JP2005132708A - Method for manufacturing optical fiber or optical element in which reduced metal ion and/or rare earth ion are doped, and method for manufacturing optical fiber or optical element in which reduced metal fine particle and/or rare earth element are doped - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical fiber or an optical element in which reduced metal ions and/or rare earth ions are doped, the method by which a conventional process for manufacturing the optical fiber or the optical element can be more safely and easily utilized than a conventional method. <P>SOLUTION: The method for manufacturing the optical fiber or the optical element, in which reduced metal ions and/or rare earth ions are doped, includes a step for forming partially sintered fine structure in a base material for manufacturing the optical fiber or the optical element, a step for impregnating the fine structure with a metal ion and/or rare earth ion doping solution containing a reductant, a step for drying the fine structure impregnated with the metal ions and/or the rare earth ions, and a step for heating the dried fine structure so that the dried fine structure is sintered. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for manufacturing an optical fiber or an optical element, and more particularly, a method for manufacturing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions, and reduction. The present invention relates to a method of manufacturing an optical fiber or an optical element doped with the fine metal particles and / or rare earth elements.

  Optical fibers added with metal ions and / or rare earth ions are classified as special optical fibers because they have various applications such as optical amplifiers and optical switching elements. Therefore, research on this has been actively conducted.

  One of the research subjects is a technique for reducing doped metal ions and rare earth ions. In general, the atomic energy level distribution changes depending on the valence of atoms, so that the spectroscopic characteristics such as light absorption and light emission are different. Therefore, various optical absorption and emission characteristics can be obtained by changing the valence, and optical fibers and optical elements having various optical amplification and optical switching characteristics can be obtained. As an example, when the valence of the rare earth ion is “+3”, the light absorption characteristic due to the electronic transition between the electron shell of 4f and the electron shell of 5d appears only in the ultraviolet region, but the valence is “2+”. If it is changed to ', light absorption characteristics will occur in the visible and infrared regions. Therefore, there is a need for a technique for allowing doped metal ions and rare earth ions to have a desired valence. On the other hand, there is a valence mainly present for each element, and a special process is required to make this a desired valence.

  For example, rare earth ions often have a valence of '3+'. In order to stably produce this to a valence of ‘2+’, ‘1+’ or ‘0’, ion reduction treatment is required. The following reduction treatment methods have been proposed to date.

First, a method of irradiating a rare earth metal ion having a valence of 3+ with gamma rays. As an example, a method for obtaining Tm ²⁺ ions by irradiating a CaF ₂ crystal added with Tm ³⁺ ions with gamma rays has been reported.

  However, this method has a problem in that there is a danger in the handling of the gamma ray light source, and the cost due to this is high.

Another proposed method is a method that utilizes a raw material in aerosol form. This method requires an improved chemical vapor deposition (MCVD) process. That is, this method includes an MCVD step of laminating a glass layer to which rare earth ions are added in a quartz glass tube using an aerosol-form raw material that generates carbon together with rare earth ions and powder that forms glass upon combustion. . Next, a process of removing carbon and OH groups, a glass sintering process, and a glass tube depression process are sequentially performed to obtain an optical fiber preform. As an example, there is a glass optical fiber having a component of SiO ₂ —Al ₂ O ₃ in which Eu ³⁺ and Sm ³⁺ are reduced to Eu ²⁺ and Sm ²⁺ , respectively.

  Thus, the method of using the raw material in the aerosol form has been performed only through the MCVD process until now, and a desired rare earth ion raw material in the aerosol form and an additional aerosol supply device are required.

In addition, there has been proposed a method for obtaining reduced rare earth ions by injecting a mixed gas such as H ₂ and Ar in the glass melting process. As an example, there is a glass having a component of SiO ₂ —Al ₂ O ₃ or SiO ₂ —B ₂ O ₃ in which Sm ³⁺ is reduced to Sm ²⁺ .

In this method, the manufacturing process of the optical fiber preform is complicated compared to the existing manufacturing process of the optical fiber preform, and has not yet been generalized.

  The present invention provides an optical fiber or light to which reduced metal ions and / or rare earth ions are added, which can use a conventional optical fiber or optical element manufacturing process more safely and easily than the above-described existing methods. It is an object of the present invention to provide a method for producing an element and a method for producing an optical fiber or an optical element doped with reduced metal fine particles and / or rare earth elements.

  According to the present invention, a doping solution containing a reducing agent together with metal ions and / or rare earth ions is formed by forming a partially sintered microstructure on an optical fiber or an optical element manufacturing substrate. And a metal ion and / or rare earth ions are doped into the microstructure together with the reducing agent to obtain metal ions and / or rare earth ions reduced through the reducing agent. To do.

  The method for producing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions according to the present invention includes a step of forming a partially sintered microstructure on the optical fiber or optical element manufacturing substrate. A step of impregnating the microstructure with a metal ion and / or rare earth ion doping solution containing a reducing agent, a step of drying the microstructure impregnated with the metal ion and / or rare earth ion, and a step of drying the microstructure. Heating to be sintered.

  The method of manufacturing an optical fiber or an optical element doped with reduced metal fine particles and / or rare earth elements according to the present invention includes a step of forming a partially sintered microstructure on the optical fiber or an optical element manufacturing substrate. Impregnating the microstructure with a metal ion and / or rare earth ion doping solution containing a reducing agent having a strong reduction potential, drying the microstructure impregnated with the metal ion and / or rare earth ion, and drying. Heating the formed microstructure to be sintered to form metal particulates and / or rare earth elements.

  The reducing agent is desirably a hydrocarbon compound. Examples include glucose, sucrose, glycerine, starch, dextrin, benzene, phenol, hexane, toluene, styrene, naphthalene. (naphthalene).

  Examples of the reducing agent include alkoxides such as TEOS (tetraethyl orthosilicate), TMOS (tetramethyl orthosilicate), TEOC (tetraethyl orthocarbonate), and TMOC (tetramethyl orthocarbonate).

  Doped metal ions and / or rare earth ions are Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Sc, Ti, V, Cr. , Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Hf, Ta, W, Re, Os, Ir, Pt , One or more ions selected from the group consisting of Au, Tl, Pb, Bi, and mixtures thereof.

An optical fiber or an optical element manufacturing base material is silicon oxide (SiO ₂ ), or silicon oxide with germanium oxide (GeO ₂ ), boron oxide (B ₂ O ₃ ), phosphor oxide (P ₂ O ₅ ). And an oxide series containing one or more selected from titanium oxide (TiO ₂ ).

Desirably, the substrate for optical fiber or optical element production is silica (SiO ₂ ), germanosilicate (SiO ₂ -GeO ₂ ), phosphorosilicate (SiO ₂ -P ₂ O ₅ ), phosphorogel manosilicate (SiO ₂ ). ₂ -GeO ₂ -P ₂ O ₅ ), borosilicate (SiO ₂ -B ₂ O ₃ ), borophosphorosilicate (SiO ₂ -P ₂ O ₅ -B ₂ O ₃ ), borogermanosilicate (SiO _2- GeO ₂ -B ₂ O ₃ ), titanosilicate (SiO ₂ -TiO ₂ ), phosphoro titanosilicate (SiO ₂ -TiO ₂ -P ₂ O ₅ ) or borotitanosilicate (SiO ₂ -TiO ₂ -B ₂ O ₃ ) is the basic composition.

  In the present invention, the optical element includes a planar optical element such as a planar optical amplifier, a laser for optical communication, and a planar optical switching element.

  The method of the present invention comprises the steps of forming a partially sintered microstructure on an optical fiber or a base material for manufacturing an optical device, and forming the microstructure into metal ions and / or rare earth ions and a reducing agent. Soaking in a doping solution containing a hydrocarbon compound or alkoxide and maintaining for 1 to 1.5 hours. That is, the reducing agent is doped with the metal ions and / or rare earth ions into the microstructure of the optical fiber or the substrate for manufacturing the optical element. Metal ions and / or rare earth ions reduced by this doped reducing agent are obtained.

  The method of the present invention is a modification of the solution addition method in which metal ions and / or rare earth ions can be added to optical fibers or optical elements. This solution addition method is already widely used, such as improved chemical vapor deposition (MCVD), vapor-axis axial deposition (VAD), and outside vapor deposition (OVD). It is a method of doping rare earth ions or (transition) metal ions into the optical fiber core, which can be used with any of the optical fiber preforms (semi-finished products) used. The solution addition method is also used as a doping method for all metal ions and / or rare earth ions that can be prepared in a solution form in a flat glass optical device manufacturing process through flame hydrolysis deposition (FHD). ing.

  As an example, a solution addition method through an MCVD process (JE Townsend, et al., “Solution doping technique for fabrication of rare-earth doped optical fibers”, Electron. Lett., Vol. 23, pp329-331, 1987 Reference) is as follows. Here, in order to obtain reduced rare earth ions, an aqueous solution in which sucrose, a strong reducing agent, is dissolved together with rare earth chloride is used as a doping solution. First, an existing MCVD process is used to partially sinter the interior of the silica tube to form a core layer with many voids (see MacChesney et al., “Optical fiber fabrication and resulting product”, U.S. Patent, 1997). The tube is then filled with an aqueous solution in which sucrose is dissolved along with the rare earth chloride. After maintaining for 1 to 1.5 hours so that the solution can sufficiently penetrate into the voids of the core layer, the aqueous solution is discharged. As a result, the doping solution remains in the voids. Using an MCVD process, the core layer doped with the aqueous solution is dried by maintaining the temperature at 100 to 250 ° C. while allowing only an inert gas such as helium to flow. At this time, ethanol and moisture are removed. Then, using the hydrogen-oxygen spark, the core layer is heated at a high temperature of about 2000 ° C. until the carbon produced from sucrose is removed and the core layer is completely sintered (MF Yan, et al., “ Sintering of optical wave-guide glasses ”, J. of Mater. Sci., Pp 1371-1378, 1980). After that, a depression process (see JB MacChesney, et al., “Optical fiber fabrication and resulting product”, US Patent, 1997) is performed at a high temperature of 2200 ° C. or higher using a hydrogen-oxygen spark while flowing an inert gas. After that, an optical fiber preform is produced. This optical fiber preform is manufactured into an optical fiber to which rare earth ions reduced through drawing are added.

Sucrose contained in the doping solution is a substance composed of C, H, and O components. In the aforementioned drying process, a substantial portion of H and O are removed from these components, leaving only carbon (C). The carbon (C) is combined with oxygen (O ₂ ) remaining at a high temperature of about 2000 ° C. to form carbon monoxide (CO), thereby reducing the doped rare earth ions. At this time, the temperature applied for the reaction for forming carbon monoxide is determined by a temperature at which rare earth ions can be reduced using the Ellingham Diagram. At the same time, a strong reducing atmosphere is formed by injecting only an inert gas that does not cause a reaction in the silica glass tube so that carbon can participate in the reduction of rare earth ions as much as possible. Further, preferably, the depression process for manufacturing the optical fiber preform is configured so that the reducing atmosphere can be composed to the maximum by flowing only the inert gas.

EXAMPLES Hereinafter, although this invention is demonstrated in detail through an Example, this invention is not limited to these Examples.

The method of the present invention includes improved chemical vapor deposition (MCVD), vapor-phase axial deposition (VAD), and outside vapor deposition (OVD), which have been widely used in the past. Thus, an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions can be manufactured through an easy solution addition method.

Example 1
First, thulium salt (TmCl ₃ · 6H ₂ O) and sucrose (C ₁₂ H ₂₂ O ₁₁ ) are dissolved in deionized water at concentrations of 0.04M and 2.17M, respectively. A doping solution containing Tm ³⁺ and the reducing agent sucrose was prepared. Here, hydrocarbon compounds or alkoxides can be used as the reducing agent.

As shown in FIG. 1, through the MCVD process, the inner glass wall of the silica glass tube having an inner diameter of 19 mm and an outer diameter of 25 mm is porous so that the glass basic composition of the portion that becomes the optical fiber core becomes SiO ₂ —GeO _2. A fine microstructure was formed. The produced doping solution was poured into the glass tube, maintained for 1 hour, and then discharged. Then, using the MCVD apparatus again, the core layer was dried by heating to 100 to 250 ° C. while flowing only helium.

Next, the above-mentioned complete sintering and depression processes at about 2000 ° C. were repeated 8 times and 15 times, respectively. As a result, an optical fiber preform doped with Tm ²⁺ ions was obtained. This optical fiber preform was manufactured into optical fibers through drawing.

FIG. 2 shows the light absorption spectrum of the optical fiber of the present invention produced by the doping solution containing the reducing agent sucrose. The light absorption spectrum shown in FIG. 2 at 465 nm, 680 nm, 785 nm, 1210 nm, and 1600 nm is formed by Tm ³⁺ ions, and the light absorption spectrum widely distributed from 400 nm to 900 nm is due to Tm ²⁺ ions. It is formed.

Comparative Example 1
A doping solution in which thulium salt (TmCl ₃ .6H ₂ O) and aluminum salt (AlCl ₃ .6H ₂ O) were dissolved in ethanol at concentrations of 0.04M and 0.19M, respectively, without the reducing agent sucrose. Prepared.

  In the same manner as in Example 1, a core layer having a porous microstructure was formed on the inner wall of the silica glass tube. Thereafter, the doping solution was injected into the glass tube, maintained for 1 hour, and then discharged. Next, the core layer was dried while flowing helium, oxygen and chlorine.

The complete sintering and depression processes at 2000 ° C. as in Example 1 were repeated 3 times and 7 times, respectively. As a result, an optical fiber preform doped with Tm ³⁺ ions was obtained. This optical fiber preform was manufactured into optical fibers through drawing.

FIG. 3 shows the light absorption spectrum of the optical fiber manufactured by the doping solution not containing the reducing agent sucrose. Unlike the result of Example 1 using a reducing agent, only the light absorption spectrum by Tm ³⁺ ions is shown.

Example 2
Europium salt (EuCl ₃ xH ₂ O) and sucrose (C ₁₂ H ₂₂ O ₁₁ ) are dissolved in deionized water at concentrations of 0.097 M and 0.518 M, respectively, and rare earth ions Eu ³⁺ And a doping solution containing the reducing agent sucrose.

Thereafter, in the same manner as in Example 1, an optical fiber doped with Eu ²⁺ ions was obtained.

FIG. 4 shows the light absorption spectrum of the optical fiber manufactured by the doping solution containing the reducing agent sucrose. The light absorption spectrum widely distributed between 600 nm and 1200 nm in the light absorption spectrum of FIG. 4 is not seen with Eu ³⁺ ions, but is formed with Eu ²⁺ ions.

Comparative Example 2
A doping solution in which europium salt (EuCl ₃ .xH ₂ O) and aluminum salt (AlCl ₃ .6H ₂ O) were dissolved in ethanol at concentrations of 0.097 M and 0.518 M, respectively, without the reducing agent sucrose. Prepared.

Thereafter, in the same manner as in Comparative Example 1, an optical fiber doped with Eu ³⁺ ions was obtained.

FIG. 5 shows the light absorption spectrum of the optical fiber produced by the doping solution not containing the reducing agent sucrose. Unlike the result of Example 2 using a reducing agent, only the light absorption spectrum by Eu ³⁺ ions is shown.

Examples 1 and 2 exemplify that an optical fiber preform doped with Tm ²⁺ ions and an optical fiber preform doped with Eu ²⁺ ions can be obtained with a doping solution containing a reducing agent. However, it was confirmed that the reduction potential of the reducing agent can be reduced from trivalent to divalent, monovalent, and in some cases to zero. When it is reduced to zero, an optical fiber preform or optical element doped with metal fine particles or rare earth elements is formed.

  As can be seen from the above results, the present invention uses an easy solution addition method to produce an optical fiber or optical element doped with reduced metal ions and / or rare earth ions having a desired valence. be able to.

It is a schematic diagram of the apparatus with which the process of this invention is performed. 4 is a graph showing a light absorption spectrum of an optical fiber prepared by Example 1 of the present invention and doped with reduced rare earth ions (Tm ²⁺ ). It is the graph which showed the light absorption spectrum of the optical fiber manufactured by the comparative example 1 which does not use a reducing agent. 6 is a graph showing a light absorption spectrum of an optical fiber doped with reduced rare earth ions (Eu ²⁺ ) manufactured according to Example 2 of the present invention. It is the graph which showed the light absorption spectrum of the optical fiber manufactured by the comparative example 2 which does not use a reducing agent.

Claims (12)

Forming a partially sintered microstructure on an optical fiber or optical element manufacturing substrate;
Impregnating the microstructure with a metal ion and / or rare earth ion doping solution containing a reducing agent;
Drying the microstructure impregnated with the metal ions and / or rare earth ions;
Heating the dried microstructure so that it is sintered,
A method for producing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions.
The method of manufacturing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions according to claim 1, wherein the reducing agent is a hydrocarbon compound.
3. The reduced metal according to claim 2, wherein the hydrocarbon compounds are any one selected from the group consisting of glucose, sucrose, glycerin, starch, benzene, phenol, hexane, toluene, styrene, and naphthalene. A method of manufacturing an optical fiber or an optical element doped with ions and / or rare earth ions.
The method for manufacturing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions according to claim 1, wherein the reducing agent is an alkoxide.
5. The optical fiber doped with reduced metal ions and / or rare earth ions according to claim 4, wherein the alkoxide is any one selected from the group consisting of TEOS, TMOS, TEOC, and TMOC. Manufacturing method of optical element.
The metal ions and / or rare earth ions are Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Sc, Ti, V, Cr, Mn. Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Hf, Ta, W, Re, Os, Ir, Pt, Au The reduced metal ions and / or rare earth ions according to claim 1 are doped with at least one selected from the group consisting of Tl, Pb, Bi, and mixtures thereof. Optical fiber or optical element manufacturing method.
The optical fiber or the substrate for manufacturing an optical element includes silicon oxide, or an oxide series including at least one selected from germanium oxide, boron oxide, phosphorous oxide, and titanium oxide in silicon oxide. The method for producing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions according to claim 1, wherein the optical fiber or optical element has a basic composition.
The optical fiber or the substrate for producing an optical element is made of silica, germanosilicate, phosphorosilicate, phosphorogel manosilicate, borosilicate, borophosphorosilicate, borogermanosilicate, titanosilicate, phosphorotitanosilicate or The method for producing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions according to claim 1, wherein borotitanosilicate is a basic composition.
The step of forming a partially sintered microstructure on the optical fiber or optical device manufacturing substrate comprises an improved chemical vapor deposition method, a vapor axial deposition method, an external vapor deposition method and a flame hydrolysis deposition method. The method for producing an optical fiber or an optical element doped with reduced metal ions and / or rare earth ions according to claim 1, wherein the method is performed in a process selected from the group.
Forming a partially sintered microstructure on an optical fiber or optical element manufacturing substrate;
Impregnating the microstructure with a metal ion and / or rare earth ion doping solution containing a reducing agent having a strong reduction potential;
Drying the microstructure impregnated with the metal ions and / or rare earth ions;
Heating the dried microstructure to sinter to form fine metal particles and / or rare earth elements,
A method for producing an optical fiber or an optical element doped with reduced metal fine particles and / or rare earth elements.
The method according to claim 10, wherein the reducing agent is a hydrocarbon compound, wherein the reduced metal fine particles and / or rare earth elements are doped.
  The method according to claim 10, wherein the reducing agent is an alkoxide. The method of claim 10, wherein the reduced metal fine particles and / or rare earth elements are doped.

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