A bifunctional hollow-core anti-resonant optical fiber device based on surface plasmon effect

Abstract

The application discloses a kind of based on the dual-function hollow-core anti-resonant optical fiber device of surface plasmon effect, belong to optical fiber communication and optical fiber sensor device technical field.The device includes central core, asymmetric anti-resonant cladding surrounding central core and outer support pipe being sleeved in the outside of anti-resonant cladding;Anti-resonant cladding is divided into X direction transmission subarea and Y direction coupling subarea;X direction transmission subarea includes 4 continuous anti-resonant pipe units of symmetrical arrangement;Y direction coupling subarea includes 2 double-layer nested pipe units of symmetrical arrangement;Central core and cladding hole are filled with thermosensitive mixed solution.The application satisfies phase matching condition by adjusting the gradient wall thickness of outer sleeve pipe in double-layer nested pipe unit, excites surface plasmon resonance at gold film and thermosensitive mixed solution interface, to realize the dual-function integration of polarization filtering and temperature sensing.The application device can realize polarization filtering and temperature sensing function, and has good bending stability.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication and optical fiber sensor technology, specifically relating to a bifunctional hollow-core antiresonant optical fiber device based on the surface plasmon resonance effect. This device can be used in polarization control, temperature monitoring, and optical fiber communication. Background Technology

[0002] Modern optical communication networks and industrial monitoring systems increasingly demand compact, multifunctional optical components to ensure stable operation in complex environments. Hollow-core anti-resonant fiber (HC-ARF) provides an excellent platform for integrating multifunctional devices due to its low transmission loss and flexible structural tunability. Integrating polarization filtering and temperature sensing functions into a single fiber structure not only reduces system complexity but also enhances the system's resistance to environmental thermal disturbances and polarization fluctuations, which is of great significance for achieving miniaturization and high reliability of fiber optic devices.

[0003] Currently, fiber optic devices based on the surface plasmon resonance (SPR) effect have been extensively studied, mainly including sensors based on photonic crystal fiber (PCF) and hollow-core antiresonant fiber. However, traditional solid-core PCF is often limited by the intrinsic absorption of the substrate material (such as silicon dioxide) in specific wavelength bands and the low mode field overlap between the optical field and the analyte, restricting its performance in high-sensitivity detection applications. In contrast, hollow-core antiresonant fiber has a larger hollow core and cladding holes, which facilitates the introduction of functional liquids or metal functional layers, thereby enhancing the interaction between the guided mode and the functional liquid / metal interface, which is beneficial to improving the sensing and control performance of the device. Although some studies have achieved high-sensitivity sensing or single-polarization transmission by introducing metal coatings or asymmetric structures, achieving both high polarization extinction ratio (PER) and high temperature sensitivity on a single fiber platform remains a significant challenge.

[0004] In summary, most existing hollow-core fiber devices are optimized for a single function. Furthermore, the complex coupling mechanism between the fiber core fundamental mode and the surface plasmon polariton (SPP) mode easily leads to a trade-off between polarization filtering purity and sensing sensitivity. Therefore, existing technologies struggle to maintain high sensitivity to changes in ambient temperature while ensuring effective polarization filtering. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a dual-function hollow-core anti-resonant fiber device based on surface plasmon resonance effect. Through an asymmetric cladding structure design, it integrates polarization filtering and temperature sensing functions.

[0006] The technical solution of the present invention to solve the above problems is:

[0007] A dual-function hollow-core anti-resonant fiber device based on surface plasmon resonance effect includes a central fiber core, an asymmetric anti-resonant cladding surrounding the central fiber core, and an outer support tube sleeved on the outside of the asymmetric anti-resonant cladding.

[0008] Let the fiber axis be the z-axis. The asymmetric anti-resonant cladding is divided into an X-axis transmission partition and a Y-axis coupling partition along the orthogonal coordinate axis of the fiber cross-section.

[0009] The X-direction transmission partition includes four symmetrically arranged integrated anti-resonant tube units; the integrated anti-resonant tube unit is generally gourd-shaped and consists of a flat glass plate and a large and a small circular tube located on both sides of it; the anti-resonance mechanism is used to confine the light field to the central fiber core region, providing a low-loss transmission channel for the X-polarization fundamental mode.

[0010] The Y-axis coupling partition includes two symmetrically arranged double-layer nested tube units; each double-layer nested tube unit consists of an inner tube and an outer tube, both of which are arc-shaped structures. The ends of the arc-shaped structures are connected to an outer support tube. The wall thickness of the outer tube gradually decreases from the apex to the edge, used to construct phase-matching conditions over a wide spectral range. An arc-shaped annular interlayer is formed between the inner and outer tubes, and a gold film for exciting surface plasmon resonance is deposited within this arc-shaped annular interlayer.

[0011] The holes in the central fiber core and the asymmetric anti-resonant cladding are filled with a thermosensitive mixed solution.

[0012] Through the synergistic effect of gradually varying wall thickness, gold film, and thermosensitive mixed solution, the resonant coupling between the Y-polarized fundamental mode and the surface plasmon mode is enhanced, allowing the energy of the Y-polarized fundamental mode to be coupled to the surface of the gold film, thereby filtering out the Y-polarized state. At the same time, the thermo-optic effect of the thermosensitive refractive index tunable liquid medium is used to convert the external temperature change into a shift in the surface plasmon resonance wavelength, thus simultaneously completing the fiber optic temperature sensing detection.

[0013] Furthermore, the integrated anti-resonant tube unit, the double-layer nested tube unit, and the outer support tube are all made of silicon dioxide material.

[0014] Furthermore, in the integrated anti-resonant tube unit, the centers of the large circular tube, the small circular tube, and the hollow fiber core are located on the same straight line, and this straight line is perpendicular to the planar glass plate.

[0015] Furthermore, the large circular tube is tangent to the inner wall of the asymmetric anti-resonant cladding.

[0016] Furthermore, the diameter D of the central fiber core c It is 10μm.

[0017] Furthermore, in the integrated anti-resonant tube unit, the radius r1 of the large circular tube ranges from 5.5μm to 6.5μm, and the radius r2 of the small circular tube ranges from 4.5μm to 5.5μm.

[0018] Furthermore, in the double-layer nested tube unit, the radius r3 of the outer sleeve is 14 μm, and the radius r4 of the inner sleeve is 11 μm; the maximum wall thickness t of the outer sleeve... a The minimum wall thickness is 1.3 μm, t. b The thickness is 0.6 μm, and the change in tube wall thickness is a cosine gradient.

[0019] Furthermore, the wall thickness T1 of the outer support tube is 5 μm, and the fiber radius R is 28 μm.

[0020] Furthermore, the thermosensitive mixed solution is prepared by mixing ethanol and chloroform in a volume ratio of 1:1.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. Dual-function integration of polarization filtering and temperature sensing: This invention uses an asymmetric cladding structure design to simultaneously construct a low-loss transmission channel for X-polarization and a surface plasmon resonance coupling channel for Y-polarization in the same hollow anti-resonant fiber, thereby achieving the filtering out of non-target polarization states; at the same time, it utilizes the thermo-optic effect of a thermosensitive mixed solution to convert temperature changes into resonant wavelength shifts, thereby achieving temperature sensing.

[0023] 2. High polarization extinction ratio and wide filtering bandwidth: Utilizing the coupling effect induced by the nested tube with gradient wall thickness, the device has a peak polarization extinction ratio of over 300 in the working band, and a polarization extinction ratio greater than 100 in the 280nm wide spectral range from 1.06μm to 1.34μm, which enables single polarization transmission with high polarization extinction ratio.

[0024] 3. High temperature sensitivity and good linearity: Within the temperature range of -10℃ to 60℃, the average temperature sensitivity reaches 3.42nm / ℃, and the linear fit goodness R² is 0.9983, which enables relatively accurate monitoring of ambient temperature.

[0025] 4. Good bending resistance: When the bending radius is as low as 5cm, the X-polarization transmission loss is still less than 0.34dB / cm, and the resonant wavelength remains stable, which helps to ensure the reliability of the device in complex deployment environments.

[0026] 5. Larger manufacturing process tolerance: Since the resonant wavelength is mainly determined by the double-layer nested tube unit structure of the Y-direction coupling partition, the fluctuation of the size and uniform wall thickness of the integrated anti-resonant tube unit of the X-direction transmission partition within a reasonable range has little impact on the core performance of the device, which helps to reduce the difficulty of the fiber drawing process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the cross-sectional structure of the dual-function hollow-core anti-resonant optical fiber device proposed in this invention;

[0028] Figure 2 This is a performance analysis diagram of the embodiment of the present invention under optimal structural parameters; wherein (a) is the effective refractive index curve of the Y-polarized fundamental mode and the surface plasmon mode and the confinement loss curve of the Y-polarized fundamental mode at the operating temperature of 20℃, and the inset shows the mode field distribution at the wavelengths corresponding to the phase matching point and the non-phase matching point; (b) is the confinement loss spectrum of the Y-polarized fundamental mode and the X-polarized fundamental mode at different temperatures, (c) is the polarization extinction ratio spectrum at different temperatures, and (d) is the linear fitting curve of the resonance wavelength changing with temperature;

[0029] Figure 3 This is the curve showing the effect of the large circle radius r1 of the integrated anti-resonant tube unit on the Y-polarized fundamental mode confinement loss spectrum;

[0030] Figure 4 The curves show the influence of the large circle radius r1 of the integrated anti-resonant tube unit on the polarization filtering and temperature sensing performance of the device; where (a) is the polarization extinction ratio spectrum under different r1, and (b) is the curve of resonance peak confinement loss and temperature sensitivity as a function of r1.

[0031] Figure 5 This is the curve showing the effect of the small circular tube radius r2 of the integrated anti-resonant tube unit on the Y-polarized fundamental mode confinement loss spectrum;

[0032] Figure 6 The curves show the influence of the small circular tube radius r2 of the integrated anti-resonant tube unit on the polarization filtering and temperature sensing performance of the device; where (a) is the polarization extinction ratio spectrum under different r2, and (b) is the curve of resonance peak confinement loss and temperature sensitivity as a function of r2.

[0033] Figure 7 It is the maximum value of the gradient wall thickness t a The effect curve on the Y-polarized fundamental mode confinement loss spectrum;

[0034] Figure 8 It is the maximum value of the gradient wall thickness t a The curves show the effects of device polarization filtering and temperature sensing performance; where (a) represents different t values. a The polarization extinction ratio spectral lines below, (b) are the resonance peak confinement loss and temperature sensitivity as ta The curve of change;

[0035] Figure 9 It is the minimum value t of the gradient wall thickness. b The effect curve on the Y-polarized fundamental mode confinement loss spectrum;

[0036] Figure 10 It is the minimum value t of the gradient wall thickness. b The curves show the effects of device polarization filtering and temperature sensing performance; where (a) represents different t values. b The polarization extinction ratio spectral lines below, (b) are the resonance peak confinement loss and temperature sensitivity as t b The curve of change;

[0037] Figure 11 This is the curve showing the effect of uniform tube wall thickness t on the Y-polarized fundamental mode confinement loss spectrum;

[0038] Figure 12 The curves show the effect of uniform tube wall thickness t on the polarization filtering and temperature sensing performance of the device; where (a) is the polarization extinction ratio spectrum at different t, and (b) is the curve of resonance peak confinement loss and temperature sensitivity as a function of t.

[0039] Figure 13 The curves show the bending loss characteristics of the present invention when it is bent along the X-axis (bending angle α=0°); where (a) is the bending loss spectrum of the X-polarized fundamental mode and the Y-polarized fundamental mode under different bending radii, and (b) is the bending loss curve of the X-polarized fundamental mode and the Y-polarized fundamental mode at the resonance wavelength as a function of the bending radius.

[0040] Figure 14 The curves show the bending loss characteristics of the present invention when it is bent along the Y-axis (bending angle α = 90°); where (a) is the bending loss spectrum of the X-polarized fundamental mode and the Y-polarized fundamental mode under different bending radii, and (b) is the bending loss curve of the X-polarized fundamental mode and the Y-polarized fundamental mode at the resonance wavelength as a function of the bending radius.

[0041] Explanation of the reference numerals: 1. Central fiber core, 2. Integrated anti-resonant tube unit, 3. Outer support tube, 4. Inner sleeve, 5. Gold film, 6. Outer sleeve. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0043] like Figure 1 As shown, the present invention provides a dual-function hollow-core anti-resonant optical fiber device, comprising a central fiber core, an asymmetric anti-resonant cladding surrounding the central fiber core, and an outer support tube sleeved on the outside of the asymmetric anti-resonant cladding.

[0044] Let the optical fiber axis be the z-axis. The asymmetric anti-resonant cladding is divided into an X-axis transmission partition and a Y-axis coupling partition along the orthogonal coordinate axis of the optical fiber cross-section.

[0045] The X-direction transmission partition includes four symmetrically arranged integrated anti-resonant tube units; the integrated anti-resonant tube unit is generally gourd-shaped and consists of a flat glass plate and a large and a small circular tube located on both sides of it; the anti-resonance mechanism is used to confine the light field to the central fiber core region, providing a low-loss transmission channel for the X-polarized fundamental mode.

[0046] The Y-axis coupling partition includes two symmetrically arranged double-layer nested tube units; each double-layer nested tube unit consists of an inner tube and an outer tube, both of which are arc-shaped structures. The two ends of the arc-shaped structures are connected to an outer support tube. The wall thickness of the outer tube gradually decreases from the apex to the edge in a continuous cosine gradient, which is used to construct phase matching conditions in a wide spectral range. An arc-shaped annular sandwich is formed between the inner tube and the outer tube, and a gold film for exciting surface plasmon resonance is deposited in the arc-shaped annular sandwich.

[0047] The holes in the central fiber core and the asymmetric anti-resonant cladding are filled with a thermosensitive mixed solution; the thermosensitive mixed solution is a mixture of ethanol and chloroform in a volume ratio of 1:1.

[0048] After optimization, the optimal parameters of the optical fiber structure determined in this embodiment are shown in Table 1.

[0049] Fiber radius R 28μm Support tube thickness <![CDATA[T1]]> 5μm Central core diameter <![CDATA[D c ]]> 10μm The thickness of the integrated anti-resonant tube unit and the inner sleeve wall t 0.65μm Inner radius of the large circular tube of the integrated anti-resonant tube unit <![CDATA[r1]]> 6μm Inner radius of the small circular tube in the integrated anti-resonant tube unit <![CDATA[r2]]> 5μm Outer sleeve inner radius <![CDATA[r3]]> 14μm Inner radius of inner sleeve <![CDATA[r4]]> 11μm Maximum gradient wall thickness <![CDATA[t a ]]> 1.3μm Minimum gradient wall thickness <![CDATA[t b ]]> 0.6μm

[0050] The asymmetric cladding structure proposed in this invention achieves mode coupling by controlling the tube wall thickness. First, to induce surface plasmon resonance at the target operating wavelength, the cladding tube thickness must satisfy the resonance condition in the anti-resonant reflecting optical waveguide (ARROW) model. The resonant thickness t of the cladding tube... res The calculation formula is as follows:

[0051]

[0052] Where m is the resonance order (taken as 1 in this invention), λ is the operating wavelength, and n clad n is the refractive index of the silicon dioxide substrate material. core The refractive index of the filling fluid within the core and cladding pores is denoted by t. This is achieved by adjusting the apex thickness t of the gradient wall thickness outer tube. a With edge thickness t b To approximate this resonance condition, an efficient coupling channel is established.

[0053] To achieve phase matching over a wide spectral range, the radial wall thickness t(θ) of the outer sleeve follows the cosine gradient distribution model as follows:

[0054]

[0055] In the formula, It is the azimuth angle starting from the vertex position closest to the central fiber core. The azimuth angle is the boundary angle of the outer sleeve wall. This continuous thickness transition facilitates the formation of a smooth phase-matched distribution over a wide spectral range, which helps to extend the operating bandwidth of the polarization filter.

[0056] To achieve precise temperature sensing, an ethanol-chloroform mixture solution filled in the core and cladding pores has a refractive index n. liquid The variation of (T) with ambient temperature T approximately follows a linear weighted model:

[0057]

[0058] In the formula, The value represents the volume fraction of chloroform, T0 is the reference temperature (293.15 K, i.e., 20 °C), and n... chl and n eth These are the refractive indices of the components at the reference temperature. and For each, represents its respective thermo-optic coefficient.

[0059] The gold film deposited in the gaps between the nested tubes is the core of the SPR effect, and its complex permittivity is crucial. The Drude-Lorentz model is used for characterization:

[0060]

[0061] This model accurately describes the intrinsic dispersion characteristics of gold in the infrared band, where ε ∞ Let ω be the dielectric constant at infinite frequency, and ω be the incident light angular frequency. D γ is the plasma frequency. D Ω is the damping frequency, Δε is the Lorentz oscillator weighting factor, and Ω is the oscillator frequency. L Γ is the center frequency of the Lorentz oscillator. L The spectral width of the Lorentz oscillator.

[0062] When evaluating the bending resistance of the device, this invention uses the conformal mapping method to equate the bent optical fiber to one with a corrected refractive index distribution n. eq Straight optical fiber:

[0063]

[0064] Where, n material R is the original refractive index. b α is the bending radius, and α is the angle between the bending direction and the x-axis (α=0° indicates bending along the x-axis, α=90° indicates bending along the y-axis).

[0065] The energy attenuation of the optical fiber in each polarization state is evaluated using the imaginary part of the effective refractive index calculated by the finite element method. The formula for calculating its confinement loss (CL) is as follows:

[0066]

[0067] As core indicators for evaluating the polarization filtering and temperature sensing performance of this invention, the polarization extinction ratio (PER) and temperature sensitivity (P0) are... The calculation formulas for ) are as follows:

[0068]

[0069]

[0070] Among them, CL y and CL x The limiting losses for the Y-polarized fundamental mode and the X-polarized fundamental mode, respectively. This represents the resonant loss peak shift. This represents the change in ambient temperature.

[0071] I. Sensing and Filtering Performance Analysis

[0072] Combination Figure 2(a) to Figure 2 As shown in (d), at 20℃, the effective refractive index curves of the Y-polarization Fundamental Mode (YPFM) and the SPP mode intersect at 1.18 μm, satisfying the phase-matching condition and inducing resonant absorption, generating a confinement loss peak of approximately 49 dB / cm, verifying the effect of gradient wall thickness design on enhancing resonant coupling. Figure 2 As shown in (b), within the operating temperature range of -10℃ to 60℃, due to the significant thermo-optic effect of the filled thermosensitive mixed solution, the resonance loss peak exhibits a redshift with increasing temperature; simultaneously, the X-polarization Fundamental Mode (XPFM), due to its asymmetric structural design, remains mismatched with the gold film, maintaining low-loss transmission below 5dB / cm within the studied spectral range, and exhibits no significant resonance fluctuations. Figure 2 As shown in (c), quantitative evaluation results indicate that the device's peak polarization extinction ratio (PER) exceeds 300, and by adjusting the ambient temperature, a PER greater than 100 can be maintained across a broad spectral range of 280 nm from 1.06 μm to 1.34 μm. Figure 2 As shown in (d), by linearly fitting the resonant wavelength at different temperatures, the average temperature sensitivity of the device reaches 3.42 nm / ℃, and the goodness of fit R² is 0.9983, indicating that the structure can realize the dual functions of single polarization transmission and temperature monitoring.

[0073] II. Structural Parameter Analysis and Performance Optimization

[0074] To achieve better filtering and sensing performance and to evaluate the manufacturing tolerance of the device, this invention studies five core structural parameters (r1, r2, t). a ,t b The impact of ,t) on device performance.

[0075] 1. The effect of the radius r1 of the large circular tube in the integrated anti-resonant tube unit on performance

[0076] To evaluate the modulation effect of the integral tube geometry on the dual-function characteristics of the optical fiber, while keeping other parameters constant, the radius of the large circular tube of the integral anti-resonant tube unit was varied from 5.5 μm to 6.5 μm. Figure 3 The relationship between the confinement loss of the Y-polarized fundamental mode and r1 at different temperatures is shown. Figure 4 (a) shows the relationship between the PER spectral lines and r1; Figure 4 (b) shows the curves of resonance peak loss and temperature sensitivity as a function of r1. Figure 3As shown, changing r1 has little effect on the central resonant wavelength, which stabilizes at approximately 1.145 μm and 1.18 μm at 10°C and 20°C, respectively, indicating that the resonant wavelength is mainly determined by the Y-axis nested tube structure. Figure 4 As shown in (a) and (b), the polarization extinction ratio increases with the increase of r1; when r1 = 6.0 μm, the confinement loss and temperature sensitivity reach their maximum values ​​simultaneously, approximately 49 dB / cm and 3.5 nm / °C, respectively. Considering both resonant coupling strength and sensitivity, the radius r1 of the large circular tube of the integrated anti-resonant tube unit was finally selected as 6.0 μm, which also exhibits good performance in the range of 5.5~6.5 μm and has good fabrication tolerance.

[0077] 2. The effect of the small circle radius r2 of the integrated anti-resonant tube unit on performance

[0078] To further determine the parameters of the internal structure of the integrated tube, while keeping other parameters constant, the radius r2 of the small circular tube of the integrated anti-resonant tube unit was varied from 4.5 μm to 5.5 μm. Figure 5 The relationship between the confinement loss of the Y-polarized fundamental mode and r2 at different temperatures is shown. Figure 6 (a) shows the relationship between the PER spectral lines and r2; Figure 6 (b) shows the relationship between resonance peak confinement loss and temperature sensitivity as a function of r2. Figure 5 As shown, the central resonant wavelength is relatively insensitive to changes in r2, exhibiting good wavelength stability. Figure 6 As shown in (a), increasing r2 is beneficial for enhancing the attenuation of Y-polarized light, increasing the peak PER from approximately 180 to over 360. Figure 6 As shown in (b), the temperature sensitivity reaches a peak of approximately 3.5 nm / ℃ at r2 = 5.0 μm. Considering the resonant coupling strength, polarization extinction ratio, and temperature sensitivity, the radius r2 of the small circular tube of the integrated anti-resonant tube unit was finally selected as 5.0 μm, which exhibits good performance in the range of 4.5~5.5 μm and has good fabrication tolerance.

[0079] 3. Maximum gradient wall thickness t a Impact on performance

[0080] To control the operating band of the device while keeping other parameters constant, the maximum gradient wall thickness t is set... a It changed from 1.1 μm to 1.5 μm. Figure 7 Different t were shown a The confinement loss of the Y-polarized fundamental mode as a function of wavelength; Figure 8 (a) shows different t a PER lines below; Figure 8 (b) shows the limiting loss and temperature sensitivity as a function of t. aThe curve of change. For example... Figure 7 As shown, increasing t a The induced loss peak exhibits a significant redshift, with the resonance wavelength shifting from 1.06 μm to 1.30 μm at 20 °C, indicating that t a It plays a major role in controlling the phase-matching wavelength. For example... Figure 8 As shown in (b), the temperature sensitivity varies with t a The increase in [value] showed a linear positive correlation, rising from 3.0 nm / ℃ to 4.0 nm / ℃. To balance the polarization extinction ratio and temperature sensitivity, the maximum gradient wall thickness, t, was ultimately selected. a It is 1.3μm.

[0081] 4. Minimum gradient wall thickness t b Impact on performance

[0082] To optimize the impact of gradient evolution on coupling strength, while keeping other parameters constant, the minimum gradient wall thickness t is set. b It changed from 0.4 μm to 0.8 μm. Figure 9 Different t were shown b The confinement loss of the Y-polarized fundamental mode as a function of wavelength; Figure 10 (a) shows different t b PER lines below; Figure 10 (b) shows the limiting loss and temperature sensitivity as a function of t. b The curve of change. For example... Figure 9 As shown, t b The increase only causes a slight redshift of the resonant wavelength, mainly playing a fine-tuning role. For example... Figure 10 As shown in (a) and (b), the smaller t b This induces stronger polarization coupling, causing the confinement loss to be lower than t. b The peak value is reached near 0.5 μm. Considering t b Although the confinement loss is slightly higher at 0.5 μm, the preparation is more difficult, and the temperature sensitivity is related to t. b The gradient wall thickness is close to 0.6 μm. Considering energy coupling efficiency, fabrication tolerance, and filtering performance, the minimum gradient wall thickness t is ultimately selected. b It is 0.6μm.

[0083] 5. The influence of the combined anti-resonant tube unit and the inner sleeve wall thickness t on performance

[0084] To evaluate the fabrication robustness of the anti-resonant layer, while keeping other parameters constant, the wall thickness t of the integrated anti-resonant tube unit and the inner sleeve was varied from 0.60 μm to 0.70 μm. Figure 11 The curves showing the confinement loss of the Y-polarized fundamental mode as a function of wavelength at different t values ​​are presented. Figure 12 (a) shows the PER spectral lines at different t values; Figure 12(b) shows the relationship between limiting loss and temperature sensitivity as a function of t. For example... Figure 11 As shown, fluctuations in t have little impact on the central resonant wavelength, demonstrating good wavelength stability. Figure 12 As shown in (b), within the studied range, the temperature sensitivity stabilizes at approximately 3.5 nm / ℃, and the confinement loss reaches its maximum at t = 0.65 μm. To ensure optimal coupling matching, a combined anti-resonant tube unit and an inner sleeve wall thickness of 0.65 μm were ultimately selected, which exhibits good performance within the range of 0.6–0.7 μm and demonstrates good fabrication tolerance.

[0085] III. Bending Loss

[0086] To evaluate the bending resistance of this invention in practical applications, the transmission characteristics under macroscopic bending were numerically simulated using the conformal mapping method. For example... Figure 13 As shown, when the optical fiber is bent along the X-axis (α=0°), the transmission channel exhibits good stability due to the effective confinement of the fiber core energy by the integrated anti-resonant tube unit; simulation results show that even at a bending radius R... b Even when the wavelength is reduced to 5 cm, the bending loss of the X-polarized fundamental mode at the resonant wavelength of 1.18 μm is still less than 0.34 dB / cm, and the peak resonant loss of the Y-polarized fundamental mode is stable at around 48.0 dB / cm, indicating that the structure has a strong mode field confinement capability when bending in the X-axis direction.

[0087] like Figure 14 As shown, when the optical fiber bends along the Y-axis (α=90°), the compression of the mode field into the Y-axis nested tube SPR resonant channel enhances the spatial overlap between the core mode and the gold film-mixed solution interface, resulting in an increase in the resonant intensity of the Y-polarized fundamental mode as the bending radius decreases; when R b At a wavelength of 5 cm⁻¹, the peak loss increases to approximately 58 dB / cm, but the central resonant wavelength remains stable around 1.18 μm without significant shift. In summary, the device proposed in this invention exhibits good bending robustness, which not only helps ensure the stability of signal transmission but also maintains a consistent wavelength for the sensing response, facilitating its reliable application in practical deployment environments.

[0088] In summary, this invention achieves dual-function integration of polarization filtering and temperature sensing by constructing an asymmetric cladding structure composed of an X-axis integral anti-resonant tube unit and a Y-axis gradient wall thickness nested tube structure, and by combining gold film deposition with thermosensitive mixed solution filling. It also exhibits good temperature response characteristics and bending stability.

[0089] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the scope of protection of the present invention.

Claims

1. A dual-function hollow-core anti-resonant fiber device based on surface plasmon resonance effect, comprising a central fiber core, an asymmetric anti-resonant cladding surrounding the central fiber core, and an outer support tube sleeved on the outside of the asymmetric anti-resonant cladding; Its features are, Let the fiber axis be the z-axis. The asymmetric anti-resonant cladding is divided into an X-axis transmission partition and a Y-axis coupling partition along the orthogonal coordinate axis of the fiber cross-section. The X-direction transmission partition includes four symmetrically arranged integrated anti-resonant tube units; the integrated anti-resonant tube unit is generally gourd-shaped and consists of a flat glass plate and a large and a small circular tube located on both sides of it; the anti-resonance mechanism is used to confine the light field to the central fiber core region, providing a low-loss transmission channel for the X-polarization fundamental mode. The Y-axis coupling partition includes two symmetrically arranged double-layer nested tube units; each double-layer nested tube unit consists of an inner tube and an outer tube, both of which are arc-shaped structures. The ends of the arc-shaped structures are connected to an outer support tube. The wall thickness of the outer tube gradually decreases from the apex to the edge, used to construct phase-matching conditions over a wide spectral range. An arc-shaped annular interlayer is formed between the inner and outer tubes, and a gold film for exciting surface plasmon resonance is deposited within this arc-shaped annular interlayer. The holes in the central fiber core and the asymmetric anti-resonant cladding are filled with a thermosensitive mixed solution.

2. The bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 1, characterized in that, The integrated anti-resonant tube unit, the double-layer nested tube unit, and the outer support tube are all made of silicon dioxide material.

3. The bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 2, characterized in that, In the integrated anti-resonant tube unit, the centers of the large circular tube, the small circular tube, and the hollow fiber core are located on the same straight line, and this straight line is perpendicular to the plane glass plate.

4. A bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 3, characterized in that, The large circular tube is tangent to the inner wall of the asymmetric anti-resonant cladding.

5. A bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 4, characterized in that, The diameter D of the central fiber core c It is 10μm.

6. A bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 5, characterized in that, In the connected anti-resonant tube unit, the radius r1 of the large circular tube ranges from 5.5μm to 6.5μm, and the radius r2 of the small circular tube ranges from 4.5μm to 5.5μm.

7. A bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 5 or 6, characterized in that, In the double-layer nested tube unit, the outer sleeve radius r3 is 14μm, and the inner sleeve radius r4 is 11μm; the maximum wall thickness t of the outer sleeve... a The minimum wall thickness is 1.3 μm, t. b The thickness is 0.6 μm, and the change in tube wall thickness is a cosine gradient.

8. A bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 7, characterized in that, The wall thickness T1 of the outer support tube is 5 μm, and the fiber radius R is 28 μm.

9. A bifunctional hollow-core antiresonant fiber device based on surface plasmon resonance effect as described in claim 8, characterized in that, The thermosensitive mixed solution is prepared by mixing ethanol and chloroform in a volume ratio of 1:1.

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