阅读说明：本技术 一种掺磷有源光纤的制备方法 (Preparation method of phosphorus-doped active optical fibers ) 是由 卞新海 冯术娟 赵霞 缪振华 韩婷婷 徐律 张俊逸 周震华 于 2019-10-11 设计创作，主要内容包括：本发明涉及一种掺磷有源光纤的制备方法,步骤包括(1)基管预处理；(2)在基管内壁沉积二氧化硅疏松体；(3)切断尾管,将基管浸泡到含有磷酸的掺杂离子溶液中,吸附包含磷在内的掺杂离子；(4)浸泡结束后吹干二氧化硅疏松体层内的水分；(5)将吹干的基管重新接上尾管,通入氧气氧化掺杂离子,通入氯气对疏松体干燥；(6)将二氧化硅疏松体层烧结成芯层；(7)重复步骤(2-6)n次,其中n为芯层的总沉积次数,获得基管内的沉积芯层；(8)在He、POCl<Sub>3</Sub>的气氛下塌缩制得掺磷有源光纤预制棒。解决了光纤预制棒在高温塌缩时芯层离子掺杂浓度不均匀的难题。(The invention relates to a preparation method of phosphorus-doped active optical fibers, which comprises the steps of (1) preprocessing a base pipe, (2) depositing a silica loose body on the inner wall of the base pipe, (3) cutting off a tail pipe, soaking the base pipe into a doping ion solution containing phosphoric acid, adsorbing doping ions containing phosphorus, (4) blowing off moisture in the silica loose body after soaking, (5) reconnecting the blow-dried base pipe to the tail pipe, introducing oxygen to oxidize the doping ions, and introducing chlorine to dry the loose body, (6) sintering the silica loose body into a core layer, (7) repeating the step (2-6) n times, wherein n is the total deposition times of the core layer, and obtaining the deposition core layer in the base pipe, (8) depositing the core layer in He and POCl 3 The active optical fiber preform doped with phosphorus is prepared by collapsing in the atmosphere of (1). The problem of uneven core layer ion doping concentration when the optical fiber perform collapses at high temperature is solved.)

A process for preparing 1, phosphorus-doped active optical fibers includes such steps as preparing the prefabricated rod of phosphorus-doped active optical fiber from external cladding layer and core layer inside the external cladding layer

(1) Base pipe pretreatment: a quartz tube is used as a base tube;

(2) depositing a silica loose body on the inner wall of the base pipe;

(3) cutting off a tail pipe, soaking the base pipe into a doping ion solution containing phosphoric acid, and adsorbing doping ions containing phosphorus;

(4) drying the water in the silicon dioxide loose body layer after soaking;

(5) connecting the blow-dried base pipe with a tail pipe again, oxidizing the doped ions in the silica loose body, and introducing chlorine gas to dry the silica loose body layer;

(6) vitrifying and sintering the silicon dioxide loose layer into a core layer;

(7) repeating the steps (2) to (6) n times, wherein n is the total deposition times of the core layer, and obtaining the core layer in the base tube;

(8) in He, POCl₃The active optical fiber preform is prepared by collapsing under the atmosphere condition.

2. The method of making a phosphorus-doped active optical fiber of claim 1, wherein: in the step (1), the quartz tube is heated to 1400 ℃, polished and the impurities and bubbles on the inner wall of the base tube are removed.

3. The method of making a phosphorus-doped active optical fiber of claim 1, wherein: in the step (3), the doping ion solution contains AlCl₃、YbCl₃And H₃PO₄In which AlCl is present₃The molar concentration of (A) is 0.25%，YbCl₃Has a molar concentration of 0.05%, H₃PO₄The molar concentration of (a) is 0.2%.

4. The method of making a phosphorus-doped active optical fiber of claim 1, wherein: and (4) blowing the water in the silicon dioxide loose body layer by using nitrogen.

5. The method of making a phosphorus-doped active optical fiber of claim 1, wherein: and (5) oxidizing the doped ions in the silicon dioxide loose body by introducing oxygen.

6. The method of making a phosphorus-doped active optical fiber of claim 1, wherein: in the step (6), O is in the glass sintering atmosphere₂The gas flow rates of He and He were 150sccm and 300sccm, respectively.

7. The method of making a phosphorus-doped active optical fiber of claim 1, wherein: in the step (8), in a collapsing atmosphere, He and POCl₃The gas flow rates of (1) and (2) are respectively 150sccm and 40 sccm.

8. The method of making a phosphorus-doped active optical fiber of claim 1, wherein: in the step (8), the collapsing comprises forward collapsing and reverse collapsing.

Technical Field

The invention relates to a preparation method of active optical fibers, in particular to a preparation method of phosphorus-doped active optical fibers.

Background

Compared with other types of laser instruments, the fiber laser has the unique advantages of high efficiency, good beam quality, wide spectral range, long service life and the like, and has been widely applied to the civil and military fields of material processing, beauty and medical treatment, military science and technology, fiber communication and the like by .

The rare earth doped active fiber is used as a gain medium and a transmission channel of the fiber laser, and is of a core device of the fiber laser, active ions are doped into a fiber preform core rod at present, and aluminum ions and phosphorus ions are used as co-doping agents, so that the possibility of quartz material crystallization can be reduced, and more importantly, the photon darkening effect of the active fiber can be inhibited.

The chemical property of the phosphorus ions is more active, the phosphorus ions are extremely volatile at high temperature, and the active ions in the optical fiber are taken away while the phosphorus ions are volatilized, so that the doping concentration in the middle of a core layer is very low easily when an optical fiber perform is collapsed into a transparent optical rod in the traditional preparation process, the refractive index profile of the optical rod is M-shaped with high two sides and low middle, and the output power and the beam quality of the optical fiber laser are greatly reduced.

Disclosure of Invention

The invention provides a preparation method of phosphorus-doped active optical fibers, which aims to overcome the defects that phosphorus ions volatilize at high temperature in the optical fiber preparation process, active ions are taken away, the doping uniformity of the active optical fibers is affected, the phenomena of optical fiber clustering, crystallization and the like are caused, and the output power and the beam quality of an optical fiber laser are further deteriorated.

The technical scheme adopted by the invention for solving the problems is as follows: according to the invention, phosphorus oxychloride gas is added into the mixed atmosphere in the process of collapsing the optical fiber preform, so that the volatilization of phosphorus ions and the escape of active ions at high temperature are inhibited, the uniform concentration of doped ions of the active optical fiber core layer is ensured, and the output power and the beam quality of the optical fiber laser are improved.

A method for preparing phosphorus-doped active optical fiber, wherein the preform comprises an outer cladding and a core layer inside the outer cladding

(1) Base pipe pretreatment: taking a quartz tube as a base tube, and correspondingly forming the outer cladding;

(2) depositing a silica loose body on the inner wall of the base pipe;

(3) cutting off a tail pipe, soaking the base pipe into a doping ion solution containing phosphoric acid, and adsorbing doping ions containing phosphorus;

(4) drying the water in the silicon dioxide loose body layer after soaking;

(5) connecting the blow-dried base pipe with a tail pipe again, oxidizing the doped ions in the silica loose body, and introducing chlorine gas to dry the silica loose body layer;

(6) vitrifying and sintering the silicon dioxide loose layer into a core layer;

(7) repeating the steps (2) to (6) n times, wherein n is the total deposition times of the core layer, and obtaining the core layer in the base tube;

(8) in He, POCl₃Is subjected to forward and reverse collapse under the atmosphere condition to prepare the phosphorus-doped active optical fiber preformA rod.

Preferably, in the step (1), the quartz tube is heated to 1400 ℃, polished, and impurities and bubbles on the inner wall of the substrate tube are removed.

Preferably, in the step (3), the doping ion solution contains AlCl₃、YbCl₃And H₃PO₄In which AlCl is present₃Has a molar concentration of 0.25%, YbCl₃Has a molar concentration of 0.05%, H₃PO₄The molar concentration of (a) is 0.2%.

Preferably, the moisture in the silicon dioxide loose body layer is blown dry by nitrogen in the step (4).

Preferably, the doping ions in the silica loose body are oxidized by introducing oxygen in the step (5).

Preferably, in the step (6), O is in the glass sintering atmosphere₂The flow rates of the He gas are 150sccm and 300sccm, respectively.

Preferably, in the step (8), He or POCl is performed in a collapsing atmosphere₃The gas flow rates of (1) and (2) are respectively 150sccm and 40 sccm.

Compared with the prior art, the invention has the advantages that: set in POCl when collapsed at high temperature₃The method is carried out in the atmosphere to inhibit the volatilization loss of phosphorus and the escape of active ions so as to ensure the uniform concentration of the doped ions of the core layer of the active optical fiber.

Drawings

FIG. 1 is a flow chart of an embodiment of a phosphorus-doped active optical fiber preform according to the present invention;

FIG. 2 is a cross-sectional view showing refractive indexes of an optical fiber preform manufactured according to the present invention;

FIG. 3 is a distribution diagram of doping elements in a cross section of an optical fiber preform prepared according to the present invention.

Detailed Description

The invention is described in further detail with reference to the following embodiments of the drawings.

This example relates to a method for preparing kinds of active optical fibers, which comprises the following steps

(1) Preparing a quartz tube as a base tube for deposition, preheating the base tube at 1400 ℃ for polishing, and effectively eliminating impurities and bubbles on the inner wall of the base tube by matching with acid washing; wherein the diameter of the base tube is 32mm, and the wall thickness is 2.5 mm;

(2) depositing on the inner wall of the treated base tube, and designing the total number of deposited layers to be 5;

(3) introducing SiCl into the base tube deposited in the step (2) at 1500 DEG C₄Gas to silica soot deposition, SiCl₄The gas flow is 180sccm, the tail pipe of the base pipe is cut off after the deposition is finished, and then the base pipe is immersed in the doped ion solution for 1 hour, wherein the doped ion solution contains AlCl₃、YbCl₃And H₃PO₄In which AlCl is present₃Has a molar concentration of 0.25%, YbCl₃Has a molar concentration of 0.05%, H₃PO₄The molar concentration of the N is 0.2 percent, and N is introduced into the base pipe after the soaking is finished₂Drying the moisture in the silicon dioxide loose body layer;

(4) connecting the base pipe dried in the step (3) with a tail pipe again, and introducing O at 900 DEG C₂Oxidizing Al, Yb and P in the loose body of silicon dioxide in the base tube, O₂The time of introduction was 30 minutes, O₂The volume flow of the gas is 150 sccm; then introducing Cl₂Drying the silica bulk layer in the substrate tube, Cl₂The time of passage was 30 minutes, Cl₂The volume flow of the gas is 110 sccm; then the temperature is raised to 1700 ℃ at O₂And He atmosphere, sintering the silicon dioxide loose layer at a glass transition temperature of 2000 ℃ to form a core layer, wherein O₂The flow rate of the He gas is 150sccm and 300sccm respectively;

(5) continuously repeating the step (3) and the step (4) for 3 times to obtain four settled layers;

(6) heating the base tube obtained in the step (5) to 1580 ℃ to ensure that the temperature of the deposition loose body is ℃, and introducing SiCl₄Gas to silica soot deposition, SiCl₄The volume flow of the introduced gas is 150sccm, the tail pipe of the substrate tube is cut off after the deposition is finished, then the substrate tube is immersed in the doping ion solution which is the same as that in the step (3) for 0.6 hour, and N is introduced into the substrate tube after the immersion is finished₂Drying the moisture in the silicon dioxide loose body layer;

(7) connecting the base pipe dried in the step (6) with a tail pipe again, and introducing O at 900 DEG C₂Oxidizing Al, Yb and P in the loose body of silicon dioxide in the base tube₂The time of introduction was 45 minutes, O₂The volume flow of the gas is 160 sccm; then introducing Cl₂Drying the silica bulk layer in the substrate tube, Cl₂The time of introduction was 40 minutes, Cl₂The volume flow of the gas is 120 sccm; then the temperature is raised to 1800 ℃ in the presence of O₂In He atmosphere, vitrifying the bulk layer of silicon dioxide into a core layer, where O₂The gas flow rate of He is 150sccm and 300sccm respectively;

(8) heating the base tube sintered with the fifth core layer in the step (7) to 2150 ℃ under He or POCl conditions₃Under the atmospheric conditions of (1) forward and reverse collapse, wherein He and POCl₃The gas flow rates of the two are respectively 150sccm and 40sccm, and the active optical fiber preform is prepared.

FIG. 2 is a schematic cross-sectional view showing the refractive index of the optical fiber preform, which is composed of an outer cladding layer and a core layer in this order from the outside to the inside; FIG. 3 is a cross-sectional composition diagram of doping elements of an optical fiber preform, wherein the main components are silica, and the molar percentage of aluminum is as follows: 2.2 percent, and the molar percentage of ytterbium: 0.05 percent, and the mol percentage content of phosphorus is as follows: 2 percent.

It can be seen from fig. 2 that the refractive index of the core layer tends to along the radial direction, eliminating the large waviness of the refractive index profile of the optical rod, it can be seen from fig. 3 that the doping concentrations of aluminum and ytterbium tend to along the radial direction, and are uniformly distributed.

The collapsing process of the optical fiber perform is carried out under the atmosphere condition of phosphorus oxychloride gas, the problem that the middle doping concentration of a core layer is low easily caused when the optical fiber perform is collapsed into a transparent optical rod in the traditional method, the refractive index profile of the optical rod is M-shaped with high two sides and low middle is solved, and the step of improving the doping uniformity of the active optical fiber is further carried out, so that the probability of clustering and crystallization of the active optical fiber is reduced, the output power and the beam quality of the optical fiber laser are improved, and the use requirements of all aspects are met.

Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that modifications and variations of the present invention are possible to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.