A method for preparing a high rare earth doped low loss boron containing glass optical fiber

Abstract

This invention discloses a method for preparing high rare-earth-doped low-loss boron-containing glass optical fibers. The steps are as follows: weigh glass raw materials containing rare-earth oxides and boron oxide, mix them uniformly, and place them in a high-temperature furnace. First, heat the mixture under a high-purity nitrogen atmosphere, then switch to a high-purity oxygen atmosphere or a high-purity air atmosphere for continued heating. The resulting glass melt is cooled and annealed to obtain a large glass block. The glass is then processed into a preform and placed in an optical fiber drawing furnace for fiber drawing under a high-purity oxygen atmosphere, thus achieving the preparation of high rare-earth-doped low-loss glass optical fibers. This invention eliminates the additional glass matrix absorption in the near-infrared region caused by boron in boron-containing glass optical fibers and also transforms the transition metal impurity ions from a low valence state with broad absorption in the near-infrared region to a high valence state with narrow low absorption in the near-infrared region. Both of these aspects significantly reduce the matrix absorption of boron-containing glass optical fibers, providing possibilities for the application of high rare-earth-doped low-loss glass optical fibers.

Description

Technical Field

[0001] This invention belongs to the field of optical glass materials, and specifically relates to a method for preparing a high rare earth doped low loss boron-containing glass optical fiber. Background Technology

[0002] Single-frequency fiber lasers have found crucial applications in civilian and military fields such as quantum communication and quantum radar. High rare-earth doping concentration and low transmission loss laser fibers are core components of high-performance single-frequency fiber lasers; therefore, the development of highly doped, low-loss glass fibers has received widespread attention. With the availability of high-brightness semiconductor laser pump sources and revolutionary innovations in technologies such as silica fiber fabrication, the output power of silica fiber lasers has reached the tens of thousands or even hundreds of thousands of watts. However, the rigid and regular chemical structure of silica glass limits the concentration of rare-earth doping, inhibiting the possibility of silica fiber as a high-gain fiber. In this regard, multi-component glass fibers have irreplaceable advantages.

[0003] Silicate glasses share the same three-dimensional principal structural unit as quartz glasses, while phosphate glasses possess a unique two-dimensional layered structure. To accommodate more rare earth ions, a greater amount of alkali metal and alkaline earth metal ions must be introduced into the composition. However, excessive introduction of these ions degrades the glass's chemical stability and fiber-forming properties. Boron, as one of the glass network forgers, can act as a flux to lower the glass melting temperature, allowing for improvements in optical quality. It can also connect with silicon or phosphorus ions, increasing the stability of the glass network structure. Its twisted structural units also provide more space for accommodating rare earth ions. Therefore, research on boron-containing multicomponent glasses is expected to provide strong material support for the generation of near-infrared lasers.

[0004] However, boron in glass has a broad absorption band around 1 micrometer, resulting in persistently high matrix loss in boron-doped multicomponent glass fibers, which degrades the laser performance of rare-earth ions in the near-infrared band. Therefore, current designs for highly rare-earth-doped multicomponent glass fibers avoid adding boron as much as possible, but this also leads to limitations in fabrication techniques such as higher glass melting temperatures and limited rare-earth ion doping concentrations.

[0005] Transition metal ions in glass generally exhibit absorption bands of varying widths. For example, the main transition metal impurity ion, iron, typically exists in glass in two chemical valence states: high and low. 3+ or Fe 2+ The ions exhibit a weak and narrow absorption peak in the near-infrared band (Fe). 3+ ) and strong and broad absorption bands (Fe 2+By changing the melting atmosphere during the melting process, iron and other transition metal impurity ions that are difficult to remove from the raw materials using existing purification techniques can be converted from a low valence state with broad and strong absorption in the near-infrared region to a high valence state with only narrow and low absorption in the near-infrared region.

[0006] To improve the optical quality of glass and reduce absorption in the glass matrix while simultaneously increasing rare-earth ion doping, thereby achieving the fabrication of highly doped, low-loss glass fibers, this invention innovates the glass and fiber preparation process. Specifically, during the melting of boron-containing glass melt, a method is employed where a pure nitrogen atmosphere is first used, then switched to a pure oxygen or pure air atmosphere before casting. During fiber drawing, a pure oxygen atmosphere is also maintained. This ultimately enables the fabrication of highly rare-earth-doped, low-loss glass fibers. Summary of the Invention

[0007] To address the issue that boron has a broad absorption band around 1 μm, leading to persistently high matrix loss in boron-doped glass optical fibers and deterioration of laser performance in the near-infrared band due to the presence of rare-earth ions, this invention provides a method for preparing highly rare-earth-doped, low-loss boron-doped glass optical fibers. This method is simple and reasonable, overcomes the shortcomings of existing preparation techniques, and achieves excellent results.

[0008] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution:

[0009] A method for preparing a high rare-earth-doped, low-loss boron-containing glass optical fiber includes the following steps:

[0010] Step 1: Weigh out the glass raw material containing rare earth oxides and boron oxide, and mix them evenly.

[0011] Step 2: Place the uniformly mixed glass raw material into a high-temperature furnace that has been preheated to a specific temperature. First, heat it for a period of time under a high-purity nitrogen atmosphere. Then, switch the high-purity nitrogen atmosphere to a high-purity oxygen atmosphere or a high-purity air atmosphere, and continue heating for a period of time to melt it into glass liquid.

[0012] Step 3: Pour the molten glass into a preheated cast iron mold. After it has fully solidified, place it in an annealing furnace to cool to room temperature and then remove it to obtain a colorless large piece of glass, thus achieving the preparation of glass with low matrix absorption.

[0013] Step 4: Process the obtained colorless bulk glass into a preform, place the preform into an optical fiber drawing furnace, and perform fiber drawing operation in a high-purity oxygen atmosphere to realize the preparation of high rare earth doped low-loss glass optical fiber.

[0014] Furthermore, the glass includes borate glass, boron-containing silicate glass, phosphate glass, germanate glass, tellurate glass, and bismuthate glass, as well as hybrid glasses of the above-mentioned glasses, wherein the hybrid glasses include phosphosilicate glass, germanium tellurate glass, and tellurium bismuthate glass.

[0015] Furthermore, the rare earth elements used in the glass cover all 17 rare earth elements, and the weight percentage of rare earth oxides is less than or equal to 25%.

[0016] Furthermore, the weight percentage of boron oxide contained in the glass composition is less than or equal to 15%.

[0017] Furthermore, a high-purity atmosphere protection device is placed in the high-temperature furnace. High-purity nitrogen is first introduced into the protection device, followed by high-purity oxygen or high-purity air.

[0018] The beneficial technical effects of this invention are as follows:

[0019] To address the drawback of high matrix loss in boron-doped glass fibers caused by the broad absorption band of boron in the glass around 1 μm, this invention employs an atmosphere conversion method during the high-temperature glass melting process. This method reduces the additional absorption in the near-infrared region of the glass matrix caused by boron and transition metal impurity ions, achieving low absorption in the glass matrix. It also maintains the advantages of boron in increasing the solubility of rare earth ions in the glass and improving the optical quality of the glass, ultimately enabling the fabrication of highly rare earth-doped, low-loss glass fibers. Attached Figure Description

[0020] Figure 1 The transmission spectra of the glass prepared in Comparative Example 1, Examples 1 and 2 of this invention are shown. Detailed Implementation

[0021] The technical solution of the present invention will now be described in detail with reference to the embodiments and accompanying drawings:

[0022] A method for preparing a high rare-earth-doped, low-loss boron-containing glass optical fiber includes the following steps:

[0023] Step 1: Weigh out the glass raw material containing rare earth oxides and boron oxide, and mix them evenly.

[0024] Step 2: Place the uniformly mixed glass raw material into a high-temperature furnace that has been preheated to a specific temperature. First, heat it for a period of time under a high-purity nitrogen atmosphere. Then, switch the high-purity nitrogen atmosphere to a high-purity oxygen atmosphere or a high-purity air atmosphere, and continue heating for a period of time to melt it into glass liquid.

[0025] Step 3: Pour the molten glass into a preheated cast iron mold. After it has fully solidified, place it in an annealing furnace to cool to room temperature and then remove it to obtain a colorless large piece of glass, thus achieving the preparation of glass with low matrix absorption.

[0026] Step 4: Process the obtained colorless bulk glass into a preform, place the preform into an optical fiber drawing furnace, and perform fiber drawing operation in a high-purity oxygen atmosphere to realize the preparation of high rare earth doped low-loss glass optical fiber.

[0027] Specifically, the glass includes borate glass, boron-containing silicate glass, phosphate glass, germanate glass, tellurate glass and bismuthate glass, as well as hybrid glasses of the above, including phosphosilicate glass, germanate tellurate glass and tellurate bismuthate glass.

[0028] Specifically, the rare earth elements used in the glass cover all 17 rare earth elements, and the weight percentage of rare earth oxides is less than or equal to 25%.

[0029] Specifically, the weight percentage of boron oxide contained in the glass composition is less than or equal to 15%.

[0030] Specifically, a high-purity atmosphere protection device is placed in the high-temperature furnace. High-purity nitrogen is first introduced into the protection device, followed by high-purity oxygen or high-purity air.

[0031] The following description, in conjunction with comparative examples and embodiments, provides further clarification:

[0032] Table 1 shows the actual amount of raw materials required to prepare 100 grams of glass in one comparative example and three examples. The oxides of alkali metals and alkaline earth metals were introduced as more stable carbonates.

[0033] Table 1

[0034]

[0035]

[0036] Comparative Example 1

[0037] Fabrication of borosilicate glass optical fibers:

[0038] 1-1) First, accurately weigh the oxides or carbonates corresponding to Comparative Example 1 in Table 1 according to the actual amount of raw materials required to prepare 250 grams of glass. Then, carefully and evenly mix them in an agate mortar and place them into a platinum crucible. The crucible is then placed in a high-temperature furnace preheated to 1500 degrees Celsius and equipped with a high-purity atmosphere protection device. High-purity nitrogen is introduced into the high-purity atmosphere protection device, and the mixture is heated to melt into glass. This temperature is maintained for 24 hours to allow the various raw materials to fully react. The glass melt is then poured into a preheated cast iron mold. After sufficient solidification, it is placed in an annealing furnace and cooled to room temperature before being removed to obtain a colorless large piece of glass. The glass transmission spectrum is as follows: Figure 1 As shown, in addition to the characteristic absorption peak of Yb ions, a broad absorption band centered at 1 μm can also be seen in the glass baseline, with its influence extending to around 2 μm.

[0039] 1-2) The colorless bulk glass obtained in step 1-1) is processed into preforms;

[0040] 1-3) The preforms that have been processed are placed in a drawing furnace with high-purity nitrogen protection for drawing to obtain the corresponding optical fibers.

[0041] Example 1

[0042] Fabrication of borosilicate glass optical fibers:

[0043] 1-1) The glass composition was exactly the same as Comparative Example 1. The corresponding oxides or carbonates were accurately weighed according to the actual amount of raw materials required to prepare 250 grams of glass. They were then carefully and evenly mixed in an agate mortar and placed into a platinum crucible. The crucible was then placed in a high-temperature furnace preheated to 1500 degrees Celsius and equipped with a high-purity atmosphere protection device. High-purity nitrogen gas was first introduced into the high-purity atmosphere protection device, and the mixture was heated to melt the glass. This temperature was maintained for 22 hours to allow the various raw materials to react fully. Then, the high-purity nitrogen atmosphere was switched to a high-purity oxygen atmosphere and maintained for 2 hours. The molten glass was then poured into a preheated cast iron mold. After sufficient solidification, it was placed in an annealing furnace and cooled to room temperature before being removed, yielding a colorless large piece of glass. The glass transmission spectrum is as follows: Figure 1 As shown, the broad absorption band centered at 1 μm in the glass baseline has basically disappeared, leaving only the characteristic absorption peak of Yb ions.

[0044] 1-2) The colorless bulk glass obtained in step 1-1) is processed into preforms;

[0045] 1-3) The preforms that have been processed are placed in a drawing furnace with high-purity oxygen protection for drawing to obtain the corresponding optical fibers.

[0046] Example 2

[0047] Fabrication of borosilicate glass optical fibers:

[0048] 2-1) The glass composition was exactly the same as Comparative Example 1. The corresponding oxides or carbonates were accurately weighed according to the actual amount of raw materials required to prepare 250 grams of glass. They were then carefully and evenly mixed in an agate mortar and placed into a platinum crucible. The crucible was then placed in a high-temperature furnace preheated to 1500 degrees Celsius and equipped with a high-purity atmosphere protection device. High-purity nitrogen gas was first introduced into the high-purity atmosphere protection device, and the mixture was heated to melt the glass. This temperature was maintained for 22 hours to allow the various raw materials to react fully. Then, the high-purity nitrogen atmosphere was switched to a high-purity air atmosphere and maintained for 2 hours. The molten glass was then poured into a preheated cast iron mold. After sufficient solidification, it was placed in an annealing furnace and cooled to room temperature before being removed, yielding a colorless large piece of glass. The glass transmission spectrum is as follows: Figure 1 As shown, the broad absorption band centered at 1 μm in the glass baseline has basically disappeared, leaving only the characteristic absorption peak of Yb ions. However, the substrate absorption is slightly larger than that in Example 1, indicating that the oxygen concentration in the air is limited and a longer time is required for complete conversion.

[0049] 2-2) The colorless bulk glass obtained in step 2-1) is processed into preforms;

[0050] 2-3) The preforms that have been processed are placed in a drawing furnace with high-purity oxygen protection for drawing to obtain the corresponding optical fibers.

[0051] Example 3

[0052] Fabrication of borophosphate glass optical fibers:

[0053] 3-1) Accurately weigh the oxides or carbonates corresponding to Example 3 in Table 1 according to the actual amount of raw materials required to prepare 250 grams of glass. Then, carefully and evenly mix them in an agate mortar and place them into a platinum crucible. Then, place the crucible together into a high-temperature furnace preheated to 1400 degrees and equipped with a high-purity atmosphere protection device. First, introduce high-purity nitrogen into the high-purity atmosphere protection device, heat and melt it into glass liquid, and keep it at this temperature for 22 hours to allow the various raw materials to react fully. Then, switch the high-purity nitrogen atmosphere to a high-purity oxygen atmosphere and continue for 2 hours. Then, pour the glass liquid into a preheated cast iron mold. After it has fully solidified, put it into an annealing furnace to cool to room temperature and take it out to obtain a colorless large piece of glass.

[0054] 3-2) The colorless bulk glass obtained in step 3-1) is processed into preforms;

[0055] 3-3) The preformed rods are placed in a drawing furnace with high-purity oxygen protection for drawing to obtain the corresponding optical fibers.

[0056] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a high rare-earth-doped, low-loss boron-containing glass optical fiber, characterized in that, Includes the following steps: Step 1: Weigh out the glass raw material containing rare earth oxides and boron oxide, and mix them evenly. Step 2: Place the uniformly mixed glass raw material into a high-temperature furnace that has been preheated to a specific temperature. First, heat it for a period of time under a high-purity nitrogen atmosphere. Then, switch the high-purity nitrogen atmosphere to a high-purity oxygen atmosphere or a high-purity air atmosphere, and continue heating for a period of time to melt it into glass liquid. The high-temperature furnace is equipped with a high-purity atmosphere protection device. High-purity nitrogen is first introduced into the protection device, followed by high-purity oxygen or high-purity air. Step 3: Pour the molten glass into a preheated cast iron mold. After it has fully solidified, place it in an annealing furnace to cool to room temperature and then remove it to obtain a colorless large piece of glass, thus achieving the preparation of glass with low matrix absorption. Step 4: The obtained colorless bulk glass is processed into a preform, and then the preform is placed in an optical fiber drawing furnace to perform fiber drawing operation in a high-purity oxygen atmosphere to realize the preparation of high rare earth doped low-loss glass optical fiber.

2. The method for preparing a high rare-earth-doped low-loss boron-containing glass optical fiber according to claim 1, characterized in that, The glass includes borate glass, boron-containing silicate glass, phosphate glass, germanate glass, tellurate glass or bismuthate glass, and hybrid glass of the above glasses, wherein the hybrid glass is phosphosilicate glass, germanate tellurate glass or tellurate bismuthate glass.

3. The method for preparing a high rare-earth-doped low-loss boron-containing glass optical fiber according to claim 1, characterized in that, The weight percentage of rare earth oxides is less than or equal to 25%.

4. The method for preparing a high rare-earth-doped low-loss boron-containing glass optical fiber according to claim 1, characterized in that, The weight percentage of boron oxide contained in the glass composition is less than or equal to 15%.

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