SPR sensor based on MZI structure

Abstract

The utility model provides a kind of SPR sensor based on MZI structure, and the sensor includes multimode fiber, quartz capillary, gold film and chitosan functional film.Two multimode fibers middle fusion quartz capillary forms MZI, quartz capillary is filled with thermosensitive material, quartz capillary is plated with gold film, and the outside of gold film is coated with a layer of chitosan functional film.The sensor uses the thermosensitive material in quartz capillary to cause MZI resonance spectrum drift with temperature change to measure temperature, and uses chitosan functional film and copper ion chelation to cause SPR resonance spectrum drift to measure concentration.The utility model realizes the double-parameter simultaneous measurement of copper ion concentration and temperature by composite structure design, with the characteristics of compact structure and high sensitivity.

Description

Technical Field

[0001] This utility model relates to the field of sensor technology, specifically to an SPR sensor based on an MZI structure. Background Technology

[0002] Fiber optic sensors, as label-free optical sensors, possess advantages such as small size, resistance to electromagnetic interference, suitability for remote deployment, and low cost, and are widely used in fields such as biomedicine, environmental monitoring, food safety, and chemical detection. Fiber optic sensors can be classified into five categories based on their sensing principles: fiber Bragg grating sensors, fiber Fabry-Perot sensors, fiber Mach-Zehnder interferometers, Sagnac interferometers, and surface plasmon resonance sensors. However, these sensors struggle to simultaneously achieve dual-parameter detection. Since the thermo-optical effect of materials leads to a close correlation between refractive index and temperature, and sensors based on the Mach-Zehnder interferometry principle and surface plasmon resonance exhibit high sensitivity and ease of fabrication, this paper proposes a fiber optic sensor capable of simultaneously measuring copper ion concentration and temperature. This is of significant importance for studying the parametric performance of the sample under test.

[0003] In recent years, some scholars have also conducted research on multi-parameter measurements. However, due to the thermal expansion of the fiber cladding caused by temperature changes, the effective refractive index of the MZI changes, resulting in a cross-sensitivity effect. This multi-parameter coupling phenomenon makes it difficult for traditional single-variable demodulation algorithms to accurately separate the target parameters. This problem complicates signal demodulation and reduces detection accuracy. Therefore, it is essential to develop a dual-parameter fiber. Utility Model Content

[0004] The purpose of this invention is to provide an SPR sensor based on the MZI structure, which solves the shortcomings of traditional detection technology, such as high cross-sensitivity effect, single measurement parameters, and low sensitivity.

[0005] To achieve the above objectives, this utility model employs the following technical solution: an SPR sensor based on an MZI structure, comprising: multimode optical fiber, a quartz capillary, a gold film, and a chitosan functional film. The first segment of the multimode optical fiber is fused to one end of the quartz capillary using an optical fiber fusion splicer. The other end of the quartz capillary is fused to a second segment of the multimode optical fiber to form an MZI. A thermistor is then injected for external temperature sensing. The surface of the quartz capillary is coated with a gold film, serving as the excitation interface for SPR. Finally, a chitosan functional film is coated on the outermost layer. The multimode optical fiber has an inner diameter of approximately 105 μm and an outer diameter of approximately 125 μm; the quartz capillary has an inner diameter of approximately 30 μm, an outer diameter of approximately 125 μm, and a length of 4 ± 0.1 mm. -5In a vacuum environment of Pa, a 50 nm thick gold film was deposited on the outer surface of a quartz capillary using electron beam evaporation, ensuring uniform coverage of the entire surface. The chitosan functional membrane uses chitosan as the functional monomer. Because chitosan is not easily soluble in water, acetic acid solution was used as the solvent, and glutaraldehyde as the crosslinking agent. The thickness of the chitosan functional membrane was 67 nm.

[0006] A 650nm optical signal is incident on the inner wall of a capillary via an input optical fiber and undergoes total internal reflection. The light is transmitted to the surface of a gold film within the quartz capillary. When the SPR condition is met, a surface plasmon wave is excited. A chitosan functional film is then deposited on the surface of the metal film. Changes in the refractive index of the surrounding environment directly affect the characteristics of the surface plasmon wave. The chitosan functional film can chelate with copper ions in the solution, specifically adsorbing copper ions. After the chitosan functional film binds to copper ions, it changes its refractive index. This change in refractive index can be detected by SPR resonant spectral drift, thus enabling the detection of copper ion concentration.

[0007] When a beam of light is incident into a quartz capillary filled with a thermosensitive material, the beam is split into two paths. One path is coupled to the cladding, and the other path is coupled to the core of the quartz capillary. Finally, these two paths are coupled into the core of a multimode fiber to form a Mach-Zehnder interference. Temperature causes a change in the refractive index of the thermosensitive material. The temperature change can be demodulated by recording the drift of the MZI resonant spectrum using a fiber optic spectrometer.

[0008] This invention provides an SPR sensor based on an MZI structure. It has the following advantages:

[0009] 1. This invention enables the sensor to detect the concentration of copper ions with high sensitivity through SPR technology. Compared with traditional detection methods, the SPR sensor based on the MZI structure can detect lower concentrations of copper ions, thereby improving the accuracy of detection.

[0010] 2. This invention makes the MZI structure more sensitive to temperature by injecting a thermosensitive material into the quartz capillary cavity, thereby achieving high-sensitivity temperature detection.

[0011] 3. The sensor design of this invention is simple and compact, suitable for simultaneous measurement of two parameters, and occupies little space, thus achieving portability and ease of operation. Attached Figure Description

[0012] Figure 1 This is a perspective view of the SPR sensor based on the MZI structure of the present invention;

[0013] Among them, 1. multimode optical fiber; 2. quartz capillary; 3. chitosan functional film; 4. gold film; 5. pinhole; 6. thermosensitive material. Detailed Implementation

[0014] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings.

[0015] Please see the appendix Figure 1 This invention provides an SPR sensor based on an MZI structure, comprising a multimode fiber 1, a quartz capillary 2, a chitosan functional film 3, and a gold film 4. The multimode fiber 1 is fused to both ends of the quartz capillary. Two small holes 5 are drilled on the surface of the quartz capillary using a femtosecond laser, and then a thermosensitive material 6 is injected using a fabricated micro-syringe. A gold film 4 of approximately 50 nm is deposited on the outer surface of the quartz capillary 2 to form surface plasmon waves. A chitosan functional film 3 with a thickness of 10 μm is coated on the outer surface of the quartz capillary 2. The inner diameter of the multimode fiber 1 is 1... The inner diameter of the quartz capillary 2 is 30 μm, the outer diameter is 125 μm, and the length is 4 mm. The chitosan functional membrane 3 uses chitosan as the functional monomer. Since chitosan is not easily soluble in water, glacial acetic acid is used as the solvent and glutaraldehyde is used as the crosslinking agent. The chitosan functional membrane can chelate with copper ions in the solution and specifically adsorb copper ions. After the chitosan functional membrane binds with copper ions, it will change its refractive index. The change in its refractive index can be detected by SPR resonance spectral drift, thus it can be used to detect the concentration of copper ions.

[0016] When a beam of light is incident on a quartz capillary filled with a thermistor, the beam is split into two paths. One path couples to the cladding, and the other to the core of the capillary. Finally, these two paths couple into the core of a multimode fiber, forming a Mach-Zehnder interferometer, which is used for external temperature sensing. Temperature changes cause changes in the refractive index of the thermistor, thus affecting the propagation characteristics of light in the fiber. The temperature change can be demodulated by recording the drift of the MZI resonant spectrum using a fiber optic spectrometer.

Claims

1. A SPR sensor based on an MZI structure, comprising a multimode optical fiber, a quartz capillary, a gold film, and a chitosan functional membrane, characterized by: The multimode optical fiber is fused with the quartz capillary to form MZI. The quartz capillary contains a thermosensitive material for external temperature sensing. The surface of the quartz capillary is coated with a gold film as the excitation interface for SPR. The gold film is coated with a chitosan functional film.

2. The SPR sensor based on the MZI structure according to claim 1, characterized in that: Multimode optical fiber with an inner diameter of approximately 105 μm and an outer diameter of approximately 125 μm; quartz capillary with an inner diameter of approximately 30 μm, an outer diameter of approximately 125 μm, and a length of 4 ± 0.1 mm.

3. The SPR sensor based on the MZI structure according to claim 1, characterized in that: In 10 -5 In a vacuum environment of Pa, a 50nm thick gold film is deposited on the outer surface of a quartz capillary by electron beam evaporation, so that the gold film uniformly covers the entire surface.

4. The SPR sensor based on the MZI structure according to claim 1, characterized in that: Chitosan functional membrane uses chitosan as the functional monomer. Because chitosan is not easily soluble in water, acetic acid solution is used as the solvent and glutaraldehyde is used as the crosslinking agent. The thickness of the chitosan functional membrane is 67 nm.

5. The SPR sensor based on the MZI structure according to claim 1, characterized in that: The quartz capillary has two holes in its wall, and the cavity of the quartz capillary is filled with a thermosensitive material.

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