Terahertz narrow-band band-pass filter based on all-metal metamaterial

Abstract

A terahertz narrow-band band-pass filter based on all-metal metamaterials is characterized in that the terahertz narrow-band band-pass filter comprises a plurality of terahertz narrow-band band-pass filter unit structures which are periodically arranged in a single-layer mode, the whole metal hole unit structure is of a square all-metal structure, and V-shaped through holes which are symmetrical left and right are formed in the center of the metal hole unit structure; the overall length h of the V-shaped through hole is smaller than the side length p of the metal hole unit structure, the distance between the tip point of the center of the V-shaped through hole and the upper end of the V-shaped through hole is h / 2, the transverse width of a single-side supporting foot at the upper end of the V-shaped through hole is w, and the distance between the center line of the V-shaped through hole and the inner end point of the upper end of the V-shaped through hole is l. The working frequency of the terahertz narrow-band band-pass filter can be regulated and controlled by adjusting the structural parameters of the metal hole unit structures. The filter has the advantages that the working frequency of the filter can be flexibly regulated and controlled, the transmittance filtering performance is high, the 3dB bandwidth is narrow, the process cost is low and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz wave functional devices, and in particular relates to a terahertz narrowband bandpass filter based on an all-metal metamaterial. Background Art

[0002] Terahertz waves (THz) are located between the optical band and the microwave band, with a frequency range of 0.1THz to 10THz, and have the characteristics of low photon energy and good penetration. Compared with light waves and microwaves, terahertz waves have many special properties and have important research value in scientific research, security inspection and national defense, biomedicine, radar imaging, short-distance high-speed communication, and astronomy. The application scenarios of terahertz technology in the field of communication are constantly enriched with the deepening of research, such as indoor communication, nanocommunication, short-distance ultra-high-speed wireless communication, object-to-object interconnection, and intersatellite communication. Terahertz filters play an indispensable role in noise suppression, signal separation, feature signal extraction, and frequency screening in terahertz detection and communication systems. At present, terahertz filters mainly use electronic components and optical devices to achieve precise control and manipulation of frequency characteristics in terahertz systems. However, with the development of metamaterials, terahertz filters based on metamaterials have attracted much attention because of their superior performance in terahertz communication and sensing systems. Compared with traditional terahertz passive filters, terahertz filters based on metamaterials have the advantages of flexible regulation, wide frequency coverage, and miniaturization, and are more suitable for the application of terahertz waves in fields such as communications.

[0003] In recent years, with the development of metamaterial theory and micro-nano processing technology, researchers have proposed many terahertz filters based on metamaterials. Using artificial metamaterial structural units, the working performance of terahertz filters can be designed according to application requirements, and single-band, multi-band and broadband terahertz filtering can be achieved. Limited by the resonance characteristics, most of the existing terahertz metamaterial narrow-band high-pass filters use all-metal hole structures. Among them, Lee JW et al. from South Korea proposed in 2006 that high-pass filtering can be achieved in the terahertz band using metal holes of different geometric shapes, and verified it through experiments (Optics Express, Vol. 14, No. 3, pp. 1253-1259 (2006)). Existing studies have shown that terahertz filters based on all-metal holes have the advantages of low insertion loss and easy control of center frequency, but the 3dB bandwidth of such terahertz filters is difficult to be less than 30GHz, and the out-of-band suppression effect is poor due to the resonance characteristics of the all-metal structure. Especially when the operating frequency is greater than 0.5THz, the ohmic loss of metal materials in the terahertz band is large, which limits the performance of all-metal-based terahertz metamaterial narrowband pass filters. It can be seen that metal hole metamaterials can achieve high-pass filtering of specific frequencies in the terahertz band, but at the same time also limit the performance of the filter. Therefore, there is still room for further research and improvement in improving design flexibility and performance optimization.

[0004] In view of the above problems, the present invention proposes a new all-metal terahertz narrowband bandpass filter, which adopts a simple structural design, has excellent out-of-band suppression performance, high transmittance, and can accurately control the filtering frequency in the range of 0.4-0.37THz using structural parameters. The filter introduces Anapole resonance in the all-metal structure to form a special surface current distribution, thereby effectively coupling and transmitting the electromagnetic field, so that the electromagnetic wave can effectively transfer energy between the surface and the internal area of ​​the structure, thereby enhancing the transmission capability. In addition, the filter design structure of the present invention is simple, the reliability is high, the frequency adjustment is flexible, and the processing technology is simpler. Summary of the invention

[0005] The present invention aims to provide a terahertz narrowband bandpass filter based on Anapole resonant all-metal metamaterial to solve the shortcomings of the current terahertz metamaterial narrowband bandpass filter. The filter has a simple structure and low process cost. By adjusting the structural parameters, the filter center frequency can be accurately adjusted within the range of 0.4THz to 0.7THz. Within this operating frequency range, not only can the transmittance be maintained above 81%, but the 3dB bandwidth is less than 37GHz, and it also has excellent out-of-band suppression performance.

[0006] To this end, the technical solution adopted by the present invention is: a terahertz narrowband bandpass filter based on an all-metal metamaterial, characterized in that: it includes a plurality of periodically single-layer arranged terahertz narrowband bandpass filter unit structures, the metal hole unit structure is an overall square all-metal structure, and a left-right symmetrical "V"-shaped through hole is arranged in the center, the overall length h of the "V"-shaped through hole is less than the side length p of the metal hole unit structure, the distance between the tip point on the center of the "V"-shaped through hole and the upper end is h / 2, the lateral width of the single-sided support leg at the upper end of the "V"-shaped through hole is w, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole is l, and the operating frequency of the terahertz narrowband bandpass filter can be controlled by adjusting the structural parameters of the metal hole unit structure.

[0007] As a preferred embodiment of the above scheme, the side length p of the metal hole unit structure is 400 μm, and the metal thickness is 1 μm to 170 μm, which is a reasonable size.

[0008] More preferably, the operating frequency of the terahertz narrowband bandpass filter is 0.4 THz to 0.7 THz, which is a reasonable frequency.

[0009] More preferably, the metal hole unit structure material is gold, the material selection is reasonable, the manufacturing process is simple, the processing difficulty is low, and the process cost is effectively reduced.

[0010] More preferably, the metal hole unit structure material is silver, the material selection is reasonable, the manufacturing process is simple, the processing difficulty is low, and the process cost is effectively reduced.

[0011] More preferably, the metal hole unit structure material is copper, the material selection is reasonable, the manufacturing process is simple, the processing difficulty is low, and the process cost is effectively reduced.

[0012] More preferably, the metal hole unit structure material is stainless steel, which has reasonable material selection, simple manufacturing process, low processing difficulty, and effectively reduces process costs.

[0013] Beneficial effects of the present invention:

[0014] (1) Compared with the existing terahertz metamaterial narrowband pass filter, which is difficult to simultaneously ensure narrowband, high transmittance, out-of-band suppression performance and flexible adjustment of operating frequency, the present invention adopts a periodic "V"-shaped metal hole structure to achieve narrowband pass filtering in the frequency band of 0.4THz to 0.7THz by adjusting the structural parameters, that is, adjusting the lateral width w of the "V"-shaped through hole, the distance l between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole, and the overall length h of the "V"-shaped through hole to flexibly adjust the operating frequency of the terahertz narrowband pass filter. The design is ingenious, the structure is simple, the processing difficulty is low, the process cost is low, and it can meet the needs of mass production.

[0015] (2) The terahertz narrow-band pass filter proposed in the present invention can achieve excellent narrow-band pass filtering for linearly polarized terahertz waves, left-handed circularly polarized (LCP) terahertz waves, and right-handed circularly polarized (RCP) terahertz waves.

[0016] (3) When a terahertz wave is incident on the metamaterial narrow-band pass filter, the "V"-shaped metal hole generates anapole resonance, so that the energy consumption of the all-metal resonant unit structure is low when resonating in the terahertz band. The transmittance of the filter at the operating frequency can reach more than 81%, and can reach up to 89%.

[0017] (4) Compared with the existing terahertz all-metal bandpass filters, the terahertz narrowband bandpass filter proposed in the present invention has a narrow 3dB bandwidth in the frequency band of 0.4THz to 0.7THz, which can reach a minimum of 26.51GHz, and has excellent out-of-band suppression performance.

[0018] In summary, the present invention has the advantages of flexible adjustment of the filter operating frequency, high transmittance filtering performance, narrow 3dB bandwidth, excellent out-of-band suppression performance, simple structure and low process cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the unit structure of the terahertz metamaterial narrowband bandpass filter.

[0020] Figure 2 Schematic diagram of the periodic arrangement of terahertz metamaterial narrow-band pass filters.

[0021] Figure 3 It is the transmittance spectrum of the y-polarized terahertz wave vertically incident on the terahertz narrow-band pass filter based on metallic silver, and the working center frequency is 0.4 THz.

[0022] Figure 4 It is the transmittance spectrum of the y-polarized terahertz wave vertically incident on the terahertz narrow-band pass filter based on metallic silver, and the working center frequency is 0.5 THz.

[0023] Figure 5 The transmittance spectrum of the Y-polarized terahertz wave vertically incident on the terahertz narrow-band pass filter based on metallic silver, with an operating center frequency of 0.6 THz

[0024] Figure 6 It is the transmittance spectrum of the y-polarized terahertz wave vertically incident on the terahertz narrow-band pass filter based on metallic silver, and the working center frequency is 0.7 THz.

[0025] Figure 7 It is the transmittance spectrum of LCP terahertz wave vertically incident on the terahertz narrow-band pass filter based on metallic silver, and the working center frequency is 0.4THz.

[0026] Figure 8 It is the transmittance spectrum of RCP terahertz wave vertically incident on the terahertz narrow-band pass filter based on metallic silver, and the working center frequency is 0.4 THz.

[0027] Fig. 9 The relationship between the length h of different “V”-shaped through holes and the operating frequency when the y-polarized terahertz wave is vertically incident on the metallic silver-based terahertz narrow-band pass filter.

[0028] Fig.10 The relationship between the lateral width w of the single-side leg at the upper end of different "V"-shaped through holes and the operating frequency when the y-polarized terahertz wave is vertically incident on the metallic silver terahertz narrow-band bandpass filter.

[0029] Fig.11 The relationship between the distance l between the center line of the “V”-shaped through hole and the upper inner end point of the “V”-shaped through hole of the y-polarized terahertz wave vertically incident on the metallic silver terahertz narrow-band bandpass filter and the operating frequency.

[0030] Fig.12 Figure 2 is the transmittance spectrum of the y-polarized terahertz wave vertically incident on the metallic silver-based terahertz narrow-band pass filter with different metal thicknesses t.

[0031] Fig.13 The transmittance spectrum of the y-polarized terahertz wave vertically incident on a narrow-bandpass filter based on different metals, with an operating center frequency of 0.4 THz.

[0032] Fig.14 Micrograph of a terahertz metasurface narrow-bandpass filter made of 20 μm thick stainless steel using laser scanning cutting technology.

[0033] Fig.15 The transmittance spectrum of the y-polarized terahertz wave is vertically incident on the stainless steel terahertz narrow-band pass filter. The working center frequency is 0.4 THz. DETAILED DESCRIPTION

[0034] In order to further explain the embodiments of the present invention in detail, Figure 1 — Fig.15 The embodiments are briefly introduced. It is necessary to point out that the drawings are only embodiments of the present invention and do not mean any limitation on the protection scope of the present invention.

[0035] A terahertz narrowband bandpass filter based on all-metal metamaterials is composed of a plurality of periodically arranged single-layer terahertz narrowband bandpass filter unit structures a1.

[0036] The metal hole unit structure a1 is a square all-metal structure as a whole, with a left-right symmetrical "V"-shaped through hole a2 in the center.

[0037] The overall length h of the "V"-shaped through hole a2 is smaller than the side length p of the metal hole unit structure a1, the distance between the tip point at the center of the "V"-shaped through hole a2 and the upper end is h / 2, the lateral width of the single-sided leg at the upper end of the "V"-shaped through hole a2 is w, and the distance between the center line of the "V"-shaped through hole a2 and the inner end point at the upper end of the "V"-shaped through hole a2 is l. The operating frequency of the terahertz narrowband bandpass filter can be controlled by adjusting the structural parameters of the metal hole unit structure a1.

[0038] The side length p of the metal hole unit structure is 400 μm, and the metal thickness t is 1 μm to 170 μm.

[0039] Figure 1 It shows that the structural unit a1 of the filter is a square all-metal structure as a whole, and a left-right symmetrical "V"-shaped through hole a2 is arranged in the center.

[0040] Figure 2 It is a schematic diagram of an array of periodically arranged metal hole unit structures. As can be seen from the figure, a terahertz narrow-band bandpass filter based on an all-metal metamaterial proposed in the present invention is composed of a plurality of uniformly arranged single-layer metal hole unit structures a1.

[0041] When the metal hole unit structure material is silver, the side length p = 400μm, the metal thickness t = 5μm, the overall height of the "V"-shaped metal hole structure parameters h = 310μm, the lateral width w = 83μm, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 20μm, the transmittance spectrum of the y-polarized terahertz wave vertically incident on the narrow-band bandpass filter is as follows Figure 3 As shown in the figure, it can be seen that the central operating frequency of the filter is 0.4THz, and the transmittance T at the central frequency is 89.92% (T = S 21 2 , T is transmittance, S 21 is the transmittance coefficient), the 3dB bandwidth is 26.69GHz, and the out-of-band suppression effect is good.

[0042] When the metal hole unit structure material is silver, the side length p = 400μm, the metal thickness t = 5μm, the overall height of the "V"-shaped metal hole structure parameters h = 262μm, the lateral width w = 10μm, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 90μm, the transmittance spectrum of the y-polarized terahertz wave vertically incident on the narrow-band bandpass filter is as follows Figure 4 As shown in the figure, it can be seen that the center frequency of the filter is 0.5THz, the transmittance T at the center frequency is 87.73%, the 3dB bandwidth is 35.13GHz, and the out-of-band suppression effect is good.

[0043] When the metal hole unit structure material is silver, the side length p = 400μm, the metal thickness t = 5μm, the overall height of the "V"-shaped metal hole structure parameters h = 200μm, the lateral width w = 10μm, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 78μm, the transmittance spectrum of the y-polarized terahertz wave vertically incident on the narrow-band bandpass filter is as follows Figure 5 As shown in the figure, it can be seen that the center frequency of the filter is 0.6THz, the transmittance T at the center frequency is 83.50%, the 3dB bandwidth is 28.71GHz, and the out-of-band suppression effect is good.

[0044] When the metal hole unit structure material is silver, the side length p = 400μm, the metal thickness t = 5μm, the overall height of the "V"-shaped metal hole structure parameters h = 122.5μm, the lateral width w = 10μm, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 82μm, the transmittance spectrum of the y-polarized terahertz wave vertically incident on the narrow-band bandpass filter is as follows Figure 6 As shown in the figure, it can be seen that the center frequency of the filter is 0.7THz, the transmittance T at the center frequency is 81.53%, the 3dB bandwidth is 26.51GHz, and the out-of-band suppression effect is good.

[0045] When the metal hole unit structure material is silver, the side length p = 400μm, the metal thickness t = 5μm, the overall height of the "V"-shaped metal hole structure parameters h = 310μm, the lateral width w = 83μm, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 82μm, the transmittance spectrum of the left-handed circularly polarized (LCP) terahertz wave vertically incident on the narrow-band bandpass filter is as follows Figure 7 As shown in the figure, it can be seen that the center frequency of the filter is 0.4THz, the transmittance T at the center frequency is 89.92%, the 3dB bandwidth is 26.69GHz, and the out-of-band suppression effect is good.

[0046] When the unit structure materials and structural parameters are the same as above, the transmittance spectrum of the right-handed circularly polarized (RCP) terahertz wave vertically incident on the narrow-band bandpass filter is as follows: Figure 8 As shown in the figure, it can be seen that the center frequency of the filter is 0.4THz, the transmittance T at the center frequency is 89.92%, the 3dB bandwidth is 26.69GHz, and the out-of-band suppression effect is good.

[0047] When the metal hole unit structure material is silver, the side length p = 400 μm, the metal thickness t = 5 μm, the lateral width w = 83 μm, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 20 μm, the relationship between the operating frequency of the terahertz narrowband bandpass filter and the overall height h of the "V"-shaped metal hole structure parameters is as follows: Fig. 9As shown in the figure, it can be seen that as h increases from 140μm to 390μm, the operating frequency of the filter decreases from 0.6229THz to 0.3358THz. It can be seen that by adjusting the structural parameter h in the range of 140μm to 390μm, the operating frequency of the filter can be effectively adjusted within a certain range.

[0048] When the metal hole unit structure material is silver, the side length p = 400μm, the metal thickness t = 5μm, the overall height of the "V"-shaped metal hole structure parameters h = 310μm, and the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 20μm, the relationship between the operating frequency of the terahertz narrowband bandpass filter and the lateral width w of the upper end leg of the "V"-shaped metal hole structure is as follows: Fig.10 As shown in the figure, it can be seen that as w increases from 40μm to 110μm, the operating frequency of the filter decreases from 0.4321THz to 0.3826THz. It can be seen that by adjusting the structural parameter w in the range of 40μm to 110μm, the operating frequency of the filter can be effectively adjusted within a certain range.

[0049] When the metal hole unit structure material is silver, the side length p = 400 μm, the metal thickness t = 5 μm, the overall height of the "V"-shaped metal hole structure parameters h = 310 μm, and the lateral width of the single-side leg at the upper end of the "V"-shaped through hole w = 83 μm, the relationship between the operating frequency of the terahertz narrowband bandpass filter and the distance l between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped metal hole structure is as follows: Fig.11 As shown in the figure, it can be seen that as l increases from 5μm to 95μm, the operating frequency of the filter decreases from 0.4069THz to 0.3421THz. It can be seen that by adjusting the structural parameter l in the range of 55μm to 95μm, the operating frequency of the filter can be effectively adjusted within a certain range.

[0050] It can be seen that the operating frequency of the terahertz narrowband bandpass filter is preferably 0.4 THz to 0.7 THz.

[0051] The lateral width w of the single-side leg at the upper end of the “V”-shaped through hole a2 can be adjusted in the range of 40 μm to 110 μm.

[0052] The control range of the distance l between the center line of the "V"-shaped through hole a2 and the inner end point of the upper end of the "V"-shaped through hole a2 is 5μm to 95μm.

[0053] The height h of the “V”-shaped through hole a2 can be adjusted in the range of 140 μm to 390 μm.

[0054] When the metal material is silver, the height of the "V"-shaped metal hole is h = 310 μm, the distance between the center line of the "V"-shaped metal hole and the inner side of the upper end is l = 20 μm, and the lateral width of the single-side leg at the upper end of the "V"-shaped metal hole is w = 83 μm, the influence of different metal thicknesses t on the transmittance T is as follows Fig.12 As shown in the figure, as t increases from 1μm to 170μm, the operating frequency of the filter decreases from 0.4033THz to 0.3637THz (the transmission peak is red-shifted in the transmittance spectrum). At the same time, the transmittance also decreases from 88.82% to 76.80%. It can be seen that the metal thickness in the range of 1μm to 170μm has little effect on the operating center frequency and transmittance T of the filter.

[0055] Fig.13 It can be seen from the figure that when the metal hole unit structure parameter side length p = 400μm, metal thickness t = 5μm, "V" type metal hole structure parameter overall height h = 310μm, the distance between the center line of the "V" type through hole and the inner end point of the "V" type through hole l = 83μm, and the lateral width of the single-side leg at the upper end of the "V" type metal hole w = 83μm, the metal material is gold (conductivity is 4.566×10 7 S / m), silver (conductivity is 6.30×10 7 S / m) and copper (conductivity is 5.96×10 7 S / m) are all greater than 85%, and the out-of-band suppression effect is good, and the filtering performance is excellent. 6 S / m), the filter transmittance T is about 75%, and the out-of-band suppression effect is excellent. It can be seen that when the metal material is silver, the filtering efficiency is the highest, but the filter based on stainless steel has the same excellent performance and lower cost.

[0056] Therefore, the material of the metal pore unit structure a1 is preferably gold.

[0057] The material of the metal hole unit structure a1 is preferably silver.

[0058] The material of the metal hole unit structure a1 is preferably copper.

[0059] The material of the metal hole unit structure a1 is preferably stainless steel.

[0060] In order to verify the performance of the filter based on stainless steel material, the present invention uses laser scanning and cutting technology to process a "V"-shaped metal hole array on a 20μm thick polished stainless steel sheet (the surface has a mirror effect and is relatively smooth). The "V"-shaped metal hole unit structure parameters are side length p = 400μm, the overall height of the "V"-shaped metal hole h = 310μm, the distance between the center line of the "V"-shaped through hole and the inner end point of the upper end of the "V"-shaped through hole l = 83μm, and the lateral width between the center line of the "V"-shaped through hole and the inner end point of the "V"-shaped through hole leg w = 20μm. The microscopic photo of the processed array is shown in the figure. Fig.14 shown.

[0061] When the y-polarized terahertz wave is vertically incident on the stainless steel-based terahertz narrowband bandpass filter, the transmittance spectrum of the experimental test is as follows: Fig.15 As shown in the figure. It can be seen from the figure that the center frequency of the filter measured in the experiment is 0.3822THz, the transmittance T is 85.54%, the 3dB bandwidth is 41GHz, and the out-of-band suppression effect is excellent. Since the thickness t of the processed stainless steel increases to 20μm, the center frequency is red-shifted (i.e., reduced) in the transmittance spectrum. The stainless steel used in the experiment has excellent performance, so the transmittance T is relatively increased. It can be seen that the experimental results are in good agreement with the simulation results, and the differences are mainly caused by the conductivity and loss of stainless steel and processing errors.

Claims

1. A terahertz narrowband bandpass filter based on all-metal metamaterials, characterized in that: The invention comprises a plurality of periodically arranged single-layer terahertz narrow-band bandpass filter unit structures (a1), wherein the metal hole unit structure (a1) is a square all-metal structure as a whole, and a left-right symmetrical "V"-shaped through hole (a2) is arranged in the center, the overall length h of the "V"-shaped through hole (a2) is less than the side length p of the metal hole unit structure (a1), the distance between the central tip point of the "V"-shaped through hole (a2) and the upper end is h / 2, the lateral width of the single-side support leg at the upper end of the "V"-shaped through hole (a2) is w, and the distance between the center line of the "V"-shaped through hole (a2) and the inner end point of the upper end of the "V"-shaped through hole (a2) is l, and the operating frequency of the terahertz narrow-band bandpass filter can be controlled by adjusting the structural parameters of the metal hole unit structure (a1).

2. The terahertz narrowband bandpass filter based on all-metal metamaterial according to claim 1, characterized in that: The side length p of the metal hole unit structure is 400 μm, and the metal thickness t is 1 μm to 170 μm.

3. The terahertz narrowband bandpass filter based on all-metal metamaterial according to claim 1, characterized in that: The operating frequency of the terahertz narrowband bandpass filter is 0.4THz to 0.7THz.

4. The terahertz narrowband bandpass filter based on all-metal metamaterial according to claim 1, characterized in that: The material of the metal unit structure (a1) is gold.

5. The terahertz narrowband bandpass filter based on all-metal metamaterial according to claim 1, characterized in that: The material of the metal unit structure (a1) is silver.

6. The terahertz narrowband bandpass filter based on all-metal metamaterial according to claim 1, characterized in that: The material of the metal unit structure (a1) is copper.

7. The terahertz narrowband bandpass filter based on all-metal metamaterial according to claim 1, characterized in that: The material of the metal unit structure (a1) is stainless steel.

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