Laser interference device and preparation method thereof, interference generation method and measurement system
Through the design and preparation method of laser interference device, the defects in the manufacturing process of fiber sensors are solved, the optical signal stability and mechanical strength are improved, and the sensitivity of high-precision measurement is improved.
Patent Information
- Application Number
- CN202510471348.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-15
- Publication Date
- 2025-07-29
AI Technical Summary
Existing optical fiber sensors have defects in manufacturing processes, resulting in unstable optical signals and low mechanical strength, making it difficult to meet the needs of high-precision measurements.
Using laser interference devices, the first, second and third optical fiber modules are connected in sequence. The second optical fiber module is equipped with a cavity and microwave guide. The microwave guide is prepared by femtosecond laser two-photon polymerization technology to avoid defects in the traditional cone drawing process, enhance mechanical strength and provide a fine optical signal transmission path.
It improves the stability of optical signal transmission and the mechanical strength of the sensor, improves the sensitivity of the sensor, and meets the needs of high-precision measurement.
Smart Images
Figure CN120385376A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of fiber optic sensors, and specifically relates to a laser interference device, a preparation method thereof, an interference generation method, and a measurement system. Background Art
[0002] As an advanced detection tool, fiber optic sensors have been widely used in many fields in recent years. It utilizes the optical properties of optical fibers and senses the changes in the measured physical quantities through the principles of light transmission, reflection, refraction, etc., and has the advantages of anti-electromagnetic interference, high sensitivity, and remote measurement. However, some problems have emerged in the actual use of existing fiber optic sensors. The manufacturing process of the core component, the tapered fiber, has defects, which affects the stable transmission of optical signals and also reduces the mechanical strength of the sensor. In addition, the internal structure of existing fiber optic sensors is relatively simple and lacks an effective fine-tuning mechanism, making it difficult to improve the sensitivity of the sensor and unable to meet the requirements of high-precision measurement. These problems limit the further application of fiber optic sensors in the field of high-precision measurement and need to be solved urgently. Summary of the Invention
[0003] The present invention provides a laser interference device, a preparation method thereof, an interference generation method, and a measurement system, which can improve the structure that generates laser interference and is beneficial to improving the performance of fiber optic sensors.
[0004] The present invention provides a laser interference device, which includes a first fiber optic module, a second fiber optic module, and a third fiber optic module that are sequentially connected to form an optical path channel; The input end of the first fiber optic module is used to input laser light, and the output end of the third fiber optic module is used to output the laser light; A cavity is provided inside the second fiber optic module, and a microwave waveguide is provided inside the cavity; One end of the microwave waveguide is connected to the output end of the first fiber optic module, and the other end of the microwave waveguide is connected to the input end of the third fiber optic module.
[0005] Optionally, the first fiber optic module, the second fiber optic module, and the third fiber optic module are all cylindrical tubes; The outer diameters of the first fiber optic module, the second fiber optic module, and the third fiber optic module are the same; The centers of the cross-sections of the first fiber optic module, the second fiber optic module, and the third fiber optic module are on the same straight line.
[0006] The present invention also provides a preparation method for a laser interference device, and the preparation method is used to prepare the laser interference device as described in any one of the above; Execute the preparation method using a preset preparation system, the preparation system including a laser emitter, a laser control device, a displacement stage, and a collection device; The preparation method includes: Place the second optical fiber module on the displacement stage and place photoresist inside the second optical fiber module; Generate laser using the laser emitter; After inputting the laser into the laser control device, adjust the laser through the laser control device; The adjusted laser forms a light spot on the photoresist, and obtain the image information of the light spot through the collection device; Drive the displacement stage according to the image information, so that the photoresist polymerizes along the path where the light spot moves to form a micro-nano structure; Transfer the micro-nano structure into the second optical fiber module to form the microwave waveguide.
[0007] Optionally, the laser control device includes a first wave plate, a polarizer, a second wave plate, a beam splitter, and an objective lens; After inputting the laser into the laser control device, adjusting the laser through the laser control device includes: After passing the laser through the first wave plate and the polarizer in sequence, adjust the polarization state of the laser through the first wave plate and the polarizer, and select the laser with the target polarization direction from the laser with the adjusted polarization state; Convert the laser with the target polarization direction into circularly polarized light through the second wave plate; Use the beam splitter to divide the circularly polarized light into a first light beam and a second light beam; After obtaining the first light beam through the collection device, determine the laser parameters of the first light beam; Based on the laser parameters, adjust the second light beam through the first wave plate, the polarizer, or the second wave plate; Output the adjusted second light beam after focusing through the objective lens.
[0008] Optionally, transferring the micro-nano structure into the second optical fiber module to form the microwave waveguide includes: Use a developer to dissolve the photoresist in the target area to obtain the developed photoresist; Transfer the micro-nano structure in the developed photoresist into the second optical fiber module by etching to form the microwave waveguide; Use a remover to dissolve and remove the photoresist inside the second optical fiber module.
[0009] The present invention provides an interference generation method for a laser interference device, and the interference generation method is applied to the laser interference device as described above; Input incident light through the entrance end of the first optical fiber module; Divide the incident light into a first mode beam and a second mode beam through the microwave waveguide; The first mode beam and the second mode beam interfere when passing through the second optical fiber module and are output through the exit end of the second optical fiber module.
[0010] Optionally, the first mode beam is the fundamental mode LP01, and the second mode beam is the higher-order mode LP11; The phase difference between the first mode beam and the second mode beam is:
[0011] wherein, L is the length of the microwave waveguide, and are the effective refractive indices of the fundamental mode LP01 and the higher-order mode LP11 respectively, and λ is the wavelength of the incident light in vacuum.
[0012] The present invention provides a measurement system, and the measurement system includes a spectrometer, a light source generating device, and the laser interference device as described above; The output end of the light source generating device is connected to the entrance end of the first optical fiber module in the laser interference device, and the exit end of the third optical fiber module in the laser interference device is connected to the input end of the spectrometer; The incident light output through the output end of the light source generating device excites a first mode beam and a second mode beam in the microwave waveguide in the second optical fiber module of the laser interference device; After being coupled, the first mode beam and the second mode beam are input into the spectrometer through the exit end of the third optical fiber module; Determine the target spectral drift amount through the spectrometer according to the phase difference between the first mode beam and the second mode beam; Based on the correlation between the spectral drift amount and the ambient temperature, determine the temperature value corresponding to the target spectral drift amount.
[0013] Optionally, the first mode beam is the fundamental mode LP01, and the second mode beam is the higher-order mode LP11; The determination of the spectral drift amount satisfies:
[0014] Among them, FSR is the free spectral range of the interference spectrum, λk is the interference trough wavelength, L is the length of the microwave waveguide, and Δn is the effective refractive index difference between the fundamental mode LP01 and the high-order mode LP11.
[0015] Optionally, the correlation between the spectral drift amount and the environmental temperature is calibrated by the following method: When the environmental temperature changes, Δn changes due to the difference in the optical field distributions of the fundamental mode and the high-order mode, resulting in a change in the phase difference. Furthermore, the drift amount Δλ of the interference spectrum is linearly related to the temperature change amount ΔT. The phase difference is:
[0016] Among them, λ is the wavelength of the incident light in vacuum.
[0017] The present invention has at least the following beneficial effects: First, the laser interference device of the present invention forms an optical path channel by connecting the first, second, and third optical fiber modules in sequence. The second optical fiber module is internally provided with a cavity and a microwave waveguide, and both ends of the microwave waveguide are connected to the first and third optical fiber modules respectively. This structure avoids the defects of the traditional tapered optical fiber manufacturing process, improves the stability of optical signal transmission, and enhances the mechanical strength of the sensor. Secondly, the introduction of the microwave waveguide provides a finer transmission path for the optical signal, enabling effective regulation of the optical signal, thereby improving the sensor sensitivity and meeting the requirements of high-precision measurement. Description of the Drawings
[0018] The drawings are used to provide a further understanding of the technical solutions of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solutions of the present invention and do not constitute a limitation to the technical solutions of the present invention.
[0019] Figure 1 is a schematic structural diagram of the laser interference device of this embodiment; Figure 2 is another schematic structural diagram of the laser interference device of this embodiment; Figure 3 is a schematic cross-sectional view of the second optical fiber module in the laser interference device of this embodiment; Figure 4 is a step flow chart of the preparation method of the laser interference device of this embodiment; Figure 5 is a step flow chart of step S103 in the preparation method of the laser interference device of this embodiment; Figure 6 is a schematic structural diagram of the preparation system of this embodiment; Figure 7 is a step flow chart of step S106 in the preparation method of the laser interference device of this embodiment; Figure 8 is a flowchart of the steps of the interference generation method of the laser interference device according to this embodiment; Figure 9 is a schematic structural diagram of the measurement system according to this embodiment; Among them, 1, the first optical fiber module; 2, the second optical fiber module; 3, the third optical fiber module; 21, the microwave guide; 401, the laser emitter; 402, the first wave plate; 403, the polarizer; 404, the second wave plate; 405, the beam splitter; 406, the acquisition device; 407, the objective lens; 408, the displacement stage. Detailed implementation manners
[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0021] In the technical field, Mach-Zehnder fiber optic sensors have important applications in the fields of environmental monitoring, food safety, chemical industry, medical detection, aerospace, etc. due to their high sensitivity and high precision. According to different structures, they can be divided into three categories: tapered, misaligned fusion splicing type, and twin-core fiber type.
[0022] The tapered Mach-Zehnder fiber optic sensor forms a microfiber taper through the tapering technique. Light excites the fundamental mode and high-order modes in the taper region for transmission, and finally forms interference at the output end. Its advantages are large interference spectrum contrast, high sensitivity, and small volume. However, the diameter of the taper region is in the micron range and there is no protective layer, resulting in low mechanical strength, easy breakage, complex tapering process, poor preparation repeatability, and limited practicality.
[0023] The twin-core fiber type Mach-Zehnder sensor utilizes two independent optical paths in the optical fiber, one as the reference arm and one as the sensing arm. Light recombines at the output end to form interference. Changes in the external environment cause a change in the phase of the signal light, resulting in the drift of the interference fringes. This sensor has low cost, is easy to manufacture, and has high sensitivity. However, it requires good spatial stability, is not convenient to carry, and is limited to laboratory use.
[0024] The misaligned fusion splicing type Mach-Zehnder fiber optic sensor realizes the transmission of light in the core and cladding through fiber misaligned fusion splicing. The optical path difference between the core and the cladding causes interference. Its structure is simple and the preparation cost is low, but its sensitivity and resolution are relatively low, and its mechanical strength is reduced by the fusion splicing point.
[0025] However, the existing Mach-Zehnder fiber optic sensors have the following problems: (1) Traditional tapered optical fibers usually rely on oxyhydrogen flame heating and change the shape of the optical fiber by stretching to prepare microfiber tapers. This process requires precise control of the heating temperature and stretching speed to ensure that the tapered region has a uniform diameter. However, even with high-precision equipment, it is difficult to ensure that the tapered regions of all optical fibers are exactly the same, resulting in instability and poor repeatability of the sensor performance, thus affecting the reliability of the test results.
[0026] (2) The diameter of the tapered region of the tapered optical fiber is usually in the micron range, and its mechanical strength is relatively low, making it vulnerable to external forces and prone to breakage or fracture. This limits its application in high mechanical load or harsh environmental conditions, restricting its practicality to a certain extent.
[0027] (3) The structures of misalignment fusion type and twin-core fiber type sensors are relatively simple and lack a fine regulation mechanism, resulting in low sensitivity and difficulty in meeting the requirements of high-precision measurement.
[0028] The present invention provides a laser interference device, a preparation method thereof, an interference generation method, and a measurement system, which can improve the structure that generates laser interference, facilitating the improvement of the performance of the optical fiber sensor. The following are various embodiments of the present invention: Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the laser interference device of this embodiment.
[0029] This embodiment provides a laser interference device, which includes a first optical fiber module 1, a second optical fiber module 2, and a third optical fiber module 3 that are sequentially connected to form an optical path channel.
[0030] The entrance end of the first optical fiber module 1 is used for inputting laser, and the exit end of the third optical fiber module 3 is used for outputting laser.
[0031] The second optical fiber module 2 is internally provided with a cavity, and a microwave waveguide 21 is arranged in the cavity.
[0032] One end of the microwave waveguide 21 is connected to the exit end of the first optical fiber module 1, and the other end of the microwave waveguide 21 is connected to the entrance end of the third optical fiber module 3.
[0033] In some embodiments, the first optical fiber module 1, the second optical fiber module 2, and the third optical fiber module 3 are all cylindrical tubes.
[0034] The outer diameters of the first optical fiber module 1, the second optical fiber module 2, and the third optical fiber module 3 are the same.
[0035] The centers of the cross-sections of the first optical fiber module 1, the second optical fiber module 2, and the third optical fiber module 3 are on the same straight line.
[0036] In this embodiment, the principle of the laser interference device for generating laser interference is as follows: The light emitted by the light source enters the microwave waveguide 21 in the second optical fiber module 2 through the first optical fiber module 1 and is transmitted therein. Part of the light is coupled to excite the fundamental mode (LP 01 ), and the other part of the light is coupled to excite the high-order mode (usually HE 11 or HE 12 ). These modes have different effective refractive indices n eff . After propagating in the microwave waveguide 21, a corresponding phase difference is formed, and Mach-Zehnder type interference occurs when entering the third optical fiber module 3.
[0037] In some embodiments, both the first optical fiber module 1 and the third optical fiber module 3 are single-mode optical fibers, and the second optical fiber module 2 is a C-type optical fiber.
[0038] Please refer to Figure 2 , Figure 2 which is another schematic structural diagram of the laser interference device in this embodiment.
[0039] In some embodiments, the second optical fiber module 2 has a semi-open cavity structure. The semi-open cavity structure of the second optical fiber module 2 is beneficial for functional plating of the microwave waveguide 21 prepared therein, broadening the sensing application range of the device.
[0040] In some embodiments, the cavity of the second optical fiber module 2 is used to fill the liquid to be measured. The second optical fiber module 2 not only plays a supporting role in structure to protect the internal microwave waveguide 21, but also can be used as a sample cell to fill the liquid to be measured.
[0041] The cavity structure of the second optical fiber module 2 enables the sensor to have significant advantages in applications such as biosensing that use a small dose of the sample to be measured.
[0042] In some embodiments, the outer diameter of the second optical fiber module 2 ranges from [100, 130], with the unit of micrometer; the inner diameter of the second optical fiber module 2 ranges from [30, 80], with the unit of micrometer.
[0043] The diameter of the microwave waveguide 21 ranges from [1, 5], with the unit of micrometer.
[0044] The lengths of the second optical fiber module 2 and the microwave waveguide 21 range from [50, 300], with the unit of micrometer.
[0045] Please refer to Figure 3 , Figure 3 which is a schematic cross-sectional view of the second optical fiber module in the laser interference device of this embodiment.
[0046] Such as Figure 3As shown, the outer diameter of the second optical fiber module is 126.07 microns; the inner diameter of the second optical fiber module is 70.50 microns.
[0047] In the above embodiment, first, the laser interference device uses the first, second, and third optical fiber modules to be connected in sequence to form an optical path channel. A cavity and a microwave waveguide are provided inside the second optical fiber module, and both ends of the microwave waveguide are connected to the first and third optical fiber modules respectively. This structure avoids the defects of the traditional tapered optical fiber manufacturing process, improves the stability of optical signal transmission, and enhances the mechanical strength of the sensor. Secondly, the introduction of the microwave waveguide provides a finer transmission path for the optical signal, enabling effective regulation of the optical signal, thereby improving the sensor sensitivity and meeting the high-precision measurement requirements.
[0048] This embodiment provides a preparation method for a laser interference device, and the preparation method is used to prepare the laser interference device as described above.
[0049] The preparation method is executed using a preset preparation system, and the preparation system includes a laser emitter, a laser control device, a displacement stage, and a collection device.
[0050] Please refer to Figure 4 , Figure 4 which is the step flowchart of the preparation method of the laser interference device in this embodiment.
[0051] A preparation method for a laser interference device includes: S101. Place the second optical fiber module on the displacement stage, and place the photoresist inside the second optical fiber module.
[0052] S102. Generate laser light using the laser emitter.
[0053] S103. After inputting the laser into the laser control device, adjust the laser through the laser control device.
[0054] S104. The adjusted laser forms a light spot on the photoresist, and the image information of the light spot is obtained through the collection device.
[0055] S105. Drive the displacement stage according to the image information so that the photoresist aggregates along the path where the light spot moves to form a micro-nano structure.
[0056] S106. Transfer the micro-nano structure into the second optical fiber module to form a microwave waveguide.
[0057] It can be understood that the second optical fiber module is fused between the first optical fiber module and the third optical fiber module, and then through the above preparation method, a linear microwave waveguide is printed inside the second optical fiber module, and both ends of this micro microwave waveguide are respectively connected to the core centers of the first optical fiber module and the third optical fiber module.
[0058] It can be understood that through the above-mentioned micro-nano precision machining preparation method based on femtosecond laser two-photon polymerization technology, the diameter and length of the microwave waveguide inside the second optical fiber module can be precisely customized, and its structural parameters can be optimized for different sensing applications to increase the sensing sensitivity. Compared with the traditional micro-optical fiber device drawn by oxyhydrogen flame, the prepared laser interference device has high mechanical strength. The C-shaped optical fiber as the second optical fiber module can provide effective protection and support for the microwave waveguide inside it, and the whole device is easy to carry, greatly increasing the practicality of the device.
[0059] Please refer to Figure 5 , Figure 5 is the flowchart of step S103 in the preparation method of the laser interference device of this embodiment.
[0060] In some embodiments, step S103 includes: S201. After passing the laser through the first wave plate and the polarizer in sequence, adjust the polarization state of the laser through the first wave plate and the polarizer, and select the laser with the target polarization direction from the laser with the adjusted polarization state.
[0061] S202. Convert the laser with the target polarization direction into circularly polarized light through the second wave plate.
[0062] S203. Divide the circularly polarized light into a first light beam and a second light beam by using a beam splitter.
[0063] S204. After acquiring the first light beam through the acquisition device, determine the laser parameters of the first light beam.
[0064] S205. Based on the laser parameters, adjust the second light beam through the first wave plate, the polarizer or the second wave plate.
[0065] S206. Focus the adjusted second light beam through an objective lens and output it.
[0066] It can be understood that the laser interference device is used to control the pulse energy and convert the linear polarization state of the laser beam into a circular polarization state, thereby reducing the anisotropy effect in the two-photon polymerization process. The optimal optical power is 6.19 nJ.
[0067] Please refer to Figure 6 , Figure 6 is the structural schematic diagram of the preparation system of this embodiment.
[0068] In some embodiments, the preparation system includes a laser emitter 401, a laser control device, a displacement stage 408, and a collection device 406. The collection device 406 is a CCD. The laser control device includes a first wave plate 402, a polarizer 403, a second wave plate 404, a beam splitter 405, and an objective lens 407. The first wave plate 402 is a half-wave plate, and the second wave plate 404 is a quarter-wave plate.
[0069] Please refer to Figure 7 , Figure 7 which is the flowchart of step S106 in the method for preparing the laser interference device of this embodiment.
[0070] In some embodiments, step S106 includes: S301. Dissolve the photoresist in the target area with a developer to obtain the developed photoresist.
[0071] S302. Transfer the micro-nano structure in the developed photoresist to the inside of the second optical fiber module by etching to form a microwave waveguide.
[0072] S303. Dissolve and remove the photoresist inside the second optical fiber module with a removing solution.
[0073] In a specific embodiment, the pulse duration of the laser emitter is 306 fs, the maximum repetition frequency is 200 kHz, and the maximum pulse energy is 28.2 .
[0074] In a specific embodiment, the photoresist is an ultraviolet-insensitive two-photon polymerization 3D printing photosensitive resin TPS-PA. Based on the photosensitivity of the photoresist to ultraviolet light (light wavelength 260 nm), the photoresist will polymerize along the pre-set laser scanning path.
[0075] In a specific embodiment, after fabrication, the optical fiber is immersed in propylene glycol monomethyl ether acetate for 20 minutes and then in isopropyl alcohol for 5 minutes for development.
[0076] Please refer to Figure 8 , Figure 8 which is the flowchart of the interference occurrence method of the laser interference device of this embodiment.
[0077] This embodiment provides an interference occurrence method for a laser interference device. The interference occurrence method is applied to any one of the laser interference devices described above.
[0078] S401. Input incident light through the entrance end of the first optical fiber module.
[0079] S402. Divide the incident light into a first-mode light beam and a second-mode light beam through the microwave waveguide.
[0080] S403. The first-mode beam and the second-mode beam interfere when passing through the second fiber optic module and are output through the outlet end of the second fiber optic module.
[0081] In some embodiments, the first-mode beam is the fundamental mode LP01, and the second-mode beam is the high-order mode LP11.
[0082] The phase difference between the first-mode beam and the second-mode beam is:
[0083] where L is the length of the microwave waveguide, and are the effective refractive indices of the fundamental mode LP01 and the high-order mode LP11 respectively, and λ is the wavelength of the incident light in vacuum.
[0084] Specifically, the light emitted by the light source enters the microwave waveguide in the second fiber optic module through the first fiber optic module and is transmitted. Part of the light is coupled to excite the first-mode beam in the microwave waveguide, and the other part of the light is coupled to excite the second-mode beam. These modes have different effective refractive indices, and a corresponding phase difference is formed after propagation in the microwave waveguide. When entering the third fiber optic module, Mach-Zehnder type interference will occur.
[0085] Here, this interference phenomenon is explained by taking dual-mode interference as an example. Let the frequency of the light be ; the fundamental mode and high-order mode optical fields in the microwave waveguide are expressed as E1 and E2, and their optical field amplitudes are , , and the phases are , , respectively. Then there is:
[0086]
[0087] In the output single-mode fiber, the two modes are re-coupled into a single beam of light and transmitted in the single-mode fiber to form interference. The intensity of the superimposed light is expressed as:
[0088] where is the total light intensity of the interference superposition, and are the transmitted light intensities of the fundamental mode and the high-order mode respectively. The phase difference between the fundamental mode and the high-order mode is expressed as:
[0089] where , are the effective refractive indices of the fundamental mode and the high-order mode respectively, is the length of the microwave waveguide, is the wavelength of light in a vacuum.
[0090] When the interference intensity takes the minimum value, the phase difference needs to satisfy the condition:
[0091] m is an integer, and the wavelength corresponding to the interference wave valley is expressed as:
[0092] The free spectral range FSR of the interference spectrum can be calculated as:
[0093] When the ambient temperature around the device changes or the refractive index of the liquid filled in the C-type optical fiber changes, due to the different optical field distributions of the fundamental mode and the high-order mode, the influence amplitudes of the temperature change or the refractive index change will be different. Therefore, the phase difference between the two modes will change, resulting in the drift of the transmission spectrum.
[0094] Please refer to Figure 9 , Figure 9 which is the structural schematic diagram of the measurement system of this embodiment.
[0095] This embodiment provides a measurement system, which includes a spectrometer, a light source generating device, and a laser interference device of any one of the above.
[0096] The output end of the light source generating device is connected to the entrance end of the first optical fiber module in the laser interference device, and the exit end of the third optical fiber module in the laser interference device is connected to the input end of the spectrometer.
[0097] The incident light output from the output end of the light source generating device excites the first mode light beam and the second mode light beam in the microwave waveguide in the second optical fiber module of the laser interference device.
[0098] The first mode light beam and the second mode light beam are coupled and then input into the spectrometer through the exit end of the third optical fiber module.
[0099] According to the phase difference between the first mode light beam and the second mode light beam, the target spectral drift amount is determined by the spectrometer.
[0100] Based on the correlation between the spectral drift amount and the ambient temperature, the temperature value corresponding to the target spectral drift amount is determined.
[0101] In some embodiments, the first mode light beam is the fundamental mode LP01, and the second mode light beam is the high-order mode LP11.
[0102] The determination of the spectral drift amount satisfies:
[0103] Wherein, FSR is the free spectral range of the interference spectrum, λk is the interference valley wavelength, L is the length of the microwave waveguide, and Δn is the effective refractive index difference between the fundamental mode LP01 and the higher-order mode LP11.
[0104] In some embodiments, the correlation between the spectral drift amount and the ambient temperature is calibrated in the following manner: When the ambient temperature changes, Δn changes due to the difference in the optical field distributions of the fundamental mode and the higher-order mode, resulting in a change in the phase difference, and further causing the drift amount Δλ of the interference spectrum to be linearly related to the temperature change amount ΔT. The phase difference is:
[0105] Wherein, λ is the wavelength of the incident light in vacuum.
[0106] Here, taking temperature sensing as an example to show an application example of this Mach-Zehnder sensor. When the ambient temperature changes, the transmission spectrum of the C-shaped optical fiber will drift significantly. By monitoring the relationship between the spectral drift amount and the temperature, the sensor can be calibrated. Specifically, the laser interference device is used as a sensor and placed on a temperature-controlled breadboard. As the temperature of the temperature-controlled breadboard changes, the refractive index of the waveguide changes accordingly, while the refractive index of air basically does not change with temperature, causing a change in the phase difference between the fundamental mode and the higher-order mode in the microfiber, resulting in a drift of the transmission spectrum. As the temperature rises, the interference spectrum undergoes a blue shift with the increase in temperature. By analyzing the relationship between the spectral drift amount and the temperature, the sensor can be calibrated. The temperature sensitivity of this interferometer is -0.56 , and it has good linearity.
[0107] It can be understood that, in addition to being used as a sensor, the above-mentioned laser interference device in the embodiments can also be used for sensing various parameters (such as temperature, humidity, refractive index, etc.).
[0108] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of this application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of this application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices. It should be understood that in this application, "at least one (item)" means one or more, and "a plurality" means two or more.
[0109] In several embodiments provided by the present application, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections between each other can be indirect couplings or communication connections through some interfaces, devices, or units, and can be in electrical, mechanical, or other forms.
[0110] In addition, in each embodiment of the present application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.
[0111] Although the description of the present application has been quite detailed and several of the described embodiments have been described in particular, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as effectively covering the intended scope of the present application by considering the broadest possible interpretation of these claims in light of the prior art. In addition, the present application has been described above with embodiments foreseeable by the inventors for the purpose of providing a useful description, and non-substantive modifications to the present application that are not currently foreseeable can still represent equivalent modifications of the present application.
Claims
1. A laser interference device, characterized in that, The laser interference device includes a first optical fiber module, a second optical fiber module, and a third optical fiber module that are sequentially connected to form an optical path channel; The input end of the first optical fiber module is used to input laser, and the output end of the third optical fiber module is used to output the laser; A cavity is provided inside the second optical fiber module, and a microwave waveguide is provided inside the cavity; One end of the microwave waveguide is connected to the output end of the first optical fiber module, and the other end of the microwave waveguide is connected to the input end of the third optical fiber module.
2. The laser interference device according to claim 1, characterized in that The first optical fiber module, the second optical fiber module, and the third optical fiber module are all cylindrical tubes; The outer diameters of the first optical fiber module, the second optical fiber module, and the third optical fiber module are the same; The centers of the cross-sections of the first optical fiber module, the second optical fiber module, and the third optical fiber module are on the same straight line.
3. A preparation method of a laser interference device, characterized in that, The preparation method is used to prepare the laser interference device according to any one of claims 1 to 2; The preparation method is executed by using a preset preparation system, and the preparation system includes a laser emitter, a laser control device, a displacement stage, and a collection device; The preparation method includes: Placing the second optical fiber module on the displacement stage, and placing photoresist inside the second optical fiber module; Generating laser by using the laser emitter; After inputting the laser into the laser control device, adjusting the laser through the laser control device; The adjusted laser forms a light spot on the photoresist, and the image information of the light spot is obtained through the collection device; Driving the displacement stage according to the image information, so that the photoresist aggregates along the path where the light spot moves to form a micro-nano structure; Transferring the micro-nano structure to the inside of the second optical fiber module to form the microwave waveguide.
4. The preparation method according to claim 3, characterized in that, The laser control device includes a first wave plate, a polarizer, a second wave plate, a beam splitter, and an objective lens; After inputting the laser into the laser control device, adjusting the laser through the laser control device includes: After passing the laser through the first wave plate and the polarizer in sequence, adjusting the polarization state of the laser through the first wave plate and the polarizer, and screening out the laser with the target polarization direction from the laser with the adjusted polarization state; Converting the laser with the target polarization direction into circularly polarized light through the second wave plate; Dividing the circularly polarized light into a first light beam and a second light beam by using the beam splitter; After obtaining the first light beam through the collection device, determining the laser parameters of the first light beam; Based on the laser parameters, adjusting the second light beam through the first wave plate, the polarizer, or the second wave plate; Outputting the adjusted second light beam after focusing through the objective lens.
5. The preparation method according to claim 3, characterized in that, Transferring the micro-nano structure to the inside of the second optical fiber module to form the microwave waveguide includes: Dissolving the photoresist in the target area by using a developer to obtain the developed photoresist; Transferring the micro-nano structure in the developed photoresist to the inside of the second optical fiber module by etching to form the microwave waveguide; Dissolving and removing the photoresist inside the second optical fiber module by using a remover.
6. A method for generating interference in a laser interference device, characterized in that, The interference occurrence method is applied to the laser interference device according to any one of claims 1 to 2; Input incident light through the entrance end of the first optical fiber module; Divide the incident light into a first mode beam and a second mode beam through the microwave waveguide; When the first mode beam and the second mode beam pass through the second optical fiber module, interference occurs and they are output through the exit end of the second optical fiber module.
7. The interference occurrence method according to claim 6, characterized in that The first mode beam is the fundamental mode LP01, and the second mode beam is the higher-order mode LP11; The phase difference between the first mode beam and the second mode beam is: where L is the length of the microwave waveguide, and are the effective refractive indices of the fundamental mode LP01 and the higher-order mode LP11, respectively, and λ is the wavelength of the incident light in vacuum.
8. A measurement system, characterized in that, The measurement system includes a spectrometer, a light source generating device, and the laser interference device according to any one of claims 1 to 2; The output end of the light source generating device is connected to the entrance end of the first optical fiber module in the laser interference device, and the exit end of the third optical fiber module in the laser interference device is connected to the input end of the spectrometer; The incident light output through the output end of the light source generating device is excited in the microwave waveguide in the second optical fiber module of the laser interference device to obtain a first mode beam and a second mode beam; After the first mode beam and the second mode beam are coupled, they are input into the spectrometer through the exit end of the third optical fiber module; According to the phase difference between the first mode beam and the second mode beam, determine the target spectral drift amount through the spectrometer; Based on the correlation between the spectral drift amount and the ambient temperature, determine the temperature value corresponding to the target spectral drift amount.
9. The measurement system according to claim 8, characterized in that, The first mode beam is the fundamental mode LP01, and the second mode beam is the higher-order mode LP11; The determination of the spectral drift amount satisfies: Wherein, FSR is the free spectral range of the interference spectrum, λk is the interference valley wavelength, L is the length of the microwave waveguide, and Δn is the effective refractive index difference between the fundamental mode LP01 and the higher-order mode LP11.
10. The measurement system according to claim 9, characterized in that, The correlation between the spectral drift amount and the ambient temperature is calibrated by the following method: When the ambient temperature changes, Δn changes due to the difference in the optical field distributions of the fundamental mode and the higher-order mode, resulting in a change in the phase difference, and further causing the drift amount Δλ of the interference spectrum to be linearly related to the temperature change amount ΔT. The phase difference is: Wherein, λ is the wavelength of the incident light in vacuum.