit is a line connecting an inner arc of the second slit and the center of the conductive film.

[0017] Furthermore, the centers of the first slit and the second slit are both arranged concentrically with the center of the conductive film.

[0018] Furthermore, the radius increment of the first slit and the radius increment of the second slit are both 1-1.4 times.

[0019] Furthermore, the first slit group and the second slit group are respectively arranged at two ends of a center line of an end surface of the conductive film; the first slit group and the second slit group are centrally symmetrical about the center of the conductive film.

[0020] Beneficial effects:

[0021] (1) The present invention provides a terahertz vortex generator based on spiral slits of a conductive film on a flexible substrate, in which a conductive film is connected to the flexible substrate, and a first slit group and a second slit group with a spiral structure are designed on the conductive film to generate terahertz vortex waves in cooperation with terahertz waves. The structure is simple, easy to design, and convenient for experimental operation and preparation.

[0022] (2) The present invention provides a terahertz vortex generator based on a spiral slit of a conductive film on a flexible substrate, in which the substrate is a stretchable flexible substrate. A stretching device is used to expand the flexible substrate in proportion. Different stretching ratios change the width and radius of the slit, and vortex waves are emitted corresponding to different topological charge numbers.

[0023] (3) The terahertz vortex generator provided by the present invention based on the spiral slit of the conductive film on the flexible substrate can continuously generate high-order terahertz vortex waves with different topological charges.

[0024] (4) The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate provided by the present invention has a different action mechanism, can generate efficient and adjustable terahertz vortex waves, and has the advantages of light volume and low cost. It can be produced using PCB technology and CNC technology to reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The overall structure of the terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate of the present invention;

[0026] Figure 2 A top view of a first slit group and a second slit group of a terahertz vortex generator based on spiral slits of a conductive film on a flexible substrate according to the present invention;

[0027] Figure 3 It is a schematic structural diagram of the connection between the substrate and the conductive film of the terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate of the present invention;

[0028] Figure 4 It is a schematic diagram of the working structure of the terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate of the present invention;

[0029] Figure 5 A top view of a first slit group and a second slit group of a terahertz vortex generator based on spiral slits of a conductive film on a flexible substrate in Example 2;

[0030] Figure 6 It is a schematic diagram showing the change of different stretching multiples of the upper surface of the terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate of the present invention;

[0031] Figure 7 A diagram showing the change of topological charge under different stretching conditions of the terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate of the present invention;

[0032] Among them, 1. substrate; 2. conductive film; 3. first slit; 4. terahertz wave; 5. stretching fixture; 6. second slit. DETAILED DESCRIPTION

[0033] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below.

[0034] Example 1

[0035] Reference Figures 1 to 4 , a terahertz vortex generator based on a spiral slit of a conductive film on a flexible substrate, comprising:

[0036] A flexible substrate 1, wherein a conductive film 2 is coated on one end surface of the flexible substrate 1; a first slit group and a second slit group are arranged on the conductive film 2; the first slit group and the second slit group are respectively arranged in a spiral shape with the axis of the conductive film 2 as the center, and the spiral directions of the first slit group and the second slit group are the same;

[0037] The first slit group includes N first slits; the second slit group includes N second slits; the N first slits and the N second slit groups are arranged in sequence along two spiral directions; and N is a positive integer.

[0038] In this embodiment, preferably, the conductive film 2 is a conductive silver paste layer, and a conductive silver paste layer is coated on one end surface of the flexible substrate 1 to form the conductive film 2 .

[0039] Among them, the thickness of the conductive silver paste layer is 0.1mm-0.5mm.

[0040] Preferably, the thickness of the flexible substrate 1 is 5 mm-50 mm.

[0041] Through the above technical solution, the terahertz wave is injected into the conductive film from the flexible substrate, and forms a terahertz vortex wave after passing through the plurality of first slits 3 and the plurality of second slits 6 .

[0042] In this embodiment, a plurality of stretching fixtures 5 are connected to the flexible substrate 1 ; the plurality of stretching fixtures 5 are evenly arranged along the circumference of the edge of the flexible substrate 1 to stretch the flexible substrate 1 and change the size of the first slit 3 and the size of the second slit 6 .

[0043] The substrate 1 is a stretchable flexible material; the overall stretching ratio of the stretching fixture 5 to the substrate 1 is 1-1.4 times, so that the radius increment of the first slit 3 and the radius increment of the second slit 6 are both 1-1.4 times.

[0044] Preferably, the substrate 1 is made of polydimethylsiloxane (PDMS). The polydimethylsiloxane substrate 1 is flexible, and the flexible substrate 1 made of polydimethylsiloxane can be stretched by a stretching fixture 5 .

[0045] The arc slit array of the conductive film 2 is the main part for modulating the light field. The radius of the innermost arc slit in each first slit or second slit or the average radius of the arc slit varies within a certain range and has no effect on the vortex.

[0046] Through the above technical solution, when the flexible substrate 1 is stretched, the conductive film 2 is deformed along with the flexible substrate 1, so that by stretching the flexible substrate 1, the radius difference between the arc-shaped slits on the conductive film 2 is changed, and the number of topological charges is regulated; preferably, four stretching clamps 5 are arranged, and the four stretching clamps 5 move outward in four directions respectively, and are used to stretch the flexible substrate 1 to drive the change of the conductive film 2. The stretching is the same proportion stretching in the horizontal and longitudinal directions, and the intention is to amplify the device in the same proportion, so as to keep the ratio of the radius of the arc-shaped slit to the length and width of the device unchanged.

[0047] In this embodiment, the first slit is a convex arc-shaped structure; the circumferential angle covered by the first slit on the conductive film 2 is N / 180 degrees;

[0048] The second slit is a concave arc-shaped structure; the circumferential angle covered by the second slit on the conductive film 2 is N / 180 degrees.

[0049] The total angle occupied by the first slit group and the second slit group is 360 degrees.

[0050] In this embodiment, the first end of the second first slit 3 is overlapped with the second end of the first first slit 3, and so on, until the second end of the Nth first slit 3 is overlapped with the first end of the N-1th first slit 3; the first end of the second second slit 6 is overlapped with the second end of the first second slit 6, and so on, until the second end of the Nth second slit 6 is overlapped with the first end of the N-1th second slit 6.

[0051] In this embodiment, the first slit at the first end of the first slit group is arranged at a certain distance from the first edge of the conductive film 2; the lengths of the plurality of first slits gradually increase from the first end of the first slit group to the second end of the first slit group;

[0052] The second slit at the second end of the second slit group is arranged at a certain distance from the second edge of the conductive film 2 and is arranged between the first end of the first slit group and the second end of the first slit group; the lengths of the plurality of second slits gradually increase from the first end of the second slit group to the second end of the second slit group;

[0053] The first edge of the conductive film 2 and the second edge of the conductive film 2 are two edges on one end surface of the conductive film 2 that are arranged opposite to each other.

[0054] In this embodiment, the first end of the first slit group refers to the end of the first slit 3 with the shortest arc length among the N first slits 3, and the second end of the second slit group refers to the end of the second slit 6 with the longest arc length among the N second slits 6, and the first end of the first slit 3, the second end of the first slit 3, the first end of the second slit 6, and the second end of the second slit 6 are arranged on the same straight line.

[0055] The width of the first slit 3 is 0.5 mm-1.5 mm; the width of the second slit 6 is 0.5 mm-1.5 mm; and the length of the second slit 6 is 25 mm-100 mm.

[0056] Through the above technical solution, the terahertz wave 4 is incident from the substrate 1 into the conductive film 2 to generate a terahertz vortex wave. The incident direction of the terahertz wave 4 is the positive direction of the Z axis, and is vertically incident on the device.

[0057] In this embodiment, the radius of the plurality of first slits gradually increases from the first end of the first slit group to the second end of the first slit group; the radius of the first slit is the line between the inner arc of the first slit and the center of the conductive film 2;

[0058] The radius of the plurality of second slits gradually increases from the first end of the first slit group to the second end of the first slit group; the radius of the second slit is the line between the inner arc of the second slit and the center of the conductive film 2 .

[0059] The radius difference between two adjacent first slits 3 in the first slit group is 2 mm-4 mm; the radius difference between two adjacent second slits 6 in the second slit group is 2 mm-4 mm.

[0060] In this embodiment, the centers of the first slit and the second slit are both concentrically arranged with the center of the conductive film 2 .

[0061] The length of the first slit 3 is 25 mm to 100 mm, and the length of the second slit 6 is 25 mm to 100 mm.

[0062] In this embodiment, the radius increment of the first slit and the radius increment of the second slit are both 1-1.4 times.

[0063] In this embodiment, the first slit group and the second slit group are respectively arranged at two ends of the center line of the end surface of the conductive film 2 ; the first slit group and the second slit group are centrally symmetrical about the center of the conductive film 2 .

[0064] Through the above technical solution, the first slit group overlaps with the second slit group after rotating 180 degrees around the center of the conductive film 2, and the second slit group overlaps with the first slit group after rotating 180 degrees around the center of the conductive film 2. The first slit group and the second slit group are centrally symmetrical about the center of the conductive film 2.

[0065] The working principle of a terahertz vortex generator based on spiral slits of a conductive film on a flexible substrate provided by the present invention is that a terahertz circularly polarized wave passes through a spiral line structure composed of multiple arc-shaped slits, excites surface plasmons (SPPs) to form a vortex wave, wherein the number of topological charges is related to the radius difference between the arc-shaped slits.

[0066] like Figure 4 As shown, the test process of a terahertz vortex generator based on a spiral slit of a conductive film on a flexible substrate provided by the present invention is as follows:

[0067] The frequency of the terahertz wave 4 is 0.14 THz. The terahertz wave 4 is a right-handed circularly polarized light, and its incident direction is the positive direction of the Z axis. It is vertically incident on the device and generates a vortex after passing through the conductive film 2. The specific spiral phase is observed on the surface of the conductive film 2 away from the substrate 1, and the observation surface is parallel to the XY plane.

[0068] The terahertz wave 4 is vertically incident on the device, and the flexible substrate 1 is proportionally expanded using a stretching device. Different stretching ratios change the width and radius of the slit, and vortex waves corresponding to different topological charge numbers are emitted. The vortex generator is light and thin, and can continuously generate high-order terahertz vortex waves with different topological charges.

[0069] Example 2

[0070] This embodiment is based on the embodiment 1, and takes N=9 as an example, that is, 9 first slits are provided in the first slit group, and 9 second slits are provided in the second slit group. Figure 5 As shown;

[0071] In this embodiment, the second end of the first first slit is overlapped with the first end of the second first slit, the second end of the second first slit is overlapped with the first end of the third first slit, and so on, until the second end of the eighth first slit is overlapped with the first end of the ninth first slit; the second end of the first second slit is overlapped with the first end of the second second slit, the second end of the second second slit is overlapped with the first end of the third second slit, and so on, until the second end of the eighth second slit is overlapped with the first end of the ninth second slit.

[0072] In this embodiment, the thickness of the flexible substrate is preferably 3 mm, the thickness of the conductive film is preferably 0.2 mm, and there are two groups of slits on the conductive film. The width of the arc slits is preferably 1 mm, which can be adjusted according to the specific size of the arc slit array and the arrangement order and spacing of the arc slits.

[0073] As shown in Figure 5, the radius of the arc-shaped slits of the conductive film is uniformly expanded. Each arc-shaped slit array is composed of 9 arc-shaped slits. The radius difference of the arc-shaped slits, that is, the radius increment, is 2.3mm, so the smallest arc-shaped slit radius R1 is 25mm, and the largest arc-shaped slit radius R9 is 43.4mm.

[0074] The designed arrays for the first slit group and the second slit group are two arc-shaped slit arrays with continuously increasing radius, and the angle occupied by each arc-shaped slit is 20 degrees, that is, the circumferential angle α1 covered by the first slit on the conductive film is 20 degrees, and the circumferential angle α2 covered by the second slit on the conductive film is 20 degrees. The total angle occupied is 180 degrees. The total angle occupied by the first slit group and the second slit group is 360 degrees.

[0075] In design applications, the above parameters can be specifically adjusted to achieve more precise beam control and corresponding phase modulation.

[0076] like Figure 6 As shown, when the stretch ratio is 1, 1.1, 1.2, 1.3, and 1.39, the radius difference of the arc slit, the radius of the arc slit, and the width of the slit also change with the expansion of the stretch ratio, and the multiple is the same as the stretch ratio. Therefore, the corresponding changes of the radius difference are 2.3mm, 2.53mm, 2.76mm, 2.99mm, and 3.197mm, and the minimum radius of the arc slit changes to 25mm, 27.5mm, 30mm, 32.5mm, and 34.75mm, and the maximum radius of the arc slit changes to 43.4mm, 47.74mm, 52.08mm, 56.42mm, and 60.326mm.

[0077] like Figure 7 As shown, the right-handed terahertz beam is incident vertically on the device. Under the above stretching conditions, terahertz vortex waves with different topological charges will be generated on the other side of the substrate, and the corresponding topological charge numbers are 1, 3, 5, 7, and 9, respectively.

[0078] The present invention provides a terahertz vortex generator based on spiral slits of a conductive film on a flexible substrate. The substrate is a stretchable flexible substrate, on which a conductive film is spin-coated and a plurality of circular arc slits of equal angles and different radii are opened. An adjustable spiral line structure is formed on the flexible substrate. The flexible substrate is stretched as a whole by a stretching clamp to achieve proportional expansion of the substrate, so as to accurately control the width and radius of the slit, thereby achieving effective control of the outgoing vortex wave.

[0079] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A terahertz vortex generator based on a spiral slit of a conductive film on a flexible substrate, characterized in that: include: A flexible substrate, wherein one end surface of the flexible substrate is coated with a conductive film; The conductive film is provided with a first slit group and a second slit group; the first slit group and the second slit group are respectively arranged in a spiral shape with the axis of the conductive film as the center, and the spiral directions of the first slit group and the second slit group are the same; The first slit group includes N first slits; the second slit group includes N second slits; the N first slits and the N second slit groups are arranged in sequence along two spiral directions.

2. The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate according to claim 1, characterized in that: A plurality of stretching fixtures are connected to the flexible substrate; the plurality of stretching fixtures are evenly arranged along the circumference of the edge of the flexible substrate to stretch the flexible substrate and change the size of the first slit and the size of the second slit.

3. The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate according to claim 1, characterized in that: The first slit is a convex arc-shaped structure; the circumferential angle covered by the first slit on the conductive film is N / 180 degrees; The second slit is a concave arc-shaped structure; the circumferential angle covered by the second slit on the conductive film is N / 180 degrees.

4. The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate according to claim 1, characterized in that: The first end of the second first slit overlaps with the second end of the first first slit, and the overlapping arrangements are carried out in sequence until the second end of the Nth first slit overlaps with the first end of the N-1th first slit; the first end of the second second slit overlaps with the second end of the first second slit, and the overlapping arrangements are carried out in sequence until the second end of the Nth second slit overlaps with the first end of the N-1th second slit.

5. The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate according to claim 1, characterized in that: The first slits located at the first end of the first slit group are arranged at a certain distance from the first edge of the conductive film; the lengths of the plurality of first slits gradually increase from the first end of the first slit group to the second end of the first slit group; The second slits located at the second end of the second slit group are arranged at a certain distance from the second edge of the conductive film and are arranged between the first end of the first slit group and the second end of the first slit group; the lengths of the plurality of second slits gradually increase from the first end of the second slit group to the second end of the second slit group; The first edge of the conductive film and the second edge of the conductive film are two edges arranged opposite to each other on one end surface of the conductive film.

6. The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate according to claim 5, characterized in that: The radius of the plurality of first slits gradually increases from the first end of the first slit group to the second end of the first slit group; the radius of the first slit is a line connecting the inner arc of the first slit and the center of the conductive film; The radius of the plurality of second slits gradually increases from the first end of the first slit group to the second end of the first slit group; the radius of the second slit is a line connecting an inner arc of the second slit and the center of the conductive film.

7. The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate according to claim 6, characterized in that: The centers of the first slit and the second slit are both arranged concentrically with the center of the conductive film.

8. The terahertz vortex generator based on the spiral slit of the conductive film on the flexible substrate according to claim 6, characterized in that: The radius increment of the first slit and the radius increment of the second slit are both 1-1.4 times.

9. The terahertz vortex generator based on spiral slits of a conductive film on a flexible substrate according to claim 1, characterized in that: The first slit group and the second slit group are respectively arranged at two ends of a center line of an end surface of the conductive film; the first slit group and the second slit group are centrally symmetrical about the center of the conductive film.

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