Terahertz device integrating sensing and modulation functions based on metasurface and preparation method thereof

Abstract

The present invention discloses a terahertz device based on the integration of sensing and modulation functions on a metasurface and a preparation method thereof, which includes a substrate, a C-shaped metal resonant ring array metasurface, a graphene layer, and a cover glass sequentially arranged from bottom to top; the C-shaped metal resonant ring array metasurface is divided into two groups, namely a modulation region and a sensing region, which respectively realize the functions of terahertz amplitude modulation and liquid biological sample detection. A magnetic fluid is injected into the modulation region to form a three-layer heterojunction optical modulation structure of metasurface-graphene-magnetic fluid. On the cover glass, a liquid detection cell is arranged at the position corresponding to the sensing region, and a liquid inlet and a liquid outlet are also correspondingly arranged on the cover glass. The present invention realizes the modulation of terahertz amplitude under the control of an external magnetic field; in the sensing region, the liquid properties can be qualitatively or quantitatively detected through the frequency shift of the resonance peak. The structure of the present invention is simple and easy to process, and can respectively realize the functions of terahertz modulation and sensing.

Description

Technical Field

[0001] The present invention belongs to the technical fields of terahertz spectroscopy applications and metasurfaces, and particularly relates to a terahertz device integrating sensing and modulation functions based on a metasurface and a preparation method thereof. Background Art

[0002] Terahertz waves (THz) refer to electromagnetic waves with frequencies between 0.1 and 10 THz. This band is located between millimeter waves and infrared rays and is an important region for the transition from macroelectronics to microphotonics. Terahertz time-domain spectroscopy is used to analyze the relative change in the time-resolved electric fields of two terahertz pulses, namely, the sample signal of the terahertz pulse passing through the sample and the reference signal after it propagates the same length distance in free space. Due to the different sample structures, the changes in the terahertz pulse waveform are also different. Thus, the complex refractive index, dielectric constant, conductivity, etc. of the sample can be obtained. By deeply analyzing these optical parameters obtained from the experiments, the types of samples can be identified to a certain extent and some physical and chemical information related to the samples can be obtained.

[0003] A terahertz metasurface refers to a new type of artificial material that acts in the terahertz band and can achieve the adjustment of the amplitude or phase of terahertz waves. The metallic split-ring resonator (SRR) is one of the most common metasurface structure types. The SRR can be regarded as a circuit containing capacitance and inductance. The inductance is mainly determined by the geometric parameters of the metasurface, and the capacitance is closely related to the effective dielectric constant of the capacitor. When the metasurface is covered by other substances, the change in its local effective dielectric constant will cause a change in capacitance, thereby leading to a shift in its resonance frequency. Therefore, the liquid properties can be qualitatively or quantitatively detected by the shift of the terahertz metasurface resonance frequency.

[0004] Currently, most terahertz metasurface devices are mainly for realizing single functions, with relatively complex preparation processes and low sensing sensitivities. Therefore, how to design a terahertz device with a simple structure, easy to manufacture, and excellent modulation and sensing effects is a problem that researchers need to solve. Summary of the Invention

[0005] To solve the above problems, the present invention aims to provide a terahertz device integrating sensing and modulation functions based on a metasurface and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions: A terahertz device based on integrated sensing and modulation functions of a metasurface, comprising a substrate, a C-shaped metal resonator ring array metasurface, a graphene layer, and a cover glass arranged in sequence from bottom to top. The substrate and the cover glass are connected by interference fit. A micro-nano C-shaped metal resonator ring array metasurface is arranged on the substrate, and a single layer of graphene is deposited on the C-shaped metal resonator ring array metasurface. The C-shaped metal resonator ring array metasurface has a length of 20 mm, a width of 10 mm, and a thickness of 800 nm, and is divided into 2 groups, namely a modulation region and a sensing region, which respectively realize the functions of terahertz amplitude modulation and liquid biological sample detection. A liquid injection channel is provided on the side of the cover glass for injecting magnetic fluid, that is, iron oxide nanoparticles, into the modulation region, and the liquid injection channel is blocked by a piston to form a metasurface-graphene-magnetic fluid three-layer heterojunction optical modulation structure. On the cover glass, a liquid detection cell is arranged at the position corresponding to the sensing region, and a liquid inlet and a liquid outlet are also correspondingly arranged on the cover glass.

[0007] As a preferred embodiment of the present invention, the device has a length of 40 mm, a width of 40 mm, and a thickness of 10 mm. The materials of the substrate and the cover glass are cycloolefin copolymer, that is, COC, and its terahertz wave transmittance is about 90%.

[0008] As a preferred embodiment of the present invention, the size of the C-shaped unit structure of the C-shaped metal resonator ring array metasurface is 150 μm × 150 μm, the thickness is 800 nm, the material is gold, the outer radius R1 of the C-shaped unit structure is 60 μm, the inner radius R2 is 40 μm, and the opening a is 20 μm.

[0009] In the modulation region of the device, by utilizing the linear dichroism of the magnetic fluid and the high carrier mobility rate of graphene, under the control of an external magnetic field, the conductivity of the structure is increased and the terahertz transmittance is decreased, thereby realizing terahertz amplitude modulation, and the maximum modulation depth is about 60%. The modulation depth is defined as follows:

[0010]

[0011] where MD is the modulation depth, P max is the maximum amplitude value, P min is the minimum amplitude value.

[0012] The metasurface-graphene structure will generate a resonance absorption peak at 1.1 THz. When the liquid sample to be measured is injected into the liquid detection cell, the absorption peak undergoes a frequency shift phenomenon, and the frequency shift amount shows a fitting trend with the liquid properties, realizing the specific detection of the liquid sample.

[0013] As a preferred embodiment of the present invention, the preparation process of the device is as follows:

[0014] Step 1: Use a laser engraving machine to cut two pieces of COC square sheets as the substrate and the cover sheet. Use a milling cutter to mill the grooves in the modulation area and the sensing area on the cover sheet. And mill the liquid injection channels in the grooves of the modulation area, and use a special drill bit to drill the liquid inlet and outlet in the grooves of the sensing area.

[0015] Step 2: Clean the substrate ultrasonically with alcohol and deionized water in sequence, and dry it with nitrogen. And transversely paste heat-resistant tapes around and in the middle of the substrate.

[0016] Step 3: Spin-coat a photoresist on the substrate and place a photomask; perform exposure and development processes on the photoresist; use the measurement and control sputtering process to grow a C-type metal resonator array on the area not covered by the photoresist, and strip the photoresist.

[0017] Step 4: Prepare a graphene layer by chemical vapor deposition method, and then transfer the graphene layer to the substrate.

[0018] Step 5: Tear off the heat-resistant tape on the substrate, close the substrate and the cover sheet by using an interference fit slot, and perform a hermeticity test. Inject magnetic fluid into the modulation area through the liquid injection channel on the side of the cover sheet, and block the liquid injection channel with a piston after the injection is completed.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. The device has both terahertz sensing and modulation functions at the same time, with a simple preparation process, low material loss, corrosion resistance, and high reuse rate.

[0021] 2. The introduction of the graphene layer can greatly improve the carrier migration rate, make the conductivity change faster, and achieve high-sensitivity sensing.

[0022] 3. The magnetic fluid, namely magnetite nanoparticles, will exhibit good linear dichroism under the action of an external magnetic field, and is a new type of terahertz modulation material. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or exemplary technical descriptions. As shown in the drawings, only some embodiments of the present application are shown. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is a three-dimensional structure schematic diagram of the device of the present invention.

[0025] Figure 2 It is a three-dimensional structure schematic diagram of the COC substrate of the device of the present invention.

[0026] Figure 3This is a three-dimensional structure schematic diagram of the COC cover sheet of the device of the present invention.

[0027] Figure 4 This is a unit structure schematic diagram of the C-type metal resonant ring array of the device of the present invention.

[0028] Figure 5 This is a schematic diagram of terahertz wave amplitude modulation of the device of the present invention under the action of an external magnetic field.

[0029] Figure 6 This is a transmittance curve diagram of the sensing area of the device of the present invention in the 0.1 - 1.8 THz band.

[0030] 1 - COC substrate, 2 - COC cover sheet, 11 - C-type metal resonant ring array, 12 - graphene, 21 - modulation area, 22 - sensing area, 211 - liquid injection channel, 212 - piston, 221 - liquid detection cell, 222 - liquid inlet, 223 - liquid outlet. Detailed implementation manners

[0031] To make the advantages of the present invention easier to understand, the present invention briefly described above will be described in more detail by referring to the specific implementation manners shown in the accompanying drawings.

[0032] Refer to Figure 1 、 Figure 2 and 3 For a terahertz device integrating sensing and modulation functions based on a metasurface, the device includes a substrate 1, a C-type metal resonant ring array metasurface 11, and a cover sheet 2 arranged in sequence from bottom to top;

[0033] A graphene layer 12 is deposited on the C-type metal resonant ring array metasurface 11;

[0034] The C-type metal resonant ring array metasurface 11 is divided into two groups, namely a modulation area 21 and a sensing area 22, which respectively realize the functions of terahertz amplitude modulation and liquid biological sample detection;

[0035] A liquid injection channel 211 is provided on the side of the cover sheet 2 and is communicated with the modulation area 21 for injecting magnetic fluid into the modulation area 21; a piston 212 is provided at the entrance of the liquid injection channel 211 for blocking the liquid injection channel 211;

[0036] A liquid detection cell 221 is arranged on the cover sheet 2 in the sensing area 22, and a liquid inlet 222 and a liquid outlet 223 are provided at corresponding positions of the liquid detection cell 221.

[0037] The device of this embodiment has a length of 40 mm, a width of 40 mm, and a thickness of 10 mm. The materials of the substrate 1 and the cover sheet 2 are cyclic olefin copolymer.

[0038] The micro-nano C-shaped metal resonant ring array metasurface 11 has a length of 20 mm, a width of 10 mm, and a thickness of 800 nm. The size of the metasurface C-shaped unit structure on the C-shaped metal resonant ring array metasurface 11 is 150 μm × 150 μm, the thickness is 800 nm, the material is gold, the outer radius R1 of the C-shaped unit structure is 60 μm, the inner radius R2 is 40 μm, and the opening a is 20 μm.

[0039] The described terahertz device based on the integrated sensing and modulation functions of the metasurface has the following preparation process:

[0040] Step 1: Use a laser engraver to cut two COC square sheets with a thickness of 5 mm and a length and width of 40 mm as the substrate 1 and the cover sheet 2. Use a milling cutter to mill the slots in the modulation area 21 and the sensing area 22 with a thickness of 1 mm on the cover sheet. And mill the liquid injection channel 211 in the slot of the modulation area 21, and use a special drill bit to punch the liquid inlet 222 and the liquid outlet 223 in the slot of the sensing area 22.

[0041] Step 2: Clean the substrate 1 in ultrasonic successively with alcohol and deionized water, and dry it with nitrogen. And transversely paste heat-resistant tapes with a width of 10 mm around and in the middle of the substrate 1.

[0042] Step 3: Spin-coat photoresist on the substrate 1 and place the photomask; perform exposure and development processing on the photoresist; use the controlled sputtering process to grow the C-shaped metal resonant ring array 11 on the area not covered by the photoresist, and strip the photoresist.

[0043] Step 4: Prepare the graphene layer 12 by chemical vapor deposition method, and then transfer the graphene layer to the substrate 1.

[0044] Step 5: Tear off the heat-resistant tape on the substrate, close the substrate 1 and the cover sheet 2 by interference fit card slots, and perform airtightness test. Inject magnetic fluid into the modulation area 21 from the liquid injection channel 211 on the side of the cover sheet, and block the liquid injection channel with the piston 212 after the injection is completed.

[0045] To verify the practicability of the terahertz device of the present invention, the terahertz wave is amplitude-modulated under the external magnetic fields of 0 mT, 20 mT, 50 mT, 90 mT, and 150 mT by using this device. Through the calculation of experimental data, the maximum modulation depth of this device is 60%, which fully proves the practicability of the present invention in terahertz modulation.

[0046] Use the terahertz time-domain spectroscopy system to make the terahertz wave vertically pass through the metasurface-graphene structure on the sensing area of the device of the present invention. Through data calculation, the terahertz transmission spectrum is obtained, and it is found that the device of the present invention generates an obvious resonance absorption peak at 1.1 THz. This characteristic can be used for the specific research of liquid samples.

[0047] The present invention selects a COC material as the device housing. This material has a transmittance higher than 90% in the range of 0.1 - 2.7 THz and no characteristic vibration peaks, thereby increasing the sensitivity of measuring liquid samples in a transmission terahertz time-domain spectroscopy system.

[0048] The present invention introduces a graphene layer and a magnetic fluid layer, and utilizes the high carrier migration rate of graphene and the linear dichroism of the magnetic fluid to achieve high-sensitivity terahertz amplitude modulation.

[0049] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and cannot limit the protection scope of the present invention. All equivalent changes and modifications made to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. A terahertz device based on the integration of sensing and modulation functions of a metasurface, characterized in that, The device includes, from bottom to top, a substrate (1), a C-shaped metal resonant ring array metasurface (11), and a cover glass (2) arranged in sequence; A graphene layer (12) is deposited on the C-shaped metal resonant ring array metasurface (11); The C-shaped metal resonant ring array metasurface (11) is divided into two groups, namely a modulation region (21) and a sensing region (22), which respectively realize the functions of terahertz amplitude modulation and liquid biological sample detection; A liquid injection channel (211) is provided on the side of the cover glass (2) and communicates with the modulation region (21) for injecting magnetic fluid into the modulation region (21); A piston (212) is provided at the inlet of the liquid injection channel (211) for blocking the liquid injection channel (211); A liquid detection cell (221) is arranged at the position corresponding to the sensing region (22) of the cover glass (2), and a liquid inlet (222) and a liquid outlet (223) are provided at the liquid detection cell (221); The device has a length of 40 mm, a width of 40 mm, and a thickness of 10 mm. The materials of the substrate (1) and the cover glass (2) are cycloolefin copolymer; The micro-nano C-shaped metal resonant ring array metasurface (11) has a length of 20 mm, a width of 10 mm, and a thickness of 800 nm; The size of the metasurface C-shaped unit structure on the C-shaped metal resonant ring array metasurface (11) is 150 μm × 150 μm, the thickness is 800 nm, the material is gold, the outer radius R1 of the C-shaped unit structure is 60 μm, the inner radius R2 is 40 μm, and the opening a is 20 μm.

2. The terahertz device based on the integrated sensing and modulation functions of the metasurface according to claim 1, characterized in that, characterized in that, The injected magnetic fluid is iron oxide nanoparticles, which are used to form a three-layer heterojunction optical modulation structure of metasurface-graphene-magnetic fluid.

3. The preparation method of a terahertz device based on the integration of sensing and modulation functions of a metasurface according to claim 1 or 2, characterized in that, It includes the following steps: Step 1: Use a laser engraving machine to cut two COC square pieces as the substrate (1) and the cover glass (2); Use a milling cutter to mill grooves for the modulation region (21) and the sensing region (22) on the cover glass (2); And mill a liquid injection channel (211) in the groove of the modulation region (21), and punch a liquid inlet (222) and a liquid outlet (223) at the groove of the sensing region (22); Step 2: Clean the substrate (1) in ultrasonic with alcohol and deionized water in sequence, and dry it with nitrogen; And transversely paste heat-resistant tapes around and in the middle of the substrate (1); Step 3: Spin-coat photoresist on the substrate (1) and place a photomask; Expose and develop the photoresist; Use a controlled sputtering process to grow a C-shaped metal resonant ring array (11) on the area not covered by the photoresist, and strip the photoresist; Step 4: Prepare the graphene layer (12) by chemical vapor deposition method, and then transfer the graphene layer (12) to the substrate (1); Step 5: Tear off the heat-resistant tape on the substrate (1), close the substrate (1) and the cover glass (2) by interference fit card slots, and conduct a hermeticity test; Inject magnetic fluid into the modulation region (21) from the liquid injection channel (211) on the side of the cover glass, and block the liquid injection channel (211) with the piston (212) after the injection is completed.

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