Surface plasma resonance sensor based on polydimethylsiloxane filled hollow-core optical fiber and preparation method of surface plasma resonance sensor

Abstract

The invention belongs to the technical field of optical fiber sensing, and particularly relates to a surface plasma resonance sensor based on a polydimethylsiloxane filled hollow-core optical fiber and a preparation method thereof.The surface plasma resonance sensor comprises the hollow-core optical fiber, and a single-mode optical fiber and a multimode optical fiber are fixed to the two ends of the hollow-core optical fiber respectively; the preparation method of the surface plasma resonance sensor comprises the following steps: removing an optical fiber protection layer on the outer side of the hollow-core optical fiber, welding two ends of the hollow-core optical fiber with a single-mode optical fiber and a multi-mode optical fiber respectively, carrying out side polishing treatment on the hollow-core optical fiber, and carrying out surface plasma resonance treatment on the hollow-core optical fiber to obtain the surface plasma resonance sensor. And injecting the mixed polydimethylsiloxane into a hollow-core groove of the side-polished hollow-core optical fiber, and plating a layer of gold film and a high-refractive-index film on the surface of the polydimethylsiloxane. Compared with traditional surface plasma resonance, the low refractive index detection accuracy and sensitivity are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a surface plasma resonance sensor based on polydimethylsiloxane-filled hollow-core optical fiber and a preparation method thereof. Background Art

[0002] Refractive index is an inherent property of matter. Measuring the refractive index of a material can quickly identify and classify the material. As a method of measuring refractive index, surface plasmon resonance technology has the advantages of high sensitivity, real-time monitoring, label-free detection, multi-parameter analysis and non-destructive testing. These characteristics make it widely used in scientific research and various applications. Enhancing the sensitivity of surface plasmon resonance sensing technology has always been the focus of researchers, especially in the detection of low-concentration substances, research on biomolecular interactions, chemical reaction monitoring accuracy, as well as biosensing, gene sequencing and environmental monitoring.

[0003] Traditional surface plasmon resonance is the collective oscillation of electrons excited by transversely polarized light at the metal or waveguide interface. When total internal reflection occurs in the waveguide, an evanescent wave is generated at the interface between the optical fiber waveguide and the metal film. When the propagation constants of the evanescent wave and the surface plasmon wave match, energy is transferred to the surface plasmon wave, causing surface plasmon resonance. Therefore, surface plasmon resonance is affected by the refractive index of the waveguide, the dielectric constant of the metal, and the refractive index of the external environment.

[0004] To enhance the sensitivity of surface plasmon resonance in the entire detection range of refractive index, researchers have proposed various methods, including adjusting the incident angle, using two-dimensional materials, metal oxides, nanoparticles, etc.

[0005] For example, a multilayer surface plasmon resonance sensor and its preparation method proposed in publication number CN117433993A, compared with the traditional Au film sensor, the sensitivity of the invention is increased from 2325.4nm / RIU to 3356.3nm / RIU, an increase of 44.3%. However, the increase is only 44.3%, which cannot fully solve the sensitivity problem in the low refractive index range, which is crucial for most surface plasmon resonance detection scenarios;

[0006] In fiber-optic surface plasmon resonance sensors, the sensitivity of the sensor increases when the refractive index difference between the waveguide and the sample decreases, which provides a new approach for the design of fiber-optic surface plasmon resonance sensors.

[0007] The invention discloses a method for filling polydimethylsiloxane with side-thrown hollow core optical fiber which enhances refractive index sensitivity through polymer coating. Summary of the invention

[0008] The purpose of the present invention is to provide a surface plasmon resonance sensor based on polydimethylsiloxane-filled hollow-core optical fiber and a preparation method thereof, which effectively improves the accuracy and sensitivity of low-refractive-index detection compared with traditional surface plasmon resonance.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A surface plasmon resonance sensor based on a polydimethylsiloxane-filled hollow-core optical fiber comprises a hollow-core optical fiber, wherein a single-mode optical fiber and a multi-mode optical fiber are respectively fixed at two ends of the hollow-core optical fiber;

[0011] The interior of the hollow-core optical fiber is provided with polydimethylsiloxane, a gold film and a high-refractive-index film in sequence from the inside to the outside, and the polydimethylsiloxane, the gold film and the high-refractive-index film are bonded and arranged from the inside to the outside.

[0012] A preparation method of a surface plasmon resonance sensor based on polydimethylsiloxane-filled hollow-core optical fiber, the preparation method is used to prepare the above-mentioned surface plasmon resonance sensor, the preparation method comprises the following steps:

[0013] Step 1: Remove the outer protective layer of the hollow-core optical fiber and weld the two ends to the single-mode optical fiber and the multi-mode optical fiber respectively;

[0014] Step 2: performing side-casting treatment on the hollow-core optical fiber;

[0015] Step 3: Mix the polydimethylsiloxane, then inject the mixed polydimethylsiloxane into the hollow core groove of the hollow core optical fiber after side casting, and solidify it;

[0016] Step 4: coating a layer of the gold film on the surface of the polydimethylsiloxane, and then coating the high refractive index film on the gold film to complete the preparation of the surface plasmon resonance sensor.

[0017] The technical effects achieved by the present invention are:

[0018] The present invention uses polydimethylsiloxane as a waveguide, which effectively improves the accuracy and sensitivity of low-refractive index detection compared to the surface plasma resonance excited by the gold-plated film after side polishing of traditional multi-mode optical fiber.

[0019] The present invention uses a gold film and a high-refractive-index film to prepare a surface plasmon resonance sensor, which exhibits superior plasma performance compared to a traditional single-layer gold film surface plasmon resonance sensor. The additional high-refractive-index film changes the matching condition between the evanescent wave and the surface plasmon wave, resulting in a red shift in the resonance wavelength, an increase in the dielectric constant of the metal layer, and significantly improved sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the sensor in the present invention;

[0021] Figure 2 is a schematic cross-sectional view of a hollow core optical fiber of the present invention;

[0022] Figure 3 It is a schematic diagram of the experimental device in the present invention.

[0023] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0024] 1. Single-mode optical fiber; 2. Hollow core optical fiber; 3. Multimode optical fiber; 4. Polydimethylsiloxane; 5. Gold film; 6. High refractive index film; 7. Optical fiber protective layer; 8. Syringe pump; 9. Broad-spectrum light source; 10. Sensor; 11. Spectrum analyzer; 12. Computer. DETAILED DESCRIPTION

[0025] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0026] Embodiment 1:

[0027] See attached Figure 1-2 As shown, a surface plasmon resonance sensor based on a polydimethylsiloxane-filled hollow-core optical fiber comprises a hollow-core optical fiber 2, a single-mode optical fiber 1 and a multi-mode optical fiber 3 are respectively fixed at both ends of the hollow-core optical fiber 2, the single-mode optical fiber 1 and the multi-mode optical fiber 3 are both welded to the hollow-core optical fiber 2, and the main body of the surface plasmon resonance sensor is a section of the hollow-core optical fiber 2;

[0028] The core diameter of the single-mode optical fiber 1 is 8 μm, the thickness between the inner diameter and the outer diameter of the hollow-core optical fiber 2 is 60-85 μm, preferably 62.5 μm, the core diameter of the multi-mode optical fiber 3 is 80 μm, and the cladding diameters thereof are all 125 μm.

[0029] The interior of the hollow-core optical fiber 2 is provided with polydimethylsiloxane 4, a gold film 5 and a high-refractive-index film 6 in sequence from the inside to the outside, and the polydimethylsiloxane 4, the gold film 5 and the high-refractive-index film 6 are bonded from the inside to the outside. The diameter of the polydimethylsiloxane 4 can be 30-70 μm, the thickness of the gold film 5 can be 40-60 nm, the thickness of the high-refractive-index film 6 can be 15-45 nm, and the high-refractive-index film 6 includes zinc oxide ZnO, germanium antimony telluride mixture GST, indium tin oxide ITO and titanium dioxide TiO2. The method of filling the hollow-core optical fiber 2 with polydimethylsiloxane 4 to enhance the refractive index sensitivity of the polymer coating is used, and the polydimethylsiloxane 4 is filled as a waveguide, thereby improving the sensitivity of the sensor 10 to the low-refractive-index liquid. The additional high-refractive-index film 6 layers significantly improve the sensitivity by changing the matching condition between the evanescent wave and the surface plasma wave.

[0030] Embodiment 2:

[0031] A method for preparing a surface plasmon resonance sensor based on polydimethylsiloxane-filled hollow-core optical fiber, the method for preparing the surface plasmon resonance sensor comprises the following steps:

[0032] S1: removing the outer fiber protective layer 7 of the hollow core optical fiber 2, and welding the two ends to the single-mode optical fiber 1 and the multi-mode optical fiber 3 respectively;

[0033] S2: side-polishing the hollow-core optical fiber 2, using a wheel-type side-polishing technique to process the hollow-core optical fiber 2. During the polishing process, 8000-mesh and sensor 10000-mesh sandpapers are used in turn to polish to enhance the smoothness of the polished surface. The polishing depth is controlled to be 62.5 μm by adjusting the side-polishing time. The hollow-core optical fiber 2 is cleaned in an ultrasonic and plasma cleaning machine using a CCD camera for monitoring.

[0034] S3: Mix the polydimethylsiloxane 4, and use the syringe pump 8 to inject the mixed polydimethylsiloxane 4 into the hollow core groove of the hollow core optical fiber 2 after side casting, and cure it at 65° C. for 1 hour, and control the volume of the polydimethylsiloxane 4 injected into the hollow core optical fiber 2 by the syringe pump 8, so as to adjust the diameter of the polydimethylsiloxane 4 to 62.5 μm;

[0035] S4: A 50 nm thick gold film 5 is deposited on the surface of polydimethylsiloxane 4 using a plasma sputtering device. Subsequently, a high refractive index film 6 is deposited on the gold film 5 using a magnetron sputtering device. The fixed ratio of the germanium antimony tellurium mixture GST target material is Ge:Sb:Te=2:2:5. The sputtering voltage is 300 V. The thickness of the germanium antimony tellurium mixture GST is controlled to be 25 nm by the sputtering time. The preparation of the surface plasmon resonance sensor is completed.

[0036] The following is an experiment of the present invention using an optical fiber surface plasmon resonance sensor to detect refractive index, as follows:

[0037] like Figure 3 As shown, a syringe pump 8 is used to inject glycerol solutions with different refractive indices ranging from 1.333 to 1.373 into the sensing area, i.e., the hollow core optical fiber 2. Before the injection, an Abbe refractometer is used to measure the refractive index of the glycerol solution. Once the refractive index detection test is completed, the glycerol solution is discharged into a waste liquid bucket. A wide-spectrum light source 9 is connected to a sensor 10, and the spectral range is 450-2400nm. A spectrum analyzer 11 is used to detect the transmitted spectrum, and the wavelength range is 700-1700nm. A computer 12 is used to view and control the test time and test sequence, etc.;

[0038] Through simulation and experimental verification, the effects of different polishing depths, polydimethylsiloxane 4 thicknesses and germanium antimony telluride mixture GST thicknesses on sensor performance were investigated, and the optimal parameter combination was finally determined, that is, when the polishing depth is 62.5μm, the polydimethylsiloxane 4 thickness is 62.5μm, and the GST thickness is 25nm, the sensor 10 achieves the highest sensitivity in low refractive index liquid detection.

[0039] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A surface plasmon resonance sensor based on a polydimethylsiloxane-filled hollow-core optical fiber, comprising a hollow-core optical fiber (2), characterized in that: A single-mode optical fiber (1) and a multi-mode optical fiber (3) are respectively fixed at two ends of the hollow-core optical fiber (2); The interior of the hollow-core optical fiber (2) is provided with polydimethylsiloxane (4), a gold film (5) and a high-refractive-index film (6) in sequence from the inside to the outside, and the polydimethylsiloxane (4), the gold film (5) and the high-refractive-index film (6) are bonded together.

2. The surface plasmon resonance sensor according to claim 1, characterized in that: The thickness between the inner diameter and the outer diameter of the hollow core optical fiber (2) is 60-85 μm.

3. The surface plasmon resonance sensor according to claim 1, characterized in that: The diameter of the polydimethylsiloxane (4) is 30-70 μm.

4. The surface plasmon resonance sensor according to claim 1, characterized in that: The thickness of the gold film (5) is 40-60 nm.

5. The surface plasmon resonance sensor according to claim 1, characterized in that: The thickness of the high refractive index film (6) is 15-45 nm.

6. The surface plasmon resonance sensor according to claim 1, characterized in that: The high refractive index film (6) comprises zinc oxide, a germanium antimony tellurium mixture, indium tin oxide and titanium dioxide.

7. A method for preparing a surface plasmon resonance sensor based on polydimethylsiloxane filled hollow core optical fiber, characterized in that: The preparation method is used to prepare the surface plasmon resonance sensor according to any one of claims 1 to 6, and the preparation method comprises the following steps: S1: removing the optical fiber protective layer (7) on the outer side of the hollow core optical fiber (2), and welding the two ends to the single-mode optical fiber (1) and the multi-mode optical fiber (3) respectively; S2: performing side-casting processing on the hollow-core optical fiber (2); S3: mixing the polydimethylsiloxane (4), then injecting the mixed polydimethylsiloxane (4) into the hollow core groove of the hollow core optical fiber (2) after side casting, and curing; S4: a layer of the gold film (5) is plated on the surface of the polydimethylsiloxane (4), and then the high refractive index film (6) is plated on the gold film (5), thereby completing the preparation of the surface plasmon resonance sensor.

8. The preparation method according to claim 7, characterized in that: In the above S3, curing is performed at 65°C.

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