Design and processing method of terahertz band-stop filter based on cylindrical double-chain structure

Abstract

The present invention proposes a terahertz band-stop filter based on a cylindrical double-chain structure, wherein the input end of the filter is a metal double-chain periodic structure of parallel metal double chains, and the output end is a quartz substrate connected to the metal double-chain periodic structure, and the metal double-chain periodic structure includes a columnar double chain composed of a plurality of metal cylindrical bodies arranged regularly and closely; the filter is a band-stop filter, when the columnar double-chain periodic structure of the filter is a cylindrical double-chain periodic structure, the cylindrical body is a cylindrical unit, the angle between the double chain radial direction of the band-stop filter and the incident terahertz polarization is the polarization angle γ, the bandwidth of the band-stop filter is adjusted by adjusting the cylindrical unit spacing or the filter thickness, the bandwidth is reduced by increasing the unit spacing t, or the filtering bandwidth is reduced by reducing the cylindrical unit thickness H; the filter structure described in the present invention can be quickly designed and the device performance is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz devices and metamaterials, in particular to a design and processing method of a terahertz band-stop filter based on a cylindrical double-chain structure. Background Art

[0002] The present invention relates to the field of terahertz devices and metamaterials, and in particular to a design and processing method for a terahertz band-stop filter based on a cylindrical double-chain structure. The method uses FDTD simulation to analyze the influence of relevant structural parameters of the terahertz band-stop filter based on a cylindrical double-chain structure on device performance, determines the optimal structural parameters that meet the set center frequency and bandwidth, and uses femtosecond laser two-photon polymerization combined with photolithography to process and prepare samples. The method has the characteristics of fast design and excellent device performance. Summary of the invention

[0003] The present invention proposes a design and processing method for a terahertz band-stop filter based on a cylindrical double-chain structure. The filter structure can be quickly designed and the device performance is excellent.

[0004] The present invention adopts the following technical solutions.

[0005] A terahertz band-stop filter based on a cylindrical double-chain structure, wherein the input end of the filter is a metal double-chain periodic structure with metal double chains arranged in parallel, and the output end is a quartz substrate connected to the metal double-chain periodic structure, and the metal double-chain periodic structure includes a columnar double chain composed of a plurality of metal columns arranged regularly and closely.

[0006] The filter is a band-stop filter. When the columnar double-chain periodic structure of the filter is a cylindrical double-chain periodic structure, the cylindrical body is a cylindrical unit, and the angle between the double-chain radial direction of the band-stop filter and the incident terahertz polarization is the polarization angle γ. The bandwidth of the band-stop filter is adjusted by adjusting the cylindrical unit spacing or the filter thickness, and the bandwidth is reduced by increasing the unit spacing t, or the filtering bandwidth is reduced by reducing the cylindrical unit thickness H.

[0007] When the center frequency of the band-stop filter is 0.8 THz, the influence of the incident angle α on the filter performance can be ignored.

[0008] When the filter is used as an attenuator, the transmittance is adjusted by changing the polarization angle γ.

[0009] A design method for a terahertz band-stop filter based on a cylindrical double-chain structure, the design method comprising the following steps;

[0010] Step S1, defining the filter structure as a cylindrical double-chain periodic structure, and setting the center frequency and bandwidth performance indicators that the filter needs to achieve;

[0011] Step S2, using FDTD to simulate the double-strand spacing h, polarization angle γ, cylindrical unit thickness H and spacing t between cylindrical units of the cylindrical double-strand periodic structure, and analyzing the influence of these parameters on the transmission spectrum;

[0012] Step S3: Determine various parameters of the filter according to the analysis result of step S2.

[0013] A method for processing a terahertz band-stop filter based on a cylindrical double-chain structure, using femtosecond laser two-photon polymerization combined with photolithography to process and prepare the terahertz band-stop filter, comprising the following steps:

[0014] Step A1, using quartz glass as a substrate for processing a filter sample, cleaning and drying the quartz substrate in an ultrasonic cleaning machine, and then placing the substrate in a coating machine to evenly coat the primer and photoresist thereon;

[0015] Step A2, exposing the outer cylindrical area of ​​the substrate surface point by point using a femtosecond laser two-photon polymerization process;

[0016] Step A3, using a coating machine to evaporate gold on the workpiece processed in step A2, and finally immersing the workpiece in a degumming solution for degumming, removing the metal in the exposure area in the two-photon polymerization exposure process, and obtaining a filter workpiece after processing.

[0017] The quartz glass is a quartz glass sheet with a diameter of 15 mm and a thickness of 50 μm.

[0018] The filter workpiece manufactured in step A3 has device parameters of radius r=25 μm, spacing h=350 μm, and unit spacing t=5 μm.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The band-stop filter based on the cylindrical double-chain structure disclosed in the present invention can directly offset the influence of electric field polarization, and overcome the shortcomings of traditional filters with large bandwidth and large influence of incident angle. Compared with traditional metal patch-type band-stop filters, the terahertz band-stop filter with a cylindrical double-chain structure has more adjustable parameters and thus better performance.

[0021] 2. By rotating the angle between the double chain radial direction of the band-stop filter and the incident terahertz polarization (polarization angle γ), the transmittance at the center frequency can be adjusted. Therefore, the device can also be used as a terahertz attenuator. The filter design based on the double chain structure combines the characteristics of the patch-type band-stop frequency selective surface and the wire grid polarizer, and is a multifunctional device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0023] Attached Figure 1a Schematic diagram of the structure of the filter of the present invention (wherein the rectangle 1 is a quartz substrate, and the cylinder 2 is a metal double chain structure);

[0024] Attached Figure 1b : is the front view of the filter of the present invention (the double-chain structure periodically extends in the horizontal and vertical directions. Wherein h is the double-chain spacing, that is, the distance between two adjacent parallel metal double-chain periodic structures, and t is the unit spacing, that is, the distance between adjacent cylinders);

[0025] Attached Figure 1c : is a schematic diagram of the working filter of the filter of the present invention (the upper part is a cylindrical double-chain structure, and the lower part is a quartz substrate. H is the height of the cylindrical unit structure, and S is the thickness of the quartz substrate);

[0026] Attached Figure 2 Schematic diagram of transmission curves of a terahertz band-stop filter based on a cylindrical double-chain structure in an embodiment of the present invention under different incident angles α, different polarization angles γ, different thicknesses H, and different unit spacings t;

[0027] Attached Figure 3 This is a microscopic schematic diagram of a terahertz band-stop filter sample based on a cylindrical double-chain structure in an embodiment of the method of the present invention;

[0028] In the figure: 1-quartz substrate; 2-columnar double-chain periodic structure. DETAILED DESCRIPTION

[0029] As shown in the figure, a terahertz band-stop filter based on a cylindrical double-chain structure has an input end of a metal double-chain periodic structure with metal double chains arranged in parallel, and an output end of a quartz substrate connected to the metal double-chain periodic structure. The metal double-chain periodic structure includes a columnar double chain composed of a plurality of metal columns arranged regularly and closely.

[0030] The filter is a band-stop filter. When the columnar double-chain periodic structure of the filter is a cylindrical double-chain periodic structure, the cylindrical body is a cylindrical unit, and the angle between the double-chain radial direction of the band-stop filter and the incident terahertz polarization is the polarization angle γ. The bandwidth of the band-stop filter is adjusted by adjusting the cylindrical unit spacing or the filter thickness, and the bandwidth is reduced by increasing the unit spacing t, or the filtering bandwidth is reduced by reducing the cylindrical unit thickness H.

[0031] A design method for a terahertz band-stop filter based on a cylindrical double-chain structure, the design method comprising the following steps;

[0032] Step S1, defining the filter structure as a cylindrical double-chain periodic structure, and setting the center frequency and bandwidth performance indicators that the filter needs to achieve;

[0033] Step S2, using FDTD to simulate the double-strand spacing h, polarization angle γ, cylindrical unit thickness H and spacing t between cylindrical units of the cylindrical double-strand periodic structure, and analyzing the influence of these parameters on the transmission spectrum;

[0034] Step S3: Determine various parameters of the filter according to the analysis result of step S2.

[0035] A method for processing a terahertz band-stop filter based on a cylindrical double-chain structure, using femtosecond laser two-photon polymerization combined with photolithography to process and prepare the terahertz band-stop filter, comprising the following steps:

[0036] Step A1, using quartz glass as a substrate for processing a filter sample, cleaning and drying the quartz substrate in an ultrasonic cleaning machine, and then placing the substrate in a coating machine to evenly coat the primer and photoresist thereon;

[0037] Step A2, exposing the outer cylindrical area of ​​the substrate surface point by point using a femtosecond laser two-photon polymerization process;

[0038] Step A3, using a coating machine to evaporate gold on the workpiece processed in step A2, and finally immersing the workpiece in a degumming solution for degumming, removing the metal in the exposure area in the two-photon polymerization exposure process, and obtaining a filter workpiece after processing.

[0039] The quartz glass is a quartz glass sheet with a diameter of 15 mm and a thickness of 50 μm.

[0040] The filter workpiece manufactured in step A3 has device parameters of radius r=25 μm, spacing h=350 μm, and unit spacing t=5 μm.

[0041] Example:

[0042] like Figure 2 As shown in the figure, the performance of the band-stop filter with a center frequency of 0.8 THz is basically unaffected by the incident angle α; as the polarization angle γ increases, the center frequency remains unchanged, the transmittance decreases, and it can be used as an attenuator; as the thickness H decreases, the filter bandwidth also decreases accordingly, and the center frequency moves to high frequency; as the unit spacing t gradually increases, the bandwidth decreases significantly, and the center frequency position shifts to the right.

[0043] In this example, the bandwidth of the band-stop filter can be effectively adjusted by adjusting the cylindrical unit spacing, which is an advantage that traditional patch-type frequency selective surface filters do not have.

[0044] like Figure 3As shown in the figure, when preparing the sample, the quartz substrate is first cleaned and dried in an ultrasonic cleaner, and the substrate is placed in a coating machine to evenly coat the primer and photoresist on it. After drying, the outer area of ​​the cylinder is exposed point by point using femtosecond laser two-photon polymerization, and then the sample is evaporated with gold using a coating machine. Finally, the sample is immersed in a degumming solution for degumming, and the metal in the two-photon polymerization exposed part is removed to obtain the processed sample. The device parameters are radius r = 25 μm, spacing h = 350 μm, and unit spacing t = 5 μm.

[0045] Figure 3 (a) is a micrograph of the sample under a 5x metallographic microscope after two-photon polymerization exposure, and (b) is a micrograph of the sample under a 5x metallographic microscope after coating.

[0046] In this example, the input end of the filter is a columnar double-chain periodic structure of parallel metal double chains; when the columnar double-chain periodic structure of the filter is a spherical double-chain structure, the columnar body is a quasi-spherical structure; when the columnar double-chain periodic structure of the filter is a square double-chain structure, the columnar body is a rectangular column.

[0047] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A terahertz band-stop filter based on a cylindrical double-chain structure, characterized in that: The input end of the filter is a metal double-chain periodic structure with metal double chains arranged in parallel, and the output end is a quartz substrate connected to the metal double-chain periodic structure, and the metal double-chain periodic structure includes a columnar double chain composed of a plurality of metal columns arranged regularly and closely; The filter is a band-stop filter. When the columnar double-chain periodic structure of the filter is a cylindrical double-chain periodic structure, the columnar body is a cylindrical unit, and the angle between the double-chain radial direction of the band-stop filter and the incident terahertz polarization is the polarization angle γ. The bandwidth of the band-stop filter is adjusted by adjusting the cylindrical unit spacing or the filter thickness, and the bandwidth is reduced by increasing the unit spacing t, or the filtering bandwidth is reduced by reducing the cylindrical unit thickness H. When the filter is used as an attenuator, the transmittance is adjusted by changing the polarization angle γ.

2. The terahertz band-stop filter based on a cylindrical double-chain structure according to claim 1, characterized in that: The impact of the incident angle α on the filter performance is negligible.

3. A design method for a terahertz band-stop filter based on a cylindrical double-chain structure as claimed in claim 1, characterized in that: The design method The steps include: Step S1, defining the filter structure as a cylindrical double-chain periodic structure, and setting the center frequency and bandwidth performance indicators that the filter needs to achieve; Step S2, using FDTD to simulate the double-strand spacing h, polarization angle γ, cylindrical unit thickness H and spacing t between cylindrical units of the cylindrical double-strand periodic structure, and analyzing the influence of these parameters on the transmission spectrum; Step S3: Determine various parameters of the filter according to the analysis result of step S2.

4. A method for processing a terahertz band-stop filter based on a cylindrical double-chain structure as claimed in claim 1, characterized in that: The terahertz band-stop filter is prepared by femtosecond laser two-photon polymerization combined with photolithography. The steps include: Step A1, using quartz glass as a substrate for processing a filter sample, cleaning and drying the quartz substrate in an ultrasonic cleaning machine, and then placing the substrate in a coating machine to evenly coat the primer and photoresist thereon; Step A2, exposing the outer cylindrical area of ​​the substrate surface point by point using a femtosecond laser two-photon polymerization process; Step A3, using a coating machine to evaporate gold on the workpiece processed in step A2, and finally immersing the workpiece in a degumming solution for degumming, removing the metal in the exposure area in the two-photon polymerization exposure process, and obtaining a filter workpiece after processing.

5. The method for processing a terahertz band-stop filter based on a cylindrical double-chain structure according to claim 4, characterized in that: The quartz glass is a quartz glass sheet with a diameter of 15 mm and a thickness of 50 μm; The filter workpiece manufactured in step A3 has device parameters of radius r=25 μm, spacing h=350 μm, and unit spacing t=5 μm.

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