Improved method for making hollow laser fiber for mid-infrared lasers
By introducing a polymer layer and a dynamic rotational silver plating process into the mid-infrared laser fiber, a uniform and dense internal reflection interface is formed, which solves the problems of transmission loss, power tolerance and stability, and realizes low-loss, high-power mid-infrared laser transmission.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 萧嘉昀
- Filing Date
- 2026-03-19
- Publication Date
- 2026-06-05
AI Technical Summary
Existing mid-infrared laser fibers have shortcomings in transmission loss, power tolerance, and coating stability, which limit their use in high-precision and high-power applications.
By employing a polymer layer and dynamic spin-plating silver plating process, a uniform and dense internal reflection interface is formed by creating a polymer layer, a single Ag layer, and a silver iodide layer on the inner surface of a silica glass tube, combined with spin-plating technology.
It significantly reduces transmission loss, improves power tolerance and long-term stability, and ensures the high performance consistency and reliability of optical fibers, making it suitable for high-precision and high-power mid-infrared laser applications.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of hollow waveguide technology, specifically relating to an improved fabrication method for hollow laser fibers used in mid-infrared lasers. Background Technology
[0002] Mid-infrared lasers, especially those with wavelengths in the 9000-11000 nm range, have significant applications in industrial processing, medical surgery (such as orthopedics and dentistry), and spectral detection. For example, lasers with wavelengths of 9300-10600 nm are considered ideal tools for precise minimally invasive surgery due to their efficient absorption characteristics in water and biological tissues (such as hard connective tissue and bone). However, to flexibly and efficiently transmit such high-power lasers to the working area, a transmission waveguide is needed that simultaneously meets the requirements of low transmission loss, high power tolerance, excellent flexibility, and Gaussian beam mode preservation.
[0003] Flexible hollow fiber waveguides have attracted widespread attention as a solution due to their advantages such as simple structure, low potential loss, and high power carrying capacity. A typical structure involves depositing a highly reflective metal layer and a dielectric layer on the inner wall of a capillary. The reflection mechanism of the inner wall confines light transmission within the hollow core, thereby avoiding the thermal damage caused by absorption by the bulk material.
[0004] In the prior art, US Patent US005440664A discloses a flexible hollow fiber waveguide for transmitting mid-infrared radiation with low attenuation and a method for manufacturing the same. This patent forms a waveguide capable of transmitting mid-infrared electromagnetic radiation in a near-Gaussian mode by sequentially chemically depositing a silver (Ag) layer and a silver iodide (AgI) layer on the inner wall of a hollow glass fiber. The reported transmission loss is less than 1.5 dB / m, which to some extent meets the demand for low-loss flexible mid-infrared laser transmission media.
[0005] However, through in-depth research and practice, the applicant has discovered that the existing technology has at least the following shortcomings: First, there is still room for further reduction in transmission loss. A loss of less than 1.5 dB / m is still too high for some high-precision, long-distance transmission applications. The fundamental reason may be that the uniformity, density, and surface roughness control of the inner wall coating have not yet reached their optimal levels. Any slight inhomogeneity or defect in the coating will cause light scattering, increase transmission loss, and affect the quality of the output beam.
[0006] Second, the power tolerance (laser damage threshold) is limited. When transmitting high-power (e.g., tens of watts) mid-infrared lasers, existing waveguides may experience localized overheating, oxidation, or even melting of the coating, leading to rapid degradation or permanent damage to the waveguide performance. This limits its application in industrial processing and medical surgery requiring continuous high-power output.
[0007] Third, the coating adhesion and long-term stability are insufficient. The adhesion between the metallic silver layer and the glass substrate is crucial to the waveguide's lifespan and mechanical reliability. The silver layer prepared in Reference Document 1 may have weak adhesion, making it prone to peeling or cracking during repeated bending or long-term use, leading to a sharp increase in loss and waveguide failure.
[0008] Therefore, there is an urgent need in this field for an improved hollow laser fiber and its fabrication method, which can achieve lower transmission loss, higher laser power carrying capacity, and better coating stability and durability while maintaining flexible transmission and near-Gaussian mode. Summary of the Invention
[0009] To address the aforementioned problems, this invention discloses an improved method for fabricating hollow laser fibers for mid-infrared lasers. The hollow laser fibers obtained by the method provided by this invention have lower losses when used as waveguides for transmitting mid-infrared electromagnetic radiation in near-Gaussian mode, and can withstand greater transmission power, making them particularly suitable for transmitting lasers with wavelengths around 9300-10600 nm.
[0010] The objective of this invention is achieved through the following technical solution.
[0011] A hollow laser fiber for mid-infrared lasers includes a silica glass tube and a coating sequentially disposed on the inner surface of the silica glass tube, the coating comprising: The polymer layer is made of polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA) and has a thickness of 0.5 μm to 5 μm. A single Ag layer, with a thickness of 0.1 μm to 2 μm, is disposed on the polymer layer; A silver iodide layer is disposed on the elemental Ag layer; The elemental Ag layer is generated in situ on the surface of the polymer layer by a silver mirror reaction, and the inner surface coating of the hollow laser fiber is formed by rotating the silica glass tube during the reaction process.
[0012] Furthermore, in the aforementioned hollow laser fiber, the wavelength of the mid-infrared laser is 9300-10600nm.
[0013] Furthermore, in the aforementioned hollow laser fiber, the inner diameter of the silica glass tube is 330 μm to 680 μm.
[0014] This invention also discloses a method for preparing the above-mentioned hollow laser fiber, comprising the following steps: S1. A polymer layer is formed by coating the inner surface of a silica glass tube; S2. Simultaneously inject the silver ammonia complex solution and reducing agent solution horizontally or vertically into the interior of the silica glass tube whose inner surface is coated with a polymer layer using a (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump). During the injection process, rotate the silica glass tube around its long axis at a speed of 0.1 to 2 revolutions per minute, and form a single Ag layer in situ on the surface of the polymer layer through a silver mirror reaction. S3. An organic solution containing elemental iodine is injected into the silica glass tube with an elemental Ag layer on its inner surface to react and generate a silver iodide layer on the surface of the elemental Ag layer.
[0015] Furthermore, in step S2 of the above method, the silver ammonia complex solution is prepared by the following method: Silver nitrate solution and ammonium hydroxide solution are mixed to form silver hydroxide precipitate. Sodium hydroxide solution is then added to adjust the alkalinity. Subsequently, ammonium hydroxide solution is added until the precipitate is completely dissolved, forming a colorless and transparent silver ammonia complex solution.
[0016] Furthermore, in step S2 of the above method, the reducing agent solution is a dextrose aqueous solution with a concentration of 2wt% to 10wt%, and an ammonium hydroxide solution accounting for 0.05% to 10% of its total volume is also added to the reducing agent solution.
[0017] Furthermore, in the above method, in step S2, the flow rate of the injected solution is set according to the aperture of the silica glass tube: When the pore size is 680 μm, the solution injection flow rate is 310 mL / h to 600 mL / h. When the pore size is 500 μm, the solution injection flow rate is 200 mL / h to 600 mL / h; When the pore size is 330 μm, the solution injection flow rate is 150 mL / h to 300 mL / h.
[0018] Furthermore, in the above method, in step S3, the organic solution containing elemental iodine is a cyclohexane solution of iodine, wherein the concentration of iodine is 8 g / L to 15 g / L.
[0019] Furthermore, in the above method, in step S3, the injection flow rate is set according to the aperture of the silica glass tube: When the pore size is 680 μm, the injection flow rate is 30 mL / 5 min to 35 mL / 5 min; When the pore size is 500 μm, the injection flow rate is 23 mL / 5 min to 28 mL / 5 min; When the pore size is 330 μm, the injection flow rate is 20 mL / 5 min to 25 mL / 5 min.
[0020] The present invention also discloses the use of the above-mentioned hollow laser fiber in the preparation of medical laser devices for cutting hard connective tissue.
[0021] Compared with existing technologies, the present invention has the following advantages and beneficial effects: This invention achieves significant advantages by introducing a polymer transition layer combined with a dynamic rotational silver plating process. Firstly, it greatly reduces transmission loss, thanks to the polymer layer significantly improving the adhesion and uniformity of the silver plating, forming an extremely smooth and dense internal reflection interface. Secondly, it significantly improves power tolerance and long-term stability; the uniform and robust plating effectively disperses and resists the thermal stress generated by high-power lasers, avoiding localized overheating and melting, and performance degradation. Thirdly, it ensures excellent consistency and reliability of product performance; the optimized fabrication process ensures that each fiber has excellent repeatability and high performance, meeting the stringent consistency requirements of medical and industrial applications. In summary, the hollow laser fiber fabricated by this invention achieves a qualitative leap in key performance indicators, providing a reliable transmission solution for high-precision, high-power mid-infrared laser applications. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention. All raw materials (including bacterial strains, etc., are commercially available products) in the embodiments of this invention are commercially available.
[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.
[0024] Example 1 The inner surface of the silica glass tube is coated with a polymer, such as polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA), to improve the adhesion of silver and protect the surface.
[0025] A. Silver ammonia complex solution Dissolve 1.05-1.55 g of 99.999% pure silver nitrate (AgNO3) in 300-500 mL of distilled deionized water (H2O) to prepare a silver nitrate solution with a molar concentration of 0.0206-0.01825 mol / L.
[0026] Subsequently, add 1-2 mL of ammonium hydroxide aqueous solution (NH4OH; 5-10%) drop by drop. Initially, a brown silver hydroxide precipitate forms, and the chemical reaction is: AgNO3 + NH4OH → Ag(OH)↓ + NH4NO3, forming a brown precipitate and yielding a silver nitrate / ammonium hydroxide solution. Gradually add 3-15 mL of ammonium hydroxide aqueous solution until the brown precipitate becomes a clear liquid again. Then, add 0.15-0.25 g of sodium hydroxide (NaOH) in 100 mL of distilled water to form a sodium hydroxide solution as a regulator, adding it to 10-20 mL of the silver nitrate / ammonium hydroxide solution to adjust the reduction reaction rate. The reduction reaction should not be too fast. Sodium hydroxide is a rate regulator; the reduction rate increases with increasing alkalinity. However, excessive alkalinity will promote the self-decomposition of the silver ammonia complex solution. The amount added should be controlled; otherwise, the brown silver hydroxide precipitate will decompose into a dark brown silver oxide precipitate, and the chemical reaction is: 2AgOH → Ag2O↓ + H2O. Continue adding approximately 3-10 mL of ammonium hydroxide aqueous solution (NH4OH; 5-10 wt%) to form a colorless and transparent silver ammonia complex solution. The chemical reaction that occurs is: Ag2O + 4NH4OH → 2Ag(NH3)2OH + 3H2O. Adding sodium hydroxide solution increases the stability of the silver ammonia complex ion, which is beneficial for improving the stability of the silver ammonia complex solution (plating bath).
[0027] B. Reducing agent solution The reducing solution used was a dextran aqueous solution, which was diluted with distilled deionized water to obtain the dextran aqueous solution (C6H). 12 O6; 4 wt% by weight). The role of the reducing solution is to reduce individual silver ions; the chemical reaction that occurs is: Ag(NH3)2OH + C6H. 12 O6→Ag↓+2NH3+H2O. Weigh 0.03-1.00 g of solid EDTA using a precision electronic balance. 5. Slowly add the weighed EDTA to the mixed solution, stirring continuously until the EDTA is completely dissolved. After preparation, mix using an ultrasonic bath to form the final reduced solution.
[0028] C. Silver plating 1. Preparation of mixed solutions: Prepare materials and equipment: Silver ammonia complex solution: Prepare in advance to ensure appropriate silver ion concentration.
[0029] Reducing agent solution: Prepared using dextrose, ensuring a concentration of 2%-10%, which is 5% in this example.
[0030] Solid ethylenediaminetetraacetic acid (EDTA): used for the detection of free silver ions.
[0031] Precision electronic balance: used for accurate weighing of EDTA.
[0032] Graduated cylinder: Used to measure the required volume of solution.
[0033] Stirring and containers: used for mixing solutions.
[0034] Operating steps: 1. Measure 1 liter of the silver ammonia complex solution prepared in step A and 1 liter of the reducing agent solution prepared in step B using a graduated cylinder. 2. Pour the silver ammonia complex solution into a stirring container and turn on the stirrer at a moderate speed. 3. Slowly add 1 liter of the reducing agent solution, continuing to stir to ensure the solution is thoroughly mixed. 4. Weigh 0.03-1.00 g of solid EDTA using a precision electronic balance. 5. Slowly add the weighed EDTA to the mixed solution, continuing to stir until the EDTA is completely dissolved. 6. Examine the solution, confirming the presence of silver ions by observing the appearance of a silver mirror reaction. The appearance of a silver mirror reaction indicates the presence of sufficient silver ions in the solution. Let the mixed solution stand to ensure the reaction is complete.
[0035] 2. Silver plating process: Prepare a silica glass tube: Select a silica glass tube with an appropriate aperture, typically 500 μm. Place the glass tube horizontally or vertically on the worktable, ensuring that both ends can be connected to the delivery pipes of a vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump).
[0036] Solution injection: 1. Pour the mixed silver ammonia complex solution and reducing agent solution sequentially or separately into the storage container of the vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump).
[0037] 2. Connect the delivery pipe of the vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump) and insert one end of the pipe into the inlet end of the silica glass tube.
[0038] 3. Set the flow rate parameters of the vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump) to uniformly inject the solution into the glass tube at a rate of 200-600 mL / hour.
[0039] 4. Start the vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump) to force the mixed solution into the glass tube at a constant pressure, ensuring that the solution flows uniformly inside the glass tube.
[0040] Rotation of the glass tube: Using a specialized rotating device, slowly rotate the glass tube at a speed of 0.5 revolutions per minute, allowing it to rotate 720° each time along its long axis. This operation helps to form a uniform silver coating on the inner wall of the glass tube, preventing uneven coating thickness caused by gravity.
[0041] Rinse and dry: 1. After the silver plating process, rinse the inside of the glass tube with a 100wt% ethanol solution to ensure thorough removal of any residual chemicals. 2. Use compressed air at 10 psi pressure to purge the inside of the glass tube for 80-180 minutes for initial drying. 3. Subsequently, use 99.999% pure nitrogen at 10 psi pressure to purge the inside of the glass tube again for 80-180 minutes to ensure complete drying and prevent residual solution or moisture from affecting subsequent processes.
[0042] D. Iodine Addition Steps First, in a warm ultrasonic bath, 100 mL of cyclohexane and 0.8–1.5 g of iodine are precisely mixed to ensure complete dissolution of the iodine. After mixing, the resulting solution is cooled to room temperature. Next, the volume of the resulting iodine / cyclohexane solution is precisely measured according to the desired aperture, target wavelength, and type of pump used to form an optimal silver iodide layer with minimal loss and diffraction limitation (i.e., spatial coherence or Gaussian beam output).
[0043] The specific implementation steps are as follows: 1. For 680μm optical fiber: When using a vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump), the solution flow rate is 30 mL / 5 min to 35 mL / 5 min; 2. For 500μm optical fiber: When using a vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump), the solution flow rate is 23 mL / 5 min to 28 mL / 5 min; 3. For 330μm optical fiber: When using a vacuum pump (vacuum pump, diaphragm pump, syringe pump, plunger pump, gear pump, peristaltic pump, bellows pump, pneumatic diaphragm pump), the solution flow rate is 20 mL / 5 min to 25 mL / 5 min.
[0044] Note: For this type of small aperture, the solution may react prematurely inside the waveguide, causing blockage. Increasing the indoor operating temperature and humidity can delay the solution reaction time.
[0045] After the plating is completed, the plated tube with the silver iodide layer needs to be rinsed with an ethanol solution. The purpose of rinsing with 100 wt% ethanol (chemical formula CH3CH2OH) is to remove the residue left inside the plated tube after the silver mirror reaction.
[0046] Finally, the plated tubes after rinsing need to be dried. The specific drying steps are as follows: 1. Use compressed air to blow dry for 80-180 minutes to ensure initial drying.
[0047] 2. Then purge with nitrogen for 80-180 minutes to further remove residual solvent and moisture.
[0048] After the above steps, a hollow optical fiber for mid-infrared lasers can be obtained, which has excellent optical performance and low loss characteristics.
[0049] The mid-infrared hollow laser fiber prepared in this embodiment can withstand a considerable amount of power. When transmitting 30W of power, it can operate continuously for 10 minutes without melting. Under a 9600nm wavelength laser, it can cut hard connective tissues, such as bone.
[0050] The hollow laser fiber for mid-infrared lasers prepared in this embodiment is used as a waveguide for transmitting mid-infrared electromagnetic radiation in near-Gaussian mode. It achieves a transmission power of up to 95% at a wavelength of 9600nm, with significantly optimized loss.
[0051] Example 2 The preparation method is basically the same as that in Example 1, except that in step C, silver plating, the flow rates of the silver ammonia complex solution and the reducing solution used for the 680μm aperture optical fiber are both 300-600mL / hour.
[0052] Example 3 The preparation method is basically the same as that in Example 1, except that in step C, silver plating, the flow rates of the silver ammonia complex solution and the reducing solution used for the 500μm aperture optical fiber are both 180-300mL / hour.
[0053] Test case To verify the beneficial effects of the improved preparation method provided by the present invention, a performance comparison test was conducted between the hollow laser fiber prepared by the method described in Example 1 of the present invention (hereinafter referred to as the "product of the present invention") and an existing product prepared by the method of US Patent US005440664A (comparative document 1) mentioned in the background art (hereinafter referred to as the "comparative product").
[0054] 1) The following is a comparison of the test results of the new and old products (2.8m sample) under 10W infrared laser, as shown in Table 1: 2) The output power of 30 2.8m samples under 10W infrared laser is compared below, as shown in Table 2.
[0055] Table 2: Comparison of single-strand output power of 30 2.8m samples under 10W infrared laser (unit: W) The above test results demonstrate that the performance of the product of this invention has achieved a significant leap forward: 1. Increased transmission efficiency and output power: The average output power of the product of this invention reaches 9.20W, which is more than double that of the control product (4.50W); the average transmission efficiency is as high as 92.0%, which is 47 percentage points higher than the control (45.0%). Moreover, the lowest efficiency of this invention (88.4%) far exceeds the highest value of the control (59.8%), which fully proves that its transmission loss has been revolutionaryly reduced.
[0056] 2. Excellent performance consistency and reliability: The output power of 30 samples of this invention is concentrated in a narrow range of 8.84W–9.49W, which is far better than the wide distribution of 3.23W–5.98W of the control product. This proves that the improved preparation process has excellent repeatability and stability and can continuously produce high-performance products.
[0057] 3. Significantly enhanced power stability: During 30 minutes of continuous operation, the output power fluctuation range of the product of this invention (±0.21W) was narrowed by 59.6% compared with the control (±0.52W), which reflects the superior thermal stability of the coating and the higher laser damage threshold.
[0058] In summary, the test data fully confirms that this invention, by introducing a polymer layer and optimizing the dynamic coating process, successfully fabricates a hollow laser fiber that combines extremely low loss, high power capacity, excellent consistency, and long-term stability, perfectly solving the key defects of existing technologies.
[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of the present invention, or equivalent structural or procedural transformations made using the content of the present invention specification, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of protection of the present invention patent.
Claims
1. A hollow laser fiber for mid-infrared lasers, comprising a silica glass tube and a coating sequentially disposed on the inner surface of the silica glass tube, characterized in that, The coating comprises: The polymer layer is made of polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA) and has a thickness of 0.5 μm to 5 μm. A single Ag layer, with a thickness of 0.1 μm to 2 μm, is disposed on the polymer layer; A silver iodide layer is disposed on the elemental Ag layer; The elemental Ag layer is generated in situ on the surface of the polymer layer by a silver mirror reaction, and the inner surface coating of the hollow laser fiber is formed by rotating the silica glass tube during the reaction process.
2. The hollow laser fiber according to claim 1, characterized in that, The wavelength of the mid-infrared laser is 9300-10600nm.
3. The hollow laser fiber according to claim 1, characterized in that, The inner diameter of the silica glass tube is 330 μm to 680 μm.
4. A method for preparing a hollow laser fiber as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. A polymer layer is formed by coating the inner surface of a silica glass tube; S2. Simultaneously inject the silver ammonia complex solution and the reducing agent solution into the interior of the silica glass tube whose inner surface is coated with a polymer layer. During the injection process, the silica glass tube is rotated around its long axis at a speed of 0.1 to 2 revolutions per minute, and a single Ag layer is formed in situ on the surface of the polymer layer through a silver mirror reaction. S3. An organic solution containing elemental iodine is injected into the silica glass tube with an elemental Ag layer on its inner surface to react and generate a silver iodide layer on the surface of the elemental Ag layer.
5. The method according to claim 4, characterized in that, In step S2, the silver ammonia complex solution is prepared by the following method: Silver nitrate solution and ammonium hydroxide solution are mixed to form silver hydroxide precipitate. Sodium hydroxide solution is then added to adjust the alkalinity. Subsequently, ammonium hydroxide solution is added until the precipitate is completely dissolved, forming a colorless and transparent silver ammonia complex solution.
6. The method according to claim 4, characterized in that, In step S2, the reducing agent solution is a dextrose aqueous solution with a concentration of 2wt% to 10wt%, and an ammonium hydroxide solution accounting for 0.05% to 10% of its total volume is also added to the reducing agent solution.
7. The method according to claim 4, characterized in that, In step S2, the flow rate of the injected solution is set according to the pore size of the silica glass tube. The following are examples using three pore sizes: When the pore size is 680 μm, the solution injection flow rate is 310 mL / h to 600 mL / h. When the pore size is 500 μm, the solution injection flow rate is 200 mL / h to 600 mL / h; When the pore size is 330 μm, the solution injection flow rate is 150 mL / h to 300 mL / h.
8. The method according to claim 4, characterized in that, In step S3, the organic solution containing elemental iodine is a cyclohexane solution of iodine, wherein the concentration of iodine is 8 g / L to 15 g / L.
9. The method according to claim 8, characterized in that, In step S3, the injection flow rate is set according to the aperture of the silica glass tube: When the pore size is 680 μm, the injection flow rate is 30 mL / 5 min to 35 mL / 5 min; When the pore size is 500 μm, the injection flow rate is 18 mL / 5 min to 23 mL / 5 min; When the pore size is 330 μm, the injection flow rate is 10 mL / 5 min to 15 mL / 5 min.
10. Use of the hollow laser fiber as described in any one of claims 1-3 in the manufacture of a medical laser device for cutting hard connective tissue.