Refractive index type MOF-spr probe with external indium tin oxide double nanowires

Abstract

This invention relates to an optical fiber probe, specifically an external indium tin oxide (ITO) double nanowire refractive index type MOF-SPR probe. The MOF-SPR probe consists of a microstructured optical fiber and two ITO nanowires. The cladding of the microstructured optical fiber has a central air hole and four symmetrically distributed elliptical air holes. D-shaped notches are located on both sides of the cladding. The two ITO nanowires are located on either side of the D-shaped notches, tangent to their midpoints. The core of the microstructured optical fiber is located above and below the central air hole and between the two elliptical air holes, forming a dual-core symmetrical microstructured optical fiber. The radius of the cladding is 16 μm; the radius of the central air hole is 0.8 μm; the radius of the ITO nanowires is 0.8 μm; and the distance from the midpoint of the D-shaped notch to the center of the cladding is 10.5 μm. This probe features a simple coating process, low loss, high sensitivity, and resistance to harsh environments.

Description

Technical Field

[0001] This invention relates to an optical fiber probe, specifically to a low-power, high-sensitivity external indium tin oxide (ITO) dual nanowire refractive index MOF-SPR probe. Background Technology

[0002] Surface plasmon resonance (SPR) technology is a representative emerging optical sensing technology in recent years. Essentially, SPR is a physical optical phenomenon. When light propagates at the interface between two materials with different refractive indices, total internal reflection occurs, generating an evanescent wave. Furthermore, photons within the fiber core coherently oscillate with free electrons on the metal surface, further exciting surface plasmon waves (SPWs). When the evanescent wave coincides with the SPW, surface plasmon resonance occurs. SPR, with its outstanding characteristics of being label-free, capable of real-time online monitoring, highly resistant to interference, and highly sensitive, has broad application prospects in many fields such as biomedicine, environmental monitoring, chemical processes, and energy.

[0003] Microstructured optical fiber (MOF) is a waveguide formed by introducing a series of air holes. Compared with ordinary single-mode fiber, MOF belongs to the category of novel special fibers, attracting much attention due to its flexible air hole arrangement design, tunable chromatic dispersion, and cutoff-free single-mode transmission, further enriching the types of micro-fiber sensing platforms. Therefore, SPR sensors based on microstructured optical fibers have been proposed. From the perspective of coating location, they can be roughly divided into two types: coating on the fiber cladding exterior and coating inside the air holes. Especially for coating inside the air holes, the small fiber size limits the maneuverable space for coating, and the fabrication process is complex, making it difficult to apply in practice. Furthermore, considering the special scenarios of long-distance optical communication transmission and engineering applications, there is an urgent need to design a MOF-SPR sensing probe with a simple coating process, low loss, high sensitivity, and resistance to harsh environments. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a refractive index-type MOF-SPR probe with external indium tin oxide dual nanowires. This probe features a simple coating process, low loss, high sensitivity, and the ability to withstand harsh environments.

[0005] The technical solution adopted in this invention is as follows: an external indium tin oxide (ITO) double nanowire refractive index MOF-SPR probe, which consists of a microstructured optical fiber and two ITO nanowires. The cladding of the microstructured optical fiber has a central air hole and four symmetrically distributed elliptical air holes. D-shaped cutouts are provided on both sides of the cladding. The two ITO nanowires are located on both sides of the D-shaped cutouts and are tangent to the midpoint of the D-shaped cutouts. The core of the microstructured optical fiber is located on the upper and lower sides of the central air hole and between the two elliptical air holes, forming a dual-core symmetrical microstructured optical fiber. The radius of the cladding is 15μm-17μm; the radius of the central air hole is 0.7μm-0.9μm; the radius of the ITO nanowires is 0.7μm-0.9μm; and the distance from the midpoint of the D-shaped cutout to the center of the cladding is 10μm-11μm.

[0006] Furthermore, the radius of the cladding is 16 μm; the radius of the central air pore is 0.8 μm; the radius of the indium tin oxide nanowire is 0.8 μm; and the distance from the midpoint of the D-shaped cut to the center of the cladding is 10.5 μm.

[0007] Furthermore, the microstructured optical fiber is a refractive index guided microstructured optical fiber, the core material of which is silicon dioxide, and the background material of the cladding has a refractive index of 1.42.

[0008] The beneficial effects of this invention: This invention provides a refractive index-type MOF-SPR probe with external indium tin oxide double nanowires. This probe has a simple coating process, low loss, high sensitivity, and can withstand harsh environments. Its main advantages are as follows:

[0009] (1) The maximum and average sensitivities are 60,000 nm / RIU and 15,571.43 nm / RIU, respectively;

[0010] (2) It has an ultra-wide refractive index detection range from 1.00 to 1.42 and can detect gaseous and liquid analytes simultaneously;

[0011] (3) It has an ultra-wide operating wavelength range from visible to infrared: 430nm-7200nm. No special light source is required in the low-band, and special applications can be solved in the high-band.

[0012] (4) The loss is limited to below 64.99dB / cm, which is beneficial for long-distance transmission;

[0013] (5) When the radius of the external indium tin oxide nanowire is in the range of 0.4 μm to 0.8 μm, the structural sensitivity is small, which makes it more tolerant and has better stability during preparation.

[0014] (6) Compared with conventional coating methods, external nanowires have a simpler manufacturing process and are easier to produce and apply in practice. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the cross-section of the microstructured optical fiber in Example 1;

[0016] Figure 2 This is a graph showing the relationship between the resonance wavelength of the MOF-SPR probe and the refractive index of the solution to be tested in Example 1. Detailed Implementation

[0017] Reference Figure 1 and Figure 2 A refractive index-type MOF-SPR probe with external indium tin oxide (ITO) double nanowires is disclosed. The MOF-SPR probe consists of a microstructured optical fiber 1 and two ITO nanowires 2. The cladding 5 of the microstructured optical fiber 1 has a central air hole 6 and four symmetrically distributed elliptical air holes 4. D-shaped cutouts 3 are located on both sides of the cladding 5. The two ITO nanowires 2 are located on either side of the D-shaped cutouts 3 and are tangent to the midpoint of the D-shaped cutouts 3. The core of the microstructured optical fiber 1 is located at... The upper and lower sides of the central air hole 6 and the space between the two elliptical air holes form a dual-core symmetrical microstructure optical fiber; the radius of the cladding 5 is 16 μm; the radius of the central air hole 6 is 0.8 μm; the radius of the indium tin oxide nanowire 2 is 0.8 μm; the distance from the midpoint of the D-shaped cut 3 to the center of the cladding 5 is 10.5 μm; the microstructure optical fiber is a refractive index guided microstructure optical fiber, the core material is silicon dioxide, and the refractive index of the background material of the cladding 5 is 1.42.

[0018] The low-power, high-sensitivity MOF-SPR probe utilizes an external indium tin oxide (ITO) nanowire as the sensing layer, with the ITO nanowire tangent to the center of the double D-shaped cut in the cladding. When light enters the microstructured optical fiber, different wavelengths of light propagate along the two core directions within the fiber in specific modes, while surface plasmon radiation propagates within the ITO nanowire in a fixed mode. When the wave vector of a certain wavelength of light within the microstructured fiber is the same as that of the surface plasmon radiation wave within the ITO nanowire, energy coupling occurs within the ITO nanowire. The light energy within the microstructured fiber is coupled back into the ITO nanowire, reducing the light energy within the microstructured fiber—that is, energy loss occurs within the microstructured fiber. The wavelength corresponding to the maximum energy loss is the resonant wavelength. An energy loss spectrum is plotted based on the relationship between energy loss and resonant wavelength. The magnitude of the resonant wavelength varies with the refractive index of the test solution outside the ITO nanowire. When the microstructured optical fiber is placed in a solution, the refractive index of the test solution can be detected by calculating the magnitude of the resonant wavelength, thus achieving the sensing purpose.

[0019] By establishing a sensing model using the finite element method and simulating its sensing behavior using a computer, the relationship curve between the resonant wavelength and the refractive index of the solution under test can be obtained, such as... Figure 2 As shown. The fitting formula for the fitted curve is:

[0020] λ R (nm) = 202404.91 - 518861.92n a +462704.19n a 2 -138975.76n a 3 , 1≤n a ≤1.42

[0021] Where, λ R Represents the resonant wavelength, with units of nm. a This represents the refractive index of the solution being tested, expressed in RIU.

[0022] The average spectral sensitivity can be calculated using the following formula:

[0023]

[0024] Where, △λ R The change in resonant wavelength, Δn a This represents the change in the refractive index of the liquid being tested. The average sensitivity is 15571.43 nm / RIU.

[0025] This probe boasts a maximum and average sensitivity of 60,000 nm / RIU and 15,571.43 nm / RIU, respectively, across an ultra-wide refractive index detection range (1.00-1.42). Its operating wavelength extends from visible to infrared (430 nm-7200 nm), eliminating the need for special light sources in the low-wavelength range and addressing specific applications in the high-wavelength range. Losses are consistently below 64.99 dB / cm, facilitating long-distance transmission. The external nanowire fabrication process is simpler than conventional coating methods, making it easier for practical production and application. Based on these advantages, this refractive index-based MOF-SPR probe can be widely applied in various scenarios across basic sciences and practical engineering fields.

Claims

1. A refractive index-type MOF-SPR probe with external indium tin oxide double nanowires, characterized in that: The external indium tin oxide (ITO) dual nanowire MOF-SPR probe consists of a microstructured optical fiber (1) and two ITO nanowires (2). The cladding (5) of the microstructured optical fiber (1) has a central air hole (6) and four symmetrically distributed elliptical air holes (4). D-shaped cutouts (3) are provided on both sides of the cladding (5). The two ITO nanowires (2) are located on both sides of the D-shaped cutouts (3) and are tangent to the midpoint of the D-shaped cutouts (3). The microstructured optical fiber (1) has two cores, one of which is... The fiber core is located above the central air hole (6) and between the two upper elliptical air holes, and the other fiber core is located below the central air hole (6) and between the two lower elliptical air holes; the radius of the cladding (5) is 15μm-17μm; the radius of the central air hole (6) is 0.7μm-0.9μm; the radius of the indium tin oxide nanowire (2) is 0.7μm-0.9μm; the distance from the midpoint of the D-shaped cut (3) to the center of the cladding (5) is 10μm-11μm.

2. The refractive index-type MOF-SPR probe with external indium tin oxide double nanowires according to claim 1, characterized in that: The radius of the cladding (5) is 16 μm; the radius of the central air hole (6) is 0.8 μm; the radius of the indium tin oxide nanowire (2) is 0.8 μm; and the distance from the midpoint of the D-shaped cut (3) to the center of the cladding (5) is 10.5 μm.

3. The refractive index-type MOF-SPR probe with external indium tin oxide double nanowires according to claim 1 or 2, characterized in that: The microstructured optical fiber is a refractive index guided microstructured optical fiber, the core material of which is silicon dioxide, and the background material of the cladding (5) has a refractive index of 1.42.

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