An ARF-SPR long-distance liquid detection sensor with an extremely simple structure

Abstract

The present invention relates to a liquid detection sensor, specifically to an ARF-SPR long-distance liquid detection sensor with a minimalist structure. The ARF-SPR long-distance liquid detection sensor is an anti-resonant optical fiber. Inside the outer large glass tube of the anti-resonant optical fiber, 6 groups of connected anti-resonant tubes are inscribed. The connected anti-resonant tubes are composed of a connected large anti-resonant tube and a small anti-resonant tube, and the 6 groups of connected anti-resonant tubes are arranged in a regular hexagon; the outer surface of the outer large glass tube is coated with a cycloolefin copolymer; the large anti-resonant tube in the positive half-axis direction of the X-axis in the connected anti-resonant tube is filled with dielectric gold, and the remaining large anti-resonant tubes with negative curvature and small anti-resonant tubes are all filled with air; the materials of the outer large glass tube, the large anti-resonant tube and the small anti-resonant tube are silicon dioxide. It not only has low loss, but also has a long detection distance.

Description

Technical Field:

[0001] The present invention relates to a liquid detection sensor, and more particularly to an ARF-SPR long-distance liquid detection sensor with an extremely simple structure. Background Art:

[0002] With the continuous development of fiber optic sensing technology, optical sensors have gradually become intelligent, systematic, and miniaturized. Surface Plasmon Resonance (SPR) technology is a sensing technology that has emerged in recent years. When a light beam with a certain frequency is incident on a metal, it will couple with the surface plasmon wave (SPW) on its surface, causing the photons and the free electrons on the metal surface to oscillate collectively. Since the wavelength corresponding to the occurrence of SPR will move regularly with the change of the refractive index of the analyte, this technology can be used for liquid refractive index detection and has great application value in the fields of biochemistry detection, oil well logging, geological exploration, etc.

[0003] Anti-resonant fiber (ARF) has a different structure from the well-known single-mode fiber, photonic crystal fiber, etc. It is composed of negatively curved anti-resonant tubes with different sizes and thicknesses stacked together, and its structure is relatively simpler and easier to produce compared to photonic crystal fiber. In recent years, anti-resonant fiber and its production method have achieved extremely remarkable results. The new type of SPR sensor based on anti-resonant fiber has attracted extensive attention in the field of fiber optic sensing due to its simple structure design, high sensitivity, small volume, low loss, long detection distance, etc., and has great potential application value, becoming a new research hotspot in the field of fiber optic sensing. However, it should be noted that currently, there are still a large number of SPR sensors based on photonic crystal fiber, and most of their structures have disadvantages such as complex manufacturing process, large loss, short detection distance, and difficult metal coating. Summary of the Invention:

[0004] The present invention makes up for and improves the deficiencies of the above-mentioned prior art, and provides an ARF-SPR liquid sensor with an extremely simple structure, which not only has low loss but also has a relatively long detection distance.

[0005] The technical solution adopted by the present invention is as follows: An ARF-SPR long-distance liquid detection sensor with an extremely simple structure (ARF-SPR is the abbreviation of anti-resonant fiber surface plasmon resonance). The ARF-SPR long-distance liquid detection sensor is an anti-resonant fiber. Six groups of conjoined anti-resonant tubes are inscribed in the outer large glass tube of the anti-resonant fiber. The conjoined anti-resonant tubes are composed of a conjoined large anti-resonant tube and a small anti-resonant tube. The six groups of conjoined anti-resonant tubes are arranged in a regular hexagon; The outer surface of the outer large glass tube is coated with cycloolefin copolymer; The large anti-resonant tube in the positive half-axis direction of the X-axis in the conjoined anti-resonant tube is filled with dielectric gold, and the remaining negatively curved large anti-resonant tubes and small anti-resonant tubes are filled with air; The materials of the outer large glass tube, the large anti-resonant tube and the small anti-resonant tube are silicon dioxide.

[0006] Further, the large anti-resonant tubes are arranged on the inner regular hexagon, and the small anti-resonant tubes are arranged on the outer regular hexagon.

[0007] Further, the inner diameter of the large anti-resonant tube is 4.5μm - 5.1μm, and the thickness of its tube wall is 0.4μm - 0.6μm.

[0008] Further, the inner diameter of the large anti-resonant tube is 4.8μm, and the thickness of its tube wall is 0.5μm.

[0009] Further, the inner diameter of the small anti-resonant tube is 3.8μm - 4.2μm, and the thickness of its tube wall is 0.4μm - 0.6μm.

[0010] Further, the inner diameter of the small anti-resonant tube is 4μm, and the thickness of its tube wall is 0.5μm.

[0011] Further, the inner diameter of the outer large glass tube is 32μm - 40μm, and the thickness of its tube wall is 0.4μm - 0.6μm.

[0012] Further, the inner diameter of the outer large glass tube is 36μm, and the thickness of its tube wall is 0.5μm.

[0013] Further, the positions in the outer large glass tube except for the six groups of conjoined tubes are filled with the solution to be measured.

[0014] The beneficial effects of the present invention: An ARF-SPR liquid sensor with an extremely simple structure is provided, which not only has low loss but also has a long detection distance. Its main advantages are as follows:

[0015] (1). The ARF-SPR liquid sensor only contains six groups of completely identical conjoined anti-resonant tubes, and the structure is extremely simple, and it can be produced by the tube stacking method;

[0016] (2) The ARF-SPR liquid sensor uses a method of filling a negative curvature tube with a gold dielectric plasma material to excite SPR, which is simpler and more convenient than the traditional method of plating a metal film in air holes;

[0017] (3) The ARF-SPR liquid sensor utilizes the anti-resonance condition unique to anti-resonant optical fibers to reduce the confinement loss, resulting in a higher fundamental mode transmission efficiency;

[0018] (4) The ARF-SPR liquid sensor is very small in volume, facilitating installation and use;

[0019] (5) The refractive index detection range of the ARF-SPR liquid sensor is 1.32 - 1.44, and it can detect the effective refractive indices of various liquids;

[0020] (6) The average wavelength sensitivity of the ARF-SPR liquid sensor is as high as 14833.33 nm / RIU;

[0021] (7) The longest detection distance of the ARF-SPR liquid sensor is up to 133.81 m

[0022] (8) The coating layer of the ARF-SPR liquid sensor selects a cycloolefin copolymer material, which is not only simple to process, but also has a lower cost and strong durability. Description of the Drawings:

[0023] Figure 1 is a cross-sectional schematic diagram of the anti-resonant optical fiber in the first embodiment;

[0024] Figure 2 is a corresponding relationship diagram between the resonant wavelength of the ARF-SPR liquid sensor and the refractive index of the solution to be measured in the first embodiment;

[0025] Figure 3 is a variation rule diagram of the refractive indices of different solutions to be measured and the detection distance of the ARF-SPR liquid sensor in the first embodiment;

[0026] Figure 4 is a process diagram of liquid refractive index detection in the first embodiment. Specific Embodiment:

[0027] Referring to the various figures, an ARF-SPR long-distance liquid detection sensor with an extremely simple structure. The ARF-SPR long-distance liquid detection sensor is an anti-resonant optical fiber. Inside the outer large glass tube 2 of the anti-resonant optical fiber, 6 groups of connected anti-resonant tubes 3 are inscribed. The connected anti-resonant tubes 3 are composed of a connected large anti-resonant tube 4 and a small anti-resonant tube 5. The 6 groups of connected anti-resonant tubes 3 are arranged in a regular hexagon; a cycloolefin copolymer 1 is coated on the outer surface of the outer large glass tube 2; in the large anti-resonant tube 4 in the positive half-axis direction of the X-axis of the connected anti-resonant tubes 3, a dielectric gold 7 is filled, and the remaining large anti-resonant tubes 4 and small anti-resonant tubes 5 are all filled with air 8; the materials of the outer large glass tube 2, the large anti-resonant tube 4, and the small anti-resonant tube 5 are silica; the large anti-resonant tubes 4 are arranged on the inner regular hexagon, and the small anti-resonant tubes 5 are arranged on the outer regular hexagon; the inner diameter of the large anti-resonant tube 4 is 4.8 μm, and the thickness of its tube wall is 0.5 μm; the inner diameter of the small anti-resonant tube 5 is 4 μm, and the thickness of its tube wall is 0.5 μm; the inner diameter of the outer large glass tube 2 is 36 μm, and the thickness of its tube wall is 0.5 μm. The outer large glass tube 2 is filled with the liquid to be measured 6.

[0028] When the propagation constant of the evanescent wave generated when the incident light enters from the optically dense medium anti-resonant tube into the optically sparse medium air is equal to the propagation constant of the surface plasmon wave in the gold medium, the SPR phenomenon will occur. At this time, the photon energy will be transferred to the metal surface and cause loss; and the wavelength corresponding to the peak of the loss is the resonance wavelength. The different refractive indices of the liquid to be measured will cause the resonance wavelength to shift, thus realizing the sensing function.

[0029] When light is incident into the anti-resonant optical fiber, an evanescent wave will be generated along the propagation direction when the light enters from the optically dense medium into the optically sparse medium, while the surface plasmon wave propagates in the gold medium in a fixed mode. When the propagation constant of the evanescent wave with a certain wavelength in the anti-resonant optical fiber is the same as that of the surface plasmon wave in the gold medium, the free electrons on the gold medium surface will undergo collective oscillation, causing the photon energy in the anti-resonant optical fiber to be coupled into the gold medium, and the photon energy in the fiber decreases, that is, energy loss occurs in the anti-resonant optical fiber. If the wavelength corresponding to the peak of the energy loss is defined as the resonance wavelength, it will move regularly with the change of the refractive index of the solution to be measured, thus realizing the function of liquid refractive index sensing.

[0030] An ARF model of the present invention can be established by the finite element method. Using the finite element analysis software COMSOL and MATLAB to simulate and post-process its sensing situation, the function relationship diagram between the resonance wavelength and the refractive index of the solution to be measured as shown in Figure 2 can be obtained. The fitting equation of the fitting straight line is:

[0031] λ(μm) = 22.52 - 14.56n a, 1.32 ≤ n a ≤ 1.44

[0032] Here, λ is the resonance wavelength in μm, and n a is the refractive index of the liquid to be measured in RIU.

[0033] The average wavelength sensitivity of this sensor can be determined by the following formula:

[0034]

[0035] Here, Δλ is the displacement of the resonance wavelength, and Δn a represents the change in the refractive index of the liquid to be measured; it should be noted that the slope of the fitting equation is the average wavelength sensitivity of the present invention, and its value is 14833.33 nm / RIU.

[0036] The detection distance of this sensor can be calculated by the following formula:

[0037]

[0038] Here and are respectively the real parts of the effective refractive indices of the two polarization states of the anti-resonant fiber fundamental mode. The detection distances of the ARF-SPR liquid sensor in different refractive index solutions to be measured are as Figure 3 shown, and the longest detection distance is up to 133.81 m.

[0039] The liquid refractive index detection process of this sensor is as Figure 4 shown. The liquid to be detected is injected into the large glass tube by means of pressurization. A single-mode fiber is connected to both sides of the sensor using an optical fiber fusion splicer. One end is connected to a light source, and the other end is connected to an optical spectrum analyzer (OSA). The OSA and the PC are connected using a data cable. After turning on the light source, adjusting it to an appropriate wavelength band and exciting SPR, the loss curve of the analyte can be obtained and the corresponding resonance wavelength can be found, and then the refractive index of the liquid to be measured can be obtained.

Claims

1. An ARF-SPR long-distance liquid detection sensor with an extremely simple structure, characterized in that: The ARF-SPR long-distance liquid detection sensor is an anti-resonant optical fiber. Inside the outer large glass tube (2) of the anti-resonant optical fiber, 6 groups of connected anti-resonant tubes (3) are inscribed. The connected anti-resonant tube (3) is composed of a connected large anti-resonant tube (4) and a small anti-resonant tube (5), and the 6 groups of connected anti-resonant tubes (3) are arranged in a regular hexagon; the outer surface of the outer large glass tube (2) is coated with a cycloolefin copolymer (1); in the large anti-resonant tube (4) in the positive half-axis direction of the X-axis in the connected anti-resonant tube (3), a dielectric gold (7) is filled, and the remaining large anti-resonant tubes (4) and small anti-resonant tubes (5) are filled with air (8); the materials of the outer large glass tube (2), the large anti-resonant tube (4) and the small anti-resonant tube (5) are silica; The large anti-resonant tubes (4) are arranged on the inner regular hexagon, and the small anti-resonant tubes (5) are arranged on the outer regular hexagon; The inner diameter of the large anti-resonant tube (4) is 4.5μm - 5.1μm, and the thickness of its tube wall is 0.4μm - 0.6μm; The inner diameter of the small anti-resonant tube (5) is 3.8μm - 4.2μm, and the thickness of its tube wall is 0.4μm - 0.6μm; The inner diameter of the outer large glass tube (2) is 32μm - 40μm, and the thickness of its tube wall is 0.4μm - 0.6μm.

2. The ARF-SPR long-distance liquid detection sensor with an extremely simple structure according to claim 1, characterized in that: The inner diameter of the large anti-resonant tube (4) is 4.8μm, and the thickness of its tube wall is 0.5μm.

3. The ARF-SPR long-distance liquid detection sensor with an extremely simple structure according to claim 1, characterized in that: The inner diameter of the small anti-resonant tube (5) is 4μm, and the thickness of its tube wall is 0.5μm.

4. The ARF-SPR long-distance liquid detection sensor with an extremely simple structure according to claim 1, characterized in that: The inner diameter of the outer large glass tube (2) is 36μm, and the thickness of its tube wall is 0.5μm.

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