A method for preparing a PMN-PT ferroelectric crystal core glass cladding composite optical fiber
By forming a pre-diffusion layer on the inner surface of the cladding glass tube, the problem of core-cladding diffusion during optical fiber fabrication is solved, enabling single-crystal recrystallization of the core and retention of its function, thus providing a simple and low-cost method for optical fiber fabrication.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2024-04-12
- Publication Date
- 2026-07-21
AI Technical Summary
During the optical fiber fabrication process, the high-temperature melting during hot drawing and single crystallization causes diffusion between the fiber core and the cladding glass, resulting in a change in the stoichiometric ratio of the fiber core material, making it impossible to recrystallize into a single crystal and thus losing its original function.
By employing a pre-diffusion layer technology, a pre-diffusion layer is formed on the inner surface of the cladding glass tube. Through diffusion reaction, the PMN-PT ferroelectric crystal core is tightly bonded to the cladding glass, suppressing diffusion reactions during subsequent hot drawing and single crystallization processes, and protecting the core material from change.
It effectively suppresses diffusion between the fiber core and cladding, ensuring that the fiber core is recrystallized into a single crystal, maintaining the original function of the optical fiber. The method is simple and low-cost.
Smart Images
Figure CN118324404B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optical fiber materials technology, specifically relating to a method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber. Background Technology
[0002] Composite glass fiber is produced by combining functional materials with different properties, such as optical, electrical, thermomechanical, acoustic, magnetic, and dielectric properties, into traditional optical fibers through various composite technologies. This allows the fiber to retain the high performance of the core material while preserving the original waveguide structure of the optical fiber. The fabrication method of composite glass fiber mainly includes two steps: the first step is thermal drawing, and the second step is core single crystallization.
[0003] Currently, the hot drawing process typically employs the core melting method. Compared to the traditional tube-rod drawing method, the biggest advantage of this method is that during the fiber drawing process, the temperature is controlled to keep the core in a molten state while the cladding remains softened, thus drawing the fiber preform into an optical fiber. The single crystallization process uses laser heating to control the slow remelting and recrystallization of the core material.
[0004] However, the high-temperature melting in both the hot drawing process and the single crystallization process will cause diffusion between the fiber core and the cladding glass, which will change the stoichiometric ratio of the fiber core material and make it impossible to recrystallize into a single crystal, thus causing the optical fiber to lose its original function. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber. The preparation method provided by this invention avoids thermal diffusion and the fiber core can be recrystallized into a single crystal.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] This invention provides a method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber, comprising the following steps:
[0008] (1) After filling the PMN-PT ferroelectric crystal core into the cladding glass tube, the PMN-PT ferroelectric crystal core is compacted, diffused until the PMN-PT ferroelectric crystal core diffuses into the cladding glass tube, and then annealed and cooled to obtain a cladding glass tube containing a pre-diffusion layer; the temperature of the diffusion reaction is 900-1100℃.
[0009] (2) Insert another PMN-PT ferroelectric crystal core into the glass tube with the pre-diffusion layer cladding and then heat-draw and recrystallize it in sequence to obtain PMN-PT ferroelectric crystal core glass cladding composite optical fiber.
[0010] Preferably, the diffusion reaction is kept at a temperature of 3 hours; the diffusion reaction is carried out in an air atmosphere.
[0011] Preferably, the heating rate of the diffusion reaction is no greater than 5°C / min.
[0012] Preferably, the diffusion reaction occurs at least once.
[0013] Preferably, the thickness of the pre-diffusion layer in the glass tube containing the pre-diffusion layer is 1 μm or more.
[0014] Preferably, the chemical composition of the pre-diffusion layer includes PMN-PT and cladding glass; the content of PMN-PT in the pre-diffusion layer is 35 wt% or more.
[0015] Preferably, the PMN-PT ferroelectric crystal core is cylindrical in shape.
[0016] Preferably, the cladding glass tube is made of quartz glass, silicate glass, phosphate glass, germanate glass, or borate glass.
[0017] Preferably, the length of the cladding glass tube is the same as that of the PMN-PT ferroelectric crystal core; the difference between the inner diameter of the cladding glass tube and the diameter of the PMN-PT ferroelectric crystal core is no greater than 0.1 mm.
[0018] Preferably, the length of the cladding glass tube is 10-30 cm and the inner diameter is 1-5 mm.
[0019] This invention provides a method for preparing a PMN-PT ferroelectric crystal core glass-clad composite optical fiber. The invention uses glass as the cladding material, which is low-cost and has a high softening point (1730℃), matching the high melting point (1280℃) of PMN-PT. Since the diffusion reaction is concentration-dependent, this invention pre-increases the PMN-PT concentration in the cladding glass by pre-filling the cladding glass with PMN-PT crystals. Under certain high-temperature conditions, the diffusion reaction is carried out, allowing ions from the PMN-PT crystals to pre-diffuse into the pores of the cladding glass. This reduces the concentration gradient between the PMN-PT ferroelectric crystal core and the cladding glass, effectively inhibiting further diffusion of the core crystal into the cladding glass, and correspondingly reducing the diffusion loss of the core.
[0020] This invention pre-forms a pre-diffusion layer on the inner surface of the cladding glass. The pre-diffusion layer is tightly bonded to the cladding glass and acts as an isolation layer, separating the fiber core from the cladding glass. This inhibits diffusion reactions during subsequent hot drawing and single crystallization processes, protecting the morphology and functional integrity of the fiber core, ensuring its composition remains unchanged, and allowing the composite optical fiber to retain its original function. The method provided by this invention is simple, low-cost, and also has reference value for other types of composite optical fibers. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is an EDS line scan of the pre-diffusion layer of the glass tube clad with the pre-diffusion layer in Example 1;
[0023] Figure 2 This is a COMSOL fitting verification diagram of the diffusion reaction between the glass tube with a pre-diffusion layer cladding and the PMN-PT ferroelectric crystal core in Example 1.
[0024] Figure 3 This is a bar chart showing the relationship between the number of pre-diffusion cycles and the PMN-PT retention in the glass tube with a pre-diffusion layer in Example 1.
[0025] Figure 4 The curve showing the diffusion coefficient versus temperature in Example 1;
[0026] Figure 5 The images show the SEM end face scan (top) and schematic diagram (bottom) of the pre-diffusion layer of the glass tube clad with the pre-diffusion layer in Example 1. Detailed Implementation
[0027] This invention provides a method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber, comprising the following steps:
[0028] (1) After filling the PMN-PT ferroelectric crystal core into the cladding glass tube, the PMN-PT ferroelectric crystal core is compacted, diffused until the PMN-PT ferroelectric crystal core diffuses into the cladding glass tube, and then annealed and cooled to obtain a cladding glass tube containing a pre-diffusion layer; the temperature of the diffusion reaction is 900-1100℃.
[0029] (2) Insert another PMN-PT ferroelectric crystal core into the glass tube with the pre-diffusion layer cladding and then heat-draw and recrystallize it in sequence to obtain PMN-PT ferroelectric crystal core glass cladding composite optical fiber.
[0030] This invention involves filling a PMN-PT ferroelectric crystal core into a clad glass tube, followed by sequential compaction, diffusion reaction until the PMN-PT ferroelectric crystal core diffuses into the clad glass tube, and annealing and cooling, to obtain a clad glass tube containing a pre-diffusion layer. In this invention, the PMN-PT ferroelectric crystal core is preferably cylindrical. The PMN-PT ferroelectric crystal in this invention is lead magnesium niobate-lead titanate crystal, and its chemical formula is [(1-x)Pb(Mg...]. 1 / 3 Nb 2 / 3[O3xPbTiO3], where x ranges from 0.15 to 0.40. PMN-PT crystals have a high effective electro-optic coefficient (above 400 pm / V) and a low Curie temperature (135 to 150 °C).
[0031] In this invention, the material of the cladding glass tube is preferably quartz glass, silicate glass, phosphate glass, germanate glass or borate glass; the length of the cladding glass tube is preferably 10-30cm, more preferably 15cm, and the inner diameter is preferably 1-5mm, more preferably 3mm.
[0032] In this invention, the length of the cladding glass tube is preferably the same as that of the PMN-PT ferroelectric crystal core; the difference between the inner diameter of the cladding glass tube and the diameter of the PMN-PT ferroelectric crystal core is preferably no greater than 0.1 mm, more preferably no greater than 0.01 mm. In this invention, the cladding glass tube and the PMN-PT ferroelectric crystal core are fitted as closely as possible, with the gap as small as possible.
[0033] In this invention, the PMN-PT ferroelectric crystal core is preferably filled into the cladding glass tube by filling the PMN-PT ferroelectric crystal core into the cladding glass tube in a vacuum glove box, then sealing it with water glass and allowing it to air dry naturally.
[0034] In this invention, the cladding glass tube is preferably pretreated before being filled with the PMN-PT ferroelectric crystal core; the pretreatment is preferably: the cladding glass tube is sequentially subjected to ultrasonic cleaning with dilute hydrochloric acid, ultrasonic cleaning with ethanol, ultrasonic cleaning with deionized water, and drying (referred to as the first drying).
[0035] In this invention, the concentration of the dilute hydrochloric acid used for ultrasonic cleaning is preferably 10-25 wt%, more preferably 15-20 wt%, the ultrasonic power is preferably 20 W / L, the ultrasonic frequency is preferably 70 kHz, and the ultrasonic time is preferably 5-10 min, more preferably 10 min.
[0036] In this invention, the ultrasonic cleaning time with ethanol is preferably 5 to 10 minutes, more preferably 10 minutes.
[0037] In this invention, the ultrasonic cleaning time with deionized water is preferably 5 to 10 minutes, more preferably 10 minutes.
[0038] In this invention, the first drying is preferably oven drying; the temperature of the first drying is preferably 80-120°C, more preferably 90-110°C, and even more preferably 100°C.
[0039] In this invention, the PMN-PT ferroelectric crystal core is preferably pretreated before being filled into the cladding glass tube; the pretreatment is preferably: the PMN-PT ferroelectric crystal core is sequentially subjected to ultrasonic cleaning with ethanol, ultrasonic cleaning with deionized water, and drying (referred to as the second drying).
[0040] In this invention, the ultrasonic power of the ethanol ultrasonic cleaning is preferably 20W / L, and the ultrasonic frequency is preferably 70kHz.
[0041] In this invention, the ultrasonic power of the deionized water ultrasonic cleaning is preferably 20W / L, and the ultrasonic frequency is preferably 70kHz.
[0042] In this invention, the second drying is preferably oven drying; the temperature of the second drying is preferably 80-120°C, more preferably 100°C, and the heat preservation time is preferably 10-60 min, more preferably 30 min.
[0043] In this invention, the temperature of the diffusion reaction is preferably 920–1080°C, more preferably 950–1050°C, and even more preferably 980–1020°C, and the holding time is preferably 3 hours; the diffusion reaction is preferably carried out in an air atmosphere; and the equipment for the diffusion reaction is preferably a muffle furnace.
[0044] In this invention, the heating rate of the diffusion reaction is preferably no greater than 5°C / min, and more preferably no greater than 3°C / min.
[0045] In this invention, the diffusion reaction is preferably performed once or more, more preferably twice or more. The number of diffusion reactions is determined according to actual needs to control the thickness of the pre-diffusion layer.
[0046] In this invention, the annealing cooling is preferably carried out in the furnace and cooled to room temperature.
[0047] In this invention, the thickness of the pre-diffusion layer in the cladding glass tube containing the pre-diffusion layer is preferably 1 μm or more, more preferably 1 to 1.4 μm; the chemical composition of the pre-diffusion layer includes PMN-PT and cladding glass; the content of PMN-PT in the pre-diffusion layer is preferably 35 wt% or more, more preferably 35 to 40 wt%. After the diffusion reaction, PMN-PT diffuses into the interior of the cladding glass, forming a pre-diffusion layer on the inner surface of the cladding glass.
[0048] After obtaining a glass tube with a pre-diffusion layer cladding, the present invention inserts another PMN-PT ferroelectric crystal core into the glass tube with the pre-diffusion layer cladding and then sequentially hot-draws and recrystallizes it to obtain a PMN-PT ferroelectric crystal core glass-clad composite optical fiber.
[0049] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.
[0050] Example 1
[0051] This embodiment provides a method for fabricating PMN-PT ferroelectric crystal core glass cladding composite optical fiber, the specific steps of which are as follows:
[0052] (1) Pretreatment of quartz glass-clad glass tubes
[0053] Take a quartz glass-clad tube with a length of 15cm and an inner diameter of 3mm. Place the quartz glass-clad tube in dilute hydrochloric acid, ethanol and deionized water for ultrasonic cleaning for more than 5 minutes, and then dry it in an oven at 80℃ for later use.
[0054] (2) Preparation of PMN-PT crystal rods and filled cladding glass tubes
[0055] The PMN-PT crystal block was cut and polished into a cylindrical rod with a length of 15cm and a diameter of 3mm. It was ultrasonically cleaned in ethanol and deionized water and dried in an oven. The cylindrical rod was then filled into the quartz glass-clad glass tube obtained in step (1) in a vacuum glove box. The tube was then sealed with water glass and allowed to air dry naturally to obtain the filled clad glass tube.
[0056] (3) Preparation of pre-diffusion layer
[0057] The filled clad glass tube prepared in step (2) is placed in a muffle furnace and a diffusion reaction is carried out in an air atmosphere. The heating time is more than 3 hours, the diffusion reaction temperature is 900℃, and the holding time is 3 hours. Then the molten PMN-PT crystal is poured out from the filled clad glass tube (operation is carried out in the furnace to maintain the fluidity of the liquid crystal). After the holding time is completed, the tube is cooled to room temperature with the furnace. After the muffle furnace is cooled to room temperature, the filled clad glass tube is taken out. After high-temperature annealing, PMN-PT diffuses into the interior of the quartz glass and forms a pre-diffusion layer on the inner surface of the quartz glass clad glass tube, thus obtaining a clad glass tube with a pre-diffusion layer.
[0058] (4) Replace the PMN-PT crystal rod with a new one as needed, and perform a second diffusion reaction on the glass tube with the pre-diffusion layer cladding to control the thickness of the pre-diffusion layer and reduce losses.
[0059] (5) Insert the PMN-PT ferroelectric crystal core into the glass tube with pre-diffusion layer cladding obtained in step (4) and then heat-draw it to obtain the initial optical fiber. Then recrystallize the core of the initial optical fiber into a single crystal state to obtain the PMN-PT ferroelectric crystal core glass cladding composite optical fiber.
[0060] Example 2
[0061] The method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber provided in this embodiment is the same as that in Example 1. The only difference is that the diffusion reaction temperature in step (3) is 950℃.
[0062] Example 3
[0063] The method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber provided in this embodiment is the same as that in Example 1. The only difference is that the temperature of the diffusion reaction in step (3) is 1000℃.
[0064] Example 4
[0065] The method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber provided in this embodiment is the same as that in Example 1. The only difference is that the temperature of the diffusion reaction in step (3) is 1050℃.
[0066] Example 5
[0067] The method for preparing PMN-PT ferroelectric crystal core glass cladding composite optical fiber provided in this embodiment is the same as that in Example 1. The only difference is that the temperature of the diffusion reaction in step (3) is 1100℃.
[0068] EDS line scanning was performed on the pre-diffusion layer of the glass tube containing the pre-diffusion layer cladding in Example 1, and the results are as follows: Figure 1 As shown. According to Figure 1 It can be seen that the pre-diffusion layer prepared by the present invention forms obvious elemental steps. Deep inside the quartz glass cladding tube is the original composition of quartz glass, which is Si and O. At the position of the pre-diffusion layer, the content of these two elements decreases significantly and is replaced by Pb. The content of Pb increases at the position of the pre-diffusion layer.
[0069] According to Fick's law, the unsteady-state formula is as follows:
[0070]
[0071] Based on experimentally measured substance concentration, diffusion depth, reaction time, and reaction temperature, the diffusion coefficient D can be calculated. Using the initial concentration and diffusion coefficient, a model can be built in COMSOL software to obtain the change curve of substance concentration at a certain point after diffusion ends over time. Comparison of the substance concentration corresponding to the time used in the experiment with the fitted data shows good agreement, proving that the diffusion calculation method used is relatively accurate. Similar verifications were conducted at 900–1100℃ and at different diffusion times. Figure 2 Let's take an example to illustrate, where x is 2μm.
[0072] The relationship between the number of pre-diffusions and the PMN-PT retention in the glass tube with pre-diffusion layer cladding in Example 1 was characterized. Diffusion in step (3) was recorded as one pre-diffusion, diffusion after replacing the crystal rod in step (4) was recorded as two pre-diffusions, and diffusion after replacing the crystal rod again was recorded as three pre-diffusions. Measurements were then taken from different batches of glass tubes with pre-diffusion layer cladding. The results are as follows: Figure 3 As shown. According to Figure 3 It can be seen that as the number of diffusion cycles increases, the PMN-PT content in the pre-diffusion layer increases, which inhibits the diffusion of PMN-PT and reduces the diffusion loss of the composite optical fiber, thereby preserving the original material of the composite optical fiber. Taking Pb as an example, as the number of diffusion cycles increases, the Pb concentration increases, which verifies the protective and preservation effect of the pre-diffusion layer on the fiber core material.
[0073] The diffusion coefficients of the diffusion reactions in Examples 1-5 were fitted with temperature to obtain fitted straight lines, as shown in the figure. Figure 4 As shown. According to Figure 4 It can be seen that the diffusion coefficient D and temperature T satisfy the following functional relationship:
[0074]
[0075] Where D0 is called the frequency factor, which is related to the number of times an atom crosses the potential barrier per unit time, and Q is the diffusion activation energy. Taking the logarithm of both sides, we get:
[0076]
[0077] Based on this straight line, the diffusion coefficient at any temperature can be predicted, thus obtaining a diffusion model at any temperature. This helps in predicting and understanding diffusion phenomena and is beneficial for the preparation of pre-diffusion layers.
[0078] SEM end-face scanning was performed on the pre-diffusion layer of the glass tube containing the pre-diffusion cladding in Example 1. The scanning electron microscope image and schematic diagram of the composite optical fiber are shown below. Figure 5 As shown. According to Figure 5 It can be seen that, after the diffusion reaction, a pre-diffusion layer with different contrast and observable by SEM can be formed on the inner surface of the cladding glass tube.
[0079] As can be seen from the above embodiments, the method provided by the present invention avoids the diffusion phenomenon in subsequent steps, and the fiber core can be recrystallized into a single crystal, thus preserving the original performance of the optical fiber.
[0080] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for fabricating a PMN-PT ferroelectric crystal core glass cladding composite optical fiber, characterized in that, Includes the following steps: (1) After filling the PMN-PT ferroelectric crystal core into the cladding glass tube, the tube is sealed in sequence, a diffusion reaction is carried out to allow the PMN-PT ferroelectric crystal core to diffuse into the cladding glass tube, and annealing and cooling are performed to obtain a cladding glass tube containing a pre-diffusion layer; the temperature of the diffusion reaction is 900~1100℃. (2) Insert another PMN-PT ferroelectric crystal core into the glass tube with the pre-diffusion layer cladding and then heat-draw and recrystallize it in sequence to obtain PMN-PT ferroelectric crystal core glass cladding composite optical fiber.
2. The preparation method according to claim 1, characterized in that, The diffusion reaction is kept at a constant temperature for 3 hours; the diffusion reaction is carried out in an air atmosphere.
3. The preparation method according to claim 1 or 2, characterized in that, The heating rate of the diffusion reaction is no greater than 5°C / min.
4. The preparation method according to claim 1 or 2, characterized in that, The diffusion reaction occurs more than once.
5. The preparation method according to claim 1, characterized in that, The thickness of the pre-diffusion layer in the glass tube containing the pre-diffusion layer is greater than 1 μm.
6. The preparation method according to claim 1 or 5, characterized in that, The chemical composition of the pre-diffusion layer includes PMN-PT and cladding glass; the content of PMN-PT in the pre-diffusion layer is more than 35 wt%.
7. The preparation method according to claim 1, characterized in that, The PMN-PT ferroelectric crystal core is cylindrical in shape.
8. The preparation method according to claim 1, characterized in that, The cladding glass tube is made of quartz glass, silicate glass, phosphate glass, germanate glass, or borate glass.
9. The preparation method according to claim 1 or 8, characterized in that, The length of the cladding glass tube is the same as that of the PMN-PT ferroelectric crystal core; the difference between the inner diameter of the cladding glass tube and the diameter of the PMN-PT ferroelectric crystal core is no greater than 0.1 mm.
10. The preparation method according to claim 1 or 8, characterized in that, The length of the cladding glass tube is 10~30cm, and the inner diameter is 1~5mm.