A terahertz metasurface sensor
By introducing a graphene layer into a terahertz metasurface sensor and adjusting its Fermi level, the problem of fixed sensing performance of metal metasurfaces was solved, enabling flexible adjustment of sensing performance and high-precision detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- INST OF APPLIED ELECTRONICS CHINA ACAD OF ENG PHYSICS
- Filing Date
- 2025-07-18
- Publication Date
- 2026-06-30
AI Technical Summary
In existing technologies, once the metal-based metasurface structure is fabricated, its sensing performance is fixed and cannot be adjusted by external means, resulting in poor flexibility of the sensor in complex and ever-changing application scenarios.
A terahertz metasurface sensor consisting of a reflective layer, an insulating substrate layer, and a graphene layer is used. The graphene layer is composed of several repeating units. The Fermi level of the graphene is adjusted by chemical doping or by applying an external bias voltage to regulate the sensing performance.
It achieves high-precision interaction between terahertz waves and the analyte, and can flexibly adjust the sensing performance to adapt to different application scenarios, thereby improving the detection accuracy and applicability of the sensor.
Smart Images
Figure CN224436148U_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of sensor technology, and specifically relates to a terahertz metasurface sensor. Background Technology
[0002] Metasurfaces are two-dimensional artificial material structures composed of a series of subwavelength units that can precisely manipulate electromagnetic waves. By cleverly adjusting the unit structure of a metasurface, it is possible to achieve a high degree of response to electromagnetic waves, a capability not found in natural materials. In the field of terahertz matter sensing, metasurfaces can significantly enhance the local electromagnetic field, thereby improving the interaction between the analyte and terahertz waves and compensating for the insufficient electromagnetic response of matter to terahertz waves in free space. However, once a metal-based metasurface structure is fabricated, its performance is permanently fixed and difficult to modulate through external means. Researchers who want to change the sensing performance of the sensor must redesign the structure and re-fabricate it, which significantly increases time and economic costs and severely reduces the application flexibility of the device. Utility Model Content
[0003] To address the shortcomings of existing technologies, a terahertz metasurface sensor is proposed to solve the technical problems of existing metasurface structures being made of metallic materials, resulting in non-tunable sensing performance and inability to adapt to complex and ever-changing application scenarios.
[0004] To achieve the above objectives, this utility model provides the following technical solution:
[0005] A terahertz metasurface sensor comprises, from bottom to top, a reflective layer, an insulating substrate layer, and a graphene layer. The graphene layer includes a plurality of repeating units made of graphene, and the repeating units are arranged in a geometric pattern.
[0006] The technical solution is further configured such that the reflective layer is a metal reflective layer and the insulating substrate layer is a high-resistivity silicon insulating substrate layer.
[0007] The technical solution is further configured such that a number of repeating units are periodically and uniformly distributed on the surface of the insulating substrate layer, and adjacent repeating units are connected by wires.
[0008] The technical solution is further configured such that the repeating unit includes two concentric rings and a cross-shaped strip whose center coincides with the center of the rings. The inner ring is an open ring and the open ring is configured as a centrally symmetrical structure, while the outer ring is a closed ring.
[0009] The technical solution is further configured such that both sides of the cross bar extend to the edge of the repeating unit, and the two sides of the cross bar in adjacent repeating units are connected to each other.
[0010] The technical solution is further configured such that the thickness of the reflective layer is 0.2 μm, the thickness of the insulating substrate layer is 40 μm, the thickness of the graphene layer is 1 nm, the period of the repeating unit is 44 μm, the outer diameter of the inner ring is 15 μm, its inner diameter is 12 μm, and the opening width is 4 μm, the outer diameter of the outer ring is 20 μm, its inner diameter is 18 μm, and the width of each side of the cross bar is 2 μm.
[0011] The technical solution is further configured such that, within the range of 0.2 THz to 2.2 THz, the terahertz metasurface sensor generates two absorption peaks at 0.548 THz and 1.678 THz, respectively.
[0012] The technical solution is further configured such that the Fermi level of the graphene is in the range of 0.3eV-0.9eV.
[0013] The technical solution is further configured such that the substance to be tested is located above the graphene layer, the thickness of the substance to be tested is in the range of 0 µm-20 µm, and its refractive index is in the range of 1.0-2.0.
[0014] The technical solution is further configured such that the incident angle range of the terahertz wave is 0°-70°, and its polarization angle range is 0°-90°.
[0015] The beneficial effects of this utility model are:
[0016] By adding a graphene layer, not only can the interaction between terahertz waves and the analyte be enhanced, thus improving the accuracy of detection, but the sensing performance can also be flexibly adjusted by changing the Fermi level of graphene to adapt to complex and varied application scenarios. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the terahertz metasurface sensor in an embodiment of this utility model;
[0018] Figure 2 This is a top view of the repeating unit in an embodiment of the present invention;
[0019] Figure 3 This is a schematic diagram of the transmission, reflection, and absorption spectra of the present invention when no analyte is added, with a Fermi level of 0.9 eV.
[0020] Figure 4 This is a schematic diagram of the absorption spectrum and terahertz wave propagation at different Fermi levels without the addition of the analyte.
[0021] Figure 5 This is a schematic diagram of the absorption spectrum of this invention at different incident angles without the addition of the analyte.
[0022] Figure 6 To and Figure 5 The corresponding two-dimensional contour diagram;
[0023] Figure 7 This is a schematic diagram of the absorption spectrum of this invention at different polarization angles without the addition of the analyte.
[0024] Figure 8 To and Figure 7 The corresponding two-dimensional contour diagram;
[0025] Figure 9 A schematic diagram of the transmission spectrum obtained when a substance to be tested with a thickness of 0 µm-25 µm is added during the material detection of this utility model.
[0026] Figure 10 To and Figure 9 The corresponding linear fitting curve of frequency versus thickness;
[0027] Figure 11 When performing material detection for this invention, a sample of the analyte with a thickness of 20 µm and a refractive index of 1.0-2.0 is added, and the resulting transmission spectrum is shown in the schematic diagram.
[0028] Figure 12 To and Figure 11 The corresponding linear fitting curve of absorption peak and refractive index;
[0029] Figure 13 To and Figure 11 The corresponding linear fitting curve of frequency and refractive index.
[0030] In the attached diagram: 100, reflective layer; 200, insulating substrate layer; 300, repeating unit; 301, inner ring; 302, outer ring; 303, cross bar; 304, opening. Detailed Implementation
[0031] To enable those skilled in the art to better understand the technical solution of this utility model, the technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application. Furthermore, the directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the creation of this utility model.
[0032] Graphene, a two-dimensional honeycomb structure composed of a single layer of carbon atoms, has attracted much attention since its stable existence was confirmed by the scientific community in 2004 due to its unique electrical, optical, and thermal properties. Furthermore, graphene exhibits unique electrically tunable characteristics; its surface conductivity can be effectively controlled and adjusted through chemical doping or the application of an external bias voltage. This property gives graphene great flexibility and development potential in the field of optoelectronic devices. Introducing two-dimensional materials like graphene into terahertz metasurface sensors allows for flexible adjustment of the Fermi level through chemical doping or the application of an external bias voltage, thereby altering the sensor's sensing performance.
[0033] According to an embodiment of this utility model, a terahertz metasurface sensor is provided. Please refer to [link / reference]. Figures 1 to 2 It includes, from bottom to top, a reflective layer 100, an insulating substrate layer 200, and a graphene layer. The graphene layer includes a plurality of repeating units 300 made of graphene, and the repeating units 300 are arranged in a geometric pattern.
[0034] By incorporating a graphene layer, not only can the interaction between terahertz waves and the analyte be enhanced, thus improving detection accuracy, but the sensing performance can also be flexibly adjusted by changing the Fermi level of graphene to adapt to complex and varied application scenarios. Specifically, terahertz metasurface sensors are used in fields requiring high-precision measurements. Graphene's extremely high conductivity and electron mobility result in very low intrinsic loss and high sensitivity to changes in the external dielectric environment. Therefore, this invention uses graphene to fabricate the repeating unit 300, further improving the sensor's detection accuracy.
[0035] For the terahertz metasurface sensor in this embodiment, please refer to [link / reference]. Figures 1 to 2 The reflective layer 100 is a metal reflective layer, and the insulating substrate layer 200 is a high-resistivity silicon insulating substrate layer.
[0036] The function of the reflective layer 100 is to reflect electromagnetic waves incident on its surface. Its thickness must satisfy the condition that electromagnetic waves cannot penetrate the reflective layer 100, ensuring that the transmittance approaches zero. Specifically, the reflective layer 100 can be a metal reflective layer made of high-conductivity metals such as gold, silver, aluminum, or copper. When electromagnetic waves pass through the insulating substrate layer 200, they undergo a specific phase change. The thickness of the insulating substrate layer 200 must satisfy the condition that the electromagnetic wave produces an absorption peak, and the parameter corresponding to the sharpest absorption peak is the preferred thickness. High-resistivity silicon is a silicon material with high resistivity. Generally, ordinary single-crystal silicon has a wide resistivity range, but high-resistivity silicon specifically refers to silicon materials with resistivity significantly higher than conventional values. Specifically, the insulating substrate layer 200 can be a high-resistivity silicon insulating substrate layer made of low-loss dielectric materials such as polydimethylsiloxane (PDMS), polyimide (PI), silicon dioxide (SiO2), or silicon (Si) to avoid energy dissipation.
[0037] For the terahertz metasurface sensor in this embodiment, please refer to [link / reference]. Figures 1 to 2 Several repeating units 300 are periodically and uniformly distributed on the surface of the insulating substrate layer 200. Adjacent repeating units 300 are connected by wires. This periodic layout and interconnection structure can enhance the sensitivity, resolution and response speed of the terahertz metasurface sensor.
[0038] Furthermore, several repeating units 300 can be distributed in the form of a square lattice, a hexagonal lattice, an array, or a geometric pattern (such as a circle, a triangle, or other polygons).
[0039] Preferably, the repeating units 300 are distributed in a two-dimensional array, which maximizes the use of space within a limited planar area, has a high degree of symmetry, and ensures consistent sensing characteristics at each location. By adjusting the periodicity of the repeating units 300, the spectral characteristics of the electromagnetic wave can be adjusted.
[0040] For the terahertz metasurface sensor in this embodiment, please refer to [link / reference]. Figures 1 to 2 The repeating unit 300 includes two concentric rings and a cross bar 303 whose center coincides with the center of the rings. The inner ring 301 is an open ring and is set as a centrally symmetrical structure, while the outer ring 302 is a closed ring.
[0041] Furthermore, the inner ring 301 is a small-radius ring with an opening 304 on its circumference; the outer ring 302 is a large-radius ring without an opening on its circumference; the center of the inner ring 301 coincides with the center of the outer ring 302, and the center is located at the geometric center of the repeating unit 300.
[0042] It should be noted that by setting an opening 304 on the inner ring 301, the limitations of the traditional closed ring are transformed into advantages of dynamic tuning, multi-frequency operation, and strong field localization. Specifically, in terms of electromagnetic field localization enhancement, a strong electric field concentration region (capacitive effect) is formed at the opening 304, which significantly enhances the oscillation intensity of surface plasmon polaritons (SPPs) on graphene. In terms of multi-frequency resonance, the design of the opening 304 enables the structure to support multiple resonance modes (such as low-frequency magnetic resonance and high-frequency electric resonance), allowing for independent dual-frequency control.
[0043] Furthermore, both sides of the cross bar 303 extend to the edge of the repeating unit 300, and the two sides of the cross bar 303 in adjacent repeating units 300 are connected to each other.
[0044] Specifically, the two sides of the cross strip 303 are the horizontal side and the vertical side, respectively. The horizontal sides of the repeating units 300 in the same row are connected, and the vertical sides of the repeating units 300 in the same column are connected; the opening 304 on the inner ring 301 is located in the area between the horizontal side and the vertical side.
[0045] For the terahertz metasurface sensor in this embodiment, please refer to [link / reference]. Figures 1 to 2 The specific parameters of the inner ring 301, the outer ring 302, and the cross bar 303 together determine the spectral characteristics of the electromagnetic wave, and the optimal parameters are selected based on the characteristics of the absorption peaks.
[0046] Specifically, the reflective layer 100 has a thickness of 0.2 μm, the insulating substrate layer 200 has a thickness of 40 μm, the graphene layer has a thickness of 1 nm, the repeating unit 300 has a period of 44 μm, the inner ring 301 has an outer diameter of 15 μm and an inner diameter of 12 μm, the opening 304 has a width of 4 μm, the outer ring 302 has an outer diameter of 20 μm and an inner diameter of 18 μm, the crossbar 303 has two sides with a width of 2 μm, all repeating units 300 are connected by a metal wire, and the Fermi level of the graphene is adjusted by applying a voltage.
[0047] For the initial resonance characteristics of the terahertz metasurface sensor at a Fermi level of 0.9 eV without the addition of the analyte, please refer to [link to relevant documentation]. Figure 3 .from Figure 3As can be seen, two sharp absorption peaks appear within the observation range of 0.2 THz-2.2 THz, at 0.548 THz and 1.678 THz, respectively, with corresponding absorption rates of 98.75% and 96.76%, indicating that the sensor achieves near-perfect absorption at these two points. For ease of subsequent research, these two frequencies are labeled and distinguished: 0.548 THz is designated as mode A, and 1.678 THz as mode B. Using impedance matching theory to explain the absorption mechanism, in modes A and B, the sensor's equivalent impedance is infinitely close to the impedance of free space, at which point the sensor's absorption performance reaches its optimal level.
[0048] The relationship between the absorption spectra of a terahertz metasurface sensor at different Fermi levels and terahertz wave propagation without the addition of the analyte is described in the following figure. Figure 4 .from Figure 4 As can be seen, as the Fermi level of graphene increases from 0.3 eV to 0.9 eV, the amplitude of the absorption peak also increases accordingly. This is because the change in the Fermi level affects the surrounding dielectric constant, leading to an enhanced resonance intensity and maximizing the absorption of incident terahertz waves entering the sensor. Regarding terahertz wave propagation, when the Fermi level is 0.3 eV, the properties of graphene are similar to those of a semiconductor. At this point, the incident terahertz wave passes through the graphene layer and enters the sensor's interior, resonating with the Fabry-Perot (FP) resonant cavity formed by the overall structure. The portion of the terahertz wave that does not participate in the resonance is reflected back after reaching the lower surface of the reflective layer 100, passing through the graphene layer again and returning to the external space. At this point, the sensor's absorption performance is relatively poor. However, when the Fermi level reaches 0.9 eV, the properties of graphene are similar to those of a metal. Most of the terahertz waves that enter the structure will be reflected back and forth between the graphene layer and the reflective layer 100. After multiple reflections, the terahertz waves will interfere with the incident waves in a specific frequency range, resulting in destructive interference and ultimately achieving perfect absorption in a certain frequency range.
[0049] Without adding the analyte, the terahertz metasurface sensor was tested at different incident angles. For the relationship between the absorption spectrum and the corresponding two-dimensional profile, please refer to [link / reference]. Figure 5 as well as Figure 6 As shown in the figure, when the incident angle increases from 0° to 60°, both Mode A and Mode B maintain an absorption rate of over 90%, demonstrating excellent absorption performance. When the incident angle increases to 70°, the absorption rate of Mode A is slightly lower than that of Mode B, but both still maintain an absorption rate of over 80%, indicating good absorption performance at this point. The contour plot shows that the resonant frequency of Mode A remains essentially unchanged, while the linewidth of the absorption peak gradually narrows, and the curve becomes increasingly sharp. The absorption peak linewidth of Mode B also exhibits a similar trend, but the resonant frequency gradually shifts towards higher frequencies.
[0050] Without the addition of the analyte, the terahertz metasurface sensor is tested at different polarization angles. For the relationship between the absorption spectrum and the corresponding two-dimensional profile, please refer to [link / reference]. Figure 7 as well as Figure 8 As can be seen from the figure, thanks to the sensor's high symmetry, the absorption spectrum curves with polarization angles of 0°-90° completely overlap. No significant shift is also observed in the profile plot.
[0051] When terahertz metasurface sensors are used for analyte detection, the analyte is typically attached to a graphene layer with a thickness ranging from 0 µm to 20 µm. With the Fermi level of graphene fixed at 1 eV and the refractive index of the analyte fixed at 1.4, the relationship between the absorption spectrum and the corresponding linear fitting curve when the thickness t of the analyte increases from 0 µm to 25 µm can be found in the provided text. Figure 9 as well as Figure 10 As shown in the figure, with the increase of the thickness of the analyte, the resonant frequency of the absorption peak exhibits a redshift, and the absorption peak value gradually decreases, tending to saturate at 25 µm. In the linear fitting plot, within the range of 0 µm to 20 µm, both Mode A and Mode B maintain a good linear relationship between the change in the thickness of the analyte and the frequency shift. However, this relationship no longer exists when the thickness of the analyte reaches 25 µm.
[0052] When a terahertz metasurface sensor is used for analyte detection, the analyte thickness is 20 µm, the Fermi level is fixed at 1.0 eV, and the refractive index n of the analyte is set in the range of 1.0–2.0. The resulting absorption spectrum can be found in [reference needed]. Figure 11 .from Figure 11 As can be seen, the absorption curves generally shift towards lower frequencies as the refractive index of the analyte increases. Mode A exhibits a relatively low frequency shift at its resonant frequency, while the absorptivity of the absorption peak remains essentially unchanged, maintaining good absorption performance. Mode B shows a larger frequency shift at its resonant frequency, resulting in greater differences in the absorptivity of the absorption peaks. For the corresponding linear fitting curves of absorption peak value, frequency, and refractive index, please refer to [link to relevant documentation]. Figure 12 as well as Figure 13 .from Figure 12 The absorption curves show that as the refractive index of the analyte gradually increases, the absorption peaks of both Mode A and Mode B decrease, but overall they still satisfy a linear relationship. Figure 13 The resonant frequency curves show that as the refractive index gradually increases, both mode A and mode B shift towards lower frequencies, which is consistent with the sensor's characteristics for sensing and detecting trace substances. The above experiments demonstrate that the terahertz metasurface sensor can achieve the sensing and detection of the analyte through changes in both the resonant frequency and the absorption peak value.
[0053] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of this application should still fall within the scope of the present invention.
Claims
1. A terahertz metasurface sensor, characterized in that, From bottom to top, it includes a reflective layer, an insulating substrate layer, and a graphene layer. The graphene layer includes a plurality of repeating units made of graphene, and the repeating units are arranged in a geometric pattern.
2. The terahertz metasurface sensor of claim 1, wherein, The reflective layer is a metal reflective layer, and the insulating substrate layer is a high-resistivity silicon insulating substrate layer.
3. A terahertz metasurface sensor according to claim 2, characterized in that, Several repeating units are periodically and uniformly distributed on the surface of the insulating substrate, and adjacent repeating units are connected by wires.
4. A terahertz metasurface sensor according to claim 1, characterized in that, The repeating unit includes two concentric rings and a cross-shaped bar whose center coincides with the center of the rings. The inner ring is an open ring with a centrally symmetrical structure, and the outer ring is a closed ring.
5. A terahertz metasurface sensor according to claim 4, characterized in that, Both sides of the crossbar extend to the edge of the repeating unit, and the two sides of the crossbar in adjacent repeating units are connected to each other.
6. A terahertz metasurface sensor according to claim 4, characterized in that, The reflective layer has a thickness of 0.2 μm, the insulating substrate layer has a thickness of 40 μm, the graphene layer has a thickness of 1 nm, the repeating unit has a period of 44 μm, the inner ring has an outer diameter of 15 μm, an inner diameter of 12 μm, and an opening width of 4 μm, the outer ring has an outer diameter of 20 μm, an inner diameter of 18 μm, and the width of each side of the cross-shaped strip is 2 μm.
7. A terahertz metasurface sensor according to claim 1, characterized in that, Within the range of 0.2 THz to 2.2 THz, the terahertz metasurface sensor produced two absorption peaks at 0.548 THz and 1.678 THz, respectively.
8. A terahertz metasurface sensor according to claim 1, characterized in that, The Fermi level of the graphene is in the range of 0.3 eV to 0.9 eV.
9. A terahertz metasurface sensor according to claim 1, characterized in that, The substance to be tested is located above the graphene layer, and the thickness of the substance to be tested ranges from 0 µm to 20 µm, and its refractive index ranges from 1.0 to 2.
0.
10. A terahertz metasurface sensor according to claim 1, characterized in that, Terahertz waves have an incident angle range of 0°-70° and a polarization angle range of 0°-90°.