Quasi-continuous domain bound state refractive index sensor based on 3D printing

Abstract

The utility model discloses a quasi-continuous domain bound state refractive index sensor based on 3D (three-dimensional) printing, which structurally comprises two layers, the lower layer is an organic silicon polyester resin structure, and the upper layer is a copper surface. The sensor is configured by adopting an asymmetric cylindrical tetramer structure, and is manufactured by combining 3D printing and magnetron sputtering technologies. Structural symmetry is broken by utilizing different radiuses of diagonal columns in four cylinders in a unit structure, a leakage path is introduced, and a continuous domain bound state is converted into a quasi-continuous domain bound state (quasi-BIC), so that ultra-narrow-band resonance characteristics and a Q value up to 2489 are obtained. Meanwhile, the sensor shows extremely high refractive index sensitivity of 532 GHz / RIU, and the performance of the sensor exceeds that of a traditional terahertz metal metasurface. According to the preparation process, the complex process of the traditional photoetching technology is simplified, the production cost is greatly reduced, and an efficient, economical and practical solution is provided for ultra-sensitive terahertz frequency sensing.

Description

Technical Field

[0001] This invention proposes a quasi-continuous domain bound state refractive index sensor based on 3D printing, belonging to the field of optical sensing technology. Background Technology

[0002] The terahertz band, situated between the microwave and infrared spectra, exhibits immense potential in materials detection and electromagnetic imaging due to its excellent penetrating power, low photon energy, and unique spectral fingerprint characteristics. Electromagnetic metamaterials, artificial structures designed to efficiently manipulate terahertz waves, possess superior properties unattainable by natural materials, paving the way for innovative applications such as metallic lenses, stealth technology, and sensing.

[0003] In sensor technology, the quality factor (Q factor) is a crucial parameter for evaluating the resonant properties of metamaterials, directly impacting the sensor's resolution and sensitivity. Although techniques such as electromagnetically induced transparency (EIT) and perfect absorption have been developed to improve the Q factor, the Q factor of traditional metamaterials typically remains around 10. 2 Magnitude.

[0004] Metamaterials based on continuous-domain bound states (BICs) have attracted widespread attention due to their ultra-high Q-factor and extremely narrow spectral bandwidth resonance properties. However, because photons are completely bound, continuous-domain bound states are difficult to directly apply to the electromagnetic spectrum. In recent years, by introducing leakage channels, researchers have transformed continuous-domain bound states into quasi-continuous-domain bound states (quasi-BICs), achieving observable ultra-high Q-factor resonances with Q factors reaching 10⁻⁶. 3 BIC-induced metamaterials can be classified into metallic and all-dielectric types based on their structure, but their traditional manufacturing processes usually rely on micro-nano fabrication technologies such as photolithography, resulting in complex and costly production, which has become a major obstacle to their widespread application.

[0005] In contrast, 3D printing, as an additive manufacturing technology, offers a simplified and efficient alternative for the fabrication of metamaterials. By layering bonding materials, 3D printing can directly transform a three-dimensional digital model into a final product, applicable to a variety of materials such as metals, resins, and ceramics. Although 3D printing has been widely used in microwave and radio frequency bands, its fabrication of micron-level features in the terahertz band is still in the exploratory stage. Summary of the Invention

[0006] In view of this, in order to solve the above-mentioned problems in the prior art, this utility model proposes a quasi-continuous domain bound state refractive index sensor based on 3D printing.

[0007] This invention proposes a 3D-printed quasi-continuous domain bound state refractive index sensor, characterized in that: the sensor has a periodically arranged structure, and its material is divided into upper and lower layers, with the upper layer being organosilicon polyester resin and the lower layer being metallic copper; each period contains four cylinders, all of which have identical structural parameters. By changing the radii of the two diagonal cylinders, structural asymmetry is created, thereby achieving a resonance peak based on the quasi-continuous domain bound state; when the sample to be tested is covered on the sensor, the refractive index of the sample is linearly related to the absorption resonance peak frequency of the sensor, thus enabling the determination of the sample's refractive index.

[0008] This invention discloses a quasi-continuous domain bound-state refractive index sensor based on 3D printing. The sensor is a periodic metamaterial structure with a period of Px = Py = 500 μm in the x and y directions. Each sensor unit consists of a square base and an asymmetric cylindrical tetramer on top. The radii of the diagonally arranged cylinders are R1 = 60 μm and R2 = 65 μm, respectively. The height of each cylinder is H1 = 100 μm, and the thickness of the square base is H2 = 150 μm. The thicknesses of the silicone polyester resin are 90 μm and 140 μm, respectively, while the thickness of the copper surface is 10 μm. The dielectric constant of the silicone polyester resin is 2.9 + 0.078i, and the conductivity of the copper is 5.96 × 10⁻⁶. 7 S / m.

[0009] The present invention relates to a quasi-continuous domain bound state refractive index sensor based on 3D printing, characterized in that: the sensor operates in the wavelength range of 0.6THz to 1.0THz, the incident beam is a terahertz wave, and it is incident perpendicularly.

[0010] The present invention discloses a quasi-continuous domain bound state refractive index sensor based on 3D printing, characterized in that: the refractive index n measured by the sensor is in the range of 1 to 1.5, and the refractive index sensitivity of the sensor reaches 532 GHz / RIU.

[0011] One objective of this invention is to disrupt structural symmetry to achieve a quasi-continuous domain bound-state refractive index sensor based on 3D printing. Specifically, the following technical solution is adopted:

[0012] For each sensor unit, the cylindrical tetramer structure parameter R1 was kept at 60 μm. Considering the difficulty of fabrication and parameter tolerance, another parameter, R2, was varied from 65 μm to 67 μm, an increment of 1 μm. With the increase of asymmetry, the linewidth of the absorption peak significantly broadened, and the resonant frequency also showed a slight redshift. At the same time, the absorption at the peak value decreased significantly, indicating that due to symmetry destruction, the mode transitioned from a symmetry-protected continuous domain bound state to a quasi-continuous domain bound state. When R2 equals 65, the Q value reached its maximum of 2489 when fitted using the Fano formula.

[0013] Specific production methods and steps:

[0014] The present invention describes a quasi-continuous domain bound-state refractive index sensor fabrication method based on 3D printing, which combines 3D printing and magnetron sputtering technologies. The specific steps are as follows:

[0015] Layering: The designed refractive index sensor unit structure model was exported as an STL file using the software CST Studio Suite, and then layered, with the thickness of each layer set to 10 μm.

[0016] 3D Printing Substrate: A silicon wafer is used as the support, and the printing material is a UV-sensitive, high-temperature resistant silicone polyester resin. A 140 μm thick square silicone polyester resin substrate is printed on the silicon substrate using a high-precision nanoscale 3D printer (such as the BMF nanoArch S140, which can achieve a printing accuracy of 10 μm). Using two-photon polymerization (TPP) technology, the 3D structure is formed layer by layer in the liquid photosensitive silicone polyester resin through UV light polymerization. After printing, residual silicone polyester resin is cleaned with isopropanol solution and cured under UV light to improve structural stability.

[0017] Metallization: First, a 10 nm thick chromium adhesion layer is applied to improve the adhesion between the metal layer and the silicone polyester resin, preventing peeling during subsequent use. Then, a 10 μm thick copper layer is uniformly deposited on the printed dielectric pillar and substrate using magnetron sputtering. The coating thickness is greater than the skin depth of the terahertz wave to ensure high conductivity.

[0018] Refractive index sensitivity test: The test material of different thicknesses (refractive index range of 1.0-1.5) is coated on the sensor surface, and the refractive index sensitivity S = 532 GHz / RIU is calculated by measuring the frequency shift of the resonance frequency.

[0019] The beneficial effects of this utility model are as follows:

[0020] The unit structure of this invention is arranged periodically. When a light beam is incident on the sensor, it will cause the ring dipole to resonate, forming a distinct peak. When in different refractive index environments, the absorption resonance peak will drift, thereby realizing refractive index sensing.

[0021] The sensor proposed in this utility model is a novel structural design that is simple in structure, easy to process, and easy to reuse.

[0022] The sensor proposed in this invention can achieve high-quality sensing in the frequency range of 0.6THz to 1.0THz, with high sensitivity, which is beneficial for its application in the detection of various types of samples, and will not damage the samples during use.

[0023] The sensor proposed in this invention is made of metallic copper and organosilicon polyester resin. By combining 3D printing with magnetron sputtering, this invention significantly reduces the complexity and cost of traditional micro-nano manufacturing technologies (such as photolithography) while achieving high-precision manufacturing of submicron-level structures.

[0024] The sensor proposed in this invention can be used as an on-chip sensor and does not require optical fiber connection with the light source and detector, which greatly increases its application range. Attached Figure Description

[0025] The sensor proposed in this invention can be used as an on-chip sensor and does not require optical fiber connection with the light source and detector, which greatly increases its application range.

[0026] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0027] Figure 2 This is a three-dimensional diagram of the unit structure of this utility model.

[0028] Figure 3 This is the absorption spectrum of this invention when the structural parameters change.

[0029] Figure 4 This is the absorption spectrum of the sensor of this invention when a terahertz wave is incident perpendicularly.

[0030] Figure 5 This is a linear fitting diagram of refractive index and frequency shift when the sample size is 300 μm. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0032] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Reference Figure 1The sensor has a periodic arrangement of materials, consisting of two layers: an upper layer of silicone polyester resin and a lower layer of copper. Each unit is tightly packed. The entire sensor array has at least six rows and six columns to ensure sufficient detection sensitivity and performance.

[0034] Reference Figure 2 The sensor's unit structure has a period of Px = Py = 500 μm in the x and y directions. Each sensor unit consists of a square base and an asymmetrical cylindrical tetramer on top. The radii of the diagonally arranged cylinders are R1 = 60 μm and R2 = 65 μm, respectively. The height of each cylinder is H1 = 100 μm, and the thickness of the square base is H2 = 150 μm. The thicknesses of the silicone polyester resin are 90 μm and 140 μm, respectively, while the thickness of the copper surface is 10 μm. The dielectric constant of the silicone polyester resin is 2.9 + 0.078i, and the conductivity of copper is 5.96 × 10⁻⁶. 7 S / m.

[0035] refer to Figure 3 For each sensor unit, the cylindrical tetramer structure parameter R1 was kept at 60 μm. Another parameter, R2, was varied from 65 µm to 67 µm in increments of 1 µm. With increasing R2, the linewidth of the absorption peak broadened significantly, and the resonance frequency also showed a slight redshift. Simultaneously, the absorption at the peak value decreased significantly, indicating a shift from a symmetry-protected continuous-domain bound state mode to a quasi-continuous-domain bound state mode due to symmetry disruption. The resonance peak was sharpest when R2 was 65 µm.

[0036] Reference Figure 4 The absorption spectrum was obtained when the incident terahertz wave was perpendicularly incident, with cylinder radii R1 of 60 µm and R2 of 65 µm. This simulation result was calculated using CST electromagnetic simulation software. The figure shows that when no material is attached to the surface of the metamaterial sensor, the resonant frequency is 0.83 THz and the absorption peak is 0.87 THz. Q is the quality factor; fitting the absorption peak using the Fano equation yields a Q value of 2489.

[0037] refer to Figure 5The sensor was used to measure the resonant frequency shift under different refractive indices when the analyte thickness was 300 µm. The resonant frequency shift at each point was calculated as the refractive index of the analyte increased from 1.0 to 1.5 in increments of 0.1. The dashed line represents the linear fitting result of the data, showing a good linear relationship between the resonant frequency of the metamaterial and the refractive index of the analyte. The sensor's sensing performance was characterized by refractive index sensitivity (S), which represents the change in resonant peak frequency per unit refractive index. Its value is S = Δf / Δn, with units of GHz / RIU, where Δf is the frequency change, Δn is the refractive index change, and RIU is the Refractive Index Unit. According to the linear fitting formula y = 532x - 520.2, the refractive index sensitivity of the sensor is 532 GHz / RIU.

[0038] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A quasi-continuous domain bound state refractive index sensor based on 3D printing, characterized by The structure of the sensor is periodic arrangement, and the material is divided into two layers, the upper layer is organic silicone polyester resin, and the lower layer is copper; four cylinders in each period, wherein the four cylinder structure parameters are same, the structural asymmetry is formed by changing the diagonal line of two cylinder radii, the resonance peak based on quasi-continuous domain bound state is realized; when the sample to be measured is covered on the sensor, the refractive index of the sample and the absorption resonance peak frequency of the sensor are linearly related, so that the refractive index of the sample is determined.

2. A quasi-continuous domain bound state refractive index sensor based on 3D printing according to claim 1, characterized in that : The sensor is a periodic metamaterial structure, the period in x and y direction is Px=Py=500μm, each sensor unit is composed of a square base and an asymmetric cylindrical tetramer on top, the radii of the cylinders arranged along the diagonal are R1=60μm and R2=65μm respectively, the height of each cylinder is H1=100μm, the thickness of the square base is H2=150μm, the thickness of the organic silicone polyester resin is 90μm and 140μm respectively, and the thickness of the copper surface is 10μm; the dielectric constant of the organic silicone polyester resin is 2.9+0.078i, and the conductivity of copper is 5.96×10 7 S / m.

3. The quasi-continuous domain bound state refractive index sensor based on 3D printing according to claim 1, characterized in that: The working wavelength range of the sensor is 0.6THz-1.0THz, the incident light beam is a terahertz wave, and the incident is perpendicular.

4. The quasi-continuous domain bound state refractive index sensor based on 3D printing of claim 1, wherein: The refractive index n measured by the sensor ranges from 1 to 1.5, and the refractive index sensitivity of the sensor reaches 532 GHz / RIU.

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