Liquid detection sensor chip based on dual-band electromagnetically induced transparency effect

Abstract

The present invention discloses a liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect. The sensor chip includes a metal layer and a base layer. The metal layer comprises a unit structure array composed of an external metal square open resonator and an internal double circular open ring dimer resonator, the unit structure array being arranged in a square periodic pattern. The base layer is used to house the metal square open resonator and the double circular open ring dimer resonator of the metal layer. When a terahertz wave is vertically irradiated onto the sensor chip, the two bright modes excited by the metal structure couple with each other, generating destructive interference and achieving a dual-band wide-window and narrow-window electromagnetically induced transparency effect. The present invention has a simple structure, is easy to process, and has high sensitivity. It has broad application prospects in liquid detection, qualitative drug detection, and early screening of cancer cells.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor devices, and in particular to a liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect. Background Art

[0002] Electromagnetically induced transparency (EIT) is a physical effect in quantum systems. Due to external conditions, a narrow transparent window can be obtained in a wider opaque spectrum. In recent years, it has been a hot topic of research in the field of quantum optics. Due to the generation of a narrow transparent window, the dispersion properties around it also change significantly, which has the effect of reducing the speed of light. The EIT effect usually occurs in three-level atomic systems and can theoretically be explained by destructive quantum interference between different transition pathways. However, the physical conditions for realizing the EIT effect in quantum systems are extremely harsh, often requiring ultra-low temperature and high-intensity pump light sources. Therefore, the application and research of the EIT effect in practical engineering are greatly limited.

[0003] Metamaterials, composed of subwavelength structural units, can effectively manipulate the amplitude, phase, and polarization of electromagnetic waves, achieving novel optical effects such as negative refraction, ideal lenses, and electromagnetic invisibility. In recent years, with the rapid development of metamaterial technology, researchers have also discovered electromagnetically induced transparency (EIT-like) effects in artificial metamaterial structures. Typically, the EIT-like effect is generated by generating either bright or dark modes from the various components of the metamaterial structure, which are then coupled to each other in the near field. Bright modes can be directly excited by incident waves and exhibit high radiation loss, a wide resonant bandwidth, and a low Q value. Dark modes, however, cannot directly couple with incident waves and are excited by coupling the near-field energy of bright modes. They exhibit low radiation loss, a narrow resonant bandwidth, and a high Q value. A distinct EIT-like window can be observed through near-field interference between the two modes. EIT-like metamaterials have properties such as slow light effect, strong nonlinearity and strong dispersion, which have attracted much attention in many application fields, including sensors, slow light devices, modulation, quantum information storage, absorbers and filters.

[0004] Liquid detection sensor chips based on dual-band electromagnetically induced transparency effects usually use EIT-like resonance characteristics and sensitivity to changes in surrounding materials to detect the movement of the resonance point caused by changes in the refractive index of the liquid.

[0005] Currently, there is little research on refractive index sensors for dual-band applications, both domestically and internationally. Furthermore, the low sensitivity of liquid detection significantly limits the application of terahertz sensors. The design of sensor chips with multi-band applications and high detection sensitivity has attracted significant attention from researchers. Summary of the Invention

[0006] The object of the present invention is to provide a liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect that has a simple structure, is easy to process, has multiple bands, a high Q value, and high sensitivity.

[0007] The technical solution for achieving the purpose of the present invention is: a liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect, comprising a metal layer and a substrate layer;

[0008] The metal layer is a unit structure array composed of an outer metal square open resonator and an inner double circular open ring dimer resonator, and the unit structure array is arranged in a square period;

[0009] The base layer is used for placing the metal square open resonator and the double circular open ring dimer resonator of the metal layer.

[0010] As a specific example, the metal square split resonator and the double circular split ring dimer resonator of the metal layer are both made of 2 μm thick aluminum, and their optical constants are described by the Drude model, where the plasma frequency w p =2.24x10 16 rad / s, damping constant γ=1.22x10 14 rad / s.

[0011] As a specific example, the base layer is made of a 20 μm thick polymer material polyimide film with a dielectric constant of 3.45.

[0012] As a specific example, the cross-section of each sensor unit structure of the metal layer is a square with a side length of 90 μm.

[0013] As a specific example, the outer metal square open resonator has an inner length of 50 μm, a width of 2 μm, and an opening spacing of 30 μm.

[0014] As a specific example, the internal double circular open ring dimer resonator includes two open rings placed back to back, each with an outer diameter of 20 μm and a width of 2 μm. The opening interval of the upper semicircular ring is 2 μm, and the arc of the lower semicircular ring is 160°.

[0015] As a specific example, the longitudinal and lateral coupling distances between the outer metal square split resonator and the inner double circular split ring dimer resonator are 3 μm and 5 μm, respectively.

[0016] As a specific example, the outer metal square open resonator and the inner double circular open ring dimer resonator of the metal layer are prepared by electron beam lithography and reactive ion etching technology.

[0017] As a specific example, under vertical irradiation of terahertz waves, the external metal square open resonator and the internal double circular open ring dimer resonator respectively provide two "bright" modes, namely the electric dipole mode and the electric quadrupole mode. When the two resonators are inlaid together, the two adjacent pairs of resonances will couple with each other, resulting in destructive interference. The two electric dipole resonances are coupled to produce broadband EIT, and the two electric quadrupoles are coupled to produce narrowband EIT, realizing two EIT-like windows. The frequencies of the two transparent peaks are 0.67 THz and 1.77 THz, respectively. The transparent window of broadband EIT is 2.5 times that of narrowband EIT.

[0018] As a specific example, the unit structure array is periodically arranged along the x and y directions, and the electromagnetic wave is incident on the unit structure array along the z axis, and the polarization direction of the incident electric field is in the x-axis direction.

[0019] Compared with the prior art, the significant advantages of the present invention are: (1) the external metal square open resonator and the internal double circular open ring dimer resonator provide two "bright" modes, namely the electric dipole mode and the electric quadrupole mode respectively. When the two resonators are embedded together, the two adjacent pairs of resonances will couple with each other, resulting in destructive interference. The two electric dipole resonant coupling produces broadband EIT, and the two electric quadrupole coupling produces narrowband EIT, realizing two EIT-like windows, obtaining electromagnetic field enhancement and high Q value resonant modes, and reducing energy loss; (2) by adjusting the structural parameters such as the opening distance and width of the external metal square open resonator and the internal double circular open ring dimer resonator, the two EIT-like effects are modulated, thereby detecting targets with different characteristic line spectrum widths; (3) the narrow window EIT-like has better sensing performance than the wide window EIT-like, and a higher sensing sensitivity characteristic is obtained in both bands; (4) the structure is simple, easy to prepare, and has high sensitivity, which provides broad prospects for applications in liquid detection, drug qualitative detection, and early screening of cancer cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a three-dimensional view of the unit structure in a liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect according to the present invention.

[0021] Figure 2 It is a front view of the unit structure in the present invention.

[0022] Figure 3 Graph showing the transmission spectrum of the external metal square split resonator, the internal double circular split ring dimer resonator, and the double-window EIT in an embodiment of the present invention.

[0023] Figure 4 Graph showing the electric field and current distribution in an embodiment of the present invention.

[0024] Figure 5 This is a diagram showing the influence of the main structural parameters on the EIT effect in an embodiment of the present invention.

[0025] Figure 6 Graphs showing the transmission spectra of the liquids to be tested with refractive indices of 1, 1.2, 1.4, 1.6, and 1.8 in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Combine Figure 1 、 Figure 2 , the present invention provides a liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect, comprising a metal layer 1 and a substrate layer 2;

[0028] The metal layer 1 is a unit structure array composed of an outer metal square open resonator and an inner double circular open ring dimer resonator, and the unit structure array is arranged in a square period;

[0029] The base layer 2 is used to place the metal square open resonator and the double circular open ring dimer resonator of the metal layer 1 .

[0030] Furthermore, the metal square open resonator and the double circular open ring dimer resonator of the metal layer 1 are both made of 2 μm thick aluminum, and their optical constants are described by the Drude model, where the plasma frequency w p =2.24x10 16 rad / s, damping constant γ=1.22x10 14 rad / s.

[0031] Furthermore, the base layer 2 is made of a 20 μm thick polymer material polyimide film with a dielectric constant of 3.45.

[0032] Furthermore, the cross-section of each sensor unit structure of the metal layer 1 is a square with a side length of 90 μm.

[0033] Furthermore, the outer metal square open resonator has an inner length of 50 μm, a width of 2 μm, and an opening spacing of 30 μm.

[0034] Furthermore, the internal double circular open ring dimer resonator includes two open rings placed back to back, each ring has an outer diameter of 20 μm and a width of 2 μm, the opening interval of the upper semicircular ring is 2 μm, and the arc of the lower semicircular ring is 160°.

[0035] Furthermore, the longitudinal and lateral coupling distances between the outer metal square split resonator and the inner double circular split ring dimer resonator are 3 μm and 5 μm respectively.

[0036] Furthermore, the metal square open resonator on the outside and the double circular open ring dimer resonator on the inside of the metal layer 1 are prepared by electron beam lithography and reactive ion etching.

[0037] Furthermore, under vertical irradiation of terahertz waves, the external metal square open resonator and the internal double circular open ring dimer resonator respectively provide two "bright" modes, namely the electric dipole mode and the electric quadrupole mode. When the two resonators are inlaid together, the two adjacent pairs of resonances will couple with each other, resulting in destructive interference. The two electric dipole resonances are coupled to produce broadband EIT, and the two electric quadrupoles are coupled to produce narrowband EIT, realizing two EIT-like windows. The frequencies of the two transparent peaks are 0.67 THz and 1.77 THz, respectively. The transparent window of broadband EIT is 2.5 times that of narrowband EIT.

[0038] Furthermore, the unit structure array is periodically arranged along the x and y directions, and the electromagnetic wave is incident on the unit structure array along the z axis, and the polarization direction of the incident electric field is in the x-axis direction.

[0039] Example 1

[0040] Combine Figure 1 , which is a schematic diagram of the unit structure of a liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect in this embodiment, a metal layer 1 and a base layer 2, wherein the metal layer 1 includes an external metal square open resonator and an internal double circular open ring dimer resonator.

[0041] Combine Figure 2 An electromagnetic wave is incident on the metamaterial along the z-axis, with the polarization of the incident electric field along the x-axis. Periodic boundary conditions are set in the x- and y-axis directions, and a perfectly matched layer is placed along the z-axis to simulate infinite space. The metamaterial is fabricated using electron beam lithography and reactive ion etching.

[0042] The metal layer 1 is made of aluminum and has a thickness of 2 μm.

[0043] The dielectric layer 2 is made of a polymer material, polyimide film, with a thickness of 20 μm.

[0044] The inner length of the outer metal square open resonator is L1 = 50 μm, the width is W = 2 μm, and the opening spacing is g1 = 30 μm.

[0045] The inner double circular split ring dimer resonator ring outer diameter R O =20μm, width W=2μm, opening moment g2=2μm, the curvature of the lower semicircular ring (lower arm) θ=160°, the longitudinal and lateral coupling distances O1 and O2 of the external metal square open resonator and the internal double circular open ring dimer resonator are 3μm and 5μm respectively.

[0046] Figure 3 (a)-(c) show the transmittance spectra calculated for the external metal square split resonator, the internal double circular split ring dimer resonator and the EIT metamaterial under normal incidence. Figure 3 As can be seen in (a), in the frequency domain of 0.1THz-2.3THz, there are two obvious transmission valleys (i.e., resonances R1 and R2) in the transmission spectrum of the external metal square open resonator metamaterial. Resonance R1 is around 0.64THz, while resonance R2 is around 1.74THz. This pair of resonance modes can be regarded as clear modes. Similarly, the internal double circular open ring dimer resonator metamaterial can also directly obtain a pair of sharper resonance responses, such as Figure 3 In (b), the dual resonances (i.e., R3 and R4) are near 1.03THz and 1.87THz respectively, and the pair of resonances responded by the internal double circular open ring dimer resonator structure can also be regarded as clear modes. Therefore, both the external metal square open resonator and the internal double circular open ring dimer resonator can directly couple the incident energy to excite two pairs of metal plasma resonances, creating conditions for the EIT effect formed by clear mode-clear mode coupling. When the two structures are placed in the same structural unit, the two pairs of clear modes excited at the same time will undergo strong near-field coupling. The resonance R1 of the external metal square open resonator and the resonance R3 of the internal double circular open ring dimer resonator form a broadband EIT-like window through near-field interference, while the resonance R2 of the external metal square open resonator and the resonance R4 of the internal double circular open ring dimer resonator generate a narrowband EIT-like window. As a result, broadband EIT and narrowband EIT appear simultaneously in the frequency domain of 0.1-2.3THz, as shown in Figure 2. Figure 3In (c), the positions of the four transmission valleys are at 0.58 THz, 1.04 THz, 1.74 THz and 1.93 THz, and the frequencies of the two transparent peaks are 0.67 THz and 1.77 THz, respectively. The transparent window of broadband EIT is about 2.5 times that of narrowband EIT.

[0047] Figure 4 Electric field and current distribution, including the electric field (Ez) and surface current distribution (indicated by black arrows) of the external metal square open resonator structure (a) R1 and (b) R2; the electric field (Ez) and surface current distribution (indicated by black arrows) of the internal double circular open ring dimer resonator structure (c) R3 and (d) R4; the electric field distribution (Ez) and surface current distribution (indicated by red arrows) of the four resonance valleys (e) to (h) of the EIT with a double EIT structure. Figure 4 (a) shows that the positive induced charge and negative induced charge are distributed on the left and right sides of the external metal square opening resonator, and the current flows from the left to the right, so it can be judged that R1 is an electric dipole resonance. For the resonant R2, as Figure 4 In (b), there are four electric field energy hot spots, which are represented by two pairs of positive and negative induced charges. They can be regarded as consisting of two electric dipoles with opposite polarities, so they can be considered as an electric quadrupole. Similarly, R3 is an electric dipole and R4 is an electric quadrupole. These resonances all have the behavioral characteristics of the LC resonance mode. Figure 4 Figures (c) to (h) show the electric field distribution Ez and surface current distribution (indicated by red arrows) in the four resonance valleys of the dual EIT. It can be observed that at the two resonance valley frequencies of the broadband EIT, the electric field distribution and surface current directions on the outer metal square split resonator are exactly opposite, suggesting a strong mutual coupling effect between the two electric dipole clear mode resonances, resulting in a transparent window. Interestingly, the electric field and surface current distributions at the two resonance valley frequencies of the narrowband EIT exhibit opposite behavior on the inner double circular split ring dimer resonator, indicating that the electric quadrupoles on the outer metal square split resonator and the inner double circular split ring dimer resonator undergo coherent cancellation, further revealing the generation principle of the dual window EIT effect.

[0048] Figure 5 is the influence of main structural parameters on EIT effect, Figure 5(a) is g1, (b) is g2, (c) is W, and (d) is θ. When g1 increases from 20μm to 40μm, dip1, dip2, and dip3 simultaneously blueshift, while having little effect on the high-frequency valley dip4. Changing g2, on the other hand, primarily affects dip2, with minimal impact on the other three resonance valleys. Increasing W from 1μm to 4μm causes dip1 and dip3 to redshift, while dip2 and dip4 to blueshift, simultaneously expanding both EIT windows. By reducing θ, the high-frequency narrowband EIT window is significantly enlarged, while the low-frequency broadband EIT window is minimally affected.

[0049] Figure 6 It shows the changes in the EIT-like transmission spectrum when the test liquids with refractive indices of 1, 1.2, 1.4, 1.6, and 1.8 are immersed around the structure. It can be seen that as long as the refractive index changes slightly, the resonant mode position of the EIT-like window can be significantly moved. As the refractive index of the test liquid increases, the four resonance valleys of EIT-like are red-shifted. The average sensitivity S of wide-window and narrow-window EIT-like are 150 GHz / RIU and 237.5 GHz / RIU, respectively, and the quality factor FOM values ​​are 7.92 and 1.67, respectively. The metamaterial sensor chip of the present invention has a simple structure, is easy to process, and has high sensitivity, providing broad prospects for applications in liquid detection, qualitative detection of drugs, and early screening of cancer cells.

[0050] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A liquid detection sensor chip based on a dual-band electromagnetically induced transparency effect, characterized in that: It comprises a metal layer (1) and a base layer (2); The metal layer (1) is a unit structure array composed of an outer metal square open resonator and an inner double circular open ring dimer resonator, and the unit structure array is arranged in a square period; The base layer (2) is used to place the metal square open resonator and the double circular open ring dimer resonator of the metal layer (1); The outer metal square open resonator has an inner length of 50 μm, a width of 2 μm, and an opening spacing of 30 μm; The internal double circular split ring dimer resonator comprises two split rings placed back to back, each with an outer diameter of 20 μm and a width of 2 μm. The spacing between the openings of the upper semicircular ring is 2 μm, and the arc of the lower semicircular ring is 160°. The longitudinal and lateral coupling distances between the outer metal square split resonator and the inner double circular split ring dimer resonator are 3 μm and 5 μm respectively; Under vertical terahertz wave irradiation, the external metal square open resonator and the internal double circular open ring dimer resonator provide two "bright" modes, namely the electric dipole mode and the electric quadrupole mode, respectively. When the two resonators are inlaid together, the two adjacent pairs of resonances will couple with each other, resulting in destructive interference. The two electric dipole resonances couple to produce broadband EIT, and the two electric quadrupoles couple to produce narrowband EIT, realizing two EIT-like windows. The frequencies of the two transparency peaks are 0.67THz and 1.77THz, respectively. The transparency window of broadband EIT is 2.5 times that of narrowband EIT.

2. The liquid detection sensor chip based on dual-band electromagnetically induced transparency effect according to claim 1, characterized in that: The metal square split resonator and the double circular split ring dimer resonator of the metal layer (1) are both made of 2 μm thick aluminum, and the optical constants are described by the Drude model, where the plasma frequency w p =2.24×10 16 rad / s, damping constant γ =1.22×10 14 rad / s.

3. The liquid detection sensor chip based on dual-band electromagnetically induced transparency effect according to claim 1, characterized in that: The base layer (2) is made of a 20 μm thick polymer material polyimide film with a dielectric constant of 3.

45.

4. The liquid detection sensor chip based on dual-band electromagnetically induced transparency effect according to claim 1, characterized in that: The cross-section of each unit structure array of the metal layer (1) is a square with a side length of 90 μm.

5. The liquid detection sensor chip based on dual-band electromagnetically induced transparency effect according to claim 1, characterized in that: The metal square open resonator outside the metal layer (1) and the double circular open ring dimer resonator inside are prepared by electron beam lithography and reactive ion etching technology.

6. The liquid detection sensor chip based on dual-band electromagnetically induced transparency effect according to claim 1, characterized in that: The unit structure array is periodically arranged along the x and y directions. When the electromagnetic wave is incident on the unit structure array along the z axis, the polarization direction of the incident electric field is in the x axis direction.

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