Sensing System and Measurement Method Based on Multi-Order Resonant All-Dielectric Terahertz Metamaterials

Abstract

The present invention relates to a sensing system and a measurement method based on a multi-order resonance all-dielectric terahertz metamaterial, which includes a terahertz emitter, a sensing device, a terahertz detector, and a post-processing system. The sensing device is composed of a multi-order resonance all-dielectric terahertz metamaterial with grooves and through holes etched on a silicon wafer. The terahertz emitter and the terahertz detector are respectively arranged above and below the sensing device for emitting and receiving terahertz signals. The terahertz detector is connected to the post-processing system to perform real-time processing and display of the detected terahertz signals. The measurement method of this system is as follows: Detect the terahertz signals without a sample, detect the terahertz signals of the multi-order resonance all-dielectric terahertz metamaterial when not loaded and loaded with a sample, and then calculate the sensitivity of the multi-order resonance all-dielectric terahertz metamaterial. This technical solution has multi-order resonance, a high quality factor, and sensing sensitivity, and can quickly and accurately perform terahertz sensing detection on samples.

Description

Technical Field

[0001] The present invention relates to the field of terahertz sensing technology, and in particular to a sensing system and a measurement method based on a multi-order resonance all-dielectric terahertz metamaterial. Background Art

[0002] As an artificial material, metamaterial has unique electromagnetic properties that natural materials do not possess. It is composed of periodically arranged sub-wavelength structures. By constructing specific structures, surface plasmon resonance can be excited to achieve the localization of strong electromagnetic fields. In particular, as a feasible sensing platform, it can solve the limited sensitivity caused by the mismatch between terahertz (THz) wavelengths and biomolecular scales. Therefore, terahertz metamaterial sensors have attracted much attention due to their excellent characteristics such as real-time, non-contact, and label-free detection, and are widely used in biochemical sensing.

[0003] Existing terahertz metamaterial sensors mainly generate a relatively divergent electric field based on the design of the structure, resulting in limited sensitivity because it is difficult for the analyte to have the maximum overlap with the electric field. In addition, most existing terahertz metamaterials are composed of sub-wavelength scale metal structures, and their inherent losses lead to a large full width at half maximum and a low quality factor (Q). Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a sensing system and a measurement method based on a multi-order resonance all-dielectric terahertz metamaterial, which has multi-order resonance, a high quality factor, and sensing sensitivity, and can quickly and accurately perform terahertz sensing detection on samples.

[0005] To achieve the above purpose, the present invention adopts the following technical scheme: A sensing system based on a multi-order resonance all-dielectric terahertz metamaterial, including a terahertz transmitter, a sensing device, a terahertz detector, and a post-processing system. The sensing device is composed of an all-dielectric terahertz metamaterial with grooves and through holes etched on a silicon wafer. The terahertz transmitter and the terahertz detector are respectively arranged above and below the sensing device for emitting and receiving terahertz signals. The terahertz detector is connected to the post-processing system to perform real-time processing and display of the detected terahertz signals.

[0006] In a preferred embodiment, the multi-order resonance all-dielectric terahertz metamaterial is composed of grooves, protrusions, and two through holes located in the middle of them. The unit period of the structure is 130 and 260 μm, the widths of the grooves and protrusions are 130 μm, the depth of the grooves is 20 μm, and the size of the through holes is 80 μm.

[0007] In a preferred embodiment, the multi-order resonance all-dielectric terahertz metamaterial serves as a carrier for loading a sample to be measured and exciting multi-order surface plasmon resonance. It is fabricated by combining multiple photolithography and deep silicon etching techniques. First, a groove array structure surface is processed by photolithography and deep silicon etching, and then a via hole structure is etched by this processing technique once again. Finally, the multi-order resonance all-dielectric terahertz metamaterial is formed.

[0008] The present invention also provides a measurement method for a sensing system based on a multi-order resonance all-dielectric terahertz metamaterial. Using the above-mentioned measurement method for a sensing system based on a multi-order resonance all-dielectric terahertz metamaterial, the method includes the following steps:

[0009] Step S1: There is no multi-order resonance all-dielectric terahertz metamaterial between the terahertz emitter and the detector. At this time, the terahertz signal obtained by detecting the optical path is a reference signal r.

[0010] Step S2: Fix the multi-order resonance all-dielectric terahertz metamaterial without loading a sample between the terahertz emitter and the detector. At this time, the terahertz signal obtained by detecting the optical path is a sample signal s1.

[0011] Step S3: Using the multi-order resonance all-dielectric terahertz metamaterial as a carrier, load the sample to be measured in the microfluidic channels and via holes formed on the surface grooves. At this time, the terahertz signal obtained by detecting the optical path is a sample signal s2.

[0012] Step S4: In the post-processing system, use the obtained reference signal r, sample signal s1, and sample signal s2 to calculate the sensitivity of the multi-order resonance all-dielectric terahertz metamaterial.

[0013] In a preferred embodiment: The calculation of the sensitivity of the multi-order resonance all-dielectric terahertz metamaterial in step S4 is specifically as follows:

[0014] Step S41: Convert the detected reference signal r, sample signal s1, and sample signal s2 into terahertz frequency domain amplitude spectral signals through fast Fourier transform FFT.

[0015] Step S42: Use the transmittance spectrum calculation formula to calculate the transmittance spectra of the sample signals s1 and s2 respectively, so as to obtain the resonance frequency of the sample.

[0016] Step S43: Finally, use the sensitivity calculation formula to calculate the sensitivity of the multi-order resonance all-dielectric terahertz metamaterial.

[0017] In a preferred embodiment: The transmittance spectrum calculation formula in step S42 is:

[0018]

[0019] Among them, E s (ω) is the terahertz frequency-domain amplitude spectrum of the sample signals s1 and s2, and E r (ω) is the terahertz frequency-domain amplitude spectrum of the reference signal r.

[0020] In a preferred embodiment: the sensitivity calculation formula in the step S43 is:

[0021]

[0022] Among them, f s1 is the resonance frequency of the sample signal s1, f s2 is the resonance frequency of the sample signal s2, and n is the refractive index of the sample to be measured.

[0023] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a sensing system based on a multi-order resonance all-dielectric terahertz metamaterial and a measurement method thereof. The system is composed of a silicon-based all-dielectric material, which is not affected by the inherent ohmic loss of metals and realizes the excitation of multi-order high-quality factor resonances. The system uses a multi-order resonance all-dielectric terahertz metamaterial as the carrier of the sensing system. Due to the special structure, the surface grooves and through holes can well serve as containers for loading samples; at the same time, the presence of through holes enhances the electric field and improves the interaction between the sample to be measured and terahertz waves, making the system have high sensitivity. Description of the Drawings

[0024] Figure 1 is the schematic diagram of the system structure of the preferred embodiment of the present invention;

[0025] Figure 2 is the schematic diagram of the structure of the sensing device including a multi-order resonance all-dielectric terahertz metamaterial in the preferred embodiment of the present invention;

[0026] Figure 3 is the performance test transmittance spectrum in the preferred embodiment of the present invention;

[0027] In the figure: 1 - terahertz emitter; 2 - incident terahertz pulse; 3 - sample to be measured; 4 - through hole; 5 - groove; 6 - silicon; 7 - transmitted terahertz pulse; 8 - terahertz detector; 9 - post-processing system. Detailed Embodiments

[0028] The present invention will be further described below with reference to the drawings and embodiments.

[0029] It should be noted that the following detailed description is illustrative and is intended to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] As Figure 1 shown, this embodiment provides a sensing system based on a multi-order resonant all-dielectric terahertz metamaterial, including a terahertz transmitter, a sensing device, a terahertz detector, and a post-processing system. The sensing device is composed of an all-dielectric terahertz metamaterial with grooves and through-holes etched on a silicon wafer 6. The terahertz transmitter 1 and the terahertz detector 8 are respectively arranged above and below the sensing device to emit and receive terahertz signals. The terahertz detector 8 is connected to the post-processing system 9 to perform real-time processing and display of the detected terahertz signals.

[0032] As Figure 2 shown, in this embodiment, the multi-order resonant all-dielectric terahertz metamaterial is composed of grooves, protrusions, and two through-holes in the middle thereof. The unit period of the structure is 130 and 260 μm, the widths of the grooves and protrusions are 130 μm, the depth of the grooves is 20 μm, and the size of the through-holes is 80 μm.

[0033] In this embodiment, the multi-order resonant all-dielectric terahertz metamaterial serves as a carrier for loading the sample to be measured 3 and exciting multi-order surface plasmon resonance. It is processed by combining multiple photolithography and deep silicon etching technologies. First, a groove array structure surface is processed by photolithography and deep silicon etching, and then the through-hole structure is etched by this processing technology once, and finally the multi-order resonant all-dielectric terahertz metamaterial is formed.

[0034] When performing sample sensing detection, in the established terahertz transmission time-domain spectroscopy detection optical path, with the multi-order resonant all-dielectric terahertz metamaterial as the carrier, it is fixed between the terahertz transmitter 1 and the terahertz detector 8. Then, the terahertz transmitter 1 and the detector 8 are started. The terahertz pulse 2 emitted by the terahertz transmitter 1 allows the terahertz wave to react with the multi-order resonant all-dielectric terahertz metamaterial in a transmission manner and then exits. The detected transmitted terahertz pulse 7 sample signal is sent to the terahertz signal post-processing system 9 to obtain the sample signal s1. Then, the sample to be measured 3 is loaded on the multi-order resonant all-dielectric terahertz metamaterial, and the above process is repeated to obtain the sample signal s2. Finally, the sensitivity of the metamaterial is calculated. The measurement method of this system specifically includes the following steps:

[0035] Step S1: There is no multi - order resonant all - dielectric terahertz metamaterial between the terahertz emitter and the detector. At this time, the terahertz signal obtained by the detection optical path is the reference signal r;

[0036] Step S2: Fix the multi - order resonant all - dielectric terahertz metamaterial without loading the sample between the terahertz emitter and the detector. At this time, the terahertz signal obtained by the detection optical path is the sample signal s1;

[0037] Step S3: Using the multi - order resonant all - dielectric terahertz metamaterial as a carrier, load the sample to be measured in the micro - channels and through - holes formed by the surface grooves. At this time, the terahertz signal obtained by the detection optical path is the sample signal s2;

[0038] Step S4: In the post - processing system, use the obtained reference signal r, sample signal s1 and s2 to calculate the sensitivity of the multi - order resonant all - dielectric terahertz metamaterial.

[0039] Among them, the calculation of the sensitivity of the multi - order resonant all - dielectric terahertz metamaterial is specifically as follows:

[0040] Step S41: Convert the detected terahertz time - domain pulse signals r, s1 and s2 into terahertz frequency - domain amplitude spectral signals through fast Fourier transform (FFT);

[0041] Step S42: Use the transmittance spectrum calculation formula to calculate the transmittance spectra of the sample signals s1 and s2 respectively, so as to obtain the resonant frequency of the sample;

[0042] Among them, the transmittance spectrum calculation formula is:

[0043]

[0044] Among them, E s (ω) and E r (ω) are the terahertz frequency - domain amplitude spectra of the sample signals (s1, s2) and the reference signal r respectively.

[0045] Step S43: Finally, use the sensitivity calculation formula to calculate the sensitivity of the multi - order resonant all - dielectric terahertz metamaterial;

[0046] Among them, the sensitivity calculation formula is:

[0047]

[0048] Among them, f s1 is the resonant frequency of the sample signal s1, f s2 is the resonant frequency of the sample signal s2, and n is the refractive index of the sample to be measured.

[0049] Performance evaluation of the terahertz metamaterial sensing system:

[0050] The performance evaluation of the developed sensing system based on multi - order resonant all - dielectric terahertz metamaterials is carried out by loading samples with different refractive indices on the surface of the metamaterials respectively, and then fixing them at designated positions for sensing detection.

[0051] The transmission spectrum is calculated from the terahertz frequency - domain amplitude spectra of different samples to be measured, and the sensing characterization is carried out according to the change Δn of the refractive index of the sample to be measured with the shift Δf of the resonant - point frequency. The performance of the terahertz metasurface sensing system is represented by the sensing sensitivity S n which is expressed as: S n = Δf / Δn, where S 1 represents the first - order resonance, S n2 represents the second - order resonance, Δf = f s1 - f s2 , Δn = n - 1.

[0052] For the performance evaluation of the terahertz metasurface sensing system, the performance test results of the embodiments of the present invention are as follows Figure 3 shown below.

[0053] It can be seen from the transmission spectrum that when the refractive index of the sample to be measured is 1, the metamaterial excites multiple resonances, defined as the first - order and second - order resonances, and their quality factors (Q - values) are 139 and 83 respectively. When the refractive index of the sample to be measured increases from 1 to 1.5, the first - order resonance redshifts from the original 0.664 THz to 0.577 THz, and the second - order resonance redshifts from the original 0.791 THz to 0.704 THz. These significant changes prove that the multi - order resonant all - dielectric terahertz metamaterials can support multi - order resonances and are sensitive to the changes in the surrounding dielectric environment. The first - order resonance sensitivity obtained according to the sensing sensitivity calculation formula of the embodiments of the present invention is S 1 = 0.174 THz / RIU, and the second - order resonance sensitivity is S 2 = 0.174 THz / RIU. Both resonances show high sensing sensitivities. Therefore, the sensing system of the multi - order resonant all - dielectric terahertz metamaterials of the present invention has good application prospects.

[0054] The above - mentioned are only the preferred embodiments of the present invention, and are not limitations of the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above - mentioned embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. Measurement method of a sensing system based on a multi-order resonance all-dielectric terahertz metamaterial, characterized in that, the sensing system based on the multi-order resonance all-dielectric terahertz metamaterial includes a terahertz emitter, a sensing device, a terahertz detector and a post-processing system. The sensing device is composed of an all-dielectric terahertz metamaterial with grooves and vias etched on a silicon wafer. The terahertz emitter and the terahertz detector are respectively arranged above and below the sensing device for emitting and receiving terahertz signals. The terahertz detector is connected to the post-processing system to perform real-time processing and display of the detected terahertz signals; the multi-order resonance all-dielectric terahertz metamaterial is composed of grooves, protrusions and two vias located exactly in the middle thereof. The unit period of the structure is 130 and 260 μm, the widths of the grooves and protrusions are 130 μm, the depth of the grooves is 20 μm, and the size of the vias is 80 μm; the multi-order resonance all-dielectric terahertz metamaterial serves as a carrier for loading a sample to be measured and exciting multi-order surface plasmon resonances. It is fabricated by combining multiple photolithography and deep silicon etching techniques. First, a groove array structure surface is processed by photolithography and deep silicon etching, and then a via structure is etched by performing this processing one more time. Finally, the multi-order resonance all-dielectric terahertz metamaterial is formed; The measurement method of the sensing system based on the multi-order resonance all-dielectric terahertz metamaterial adopts the measurement method of the sensing system based on the multi-order resonance all-dielectric terahertz metamaterial, including the following steps: Step S1: There is no multi-order resonance all-dielectric terahertz metamaterial between the terahertz emitter and the detector. At this time, the terahertz signal obtained by detecting the optical path is the reference signal r; Step S2: Fix the multi-order resonance all-dielectric terahertz metamaterial without loading a sample between the terahertz emitter and the detector. At this time, the terahertz signal obtained by detecting the optical path is the sample signal s1; Step S3: Using the multi-order resonance all-dielectric terahertz metamaterial as a carrier, load the sample to be measured into the microchannels and vias formed by the surface grooves. At this time, the terahertz signal obtained by detecting the optical path is the sample signal s2; Step S4: In the post-processing system, use the obtained reference signal r, sample signal s1 and sample signal s2 to calculate the sensitivity of the multi-order resonance all-dielectric terahertz metamaterial.

2. The measurement method of the sensing system based on the multi-order resonance all-dielectric terahertz metamaterial according to claim 1, characterized in that: the calculation of the sensitivity of the multi-order resonance all-dielectric terahertz metamaterial in step S4 is specifically as follows: Step S41: Convert the detected reference signal r, sample signal s1 and sample signal s2 into terahertz frequency domain amplitude spectral signals through fast Fourier transform FFT; Step S42: Use the transmission spectrum calculation formula to calculate the transmittance spectra of the sample signals s1 and s2 respectively, so as to obtain the resonance frequency of the sample; Step S43: Finally, use the sensitivity calculation formula to calculate the sensitivity of the multi-order resonance all-dielectric terahertz metamaterial.

3. The measurement method of the sensing system based on the multi-order resonance all-dielectric terahertz metamaterial according to claim 2, characterized in that: The calculation formula of the transmittance spectrum in step S42 is as follows: Among them, E s (ω) is the terahertz frequency-domain amplitude spectrum of the sample signals s1 and s2, and E r (ω) is the terahertz frequency-domain amplitude spectrum of the reference signal r.

4. The measurement method of the sensing system based on the multi-order resonance all-dielectric terahertz metamaterial according to claim 2, characterized in that: The calculation formula of the sensitivity in step S43 is as follows: where f s1 is the resonant frequency of the sample signal s1, f s2 is the resonant frequency of the sample signal s2, and n is the refractive index of the sample to be measured.

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