D-type photonic crystal fiber temperature sensor based on surface plasma resonance

Abstract

The invention discloses a D-type photonic crystal fiber temperature sensor based on surface plasma resonance. The D-type photonic crystal fiber temperature sensor structurally comprises a fiber core and a perfect matching layer wrapping the fiber core, and circular air holes of different sizes are periodically arranged in the fiber core; the fiber core is provided with a polished plane, and the surface of the polished plane is coated with a gold film; a loss spectrum is obtained through calculation, and then the wavelength of the surface plasma formant and the sensitivity of the sensor are calculated. According to different temperatures of the temperature-sensitive liquid samples, wavelengths of formants of the transmission loss spectrum are also different. The temperature range of a temperature-sensitive liquid sample of the sensor is-10-60 DEG C, and the sensitivity of 9.8 nm / DEG C and the resolution of 0.01 DEG C. The sensitivity and the resolution of the sensor are superior to those of an existing sensor, and the sensor is simple in structure and easy to operate and has great application prospects in the fields of biomedicine, environmental monitoring and the like.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber sensors, and in particular relates to a surface plasma photonic crystal optical fiber sensor for temperature sensing. Background Art

[0002] Surface plasmon resonance (SPR) is a physical phenomenon that occurs at the metal-dielectric interface. When light waves are incident on the interface, under specific conditions, they interact with free electrons on the metal surface, exciting surface plasmon waves that propagate along the interface. This causes the reflectivity of the incident light to drop sharply at specific angles or wavelengths, forming a resonant peak in the loss spectrum. Changes in ambient temperature cause changes in the resonant peak in the loss spectrum, and detecting this change allows for temperature measurement.

[0003] Photonic crystal fiber (PCF) is a new type of optical fiber with periodically arranged air holes. Compared with traditional optical fibers, it has the advantages of low confinement loss, flexible dispersion, high nonlinearity and high birefringence. Its structural parameters are adjustable and the design is flexible. By adjusting the air hole arrangement, the refractive index distribution of the optical fiber cross section can be changed, thereby affecting the transmission performance of the optical fiber and realizing the sensing detection of different physical quantities.

[0004] With their high sensitivity, high resolution, and wide detection range, SPR-PCF temperature sensors have broad application prospects in environmental monitoring (such as meteorological and oceanographic monitoring), industrial process control (such as reactor and pipeline temperature monitoring and control), and biomedicine (such as human body temperature measurement, cell culture, and biological reaction temperature monitoring). Therefore, how to further improve the sensitivity of sensors to make them of great research value in applications such as environmental monitoring and biomedicine, and provide accurate detection methods for various fields, has been a long-standing technical challenge in this field. Summary of the Invention

[0005] The present invention addresses the shortcomings of the existing photonic crystal fiber technology and provides a D-type photonic crystal fiber temperature sensor based on surface plasmon resonance. The SPR effect stimulated by the present invention is stimulated by coating a gold film on the surface of the polished plane, which can effectively enhance the resonance effect and make the SPR more sensitive to changes in the solution to be measured.

[0006] The technical solution adopted in the present invention is:

[0007] A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance comprises a fiber core and a perfectly matched layer coated on an analyte layer. The fiber core is provided with periodically arranged circular air holes of different sizes. The fiber core has a polished surface coated with a gold film layer.

[0008] In the above solution, the material of the fiber core is fused silica with a refractive index n=1.45.

[0009] In the above solution, the radius of the perfect matching layer is r pml =7um; the radius of the fiber core is r sio2 =5um.

[0010] In the above solution, the analyte layer is located between the core and the perfect matching layer, and the radius of the analyte layer is r bio =6um; the analyte uses a mixture of ethanol and chloroform as the temperature-sensitive liquid.

[0011] In the above solution, the circular air holes are symmetrically distributed in the fiber core, and the period between the circular air holes is Λ=2um.

[0012] In the above scheme, the circular air holes are arranged in a pentagonal array, and the air refractive index n of the large circular air holes is air =1, aperture size d1 = 1.2um; the refractive index of air in the small circular air hole n air =1, pore size d2 = 0.9um.

[0013] In the above solution, the depth H of the polishing plane is 3.1 um.

[0014] In the above solution, the thickness of the gold film coated on the surface of the polished plane is t Au =25nm.

[0015] In the above solution, the temperature measurement range of the temperature-sensitive liquid in the analyte layer is -10 to 60°C.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) By designing a D-shaped PCF and polishing the optical fiber into a flat surface, the distance between the metal layer and the fiber core can be effectively shortened, thereby enhancing the SPR effect.

[0018] (2) By designing two small circular air holes in the inner layer of the core, the coupling direction of the core mode and the SPP mode is guided. The presence of the small circular air holes reduces the n of the core mode. eff , which improves the coupling degree between the core mode and the SPP mode.

[0019] (3) By coating a gold film on the surface of the polished plane, the coupling result between the core mode and the SPP mode is improved.

[0020] (4) Through the flat-throw structure design, under the action of Y polarization, the temperature measurement range of the analyte is -10℃ to 60℃, the maximum wavelength sensitivity is 9.8nm / ℃, and the resolution is 0.01℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic cross-section of an embodiment of the present invention.

[0022] Figure 2 4 is a mode field distribution diagram of the fundamental mode according to an embodiment of the present invention.

[0023] Figure 3 4 is a mode field distribution diagram of the SPP mode according to an embodiment of the present invention.

[0024] Figure 4 is a mode field distribution diagram at the phase matching point in an embodiment of the present invention.

[0025] Figure 5 This is a loss diagram when the refractive index of the analyte changes from 1.39 to 1.4 in an embodiment of the present invention.

[0026] Explanation of the accompanying figures: 1. Polished surface; 2. Gold film layer; 3. Small circular air hole; 4. Large circular air hole; 5. Perfectly matched layer; 6. Analyte layer; 7. Fiber core. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific examples.

[0028] like Figure 1 Figure 2 shows a schematic diagram of the two-dimensional interface structure of a D-type photonic crystal fiber temperature sensor based on surface plasmon resonance. The core material is fused silica with a refractive index of n = 1.45, and the radius of the perfect matching layer is r pml =7um; the radius of the fiber core is r sio2 =5um, the radius of the analyte layer is r bio =6um, and the analyte is a 1:1 mixture of ethanol and chloroform as the temperature sensitive liquid. The period between the circular air holes is Λ=2um. The circular air holes are arranged in a pentagonal array, and the air refractive index n of the large circular air holes is air =1, aperture size d1 = 1.2um; the refractive index of air in the small circular air hole n air =1, aperture size d2 = 0.9 μm, depth of the core polishing plane H = 3.1 μm.

[0029] By coating the film thickness t on the polished surface Au = 25 nm gold film layer for excitation, which can enhance the resonance effect and make SPR more sensitive to changes in the analyte solution.

[0030] like Figure 4As shown in Figure 1, when the phase matching condition is met, the energy in the fiber core couples to the plasma on the metal surface, causing the core energy to decrease. The excitation of the surface plasmon at this point can be characterized by calculating the confinement loss of the core mode. The wavelength corresponding to this point is the resonant wavelength.

[0031] like Figure 5 As shown in the figure, when the temperature range of the thermosensitive liquid changes from -10°C to 60°C, the resonance loss peak shifts toward shorter wavelengths as the temperature increases, resulting in a blue shift. When the temperature of the thermosensitive liquid changes by ΔT = 10°C, the loss absorption peak shifts by Δλ. This calculation can be used to determine the sensitivity S and resolution R of the sensor.

[0032] Depend on Figure 5 It can be seen that when the temperature range of the thermosensitive liquid is 0℃ to -10℃, the position of the loss peak changes by Δλ=98nm, the sensitivity reaches the maximum value S=9.8nm / ℃, and the corresponding resolution R=0.01℃.

Claims

1. A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance, characterized by: Its structure includes a fiber core and a perfectly matched layer covering the outside of the fiber core. The fiber core is provided with periodically arranged circular air holes of different sizes. The fiber core has a polished surface coated with a gold film layer.

2. A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The material of the fiber core is fused silica with a refractive index n=1.

45.

3. A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The radius of the perfectly matched layer is r pml =7um; the radius of the fiber core is r sio2 =5um.

4. A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The analyte layer is located between the core and the perfect matching layer, and the radius of the analyte layer is r bio =6um.

5. The D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The circular air holes are symmetrically distributed in the fiber core, with the outer layer consisting of 9 large circular air holes and the inner layer consisting of 4 large circular air holes and 2 small circular air holes; the period between the circular air holes is Λ=2um.

6. A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 5, characterized in that: The circular air holes are arranged in a pentagonal array, and the air refractive index n of the large circular air holes is air =1, aperture size d1 = 1.2um, refractive index of air in small circular air hole n air =1, pore size d2 = 0.9um.

7. A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The depth of the polishing plane is H=3.1 um.

8. The D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The surface of the polished plane is coated with a gold film having a thickness t Au =25nm.

9. A D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The temperature range of the solution to be tested in the analyte layer is -10 to 60°C.

10. The D-type photonic crystal fiber temperature sensor based on surface plasmon resonance according to claim 1, characterized in that: The gold film layer generates surface plasmon resonance under the action of Y polarization, which is used to detect the temperature change of the analyte to be measured.

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