Terahertz electric field enhancement device based on metasurface

Abstract

The invention discloses a terahertz electric field enhancement device based on a metasurface. The terahertz electric field enhancement device is composed of a silicon dioxide substrate and the metasurface which is located on the surface of the silicon dioxide substrate and can achieve terahertz electric field enhancement. The metasurface is composed of periodic array metal structures, and each array unit comprises a square-shaped metal frame, two linear metal strips and two T-shaped metal patterns. The square-shaped metal frame is located in the center of the array unit, and the two linear metal strips are connected with the centers of the left side and the right side of the square-shaped metal frame respectively. The two T-shaped metal patterns are vertically intersected with the upper edge and the lower edge of the square-shaped metal frame respectively, horizontal arms of the two T-shaped patterns are parallel, and a gap is formed between the two arms. When the width of the gap is smaller than 100 nm, the terahertz electric field in the gap is obviously enhanced. The enhancement effect is derived from a strong localization effect generated by resonance response of the metasurface structure and incident terahertz waves. The terahertz electric field enhancement device can be applied to the fields of terahertz wave detection, imaging, sensing, communication and the like.

Description

Technical Field

[0001] The present invention relates to the field of terahertz technology, and in particular to a terahertz electric field enhancement device based on a metasurface. Background Art

[0002] The terahertz band is located between microwaves and infrared, with a frequency of 0.1THz to 10THz. It has many unique properties, such as strong penetration, good security, wide bandwidth and fingerprint spectrum characteristics for material identification. Therefore, it is widely used in imaging, biomedicine, material detection and broadband wireless communications.

[0003] However, due to the low energy of terahertz wave photons and weak electric field strength, the sensitivity of the detector is very high, which limits its use in many practical applications. Therefore, how to enhance the terahertz electric field strength is a key technical problem that needs to be solved in terahertz wave detection and sensing applications. Although traditional metal nanostructures can achieve local terahertz field enhancement, it is difficult to achieve efficient terahertz electric field enhancement due to high losses. Summary of the invention

[0004] The purpose of this invention is to address the current situation of weak terahertz electric field and great difficulty in detection, and propose a terahertz electric field enhancement device based on a metasurface to enhance the strength of the terahertz electric field, thereby expanding the application scope of terahertz technology. The specific technical solution is as follows:

[0005] A terahertz electric field enhancement device based on a metasurface is composed of a silicon dioxide substrate and a metasurface on the surface thereof that can achieve terahertz electric field enhancement. The metasurface is composed of a periodic array metal structure, and each array unit includes a square-shaped metal frame, two straight metal strips and two "T"-shaped metal patterns. The square-shaped metal frame is located in the center of the array unit, and the two straight metal strips are respectively connected to the center of the left and right sides of the square-shaped metal frame. The two "T"-shaped metal patterns are respectively perpendicular to the upper and lower sides of the square-shaped metal frame, and the horizontal arms of the two "T"-shaped patterns are parallel, and there is a gap between the two arms.

[0006] The invention discloses a terahertz electric field enhancement device based on a super surface, comprising a silicon dioxide substrate and a super surface on the surface of the silicon dioxide substrate capable of achieving terahertz electric field enhancement, wherein the side length of the super surface is equal to the side length of the silicon dioxide substrate.

[0007] When the terahertz wave is incident from above the terahertz electric field enhancement device and the terahertz frequency matches the geometric size and arrangement of the metasurface unit, a resonance effect will occur. In this process, strong coupling occurs between the terahertz wave and the metasurface unit, causing the energy to be concentrated in the area near the metasurface unit. In particular, in the gap between the horizontal arms of the two "T"-shaped metal patterns, due to the special design of the metasurface unit, the energy of the electromagnetic wave is significantly localized in this area, thereby generating a strong electric field enhancement effect in this area.

[0008] Each array unit of the two-dimensional array includes a U-shaped metal frame, two I-shaped metal strips and two T-shaped metal patterns.

[0009] The lateral width of an array unit in the two-dimensional array is 80 micrometers to 120 micrometers, and the longitudinal length is 80 micrometers to 150 micrometers.

[0010] The "T"-shaped metal pattern, the "U"-shaped metal frame and the "I"-shaped metal strip are made of any one of gold sheets, copper sheets or aluminum sheets, and have a thickness of 0.1 micrometer to 0.2 micrometer.

[0011] The length of the lower vertical bar of the "T"-shaped metal pattern is 35 micrometers to 45 micrometers, and the length of the horizontal bar is 25 micrometers to 35 micrometers.

[0012] The U-shaped metal frame comprises four metal strips, each of which is vertically interwoven with each other to form a rectangular frame, and the lengths of the transverse and longitudinal metal strips are 25 microns to 35 microns and 45 microns to 55 microns respectively.

[0013] The substrate material of the terahertz electric field enhancement device is silicon dioxide, and the thickness is 400 microns to 600 microns.

[0014] Each array unit of the terahertz electric field enhancement device has axial symmetry in the horizontal and vertical directions.

[0015] The area covered by the surface periodic array metal structure is larger than the area of ​​the light spot of the terahertz beam on the device surface.

[0016] The area covered by the surface periodic array metal structure is 1 to 3.5 times the area of ​​the terahertz beam spot irradiated on the terahertz electric field enhancement device.

[0017] Compared with the prior art, the advantages of the terahertz electric field enhancement device based on the metasurface of the present invention are as follows: 1. The device can significantly enhance the terahertz electric field, achieving the best terahertz electric field enhancement effect at a frequency of 0.145 THz, with the electric field enhancement multiple reaching about 45,000 times, effectively reducing the limitations on the application of terahertz technology due to the low energy of terahertz photons and weak electric field strength. 2. The metasurface pattern for achieving terahertz electric field enhancement is composed of horizontal and vertical structures, which is simple to manufacture and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the three-dimensional structure of a terahertz electric field enhancement device based on a metasurface;

[0019] Figure 2 for Figure 1 A cross-sectional view of

[0020] Figure 3 for Figure 1 A top view of

[0021] Figure 4 is a schematic diagram of an array unit structure;

[0022] Figure 5 The graph is a graph showing the variation of transmittance and electric field amplification factor with frequency when the width of the horizontal arm gap between two “T”-shaped metal patterns is 6 nm.

[0023] Numbers in the figure: 1 high-resistance silicon layer; 2 two-dimensional array; 21 metal strip, 22 U-shaped metal frame, 23 "T"-shaped metal pattern. DETAILED DESCRIPTION

[0024] A solution of a terahertz electric field enhancement device based on a metasurface of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] The schematic diagram of the embodiment of the terahertz electric field enhancement device based on the metasurface is shown in FIG. Figure 1 and 2 As shown, it includes a silicon dioxide substrate 1 and a two-dimensional array 2 located on the surface thereof that can realize terahertz electric field enhancement. In this example, the diameter of the normally incident terahertz beam is 500 microns. In this example, the two-dimensional array 2 has a total of 15×8 array units, and the length of the two-dimensional array is 1500 microns and the width is 800 microns.

[0026] like Figure 3 and 4 As shown, each array unit of the two-dimensional array 2 in this example includes a square metal frame 22, two straight metal strips 21 and two "T" shaped metal patterns 23. The length and width of a unit array are both h = 100 microns. In this example, the square metal frame 22, the straight metal strip 21, and the "T" shaped metal pattern 23.

[0027] The "T"-shaped metal pattern 23 in this example is composed of a horizontal metal strip and a vertical metal strip, and the two metal strips are perpendicular to each other. The horizontal metal strip length f of the "T"-shaped metal pattern 23 is 30 microns, the vertical metal strip length d is 41 microns, and the width c is 6 microns. The gap between the two arms of the two "T"-shaped metal patterns is g=6nm. The two "T"-shaped metal patterns 23 of the array unit are symmetrical up and down. The two "T"-shaped metal patterns 23 are perpendicularly intersected with the upper and lower sides of the square-shaped metal frame 22, and there is a gap between the two arms. The square-shaped metal frame 22 is composed of two pairs of parallel metal strips, and the two pairs of parallel metal strips are perpendicular to each other, with a horizontal length i=52 microns and a vertical length e=38 microns; the square-shaped metal frame 22 is located in the center of the array unit, symmetrical up and down and left and right, and the two straight metal strips 21 are connected to the center of the left and right sides of the square-shaped metal frame 22 respectively. The straight metal strip 21 has a length b=19 microns and a width a=8 microns.

[0028] When in use, the terahertz wave is incident directly from the top of the terahertz electric field enhancement device, that is, the top of the surface periodic array metal structure. In order to allow the terahertz beam on the terahertz electric field enhancement device to pass through without obstruction, the surface periodic array metal structure, that is, the area covered by all array units, is larger than the area of ​​the terahertz beam spot irradiated on the field enhancement device, which is 1 to 3.5 times the area of ​​the terahertz beam spot.

[0029] The terahertz electric field enhancement device significantly enhances the intensity of the terahertz electric field by optimizing the structural design of the metasurface, thus achieving the amplification of the terahertz electric field. In the optimization process, the geometric shape and size of the metasurface structure play a vital role and are one of the key factors in the structural design. The area where the terahertz electric field is enhanced is in the gap between the horizontal arms of the two "T"-shaped patterns. When the gap width is 6nm, the transmittance and terahertz electric field amplification of the device are as follows: Figure 5 As shown:

[0030] When the gap width is 6nm, the terahertz electric field enhancement device shows a significant terahertz electric field amplification effect. Especially at the frequency of 0.145THz, the amplification factor of the terahertz electric field reaches 45,000 times. The reason for this phenomenon is that 0.145THz happens to be the highest peak frequency of the transmission spectrum of the terahertz electric field enhancement device, at which time the resonance response of the structure and the incident terahertz wave is the strongest. At this frequency, the localization effect of the gap area on the electromagnetic wave reaches the maximum, resulting in a sharp enhancement of the terahertz electric field in this area.

[0031] In summary, the finely designed metasurface structure of the terahertz electric field enhancement device exhibits excellent electric field amplification effect, demonstrating the outstanding performance of the device and its broad application potential.

[0032] It should be noted that although the embodiments of the present invention described above are illustrative, they are not intended to limit the present invention, and therefore the present invention is not limited to the above specific embodiments. Without departing from the principles of the present invention, any other embodiments obtained by those skilled in the art under the guidance of the present invention are deemed to be within the protection of the present invention.

Claims

1. A terahertz electric field enhancement device based on a metasurface, comprising a silicon dioxide substrate (1) and a metasurface (2) on the surface thereof capable of achieving terahertz electric field enhancement. The metasurface (2) is composed of a periodic array metal structure, and each array unit comprises a U-shaped metal frame (22), two I-shaped metal strips (21) and two "T"-shaped metal patterns (23). The U-shaped metal frame (22) is located in the center of the array unit, and the two I-shaped metal strips (21) are respectively connected to the center of the left and right sides of the U-shaped metal frame (22). The two "T"-shaped metal patterns (23) are respectively perpendicular to the upper and lower sides of the U-shaped metal frame (22), and the horizontal arms of the two "T"-shaped metal patterns (23) are parallel, and there is a gap between the two arms; it is characterized in that: The U-shaped metal frame (22) comprises four metal strips, each of which is vertically interwoven with each other to form a rectangular frame. The two "T"-shaped metal patterns (23) respectively intersect vertically with the upper and lower sides of the U-shaped metal frame (22), and the two "T"-shaped metal patterns (23) are symmetrical about the horizontal axis of the array unit; The two straight metal strips (21) are respectively connected to the centers of the left and right sides of the square-shaped metal frame (22); the two straight metal strips (21) are equal in length and width and are symmetrical about the vertical axis of the array unit.

2. The terahertz electric field enhancement device based on a metasurface according to claim 1, characterized in that: The area of ​​the surface periodic array metal structure is 1 to 3.5 times the area of ​​the terahertz beam spot on the surface of the terahertz electric field enhancement device.

3. The terahertz electric field enhancement device based on a metasurface according to claim 1, characterized in that The "T"-shaped metal pattern, the "U"-shaped metal frame and the "I"-shaped metal strip are made of any one of gold, copper or aluminum, and have a thickness of 0.1 micron to 0.2 micron.

4. The terahertz electric field enhancement device based on a metasurface according to claim 1, characterized in that: The device is symmetrical left to right and top to bottom.

5. The terahertz electric field enhancement device based on a metasurface according to claim 1, characterized in that: The thickness of the silicon dioxide substrate (1) is 400 micrometers to 600 micrometers.

6. A terahertz electric field enhancement device based on a metasurface according to claim 1, characterized in that: The lateral width of an array unit in the two-dimensional array is 80 micrometers to 120 micrometers, and the longitudinal length is 80 micrometers to 150 micrometers.

7. The terahertz electric field enhancement device based on a metasurface according to claim 1, characterized in that: The length of the lower vertical strip of the "T"-shaped metal pattern is 35 microns to 45 microns, and the length of the horizontal metal strip is 25 microns to 35 microns.

8. The terahertz electric field enhancement device based on a metasurface according to claim 1, characterized in that: The width of the transverse and longitudinal metal strips of the U-shaped metal structure is equal, and the lengths are 25 microns to 35 microns and 45 microns to 55 microns respectively.

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