Photonic crystal fiber sensor

Abstract

The invention provides a photonic crystal fiber sensor which can be applied to the technical field of fiber sensing. The sensor comprises a fiber core, the fiber core is of a cylindrical structure, the upper side and the lower side of the fiber core are polished to form two parallel tangent planes, and the tangent planes are the upper side face and the lower side face respectively; the first ITO film layer is positioned on the lower side surface; the TiO2 layer is positioned on one side, far away from the lower side surface, of the first ITO film layer; the PDMS layer is positioned on one side, far away from the lower side surface, of the TiO2 layer; the gold film layer is positioned on the upper side surface; wherein the fiber core comprises two magnetic fluid filling holes, the two magnetic fluid filling holes are distributed in a central symmetry mode relative to the center of the fiber core, and the connecting line of the centers of the two magnetic fluid filling holes is parallel to the upper side face; the fiber core comprises air holes, and the air holes are distributed in a central symmetry mode relative to the center of the fiber core. Through dual polarization and internal and external sensing arrangement, three physical quantities such as temperature, refractive index and magnetic field intensity can be measured at the same time, and the sensor also has the advantages of high sensitivity, large measurement range and the like.

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) have the characteristics of small size, simple structure, anti-electromagnetic interference, and high sensitivity. With its fast response speed, it can be applied to various scenarios. With the increase in scene complexity, in addition to the need for fiber optic sensors with higher sensitivity and wider detection range, the number of parameters that can be detected by photonic crystal fiber sensors based on SPR is also gradually increasing. However, existing fiber optic sensors cannot detect more than two parameters at the same time. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In order to solve the problem that optical fiber sensors in the prior art cannot measure more than two parameters at the same time, the embodiments of the present invention provide a photonic crystal fiber sensor, which can simultaneously measure three physical quantities such as temperature, refractive index and magnetic field intensity through dual polarization and internal and external sensing settings, and also has the advantages of high sensitivity and large measurement range.

[0005] (II) Technical solution

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

[0007] According to the first aspect of the present disclosure, a photonic crystal fiber sensor is provided, comprising: a core, the core being a cylindrical structure, the upper and lower sides of the 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 core comprises two magnetic fluid-filled holes, which are centrally symmetrically distributed relative to the center of the core, and a line connecting the centers of the two magnetic fluid-filled holes is parallel to the upper side; and the core comprises air holes, which are centrally symmetrically distributed relative to the center of the 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 of the line connecting the 4 first air holes near the upper side; the other 2 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.

[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 greater 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 50nm; the thickness of the first ITO film layer is 40nm; the thickness of the TiO2 layer is 150nm; the thickness of the PDMS layer is 50nm; and the thickness of the second ITO film layer is 40nm.

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

[0015] In some exemplary embodiments, 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 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] (III) 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 as well as 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, thus achieving overall low-interference multi-parameter detection.

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

[0022] (4) A SPR-based photonic crystal fiber sensor capable of measuring three parameters simultaneously was theoretically realized through 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 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;

[0025] Figure 2 The loss spectrum of the photonic crystal fiber sensor according to the embodiment of the present disclosure is schematically shown when the temperature is 20° C., the magnetic field strength is 10 Oe, and the refractive index is 1.31;

[0026] Figure 3 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.) is schematically shown;

[0027] Figure 4 The loss spectrum of the photonic crystal fiber sensor according to the embodiment of the present disclosure at different refractive indexes (refractive index range 1.17-1.33) is schematically shown; and

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

[0029] Reference numerals:

[0030] 1-fiber core; 11-air hole; 111-first air hole; 112-second air hole; 12-magnetic fluid filling 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 is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are 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 schematically shown.

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

[0034] Glossary: ​​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 filling hole 12 is a cylindrical structure; the cylindrical inner surface of the magnetic fluid filling hole 12 is provided with a second ITO film layer 122; 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 40nm.

[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 2 groups, and 2 regular hexagons are formed with the magnetic fluid-filled hole 12 as the center, and the first air holes 111 are not set at the 2 vertices of the regular hexagon located on the center line of the two magnetic fluid-filled holes 12; 2 second air holes 112 are located in the middle position of the line connecting the 4 first air holes 111 close to the upper side; another 2 second air holes 112 are located in the middle position of the line connecting the 4 first air holes 111 close to the lower side; and the distances between adjacent air holes 11 are the same, and optionally, the distances between adjacent holes are 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 hole 111 is greater than the diameter of the second air hole 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 6 (PML), which is a ring-shaped structure and is located outside the fiber core 1. The introduction of the PML is mainly to solve the problem of the difference between the fiber model in the simulation environment and the actual fiber environment. By setting appropriate boundary conditions, the environmental difference between the two is effectively eliminated, making the simulation results closer to the actual situation. When the light beam is incident on the perfectly matched layer 6, it will not be reflected back immediately, but will gradually attenuate until it is finally completely absorbed. This non-reflective feature makes the perfectly matched layer 6 an ideal boundary condition in simulation analysis, especially when simulating and analyzing large mode area optical fibers, the use of the perfectly matched layer 6 can significantly improve the accuracy of the simulation results.

[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 the single-mode optical fiber, and the polarization controller is used to control the generation of X polarization and / or Y polarization.

[0039] The gold film layer 2 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 3 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 122 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.

[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 1000nm / 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 -0.5nm / °C. The magnetic field intensity detection range under Y polarization and X polarization is 0 to 12Oe, and the maximum magnetic field intensity sensitivity is 11.1nm / Oe.

[0041] In the embodiment of the present invention, the refractive index of the 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 according to 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 when the temperature is 20° C., the magnetic field strength is 10 Oe, and the refractive index is 1.31.

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

[0047] Figure 3 The loss spectra of the photonic crystal fiber sensor according to the 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. The absorption peak I does not change with temperature; the absorption peak II changes with temperature, with a sensitivity of -3nm / °C; the absorption peak III changes with temperature, with a sensitivity of -0.4 / °C. Figure 3 (b) thereof analyzes the change in wavelength position of absorption peak IV of the photonic crystal fiber sensor according to an 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 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) are schematically shown.

[0050] like Figure 4 As shown, Figure 4(a) schematically shows the changes in the wavelength positions of absorption peaks I, II and III when the refractive index 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 of the photonic crystal fiber sensor according to an embodiment of the present disclosure. The absorption peak I changes with the refractive index, and the sensitivity is 604nm / 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 1000nm / RIU. Figure 4 (b) schematically shows that the absorption peak IV of the photonic crystal fiber sensor according to an embodiment of the present disclosure changes with the refractive index when the refractive index is 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 in the refractive index.

[0051] Figure 5 The loss spectrum of the photonic crystal fiber sensor according to the embodiment of the present disclosure under different magnetic field intensities (magnetic field intensity range 0-12 Oe) is schematically shown.

[0052] like Figure 5 As shown, Figure 5 (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 when the magnetic field strengths are B=0Oe, B=2Oe, B=4Oe, B=6Oe, B=8Oe, B=10Oe, and B=12Oe. 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 6.6nm / Oe; the absorption peak III does not change with the magnetic field strength. Figure 5 (b) schematically shows the change in wavelength position of absorption peak IV of the photonic crystal fiber sensor according to an embodiment of the present disclosure when magnetic field strengths are B=0Oe, B=2Oe, B=4Oe, B=6Oe, B=8Oe, B=10Oe and B=12Oe. The absorption peak IV changes with the magnetic field strength, and the sensitivity is 11.1nm / Oe.

[0053] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of 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: A fiber core, wherein the fiber core is a cylindrical structure, and the upper and lower sides of the fiber core are polished to form two mutually parallel cut surfaces, namely an upper side surface and a lower side surface; A first ITO film layer, located on the lower side; A TiO2 layer, 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.

2. The photonic crystal fiber sensor according to claim 1, characterized in that: The magnetic fluid filling 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.

3. The photonic crystal fiber sensor according to claim 1 or 2, characterized in that: The air holes include 10 first air holes and 4 second air holes, The first air holes are evenly divided into two groups, each of which forms two regular hexagons with the magnetic fluid filling hole as the center, and the first air holes are not set at the two vertices of the regular hexagon located on the line connecting the centers of the two magnetic fluid filling holes; The two second air holes are located in the middle of the line connecting the four first air holes close to the upper side surface; The other two second air holes are located in the middle of the line connecting the four first air holes close to the lower side surface; and The distances between adjacent air holes are the same.

4. The photonic crystal fiber sensor according to claim 3, characterized in that: The gold film layer covers the second air hole; and The gold film layer does not cover the first air hole.

5. The photonic crystal fiber sensor according to claim 3, characterized in that: A diameter of the first air hole is greater than a diameter of the second air hole.

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

7. The photonic crystal fiber sensor according to claim 2, characterized in that: Includes at least one of the following features: The thickness of the gold film layer is 50nm; The thickness of the first ITO film layer is 40 nm; The thickness of the TiO2 layer is 150nm; The thickness of the PDMS layer is 50 nm; The thickness of the second ITO film layer is 40 nm.

8. The photonic crystal fiber sensor according to claim 3, characterized in that: Includes at least one of the following features: The diameter of the magnetic fluid filling hole is 1.98 μm; The diameter of the first air hole is 1.65 μm; The diameter of the second air hole is 1.32 μm.

9. The photonic crystal fiber sensor according to claim 2, characterized in that: 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 the single-mode optical fiber, and the polarization controller is used to control the generation of X polarization and / or Y polarization.

10. The photonic crystal fiber sensor according to claim 9, 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 plasma 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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