An all-optical pressure sensor

Abstract

The present invention discloses an all-optical pressure sensor, which includes a flexible transparent base layer, a sensitive film, a first optical fiber, a second optical fiber, and an infrared window substrate stacked in sequence from top to bottom; the sensitive film adheres to the bottom of the flexible transparent base layer; both the first optical fiber and the second optical fiber are tapered sections with thick ends and a thin middle formed by tapering, and the tapered sections of the first optical fiber and the second optical fiber are coupled to form a coupling cone region; the coupling cone region is located between the sensitive film and the infrared window substrate; the refractive indices of the flexible transparent base layer and the infrared window substrate are greater than the refractive index of air and less than the refractive indices of the first optical fiber and the second optical fiber. The all-optical pressure sensor of the present invention uses the first optical fiber and the second optical fiber to be tapered and coupled to form a coupling taper. By modulating the light source to synchronously amplify the power of the signal light source when monitoring minute pressure changes, the range of the pressure sensor can be adjusted in real time to achieve the detection of minute pressure disturbances.

Description

Technical Field

[0001] The present invention relates to the field of optical communication and optical sensing technology, and in particular to an all-optical pressure sensor. Background Art

[0002] In recent years, the development of electronic devices has been unable to meet people's growing demands for response speed, stable time and structural simplification in signal transmission due to their own performance limitations. Photonic devices have gradually replaced them and ushered in great development in the field of information transmission and control. However, traditional photonic devices have high energy loss in the conversion between "electro-optical" and "thermo-optical" during use, long response time, and complex structure, resulting in high preparation costs. Therefore, improving sensitivity, saving energy and reducing costs, and integrating photonic devices have become a development trend in this field.

[0003] With the gradual improvement of optical fiber technology, micro-nano optical fibers are widely used in waveguide and near-field optical coupling, active light-emitting devices, micro-nano optical sensors, nonlinear optics, quantum and atomic optics, surface plasmons, and optomechanics due to their remarkable characteristics such as low coupling loss, large evanescent field propagation ratio, strong light confinement ability, adjustable dispersion, and small mass.

[0004] The vigorous development of 5G and Internet of Things technologies has brought about an increasing demand for sensors in industrial production and life entertainment. Optical sensors have become the only choice for many high-response requirements and high-precision diagnosis. Among them, combining sensing technology with optical fiber materials to prepare sensors has become one of the most outstanding application results. With the continuous pursuit of high performance and versatility in the field of optical sensing, as well as the development needs of biology and nanotechnology, small-size optical fiber sensors have become an important development direction of optical sensing.

[0005] Sensors based on micro-nano optical fibers have many advantages in the field of precision sensing. The all-optical structure has optical passive characteristics, strong anti-electromagnetic interference ability, simple architecture, and a small number of leads. The size of the micro-nano optical fiber of the device is more suitable for integrated installation in a compact space. However, existing all-optical sensors are not sensitive to external stimuli (such as micro-pressure signals), and are prone to false alarms or insensitivity to tiny stimulus signals, thus limiting the application scope of all-optical devices. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a full-optical pressure sensor with adjustable signal light source, so as to improve the detection performance of the pressure sensor for tiny pressure disturbances.

[0007] Technical solution: An all-optical pressure sensor according to the present invention includes a flexible transparent base layer, a sensitive film, a first optical fiber, a second optical fiber, and an infrared window substrate stacked in sequence from top to bottom; the sensitive film adheres to the bottom of the flexible transparent base layer; both the first optical fiber and the second optical fiber are tapered sections with thick ends and thin middles formed by tapering, and the tapered sections of the first optical fiber and the second optical fiber are coupled to form a coupling cone region; the first optical fiber is connected to a signal light source, and the second optical fiber is connected to a modulation light source; the coupling cone region is located between the sensitive film and the infrared window substrate; the refractive indices of the flexible transparent base layer and the infrared window substrate are greater than the refractive index of air and less than the refractive indices of the first optical fiber and the second optical fiber.

[0008] Preferably, the flexible transparent base layer is a flexible structure made of PDMS or PMMA material.

[0009] Preferably, the material of the sensitive film is one or more of graphene, molybdenum disulfide, and platinum diselenide.

[0010] Preferably, the material of the infrared window substrate is one or more of calcium fluoride, magnesium fluoride, and lithium fluoride;

[0011] Preferably, the diameter of the infrared window substrate is 35-40 mm and the thickness is 3-5 mm.

[0012] Preferably, the coupling cone region is a single-channel micro-nano optical fiber formed by coupling and tapering two single-mode communication optical fibers.

[0013] Preferably, the diameter of the coupling cone region is 5-10 μm and the length of the cone region is 3-10 mm.

[0014] Preferably, the bottom surface of the flexible transparent base layer corresponds to the sensitive film to form a covering area, and the surface of the flexible transparent base layer forms a pressing surface in the shape of a fan, semi-ellipse or semi-circle.

[0015] Preferably, the area of the covering area is 1-2 cm 2 , and the thickness of the flexible transparent base layer is 1-4 mm.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following outstanding advantages: 1. The all-optical pressure sensor according to the embodiment of the present invention uses a first optical fiber and a second optical fiber to form a coupled taper through tapering coupling. By modulating the light source to synchronously amplify the power of the signal light source when monitoring minute pressure changes, the range of the pressure sensor can be adjusted in real time to achieve the detection of minute pressure disturbances; 2. It adopts an all-optical structure, having the advantages of small volume, high integration, low optical loss, and small system error; simple packaging and low cost; resistant to electromagnetic interference, fast response speed, and covering a wide optical band working wavelength in the visible light and near-infrared bands; 3. It uses a polymer as a flexible light-transmitting base layer, with good adhesion and wearability, avoiding excessive increase in light source loss under extrusion; 4. It uses a PDMS material to prepare a flexible transparent base layer, and by adjusting the ratio of raw materials, the refractive index is changed, and during the transmission of the light source, the evanescent field change around the micro-nano optical fiber and the device sensitivity are adjusted according to the monitoring requirements. Description of the Drawings

[0017] Figure 1 It is a three-dimensional structural schematic diagram of the all-optical pressure sensor of the present invention;

[0018] Figure 2 is Figure 1 a radial sectional view of the all-optical pressure sensor in

[0019] Figure 3 is Figure 1 a structural schematic diagram of the first optical fiber, the second optical fiber and their coupling cone region in

[0020] Figure 4 is the modulation performance curve of the all-optical pressure sensor;

[0021] Figure 5 is the saturation absorption curve of the molybdenum disulfide pressure sensor for the signal light source under different modulation light source power intensities.

[0022] Reference numerals: 1. Flexible transparent base layer; 2. Sensitive film; 3. First optical fiber; 4. Second optical fiber; 5. Coupling cone region; 6. Infrared window substrate; 7. Pressure application surface; 8. Coverage area. Specific Embodiments

[0023] 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 described clearly and completely below with reference to the accompanying drawings of the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention. Figures 1-5 As shown in the accompanying drawings of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be described clearly and completely. It is obvious that the described embodiments are some of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention fall within the scope of protection of the present invention.

[0024] Combined with Figures 1-2As shown in the figure, a kind of all-optical pressure sensor of the present invention, the all-optical pressure sensor includes a flexible transparent base layer 1, a sensitive film 2, a first optical fiber 3, a second optical fiber 4 and an infrared window substrate 6 stacked in sequence from top to bottom. The flexible transparent base layer 1 is made of PDMS or PMMA material to form a flexible structure. The PDMS material is polydimethylsiloxane material, and the PDMS material has better elasticity and viscosity to facilitate the connection between the sensitive film and the flexible transparent base layer; the PMMA material is polymethyl methacrylate material, and the PMMA material is used to make a thin and light flexible transparent base layer; the bottom surface of the flexible transparent base layer 1 corresponds to the sensitive film 2 to form a covering area 8, and a fan-shaped, semi-elliptical or semi-circular pressure-applying surface 7 is formed on the surface of the flexible transparent base layer 1; the area of the covering area 8 is 1-2 cm 2 , the thickness of the flexible transparent base layer 1 is 1-4 mm, and this shape of the flexible transparent base layer 1 can more accurately sense the pressure signal borne by the all-optical sensor. The sensitive film 2 is loaded at the bottom of the flexible transparent base layer 1, and the material of the sensitive film 2 can be made of materials such as graphene, molybdenum disulfide or platinum diselenide, etc. The sensitive film can modulate and amplify the optical signal passing through the optical fiber. Both the first optical fiber 3 and the second optical fiber 4 are single-mode communication micro-nano optical fibers. The first optical fiber 3 and the second optical fiber 4 adopt a tapered section with thick ends and a thin middle formed by the tapering process. The tapered sections of the first optical fiber 3 and the second optical fiber 4 are coupled to form a coupling cone area 5. The coupling cone area 5 is a tubular structure formed by coupling. The diameter of the coupling cone area 5 is 5-10 μm, and the length of the cone area is 3-10 mm; the first optical fiber 3 is connected to a signal light source, and the second optical fiber 4 is connected to a modulation light source. When the signal light source passes through the first optical fiber, based on the fact that the micro-nano optical fiber has a strong evanescent field and can have a strong interaction with the sensitive film, the longer coupling cone area improves the effective regulation of the light source signal by the all-optical sensor. The coupling cone area 5 is located between the sensitive film 2 and the infrared window substrate 6. The infrared window substrate 6 can be made of materials such as calcium fluoride, magnesium fluoride or lithium fluoride, etc.; the diameter of the infrared window substrate 6 is 35-40 mm, and the thickness is 3-5 mm.

[0025] The refractive indices of the flexible transparent base layer 1 and the infrared window substrate 6 are greater than the refractive index of air and less than the refractive indices of the first optical fiber 3 and the second optical fiber 4. For example, the refractive index of the flexible transparent base layer 1 is 1.413, the refractive index of the infrared window substrate 6 is 1.428, and the refractive index of the micro-nano optical fiber is 1.45. When the light source transmits in the micro-nano optical fiber of the all-optical pressure sensor, the light source transmits in the optical path in a way similar to total reflection, thereby reducing the loss of the light source in the pressure sensor.

[0026] During operation, a signal light source is introduced into the first optical fiber 3. When the all-optical pressure sensor is subjected to compression, the flexible light-transmitting base layer deforms, changing the interaction state between the sensitive film 2 and the coupling cone region 5, thereby changing the output state of the signal light source. That is, the pressure signal is converted into an optical signal output through the pressure sensor. A modulation light source is introduced into the second optical fiber. At the coupling cone region 5, the modulation light source and the signal light source change the output power and output state of the signal light source through the cross-absorption modulation effect. When the pressure sensor receives a small pressure signal, the output signal of the signal light source is amplified, making the signal light source clearer and more distinguishable, and the output index more obvious.

[0027] The preparation method of the coupling cone region 5 in the present invention mainly includes the following steps:

[0028] (1) Cleaning the optical fiber: Taking the first optical fiber and the second optical fiber as standard single-mode communication optical fibers, two 80 - 100 cm standard single-mode communication optical fibers are selected. The coating layer of the target area of the optical fiber is removed for 15 - 20 mm, and the target area of the optical fiber is wiped clean with alcohol to obtain the first optical fiber 3 and the second optical fiber 4;

[0029] (2) Fixing the optical fiber: The cleaned first optical fiber 3 and second optical fiber 4 are respectively placed parallel in the V-grooves of two translation stages. The two translation stages are respectively controlled by two stepping motors; An optical microscope is installed at the optical fiber coupling target area perpendicular to the translation stage to monitor the forming process of the coupling cone region in real time; When fixing the optical fiber, one end of the optical fiber is fixed by magnetic attraction from the inside to the outside along the middle of the V-groove, and the other end of the optical fiber is pulled along the V-groove to keep the optical fiber straight and fixed with a magnet;

[0030] (3) Heating and tapering: Start the flame stepping motor perpendicular to the translation stage to preheat the target area of the optical fiber. The operation panel of the flame tapering device is provided with a parameter adjustment area for controlling the displacement of the two horizontal translation stages and the vertical flame stage, and also a parameter adjustment area for controlling the output of the hydrogen gas flow rate. For example, the command is that the stepping motor speeds of the left and right translation stages are 0.1 mm / s and the running displacement is 400 mm; Set the tapering shape parameters, control the length of the coupling cone region to be 80 mm, and control the moving speed of the flame stepping motor to be 2 mm / s. Before the translation stage starts tapering, it is necessary to turn on the hydrogen generator and ignite at the gas outlet, move the flame to the upper part of the target area of the optical fiber in advance to preheat the target area of the optical fiber to prevent breakage during the tapering process. After the flame stepping motor runs for 30 seconds, start the left and right tapering stepping motors and move them to both sides according to the system setting until they stop;

[0031] (4) Coupling cone region: The operation panel controls the displacement of the two translation stages to drive the middle tapered sections of the first optical fiber 3 and the second optical fiber 4 to approach and fit, and controls the displacement of the flame stage to the target area to heat and couple the target area of the optical fiber to form the coupling cone region 5.

[0032] The preparation method of the all-optical pressure sensor of the present invention mainly includes the following steps:

[0033] (1) Load the sensitive film 2 on the substrate by chemical vapor deposition, and the substrate is a copper foil sheet or a silica sheet;

[0034] (2) Prepare the flexible transparent substrate 1 with PDMS or PMMA material;

[0035] (3) Transfer the sensitive film 2 from the load substrate to the bottom surface of the flexible transparent substrate 1 through a transfer process, and cut the flexible transparent substrate and the sensitive film compounded thereon into the required shape and size;

[0036] (4) Prepare the coupling cone region 5 by coupling the center of the tapered regions of the first optical fiber and the second optical fiber using the method for preparing the coupling cone region 5 as shown in Figure 3 ;

[0037] (5) Bond the infrared window substrate 6 cut into the required shape and size and the flexible transparent substrate 1 loaded with the sensitive film on both sides of the coupling cone region 5 by side bonding to obtain the all-optical pressure sensor.

[0038] Verification of the technical effect of the all-optical pressure sensor of the present invention:

[0039] 1. Detection of the modulation performance of the all-optical pressure sensor:

[0040] For the all-optical pressure sensor of the embodiment of the present invention, a 1060 nm continuous signal light source with an input power of 1 mW is input to the first optical fiber, and a 1530 nm continuous adjustable light source with an input power of 0 - 930 mW is input to the second optical fiber. Under the condition that the flexible transparent substrate of the all-optical pressure sensor is subjected to the same pressure, measure the value of the output power of the all-optical pressure sensor changing with the modulation light source power, and perform fitting.

[0041] Figure 4 is the modulation performance curve of the all-optical pressure sensor; as shown in combination with Figure 4 , it can be seen that after the modulation light source is connected to the second optical fiber, the absorption rate of the all-optical pressure sensor for the signal light source gradually decreases as the modulation light source input power increases. That is, in a low-power working environment, the signal light source induced by a small pressure can be amplified by increasing the modulation of the modulation light source, and the pressure change can be clearly monitored. In the working state of a low-power signal light source (1 mW), the amplification ability of this pressure sensor is prominent, and energy conservation and consumption reduction can be achieved.

[0042] 2. Verification of the modulation performance of the all-optical pressure sensor:

[0043] Taking the all-optical pressure sensor composed of a flexible transparent substrate of PMMA material, a sensitive thin film of molybdenum disulfide material, a single-mode communication micro-nano optical fiber, and a calcium fluoride infrared window substrate as an example, a pulsed light with a pulse width of 1.5 ps and a wavelength of 1550 nm is used as the signal light source and incident on the first optical fiber of the all-optical pressure sensor. A continuous light with a wavelength of 980 nm is used as the modulation light source and incident on the second optical fiber. The absorption characteristics of the signal light source are measured by changing the incident power of the modulation light source.

[0044] Figure 5 The saturation absorption curve of the signal light source by the molybdenum disulfide pressure sensor under different modulation light source power intensities. Combining Figure 5 As shown, it can be seen that under different modulation light source intensities (0, 140, 420 mW), the signal light source all exhibits obvious saturation absorption characteristics. As the modulation light source intensity increases from 0 mW to 420 mW, the transmittance of the signal light source gradually increases, while the non-saturation absorption loss rapidly decreases, from the original 73.1% (without modulation light) to 50.3% (modulation light source intensity of 420 mW). And the transmittance of the molybdenum disulfide thin film in the saturation state increases significantly with the introduction of the modulation light source, from the original 60.2% (without modulation light source) to 93.0% (modulation light source intensity of 420 mW). As the modulation light source intensity increases, the modulation depth of the signal light source also changes significantly, increasing in the reverse direction from the original 33.3% (without modulation light) to 43.3% (modulation light intensity of 420 mW).

[0045] The above is the preferred implementation mode of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An all-optical pressure sensor, characterized in that, It includes a flexible transparent base layer (1), a sensitive film (2), a first optical fiber (3), a second optical fiber (4), and an infrared window substrate (6) stacked in sequence from top to bottom; the sensitive film (2) adheres to the bottom of the flexible transparent base layer (1); both the first optical fiber (3) and the second optical fiber (4) are tapered sections with thick ends and a thin middle formed by tapering, and the central thin tapered sections of the first optical fiber (3) and the second optical fiber (4) are coupled to form a coupling cone region (5); the first optical fiber (3) is connected to a signal light source, and the second optical fiber (4) is connected to a modulation light source; the coupling cone region (5) is located between the sensitive film (2) and the infrared window substrate (6); the refractive indices of the flexible transparent base layer (1) and the infrared window substrate (6) are greater than the refractive index of air and less than the refractive indices of the first optical fiber (3) and the second optical fiber (4).

2. The all-optical pressure sensor according to claim 1, characterized in that, The flexible transparent base layer (1) is a flexible structure made of PDMS or PMMA material.

3. The all-optical pressure sensor according to claim 1, characterized in that, The material of the sensitive film (2) is one or more of graphene, molybdenum disulfide, and platinum diselenide.

4. The all-optical pressure sensor according to claim 1, characterized in that, The material of the infrared window substrate (6) is one or more of calcium fluoride, magnesium fluoride, and lithium fluoride.

5. The all-optical pressure sensor according to claim 1, characterized in that, The diameter of the infrared window substrate (6) is 35 - 40 mm, and the thickness is 3 - 5 mm.

6. The all-optical pressure sensor according to claim 1, characterized in that, The coupling cone region (5) is a single-channel micro-nano optical fiber obtained by coupling and tapering two single-mode communication optical fibers.

7. The all-optical pressure sensor according to claim 6, characterized in that, The diameter of the coupling cone region (5) is 5 - 10 μm, and the length of the cone region is 3 - 10 mm.

8. The all-optical pressure sensor according to claim 1, characterized in that, The bottom surface of the flexible transparent base layer (1) corresponds to the sensitive film (2) to form a covering area (8), and a fan-shaped, semi-elliptical or semi-circular pressing surface (7) is formed on the surface of the flexible transparent base layer (1).

9. The all-optical pressure sensor according to claim 8, characterized in that, The area of the coverage area (8) is 1-2 cm 2 , and the thickness of the flexible transparent base layer (1) is 1-4 mm.

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