Photonic crystal fiber sensor

Abstract

Provided is a photonic crystal fiber sensor, which can be applied to the technical field of fiber sensing. The sensor comprises: a fiber core, which is in a cylindrical structure, and upper and lower sides of the fiber core are polished to form two parallel sections, namely an upper section and a lower section; a first ITO film layer, which is located on the lower section; a TiO2 layer, which is located on a side of the first ITO film layer away from the lower section; a PDMS layer, which is located on a side of the TiO2 layer away from the lower section; and a gold film layer, which is located on the upper section; wherein the fiber core comprises two magnetic fluid filling holes, which are centrally symmetrically distributed relative to the center of the fiber core, and a line connecting the centers of the two magnetic fluid filling holes is parallel to the upper section; and the fiber core comprises an air hole, which is centrally symmetrically distributed relative to the center of the fiber core. Through dual polarization and internal and external sensing settings, three physical quantities such as temperature, refractive index and magnetic field intensity can be measured simultaneously, and the sensor has the advantages of high sensitivity and large measurement range.

Description

Technical Field

[0001] The present disclosure relates to the field of optical fiber sensing technology, and in particular to a photonic crystal optical fiber sensor. Background Art

[0002] Photonic crystal fiber sensors based on SPR (Surface Plasmon Resonance) feature small size, simple structure, immunity to electromagnetic interference, and high sensitivity. Their rapid response speed allows for application in a wide range of scenarios. As scenarios become more complex, the need for fiber optic sensors with higher sensitivity and wider detection ranges is increasing, and the number of parameters that can be detected by SPR-based photonic crystal fiber sensors is also increasing. However, existing fiber optic sensors cannot detect more than two parameters simultaneously. Summary of the Invention

[0003] (1) Technical issues to be resolved

[0004] To address the problem in the prior art that optical fiber sensors cannot measure more than two parameters simultaneously, the embodiments of the present disclosure provide a photonic crystal fiber sensor that, through dual polarization and internal and external sensing settings, can simultaneously measure three physical quantities, namely temperature, refractive index, and magnetic field intensity. It also has the advantages of high sensitivity and a large measurement range.

[0005] (2) Technical solution

[0006] In view of the above problems, an embodiment of the present disclosure provides a photonic crystal fiber sensor.

[0007] According to a first aspect of the present disclosure, a photonic crystal fiber sensor is provided, comprising: a fiber core, the fiber core having a cylindrical structure, the upper and lower sides of the fiber core being polished to form two mutually parallel cross-sections, namely an upper side and a lower side; a first ITO film layer, located on the lower side; a TiO2 layer, located on the side of the first ITO film layer away from the lower side; a PDMS layer, located on the side of the TiO2 layer away from the lower side; and a gold film layer, located on the upper side; wherein the fiber core comprises two magnetic fluid-filled holes, which are centrally symmetrically distributed relative to the center of the fiber core, and a line connecting the centers of the two magnetic fluid-filled holes is parallel to the upper side; and the fiber core comprises air holes, which are centrally symmetrically distributed relative to the center of the fiber core.

[0008] In some exemplary embodiments, the magnetic fluid-filled hole is a cylindrical structure; a second ITO film layer is disposed on the cylindrical inner surface of the magnetic fluid-filled hole; and the interior of the second ITO film layer is filled with magnetic fluid.

[0009] In some exemplary embodiments, the air holes include 10 first air holes and 4 second air holes, wherein the first air holes are evenly divided into 2 groups, forming 2 regular hexagons with the magnetic fluid-filled hole as the center, and no first air holes are set at the 2 vertices of the regular hexagon located on the line connecting the centers of the 2 magnetic fluid-filled holes; the 2 second air holes are located in the middle position of the line connecting the 4 first air holes near the upper side; the other 2 second air holes are located in the middle position of the line connecting the 4 first air holes near the lower side; and the distance between adjacent air holes is the same.

[0010] In some exemplary embodiments, the gold film layer covers the second air hole; and the gold film layer does not cover the first air hole.

[0011] In some exemplary embodiments, a diameter of the first air hole is larger than a diameter of the second air hole.

[0012] In some exemplary embodiments, a perfect matching layer is further included, which is a ring-shaped structure and is located outside the fiber core.

[0013] In some exemplary embodiments, at least one of the following features is included: the thickness of the gold film layer is 50 nm; the thickness of the first ITO film layer is 40 nm; the thickness of the TiO2 layer is 150 nm; the thickness of the PDMS layer is 50 nm; and the thickness of the second ITO film layer is 40 nm.

[0014] In some exemplary embodiments, at least one of the following features is included: a diameter of the magnetic fluid-filled hole is 1.98 μm; a diameter of the first air hole is 1.65 μm; and a diameter of the second air hole is 1.32 μm.

[0015] In some exemplary embodiments, when the photonic crystal fiber sensor is in operation, the optical signal input end of the photonic crystal fiber sensor is connected to the polarization controller through a single-mode optical fiber, and the polarization controller is used to control the generation of X polarization and / or Y polarization.

[0016] In some exemplary embodiments, the gold film layer generates surface plasmon resonance under the action of Y polarization, which is used to detect the refractive index of the analyte to be measured; the first ITO film layer generates surface plasmon resonance under the action of Y polarization, which is used to detect the refractive index and temperature changes of the analyte to be measured; and the second ITO film layer generates surface plasmon resonance under the combined action of Y polarization and X polarization, which is used to detect changes in external magnetic field intensity and temperature changes.

[0017] (3) Beneficial effects

[0018] It can be seen from the above technical solutions that the photonic crystal fiber sensor provided by the embodiments of the present disclosure has at least one of the following beneficial effects:

[0019] (1) Through dual polarization and internal and external sensing, three parameters can be detected simultaneously. Compared with traditional optical fibers, the number of detections is increased, achieving highly efficient optical fiber sensing detection.

[0020] (2) Through dual polarization and dual metal settings, simultaneous sensing of three parameters can be achieved. By combining internal sensing with external sensing, there is no crosstalk between the parameters, achieving overall low-interference multi-parameter detection.

[0021] (3) Through a symmetrical structural design, the refractive index range of the medium under Y polarization is 1.17 to 1.33, with a maximum wavelength sensitivity of 1000 nm / RIU. The temperature detection range under Y and X polarization is 20°C to 400°C, with a maximum temperature sensitivity of -0.5 nm / °C. The magnetic field intensity detection range under Y and X polarization is 0 to 12 Oe, with a maximum magnetic field intensity sensitivity of 11.1 nm / Oe. The sensor proposed in this invention has a higher detection capability than other multi-parameter detection sensors.

[0022] (4) A photonic crystal fiber sensor based on SPR that can measure three parameters simultaneously was realized through theoretical simulation using the finite element method (FEM). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above contents and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0024] Figure 1 The following schematically shows a two-dimensional interface structure diagram of a photonic crystal fiber sensor according to an embodiment of the present disclosure;

[0025] Figure 2 Schematically shows the loss spectrum of the photonic crystal fiber sensor according to an embodiment of the present disclosure at a temperature of 20° C., a magnetic field strength of 10 Oe, and a refractive index of 1.31;

[0026] Figure 3 The figure schematically shows the loss spectrum of the photonic crystal fiber sensor according to the embodiment of the present disclosure at different temperatures (temperature range 20°C-400°C);

[0027] Figure 4 Schematically shows the loss spectrum of the photonic crystal fiber sensor according to an embodiment of the present disclosure at different refractive indices (refractive index range 1.17-1.33); and

[0028] Figure 5 The figure schematically shows the loss spectra of the photonic crystal fiber sensor according to an embodiment of the present disclosure under different magnetic field intensities (magnetic field intensity range 0-12 Oe).

[0029] Reference numerals:

[0030] 1-fiber core; 11-air hole; 111-first air hole; 112-second air hole; 12-magnetic fluid-filled hole; 121-magnetic fluid; 122-second ITO film layer; 2-gold film layer; 3-first ITO film layer; 4-TiO2 layer; 5-PDMS layer; 6-perfect matching layer. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In order to make the purpose, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present disclosure.

[0032] Figure 1 A schematic diagram of a two-dimensional interface structure of a photonic crystal fiber sensor according to an embodiment of the present disclosure is shown schematically.

[0033] like Figure 1 As shown, a photonic crystal fiber sensor according to an embodiment of the present disclosure includes: a fiber core 1, the fiber core 1 is a cylindrical structure, the upper and lower sides of the fiber core 1 are polished to form two mutually parallel cross-sections, namely the upper side and the lower side, and optionally, the material of the fiber core 1 includes molten silica; a first ITO film layer 3, located on the lower side, optionally, the thickness of the first ITO film layer 3 is 40nm; a TiO2 layer 4, located on the side of the first ITO film layer 3 away from the lower side, optionally, the thickness of the TiO2 layer 4 is 150nm; PDMS Layer 5 is located on the side of the TiO2 layer 4 away from the lower side, optionally, the thickness of the PDMS layer 5 is 50nm; and the gold film layer 2 is located on the upper side, optionally, the thickness of the gold film layer 2 is 50nm; wherein, the fiber core 1 includes two magnetic fluid-filled holes 12, which are centrally symmetrically distributed relative to the center of the fiber core 1, and the line connecting the centers of the two magnetic fluid-filled holes 12 is parallel to the upper side, optionally, the diameter of the magnetic fluid-filled hole 12 is 1.98μm; and the fiber core 1 includes air holes 11, which are centrally symmetrically distributed relative to the center of the fiber core 1.

[0034] Definition: ITO film is an n-type semiconductor material with high conductivity, high visible light transmittance, high mechanical hardness and good chemical stability. PDMS (Polydimethylsiloxane) is a high molecular polymer with the chemical formula (C2H6OSi) n .

[0035] In some exemplary embodiments, the magnetic fluid-filled hole 12 is cylindrical; a second ITO film layer 122 is disposed on the cylindrical inner surface of the magnetic fluid-filled hole 12; and the interior of the second ITO film layer 122 is filled with magnetic fluid 121. Optionally, the thickness of the second ITO film layer 122 is 40 nm.

[0036] In some exemplary embodiments, the air holes 11 include 10 first air holes 111 and 4 second air holes 112, wherein the first air holes 111 are evenly divided into two groups, forming two regular hexagons with the magnetic fluid-filled hole 12 as the center, and the two vertices of the regular hexagons located on the line connecting the centers of the two magnetic fluid-filled holes 12 are not provided with first air holes 111; two second air holes 112 are located in the middle of the line connecting the four first air holes 111 near the upper side; another two second air holes 112 are located in the middle of the line connecting the four first air holes 111 near the lower side; and the distance between adjacent air holes 11 is the same, optionally, the distance between adjacent holes is 2μm. Preferably, the gold film layer 2 covers the second air holes 112; the gold film layer 2 does not cover the first air holes 111; and the diameter of the first air holes 111 is larger than the diameter of the second air holes 112. Optionally, the diameter of the first air hole 111 is 1.65 μm; the diameter of the second air hole 112 is 1.32 μm.

[0037] In some exemplary embodiments, the photonic crystal fiber sensor further includes a perfectly matched layer (PML) 6, a ring-shaped structure located outside the fiber core 1. The introduction of the PML primarily addresses the discrepancy between the fiber model in the simulation environment and the actual fiber environment. By setting appropriate boundary conditions, this environmental discrepancy is effectively eliminated, making the simulation results more realistic. When a light beam strikes the perfectly matched layer 6, it is not immediately reflected back but gradually attenuates until it is completely absorbed. This non-reflective property makes the perfectly matched layer 6 an ideal boundary condition for simulation analysis. In particular, the use of the perfectly matched layer 6 can significantly improve the accuracy of simulation results when simulating large-mode-area fibers.

[0038] When the photonic crystal fiber sensor according to the embodiment of the present disclosure is working, the optical signal input end of the photonic crystal fiber sensor is connected to the polarization controller through a single-mode optical fiber, and the polarization controller controls the generation of X polarization and / or Y polarization.

[0039] Under the action of Y polarization, the gold film layer 2 generates surface plasmon resonance for detecting the refractive index of the analyte to be measured; under the action of Y polarization, the first ITO film layer 3 generates surface plasmon resonance for detecting the refractive index and temperature changes of the analyte to be measured; and under the combined action of Y polarization and X polarization, the second ITO film layer 122 generates surface plasmon resonance for detecting changes in external magnetic field intensity and temperature changes.

[0040] In the disclosed embodiment, the upper side of the sensor is used to detect the refractive index change of the analyte to be measured. The refractive index range of the medium to be measured under Y polarization is 1.17 to 1.33, and the maximum wavelength sensitivity is 1000 nm / RIU. The lower side is used to detect the refractive index change and temperature change of the analyte to be measured. The magnetic fluid filling hole 12 is used to detect the change of magnetic field intensity. The temperature detection range under Y polarization and X polarization is 20°C to 400°C, and the maximum temperature sensitivity is -0.5 nm / °C. The magnetic field intensity detection range under Y polarization and X polarization is 0 to 12 Oe, and the maximum magnetic field intensity sensitivity is 11.1 nm / Oe.

[0041] In the embodiment of the present invention, the refractive index of the fiber core 1 is obtained according to the Sellmeier equation, which is as follows:

[0042] (1)

[0043] Where n is the refractive index, λ is the wavelength, B i and C i is the Sellmeier coefficient determined empirically.

[0044] The dielectric constants of the gold film layer 2 , the first ITO film layer 3 , and the second ITO film layer 122 are calculated based on the Drude-Lorenz model.

[0045] Figure 2 The loss spectrum of the photonic crystal fiber sensor according to an embodiment of the present disclosure is schematically shown at a temperature of 20° C., a magnetic field strength of 10 Oe, and a refractive index of 1.31.

[0046] like Figure 2Figure 2 shows the loss spectrum of a photonic crystal fiber sensor according to an embodiment of the present disclosure at a temperature of 20°C, a magnetic field strength of 10 Oe, and a refractive index of 1.31. The absorption peak for Y polarization resonating with the gold film layer 2 is Peak I, with a wavelength of 1.21 μm. The absorption peak for Y polarization resonating with the second ITO film layer 122 for internal magnetic field measurement is Peak II, with a wavelength of 1.42 μm. The absorption peak for Y polarization resonating with the first ITO film layer 3 for external temperature and refractive index measurement is Peak III, with a wavelength of 1.84 μm. The absorption peak for X polarization resonating with the second ITO film layer 122 for internal magnetic field measurement is Peak IV, with a wavelength of 1.59 μm.

[0047] Figure 3 The loss spectra of the photonic crystal fiber sensor according to an embodiment of the present disclosure at different temperatures (temperature range 20° C.-400° C.) are schematically shown.

[0048] like Figure 3 As shown, Figure 3 (a) schematically shows the changes in the wavelength positions of absorption peaks I, II, and III of the photonic crystal fiber sensor according to an embodiment of the present disclosure at T=20°C, T=40°C, T=80°C, T=120°C, T=160°C, T=200°C, T=240°C, T=280°C, T=320°C, T=360°C, and T=400°C. Absorption peak I does not change with temperature; absorption peak II changes with temperature, with a sensitivity of -3 nm / °C; absorption peak III changes with temperature, with a sensitivity of -0.4 / °C. Figure 3 (b) in the figure analyzes the change in the wavelength position of the absorption peak IV of the photonic crystal fiber sensor according to the embodiment of the present disclosure at temperatures T=20°C, T=40°C, T=80°C, T=120°C, T=160°C, T=200°C, T=240°C, T=280°C, T=320°C, T=360°C and T=400°C. The absorption peak IV changes with temperature, and the sensitivity is -0.5nm / °C.

[0049] Figure 4 The figure schematically shows the loss spectra of the photonic crystal fiber sensor according to the embodiment of the present disclosure at different refractive indices (refractive index range 1.17-1.33).

[0050] like Figure 4 As shown, Figure 4(a) of FIG. 1 schematically shows the wavelength position changes of the absorption peaks I, II, III of the photonic crystal fiber sensor according to an embodiment of the present disclosure at the refractive indices na = 1.17, na = 1.18, na = 1.20, na = 1.22, na = 1.24, na = 1.26, na = 1.28, na = 1.30, na = 1.32, and na = 1.33. The absorption peak I changes with the refractive index, and the sensitivity is 604 nm / RIU. The absorption peak II does not change with the refractive index. The absorption peak III changes with the refractive index, and the sensitivity is 1000 nm / RIU. Figure 4 (b) of FIG. 1 schematically shows the changes of the absorption peak IV with the refractive index of the photonic crystal fiber sensor according to an embodiment of the present disclosure at the refractive indices na = 1.17, na = 1.18, na = 1.20, na = 1.22, na = 1.24, na = 1.26, na = 1.28, na = 1.30, na = 1.32, and na = 1.33. It can be seen that the absorption peak IV is not affected by the change of the refractive index.

[0051] Figure 5 FIG. 2 schematically shows the loss spectrum of the photonic crystal fiber sensor according to an embodiment of the present disclosure at different magnetic field strengths (magnetic field strength range 0-120 Oe).

[0052] As shown in FIG. 3, Figure 5 Figure 5 (a) of FIG. 3 schematically shows the wavelength position changes of the absorption peaks I, II, III of the photonic crystal fiber sensor according to an embodiment of the present disclosure at the magnetic field strengths B = 0 Oe, B = 20 Oe, B = 40 Oe, B = 60 Oe, B = 80 Oe, B = 100 Oe, and B = 120 Oe. The absorption peak I does not change with the magnetic field strength. The absorption peak II changes with the magnetic field strength, and the sensitivity is 6.6 nm / Oe. The absorption peak III does not change with the magnetic field strength. Figure 5 (b) of FIG. 3 schematically shows the wavelength position changes of the absorption peak IV of the photonic crystal fiber sensor according to an embodiment of the present disclosure at the magnetic field strengths B = 0 Oe, B = 20 Oe, B = 40 Oe, B = 60 Oe, B = 80 Oe, B = 100 Oe, and B = 120 Oe. The absorption peak IV changes with the magnetic field strength, and the sensitivity is 11.1 nm / Oe.

[0053] The above describes embodiments of the present disclosure. However, these embodiments are merely for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above separately, this does not mean that the measures in each embodiment cannot be used advantageously in combination. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, which should all fall within the scope of the present disclosure.​

Claims

1. A photonic crystal fiber sensor, characterized in that: include: The fiber core is a cylindrical structure, and the upper and lower sides of the fiber core are polished to form two mutually parallel cross-sections, namely the upper side and the lower side; A first ITO film layer is located on the lower side; A TiO2 layer is located on a side of the first ITO film layer away from the lower side; a PDMS layer, located on a side of the TiO2 layer away from the lower side; and a gold film layer, located on the upper side; The fiber core includes two magnetic fluid-filled holes, which are centrally symmetrically distributed relative to the center of the fiber core, and a line connecting the centers of the two magnetic fluid-filled holes is parallel to the upper side surface; and The fiber core includes air holes, and the air holes are centrally symmetrically distributed relative to the center of the fiber core; The magnetic fluid filling hole is a cylindrical structure; A second ITO film layer is provided on the cylindrical inner surface of the magnetic fluid-filled hole; The interior of the second ITO film layer is filled with magnetic fluid; The air holes include 10 first air holes and 4 second air holes, wherein the first air holes are evenly divided into 2 groups, each forming 2 regular hexagons with the magnetic fluid-filled hole as the center, and the two vertices of the regular hexagon located on the line connecting the centers of the two magnetic fluid-filled holes are not provided with first air holes; the two second air holes are located in the middle of the line connecting the 4 first air holes near the upper side; the other two second air holes are located in the middle of the line connecting the 4 first air holes near the lower side; and the distances between adjacent air holes are the same; The gold film layer covers the second air hole; The gold film layer does not cover the first air hole; and A diameter of the first air hole is greater than a diameter of the second air hole.

2. The photonic crystal fiber sensor according to claim 1, wherein It also includes a perfect matching layer, which is a ring-shaped structure and is located outside the fiber core.

3. The photonic crystal fiber sensor according to claim 1, wherein: Includes at least one of the following features: The thickness of the gold film layer is 50 nm; The thickness of the first ITO film layer is 40 nm; The thickness of the TiO2 layer is 150 nm; The thickness of the PDMS layer is 50 nm; The thickness of the second ITO film layer is 40 nm.

4. The photonic crystal fiber sensor according to claim 1, wherein: Includes at least one of the following features: The diameter of the magnetic fluid-filled hole is 1.98 μm; The diameter of the first air hole is 1.65 μm; The diameter of the second air pores is 1.32 μm.

5. The photonic crystal fiber sensor according to claim 1, wherein: When the photonic crystal fiber sensor is working, the optical signal input end of the photonic crystal fiber sensor is connected to the polarization controller through a single-mode optical fiber, and the polarization controller controls the generation of X polarization and / or Y polarization.

6. The photonic crystal fiber sensor according to claim 5, characterized in that: The gold film layer generates surface plasmon resonance under the action of Y polarization, which is used to detect the refractive index of the analyte to be measured; The first ITO film layer generates surface plasmon resonance under the action of Y polarization, which is used to detect the refractive index and temperature changes of the analyte to be measured; and The second ITO film layer generates surface plasmon resonance under the combined action of Y polarization and X polarization, which is used to detect changes in external magnetic field intensity and temperature.

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