Multifunctional soft glass detection photonic crystal fiber

Abstract

The invention discloses a multifunctional soft glass detection photonic crystal fiber, and relates to the technical field of optical fiber detection, in the detection photonic crystal fiber, soft glass with high permeability in a middle infrared band is selected as a material of an optical fiber substrate, and a plurality of layers of circular air holes are formed in the section direction of the optical fiber substrate; then, the positions of two sample channels and two fiber cores are correspondingly designed, so that the optical fiber sensing device simultaneously realizes refractive index and temperature sensing; the nanogold rods are buried in the two sample channels respectively to generate a surface plasma mode, the distance between a fiber core base mode and the surface plasma mode can be greatly reduced by arranging the holes in the cross section of the optical fiber substrate in a plurality of layers and lattices, and the coupling effect between the surface plasma mode and the fiber core base mode can be enhanced. And meanwhile, the two fiber cores are far away from each other and are separated by a plurality of layers of circular air holes, so that the mutual crosstalk between the two fiber core molds can be avoided, and the detection sensitivity of the optical fiber sensing device is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of optical fiber detection, and particularly to a multifunctional soft glass detection photonic crystal fiber. Background Art

[0002] Optical fiber sensing devices, as an advanced sensing technology, have demonstrated their great application potential and value in many fields. In particular, photonic crystal fiber sensing devices based on surface plasmon resonance have become one of the most promising development directions in this field due to their advantages such as a large dynamic measurement range, high sensitivity, and easy integration. Currently, the research on such optical fiber sensing devices mainly focuses on the visible and near-infrared bands. These optical fiber sensing devices can not only achieve temperature and refractive index sensing, but also high-precision pressure and magnetic field sensing, etc. However, the currently reported photonic crystal fiber sensing devices based on surface plasmon resonance have some limitations: First, these optical fiber sensing devices usually use silica as the substrate material, which will cause large material absorption losses during mid-infrared sensing, thus affecting the measurement accuracy of the optical fiber sensing device; Second, the sensing detection functions of these optical fiber sensing devices are relatively single, and they cannot detect multiple physical parameters simultaneously in the mid-infrared band, which greatly limits their application scope and makes them unable to meet the current requirements of the biochemical detection field for high-precision, ultrasensitive multifunctional optical fiber sensing detection technology.

[0003] Therefore, solving the above limitations of the existing surface plasmon resonance photonic crystal fiber sensing devices, while avoiding light damage or phototoxicity to biological samples during the detection process, and improving the detection sensitivity and accuracy of the optical fiber sensing device for larger samples such as living cells, is of extremely important significance in promoting social and economic development. Summary of the Invention

[0004] The purpose of the present application is to provide a multifunctional soft glass detection photonic crystal fiber, which can reduce the material absorption loss of the optical fiber sensing device while improving the detection sensitivity and accuracy of the optical fiber sensing device.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] In a first aspect, the present application provides a multifunctional soft glass detecting photonic crystal fiber. The material of the fiber substrate is a soft glass with high permeability in the mid-infrared band, and the cross-section of the fiber substrate is circular. A plurality of layers of circular air holes are arranged from top to bottom in the cross-section direction of the fiber substrate. The plurality of layers of circular air holes are symmetric about the center of the cross-section of the fiber substrate, and the number of circular air holes in each layer decreases layer by layer from the middle layer downwards or upwards. The circular air holes at the center positions of the top layer and the bottom layer are respectively used as the first sample channel and the second sample channel. A first nanorod is buried at the bottom of the first sample channel, and a liquid to be measured for refractive index sensing monitoring is injected into the first sample channel. A second nanorod is buried at the top of the second sample channel, and a thermosensitive liquid for temperature sensing monitoring is injected into the second sample channel. The circular air holes in the second layer below the first sample channel and the circular air holes in the second layer above the second sample channel are both replaced with soft glass of the same material as the fiber substrate, and are respectively used as the first core and the second core. According to the refractive index changes of the surface plasmon modes generated on the surfaces of the first nanorod and the second nanorod and the core fundamental modes generated on the surfaces of the first core and the second core, the refractive index of the liquid to be measured and the temperature of the thermosensitive liquid are monitored.

[0007] Optionally, nine layers of circular air holes are arranged from top to bottom in the cross-section direction of the fiber substrate. The number of circular air holes in the fifth layer is 7, the number of circular air holes in the fourth layer and the sixth layer are both 6, the number of circular air holes in the third layer and the seventh layer are both 5, the number of circular air holes in the second layer and the eighth layer are both 4, and the number of circular air holes in the top layer and the bottom layer are both 3. The circular air holes in adjacent layers are symmetric along the vertical line and arranged with gaps.

[0008] Optionally, the diameter of a single circular air hole is 1.8 μm to 2.6 μm; the three circular air holes with the closest distance to each other are arranged in an isosceles triangle. The center distance between two adjacent circular air holes in the same layer is 3 μm, and the center distance between each circular air hole and the closest circular air hole in its adjacent layer is 2.58 μm.

[0009] Optionally, the refractive index n of the liquid to be measured a is 1.43 to 1.55; the thermosensitive liquid is polydimethylsiloxane, and the relationship between the refractive index n of the thermosensitive liquid and the temperature T is n a =-4.5×10 a T + 1.4176. -4

[0010] Optionally, the diameters of the first sample channel and the second sample channel are 1.7 to 2.3 μm.

[0011] Optionally, the diameter of the first gold nanorod is 360 - 600 nm, and the diameter of the second gold nanorod is 260 - 500 nm.

[0012] Optionally, the cross-sectional diameter of the optical fiber substrate is 10 - 13 μm.

[0013] According to the specific embodiments provided in this application, the following technical effects are disclosed in this application:

[0014] This application provides a multifunctional soft glass detecting photonic crystal fiber. In this detecting photonic crystal fiber, soft glass with high permeability in the mid-infrared band is selected as the material of the optical fiber substrate, which can greatly reduce the material absorption loss of the fiber sensing device. A number of layers of circular air holes are arranged in the cross-sectional direction of the optical fiber substrate, and the positions of two sample channels and two cores are correspondingly designed, enabling the fiber sensing device to simultaneously achieve refractive index and temperature sensing; gold nanorods are respectively buried in the two sample channels to generate corresponding surface plasmon modes, and by adjusting the gold nanorod structure, the effective refractive index of the surface plasmon mode can be effectively adjusted, thereby effectively expanding the detection range of the fiber sensing device; these openings on the cross-section of the optical fiber substrate in the form of several layers and lattice arrangement can greatly reduce the distance between the core fundamental mode and the surface plasmon mode, enhance the coupling effect between the surface plasmon mode and the core fundamental mode, and at the same time, since the two cores are far apart and separated by several layers of circular air holes, the mutual crosstalk between the two core modes can be avoided, thereby improving the detection sensitivity of the fiber sensing device. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the following described drawings are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a schematic cross-sectional view of a multifunctional soft glass detecting photonic crystal fiber provided by an embodiment of this application.

[0017] Figure 2 It is a schematic structural view of a multifunctional soft glass detecting photonic crystal fiber sensing device provided by an embodiment of this application.

[0018] Figure 3 It is a schematic dispersion curve view between the Y-polarized core fundamental mode in the first core and the surface plasmon mode in the first sample channel.

[0019] Figure 4Schematic diagram of the loss curve between the Y-polarized core fundamental mode in the first core and the surface plasmon mode in the first sample channel.

[0020] Figure 5 Refractive index n of the liquid to be measured in the first sample channel a Schematic diagram of the loss curve of the Y-polarized core fundamental mode in the first core when n = 1.43 to 1.49.

[0021] Figure 6 Refractive index n of the liquid to be measured in the first sample channel a Schematic diagram of the loss curve of the Y-polarized core fundamental mode in the first core when n = 1.50 to 1.55.

[0022] Figure 7 When the refractive index n of the liquid to be measured a Schematic diagram of the linear fitting curve of the resonance wavelength with respect to the refractive index of the liquid to be measured when it is in the range of 1.43 to 1.55.

[0023] Figure 8 Schematic diagram of the dispersion curve between the Y-polarized core fundamental mode in the second core and the surface plasmon mode in the second sample channel.

[0024] Figure 9 Schematic diagram of the loss curve between the Y-polarized core fundamental mode in the second core and the surface plasmon mode in the second sample channel.

[0025] Figure 10 Schematic diagram of the loss curve of the Y-polarized core fundamental mode in the second core when the temperature T of the thermosensitive liquid in the second sample channel is -10 to 100 °C.

[0026] Figure 11 Schematic diagram of the loss curve of the Y-polarized core fundamental mode in the second core when the temperature T of the thermosensitive liquid in the second sample channel is 110 to 220 °C.

[0027] Figure 12 Schematic diagram of the linear fitting curve of the resonance wavelength with respect to the temperature of the thermosensitive liquid when the temperature T is in the range of -10 to 200 °C.

[0028] Reference numerals:

[0029] 1 - optical fiber substrate; 2 - circular air holes; 3 - first sample channel; 4 - second sample channel; 5 - first nanogold rod; 6 - second nanogold rod; 7 - first core; 8 - second core; 9 - isosceles triangle; 21 - supercontinuum light source; 22 - polarizer; 23 - coupling optical lens; 24 - detection porous fiber; 25 - spectral analyzer. Detailed implementation manner

[0030] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0031] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] In an exemplary embodiment, as Figure 1 shown, a multifunctional soft glass detection photonic crystal fiber is provided, wherein: the material of the fiber substrate 1 is soft glass with high permeability in the mid-infrared band, and the cross-section of the fiber substrate 1 is circular; several layers of circular air holes 2 are provided from top to bottom in the cross-section direction of the fiber substrate 1, and the several layers of circular air holes 2 are symmetric about the center of the cross-section of the fiber substrate 1, and the number of circular air holes 2 in each layer decreases layer by layer from the middle layer downwards or upwards; the circular air holes 2 at the central positions of the top layer and the bottom layer are respectively used as the first sample channel 3 and the second sample channel 4, a first nanorod 5 is buried at the bottom of the first sample channel 3, and a liquid to be measured for refractive index sensing monitoring is injected into the first sample channel 3; a second nanorod 6 is buried at the top of the second sample channel 4, and a thermosensitive liquid for temperature sensing monitoring is injected into the second sample channel 4; the circular air holes 2 in the second layer below the first sample channel 3 and the circular air holes 2 in the second layer above the second sample channel 4 are both replaced with soft glass of the same material as the fiber substrate 1, and are respectively used as the first core 7 and the second core 8; according to the refractive index changes of the surface plasmon modes generated on the surfaces of the first nanorod 5 and the second nanorod 6 and the core fundamental modes generated on the surfaces of the first core 7 and the second core 8, the refractive index of the liquid to be measured and the temperature of the thermosensitive liquid are monitored.

[0033] In a specific embodiment, as Figure 1 shown, nine layers of circular air holes 2 are provided from top to bottom in the cross-section direction of the fiber substrate 1. The number of circular air holes 2 in the middle layer, that is, the fifth layer, is 7, the number of circular air holes 2 in the fourth layer and the sixth layer are both 6, the number of circular air holes 2 in the third layer and the seventh layer are both 5, the number of circular air holes 2 in the second layer and the eighth layer are both 4, and the number of circular air holes 2 in the top layer and the bottom layer are both 3. The circular air holes 2 in adjacent layers are symmetric along the vertical line and arranged with gaps.

[0034] The first sample channel 3 and the second sample channel 4 are located at the central position of the outermost air holes of the fiber cladding; the circular air holes 2 in the second layer directly opposite to the lower part of the first sample channel 3 and the circular air holes 2 in the second layer directly opposite to the upper part of the second sample channel 4 are both replaced with soft glass having the same material as the fiber substrate 1, serving as the first core 7 and the second core 8 respectively; this core structure can not only effectively generate the core fundamental mode, but also enhance the coupling effect between the surface plasmon mode and the core fundamental mode. At the same time, since the first core 7 and the second core 8 are far apart from each other and separated by three layers of circular air holes 2, the mutual crosstalk between the two core fundamental modes can be avoided.

[0035] As an alternative embodiment, the diameters of the first sample channel 3 and the second sample channel 4 are 1.7 - 2.3 μm. The diameter of the first nanogold rod 5 is 360 - 600 nm, and the diameter of the second nanogold rod 6 is 260 - 500 nm. The cross-sectional diameter of the fiber substrate 1 is 10 - 13 μm. The diameter of a single circular air hole 2 is 1.8 μm - 2.6 μm; the three circular air holes 2 with the closest distance to each other are arranged in an isosceles triangle, as Figure 1 shown in 9 of [reference], the center distance between two adjacent circular air holes 2 in the same layer is 3 μm, and the center distance between each circular air hole 2 and the closest circular air hole 2 in its adjacent layer is 2.58 μm. This compressive lattice arrangement form of these circular air holes 2 can greatly reduce the distance between the core fundamental mode and the surface plasmon mode, thereby further enhancing the coupling effect between the surface plasmon mode and the core fundamental mode.

[0036] As an alternative embodiment, the refractive index n of the liquid to be measured a is 1.43 - 1.55; the thermosensitive liquid is polydimethylsiloxane, and the relationship between the refractive index n of the thermosensitive liquid and the temperature T is n a =-4.5×10 a T + 1.4176. -4

[0037] In a specific embodiment, the diameter of the first sample channel 3 for refractive index sensing and monitoring is 2.0 μm, the diameter of the first nanogold rod 5 in this channel is 480 nm, the diameter of the second sample channel 4 for temperature sensing and monitoring is 2.0 μm, the diameter of the second nanogold rod 6 in this channel is 380 nm, the diameter of other single circular air holes 2 is 2.4 μm, the base length of the isosceles triangle formed by three adjacent circular air holes 2 is 3.0 μm, the waist length is 2.58 μm, the refractive index of the liquid to be measured in the first sample channel 3 is 1.46, the thermosensitive liquid in the second sample channel 4 is polydimethylsiloxane, its temperature is 20 °C, and the radius of the cross-section of the entire detection photonic crystal fiber is 12.0 μm.

[0038] To facilitate the analysis of the actual application effect of the multifunctional soft glass detection photonic crystal fiber with the above structure provided by this application, the following will specifically analyze by combining a sensing device applying this detection photonic crystal fiber.

[0039] In this embodiment, a multifunctional soft glass detection photonic crystal fiber sensing device is provided, including: a supercontinuum light source 21, a polarizer 22, a coupling optical lens 23, a detection porous fiber 24, and a spectral analyzer 25, which are sequentially connected along the optical path propagation direction; the supercontinuum light source 21 is used to provide a stable light source output; the polarizer 22 is used to adjust the polarization state of the incident light wave; the coupling optical lens 23 is used to couple the polarized incident light wave into the detection porous fiber 24; the spectral analyzer 25 is used to monitor the real-time change of the surface plasmon resonance signal in the detection porous fiber 24; the detection porous fiber 24 is the multifunctional soft glass detection photonic crystal fiber as described in the previous embodiment.

[0040] Specifically, first, the liquid to be measured is injected into the first sample channel 3 of the detection photonic crystal fiber by using the capillary phenomenon of the liquid, and the thermosensitive liquid (polydimethylsiloxane) is injected into the second sample channel 4. Then, the detection photonic crystal fiber is horizontally placed on a three-dimensional fiber adjustment frame. The function of this three-dimensional fiber adjustment frame is to be able to adjust the position of the detection photonic crystal fiber in three-dimensional space. The detection photonic crystal fiber needs to be fixed on the three-dimensional fiber adjustment frame (the fixing method is to first place the detection photonic crystal fiber in the fiber clamp and press it tightly, and then install it in the three-dimensional fiber adjustment frame for fixation), and make it coaxial with the coupling optical lens 23; the polarizer 22 is used to adjust the incident light wave to Y-polarized light, and make the central axes of the first core 7 and the second core 8 of the multifunctional soft glass detection photonic crystal fiber parallel to the polarization direction of the incident Y-polarized light. Then, the polarized incident light wave is efficiently coupled into the core of the detection photonic crystal fiber by using the coupling optical lens 23 (it is necessary to place the first core 7 or the second core 8 of the detection photonic crystal fiber at the focus of the coupling optical lens 23), and the real-time monitoring is carried out by the spectral analyzer 25 at the receiving end.

[0041] The specific working principle is as follows: when the refractive index of the liquid to be measured in the first sample channel 3 decreases or the temperature of the thermosensitive liquid in the second sample channel 4 increases, the effective mode refractive indices of the surface plasmon mode and the core fundamental mode will also decrease accordingly. However, since the decrease amplitude of the effective mode refractive index of the surface plasmon mode is smaller than that of the core fundamental mode, the coupling resonance wavelength shifts towards the long-wavelength direction, resulting in a red shift of the absorption peak of the transmitted light wave input into the spectral analyzer 25. When the refractive index of the liquid to be measured in the first sample channel 3 increases or the temperature of the thermosensitive liquid in the second sample channel 4 decreases, the effective mode refractive indices of the surface plasmon mode and the core fundamental mode will also increase accordingly. However, since the increase amplitude of the effective mode refractive index of the surface plasmon mode is larger than that of the core fundamental mode, the coupling resonance wavelength shifts towards the short-wavelength direction, resulting in a blue shift of the transmitted absorption peak in the spectral analyzer 25. Therefore, the multifunctional soft glass detection photonic crystal fiber sensing device provided in this embodiment can monitor the changes in the refractive index of the liquid to be measured and the temperature of the thermosensitive liquid in real time and online.

[0042] The characteristics of the multifunctional soft glass detection photonic crystal fiber provided in this application are studied and analyzed below in combination with the measured data. First, the refractive index sensing characteristics of the detection fiber are studied, that is, the sensing characteristics between the Y-polarized core fundamental mode in the first core 7 of the fiber and the surface plasmon mode in the first sample channel 3 are studied first. The coupling resonance characteristics between the Y-polarized core fundamental mode in the first core 7 and the surface plasmon mode in the first sample channel 3 in this embodiment are as Figures 3 - 4 shown. It can be seen from Figure 3 that: at short wavelengths, the effective mode refractive index of the surface plasmon mode is smaller than the real part of the effective mode refractive index of the Y-polarized core fundamental mode. However, as the incident wavelength increases, the effective mode refractive indices of the two modes will gradually decrease, and the difference in the effective mode refractive indices will also gradually decrease. When the incident wavelength increases to 3.668 μm, the effective mode refractive indices of the Y-polarized core fundamental mode and the surface plasmon mode are equal, that is, the phase matching between the Y-polarized core fundamental mode and the surface plasmon mode is achieved. However, when the incident wavelength is further increased, the phase matching condition between the Y-polarized core fundamental mode and the surface plasmon mode will be destroyed, causing these two modes to be in a decoupled state again.

[0043] Figure 4 shows the loss curves of the Y-polarized core fundamental mode in the first core 7 of the detection fiber and the surface plasmon mode in the first sample channel 3 in this embodiment. It can be seen from Figure 4It can be found that: except at the resonant wavelength of 3.668 μm, the loss of the surface plasmon mode is always greater than that of the Y-polarized fundamental mode, and at the resonant wavelength, the loss values of the two modes are equal, that is, a complete coupling state is achieved between the two modes. In addition, the loss value of the X-polarized fundamental mode is very small and almost unchanged throughout the simulated wavelength range. This indicates that the X-polarized fundamental mode cannot couple with the surface plasmon mode.

[0044] Figures 5 - 6 The influence of the refractive index of the liquid to be measured in the first sample channel 3 on the loss of the Y-polarized fundamental mode in the first core 7 is given when other structural parameters of the fiber optic sensing device remain unchanged. Figure 5 It can be found that: when the refractive index of the liquid to be measured remains unchanged, the loss of the Y-polarized core fundamental mode first increases and then decreases with the increase of the incident wavelength. This is because when the incident light wavelength begins to increase, the difference between the effective mode refractive indices of the Y-polarized core fundamental mode and the surface plasmon mode will gradually decrease, making the coupling strength between the Y-polarized core fundamental mode and the surface plasmon mode gradually increase, and then resulting in more mode field energy being transferred from the Y-polarized core fundamental mode to the surface plasmon mode. When the wavelength increases to the point where the difference in effective mode refractive indices between the two mutually coupled modes is zero, the energy transferred from the Y-polarized core fundamental mode to the surface plasmon mode reaches the maximum, and thus a loss peak will be formed on the loss curve of the Y-polarized core fundamental mode. When the wavelength is further increased, the coupling strength between the Y-polarized core fundamental mode and the surface plasmon mode gradually weakens, causing the energy loss of the Y-polarized core fundamental mode to also decrease. On the other hand, as Figure 6 shown, when the refractive index of the liquid to be measured increases from 1.43 to 1.55, the loss peak wavelength of the Y-polarized core fundamental mode will undergo a blue shift, that is, it decreases from 3.903 μm to 2.88 μm. Moreover, in the refractive index range of 1.43 - 1.46, the loss peak of the Y-polarized core fundamental mode will increase with the increase of the refractive index of the liquid to be measured. This means that the coupling strength between the Y-polarized mode and the surface plasmon mode will also increase with the increase of the refractive index of the liquid to be measured, and complete coupling is achieved at 1.46. In addition, the Y-polarized core fundamental mode has only one loss peak in the broadband refractive index range of 1.43 - 1.55, indicating that the porous fiber optic sensing device designed in this embodiment can not only achieve broadband refractive index sensing in the mid-infrared band, but also has very good signal-to-noise ratio.

[0045] To further study the detection performance of this fiber optic sensing device, its wavelength sensitivity is studied next. Considering that the average sensitivity within a certain refractive index range is more meaningful than the local sensitivity between two points, a linear fit is performed on the resonant wavelength in Figure 3 relative to the refractive index of the liquid to be measured, and the fitting result is as shown in Figure 7As shown. When the refractive index of the liquid to be measured is in the range of 1.43 to 1.55, its linear fitting equation is: Y = -8603.3X + 16255. Y in the formula is the resonance wavelength, and its unit is micrometer. X is the refractive index of the liquid to be measured in the first sample channel 3. The slope of the fitting equation represents the average wavelength sensitivity of the fiber optic sensing device in the refractive index range of 1.43 to 1.55, which is -8603.3 nm / RIU, and the fitting linearity is as high as 0.9988. Based on this, the high sensitivity and linearity characteristics of this fiber optic sensing device make it very suitable for the sensing detection of high refractive index samples.

[0046] Next, the temperature sensing characteristics of the fiber optic sensing device were studied. Figures 8 - 9 The coupling characteristics between the Y-polarized core fundamental mode in the second core 8 and the surface plasmon mode in the second sample channel 4 are given. From Figure 8 it can be found that: at the coupling resonance wavelength of 3.852 μm, the effective mode refractive indices of the Y-polarized core fundamental mode in the second core 8 and the surface plasmon mode in the second sample channel 4 are equal, which means that the phase matching condition between the Y-polarized core fundamental mode and the surface plasmon mode is satisfied. When the wavelength is less than 3.852 μm, the effective mode refractive index of the surface plasmon mode is smaller than that of the Y-polarized core fundamental mode. On the contrary, when the wavelength is greater than 3.852 μm, the effective mode refractive index of the surface plasmon mode is larger than that of the Y-polarized core fundamental mode. From Figure 9 it can be seen that: at the phase matching wavelength of 3.852 μm, the loss of the Y-polarized core fundamental mode in the second core 8 is equal to the loss of the surface plasmon mode in the second sample channel 4, and at other wavelengths, the loss of the surface plasmon mode is greater than the loss of the Y-polarized core fundamental mode. In addition, the loss value of the X-polarized fundamental mode is very small and almost unchanged throughout the simulation wavelength range. This shows that the X-polarized fundamental mode in the second core 8 cannot couple with the surface plasmon mode in the second sample channel 4.

[0047] Figures 10 - 11 shows the influence of the temperature of the thermosensitive liquid polydimethylsiloxane in the second sample channel 4 on the loss of the Y-polarized fundamental mode in the second core 8 when other structural parameters of the fiber optic sensing device remain unchanged. From Figures 10 - 11It can be seen that when the temperature of the thermosensitive liquid remains constant, the loss of the Y-polarized core fundamental mode first increases and then decreases as the incident wavelength increases. This is because when the incident light wavelength begins to increase, the difference between the modal effective refractive indices of the Y-polarized core fundamental mode and the surface plasmon mode gradually decreases, making the coupling strength between the Y-polarized core fundamental mode and the surface plasmon mode gradually increase, and then resulting in more modal field energy transferring from the Y-polarized core fundamental mode to the surface plasmon mode. When the wavelength increases to the phase-matching wavelength, the energy transferred from the Y-polarized core fundamental mode to the surface plasmon mode reaches the maximum, thus forming a loss peak on the loss curve of the Y-polarized core fundamental mode. When the wavelength is further increased, the coupling strength between the Y-polarized core fundamental mode and the surface plasmon mode gradually weakens, causing the energy loss of the Y-polarized core fundamental mode to decrease accordingly. On the other hand, when the temperature of the thermosensitive liquid in the second sample channel 4 increases from -10°C to 200°C, the loss peak wavelength of the Y-polarized core fundamental mode undergoes a red shift, that is, from 3.749 μm to 4.411 μm. Moreover, within the temperature range of 0 to 200°C, the loss peak of the Y-polarized core fundamental mode decreases as the temperature of the thermosensitive liquid increases. In addition, the Y-polarized core fundamental mode has only one loss peak within the wideband temperature range of -10 to 200°C, indicating that the photonic crystal fiber sensing device designed in this embodiment can not only achieve wideband temperature sensing in the mid-infrared band, but also has a very good signal-to-noise ratio.

[0048] Finally, through Figure 12 the temperature sensitivity of this fiber optic sensing device was studied. Considering that the average sensitivity within a certain temperature range is more meaningful than the local sensitivity between two points, here Figures 10 - 11 the resonance wavelength in Figure 12 was linearly fitted with respect to the temperature of the thermosensitive liquid polydimethylsiloxane, and the fitting result is shown in Figure 12 . When the temperature of the thermosensitive liquid is within the range of -10 to 200°C, its linear fitting equation is: Y = 3.1559X + 3793. Here, Y is the resonance wavelength, with the unit of micrometer, and X is the temperature of the thermosensitive liquid in the second sample channel 4. The slope of the fitting equation represents the average temperature sensitivity of the fiber optic sensing device within the temperature range of -10 to 200°C, which is 3.1559 nm / °C, and the linearity is as high as 0.9987. Based on this, this fiber optic sensing device also has a very broad application prospect in ultra-wideband mid-infrared temperature sensing.

[0049] Through the above research and analysis, it can be known that for the multifunctional soft glass detecting photonic crystal fiber provided in the above embodiments of the present application, the designed double-core and double-sample-channel structure enables the fiber optic sensing device to simultaneously achieve refractive index and temperature sensing. Moreover, since a soft glass with high permeability in the mid-infrared band is selected for drawing, the material absorption loss of the fiber optic sensing device can be greatly reduced. It can not only achieve an average wavelength sensitivity as high as -8603.3 nm / RIU in the broadband refractive index range of 1.43 to 1.55, but also achieve an average temperature sensitivity as high as 3.1559 nm / °C in the ultra-wideband temperature range of -10 to 200 °C. This is because the nano-metal rod buried structure adopted by the fiber optic sensing device can effectively adjust the mode effective refractive index, thereby effectively expanding the detection range of the fiber optic sensing device, and the lattice compression structure adopted can effectively enhance the coupling strength between the core mode and the surface plasmon mode, thereby improving the detection sensitivity of the fiber optic sensing device.

[0050] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0051] Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. At the same time, for those of ordinary skill in the art, based on the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A multifunctional soft glass detecting photonic crystal fiber, characterized in that, The material of the optical fiber substrate is soft glass with high permeability in the mid-infrared band, and the cross-section of the optical fiber substrate is circular; several layers of circular air holes are arranged from top to bottom in the cross-section direction of the optical fiber substrate. The several layers of circular air holes are symmetric about the center of the cross-section of the optical fiber substrate, and the number of circular air holes in each layer decreases layer by layer from the middle layer downwards or upwards; the circular air holes at the central positions of the top layer and the bottom layer are respectively used as the first sample channel and the second sample channel. A first nanogold rod is buried at the bottom of the first sample channel, and a liquid to be measured for refractive index sensing monitoring is injected into the first sample channel; a second nanogold rod is buried at the top of the second sample channel, and a thermosensitive liquid for temperature sensing monitoring is injected into the second sample channel; the circular air holes in the second layer below the first sample channel and the circular air holes in the second layer above the second sample channel are both replaced with soft glass of the same material as the optical fiber substrate, and are respectively used as the first core and the second core; according to the refractive index changes of the surface plasmon modes generated on the surfaces of the first nanogold rod and the second nanogold rod and the core-based modes generated on the surfaces of the first core and the second core, the refractive index of the liquid to be measured and the temperature of the thermosensitive liquid are monitored.

2. The multifunctional soft glass detecting photonic crystal fiber according to claim 1, characterized in that, Nine layers of circular air holes are arranged from top to bottom in the cross-section direction of the optical fiber substrate. The number of circular air holes in the fifth layer is 7, the number of circular air holes in the fourth layer and the sixth layer are both 6, the number of circular air holes in the third layer and the seventh layer are both 5, the number of circular air holes in the second layer and the eighth layer are both 4, and the number of circular air holes in the top layer and the bottom layer are both 3. The circular air holes in adjacent layers are symmetric along the vertical line and arranged with gaps.

3. The multifunctional soft glass detecting photonic crystal fiber according to claim 1, characterized in that, The diameter of a single circular air hole is 1.8 μm to 2.6 μm; the three circular air holes with the closest distance to each other are arranged in an isosceles triangle. The center distance between two adjacent circular air holes in the same layer is 3 μm, and the center distance between each circular air hole and the closest circular air hole in its adjacent layer is 2.58 μm.

4. The multifunctional soft glass detecting photonic crystal fiber according to claim 1, characterized in that, The refractive index n of the liquid to be measured a is 1.43 to 1.55; the thermosensitive liquid is polydimethylsiloxane, and the refractive index n of the thermosensitive liquid a The relationship with the temperature T is n a =-4.5×10 -4 T + 1.4176.

5. The multifunctional flexible glass detecting photonic crystal fiber according to claim 1, wherein The diameters of the first sample channel and the second sample channel are 1.7 to 2.3 μm.

6. The multifunctional flexible glass fiber optic probe for detecting photonic crystal fiber according to claim 1, wherein The diameter of the first nanogold rod is 360 to 600 nm, and the diameter of the second nanogold rod is 260 to 500 nm.

7. The multifunctional soft glass detecting photonic crystal fiber according to claim 1, characterized in that, The cross-section diameter of the optical fiber substrate is 10 to 13 μm.

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