JPH0345525A - Production of functional silica glass - Google Patents

Abstract

PURPOSE:To obtain the title glass with little impurities by heating a porous vitreous matrix impregnated with an oxide additive-contg. solution in an atmosphere made up of a dehydrating agent gas, oxygen and an inert gas to make the matrix transparent. CONSTITUTION:Firstly, a porous vitreous matrix is impregnated with a solution containing an oxide additive and/or a compound convertible thereto. Thence, the resulting matrix is heated in an atmosphere made up of a dehydrating agent gas and an inert gas (and oxygen) and dehydrated and made transparent, thus obtaining the objective functional silica glass with the oxide additive dispersed therein. From the present silica glass. optical fiber with low loss can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing functional quartz glass, and more specifically, it can be used as a base material for functional quartz optical fiber in the production of optical amplification, optical fiber lasers, etc. The present invention relates to a new method for producing high-performance functional quartz glass with less water and unnecessary impurities.

[Conventional technology]

Conventionally, a method for producing functional quartz glass containing rare earth elements and some transition metal elements (such as Cr) and containing extremely low levels of impurities such as Fe and Cu, 01) groups, etc., to the same level as quartz optical fibers. As a method using MCVD method [Reference; S, B, Pool el al, Elec
lroh Lett, vol UL p737~(
1985), M, WATAIIIABEet if C
, fiCOCprce, pH-100 (1985)
) and PCVD method [Reference: 1). NAM
IKAWA, JJAP.

vol 1iL, ppL 409 (1984)).

For example, in the MCVD method, as shown in FIG. 4, a subchamber 44 is provided adjacent to a hollow quartz tube 41, and while a main burner 46 is reciprocated, 5iC14, O! , GeC
A raw material such as L is introduced from one open end of the quartz tube 41, and a glass thin film is deposited on the inner surface of the quartz tube 41 by a thermal oxidation reaction to form a synthetic cladding layer 42. After this,
The auxiliary burner 45 is operated to remove trace component raw material M (for example, NdC).
t', ErCl*, etc.) is vaporized and incorporated into the deposited glass thin film, a synthetic core layer 43 containing a trace component raw material M is deposited, and then solidified to produce an optical fiber base material. ing.

This method has the advantage of being able to easily produce a glass base material with a low OH group concentration and low impurity concentration because most of the conventional manufacturing methods for optical fiber base materials can be used. There was a drawback that it was difficult to obtain a base material or a rod-shaped base material (not including a pure silica glass layer around the base material).

On the other hand, VA, which is one of the typical manufacturing methods for optical fibers,
Let us consider the synthesis of the base material in method D.

In the VAD method, a glass raw material such as Si C14 in a gas phase is supplied into an oxyhydrogen flame, and glass fine particles generated in the flame are deposited on the end face of a rotating seed rod, forming a porous structure in the axial direction of the seed rod. This is a method for producing an optical fiber base material by growing a glass base material and turning it into transparent vitrification in an inert atmosphere containing a dehydrating agent.

When synthesizing a base material containing rare earth elements or some transition elements using this VAD method, the melting point of the rare earth chloride or transition metal chloride material used is high, so it is necessary to obtain sufficient vapor pressure for these materials. It is necessary to maintain the raw material at a high temperature of 1000° C. or higher (for example, the temperature of NdC1* that gives a saturated vapor pressure of 1 m [1 g is 1048° C.). As a result,
In base material synthesis using the VAD method, all piping of the equipment is
It became necessary to maintain the temperature at about 0°C, making it difficult to synthesize the base material in practice.

As a method to solve this problem, after synthesizing a porous glass base material by the VAD method, at the time of transparent vitrification treatment, as shown in FIG. A method of adding the raw material 55 to the porous base material 51 by vapor phase diffusion by treating the porous base material 51 in an atmosphere containing the rare earth chloride raw material 55 in a furnace (vapor phase diffusion method and (abbreviation) is known (Patent Application No. 54-08350
No. 5). Note that 52 is a rotating support rod.

On the other hand, after synthesizing a porous base material by flame hydrolysis, the porous glass base material is immersed in a liquid containing rare earth chloride, dried and then heat-treated to produce an optical fiber base material doped with rare earth elements. A method (abbreviated as an impregnation method) is also known. This impregnation method has the advantage that rare earth elements can be added uniformly and at a high concentration.

[Problem to be solved by the invention]

However, when rare earths are added using the flame hydrolysis method and impregnation method described above, impurities such as Fe and Cu and OH
It was not possible to obtain functional quartz glass with sufficiently low loss due to the contamination of groups and the like.

Furthermore, in the vapor phase diffusion method, the oxide additive cannot be uniformly dispersed within the mother village, which is particularly problematic when adding at a high concentration.

The present invention aims to eliminate the drawbacks of such conventional methods and provide a new method for producing functional quartz glass in which oxide additives are uniformly dispersed in the glass body and the loss is sufficiently low. It is something.

[Means to solve the problem]

The present invention impregnates a porous glass matrix with a solution containing an oxide additive and/or a vine compound that can be converted into an oxide additive, and then heat-treats the porous glass matrix to disperse it at least in part. In the method for manufacturing functional quartz glass containing an oxide additive, the heat treatment includes heating in an atmosphere containing a dehydrating agent gas, oxygen, and an inert gas, or in an atmosphere consisting of a dehydrating agent gas and an inert gas. The present invention relates to a method for manufacturing functional quartz glass, which comprises a heat treatment step of dehydrating a porous glass base material.

The present invention is a method that further improves the conventional impregnation method and performs dehydration treatment in the vitrification step of the porous glass base material after impregnation. That is, a porous glass base material is impregnated with a solution containing an oxide additive and/or a compound that can be converted into an oxide additive (hereinafter both are collectively referred to as a compound that can be converted into an oxide additive), After drying, the porous matrix is formed by heat treatment in an atmosphere containing at least a dehydrating agent gas, followed by heating in an atmosphere containing an inert gas or vacuum, or by heating in an atmosphere containing at least a dehydrating agent gas. Along with dehydration and transparent vitrification of the material,
This is a method of converting the compound into an oxide additive, uniformly dispersing the oxide additive over at least a portion of the glass, and obtaining functional quartz glass with low OH and low impurity content.

In the present invention, the dehydrating agent gas is a chlorine compound gas, or the heat treatment for dehydration is carried out in an atmosphere consisting of st F4 and an inert gas, or in an atmosphere consisting of Si F4 and 0.5 ml of Si F4. A particularly preferred embodiment is to carry out the reaction in an atmosphere consisting of an inert gas and an inert gas.

Further, in the present invention, it is particularly preferable that the porous glass base material impregnated with the above solution has a porosity of 40 to 80%.

[Effect]

According to the method for manufacturing functional quartz glass according to the present invention, a porous glass base material (hereinafter abbreviated as porous base material) is first manufactured by a flame hydrolysis method. In the present invention, the starting porous matrix is 5iO8, for example GeOs,
It is preferable to use a material such as 5ift to which P, 05, etc. are added, and a bulk density of about 0.4 to 1.3 g/cnf is preferable. Such a porous body can be manufactured by a known method such as a VAD method or an OVA method.

This porous base material has a continuous pore network throughout and has sufficient adhesion to not collapse even when immersed in a liquid.
Adjust to 80%. If it is less than 40%, it is difficult for the solution to be impregnated into the base material, and if it exceeds 80%, the adhesion of the soot is weak and it tends to crumble, which is not preferable. The atmosphere during this porosity adjustment may be air, inert gas (for example, Iori, N8, etc.) atmosphere, or vacuum, and the temperature is 130°C.
Heating is about 0-1450°C.

The porous base material whose porosity has been adjusted is immersed in a solution to impregnate it with a desired additive. The impregnating solution may be a solution of one or more oxides desired for the glass, or of salts or other compounds that are later converted to oxides during thermal solidification of the porous matrix. Chloride of the element to be added, such as ErCb, NdCtB, TtaCb,
Aqueous solutions, alcohol solutions, etc. of PrC1, YbCe, M CIs, etc. can be used. Alternatively, a solution obtained by adding water and alcohol to the alkoxide of the additive element and hydrolyzing it may be used.

As a solvent for the oxide additive or a compound convertible thereto, water, for example, alcohol such as methanol, ethanol, propatool, etc. can be used. The concentration may be adjusted depending on the desired amount to be added to the glass.

When impregnating two or more substances as additives, the methods are: 1) directly impregnating a solution containing two or more different salts, 2) impregnating the main body with the first solution, then drying,
Any method of impregnating the second solution afterwards may be used.

The above-mentioned porous body is impregnated in a solution containing the oxide additive or compound as a solute, and the time period is not particularly limited, but is about 1 to 15 hours, for example.

However, it goes without saying that the amount of oxide additive introduced into the porous matrix according to the present invention depends on the porosity of the porous matrix, the concentration of the additive in the solution, and the soaking time.

The porous base material impregnated with the desired additive is pulled out of the solution and dried. For example, if the solvent is volatile, the solvent is evaporated and removed by drying.

Next, the porous body is first heat-treated in an atmosphere consisting of a dehydrating agent gas, oxygen, and an inert gas, or in an atmosphere consisting of a dehydrating agent gas and an inert gas. This is the heat treatment process for dehydration. As a dehydrating agent gas, for example, C1hSi
A chlorine compound gas such as CL, SOClm, (44, etc.) or a fluorine compound gas such as SiF+ can be used. In the case of a chlorine compound gas, it is preferable to coexist with oxygen, and in the case of a fluorine compound gas such as SIF. may be present with or without oxygen.

The reason for this can be explained by using, for example, εrcb as the rare earth chloride and CZ as the dehydrating agent gas.
, →2ErCl* + 3/20*, which reduces the possibility that the rare earth element chloride, which has a low vapor pressure, will volatilize.

When any of the dehydrating gases is used, an inert gas such as a mountain gas is used in combination. The dehydrating agent gas concentration at this time is, for example, about 1 to 3%, and when oxygen is used in combination, the oxygen concentration is preferably in the range of about 1 to 30%. The reason for this limitation is that the initial effect cannot be obtained below the lower limit, and no further effect can be obtained even if the upper limit is exceeded.

Further, when dehydration and transparency are performed in two stages, the temperature range of the heat treatment for the first dehydration is preferably about 1000 to 1)00°C. This is because if the temperature is below 1000°C, the effect of dehydration treatment cannot be obtained, and if it exceeds 1) 00°C, it is not convenient in terms of volatility as described above.

Next, it is heated to about 1,500 to 1,600° C. in an atmosphere containing at least an inert gas or in a vacuum to form transparent glass. Thereby, the oxide additive is uniformly dispersed in the glass body, and high quality functional quartz glass with a small amount of OH groups and a small amount of impurities can be obtained.

Further, in the present invention, dehydration and transparent vitrification can be performed in a single heat treatment in an atmosphere containing at least a dehydrating agent gas.

Once the porous matrix is essentially completely dry, the oxides or salts incorporated by impregnation are dispersed throughout the pores by clear vitrification through conventional heat treatment. As the porous matrix solidifies, it is incorporated into the molten silica glass.

However, simply applying heat treatment as in the conventional method leaves a large amount of OH groups and impurities in the silica glass, making it difficult to obtain a low-loss optical fiber when using this as a base material for optical fiber.

Therefore, in the present invention, the porous base material impregnated with additives is heated and dehydrated in an atmosphere containing dehydration gas, inert gas, and oxygen if necessary, before or during the same process as transparent vitrification. By processing, OH groups and impurities in the base material are reduced as much as possible, and in the case of chlorine-based dehydrating agents, the presence of oxygen gas prevents additives from becoming chlorides and volatilizing, allowing dehydration processing. Therefore, such means of the present invention works very effectively for the purpose of manufacturing an optical fiber from the obtained base material and obtaining a low-loss optical fiber.

〔Example〕

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 As shown in part T81 in FIG.
Glass fine particle deposit (porous base material) obtained by method D
Ia was maintained at a temperature of 1400° C. for 30 minutes in an inert gas atmosphere in a heating furnace equipped with a heater 4 and a furnace core tube 3 to obtain a porous base material with a porosity of 56%. 2 is a support rod. Next, as shown in part fb1 in the same figure, the porous base material 1b (length approximately 20an, diameter 4.5cmφ) with adjusted porosity is placed in a measuring cylinder 6 containing 500a/ml of additive-containing solution 5. immersed in. Solution 5 is 0.954 g of hydrated erbium chloride (CfarC1m.68*O) in methanol.
(Er concentration 0.005 sol/
f).

Figure 2 shows the relationship between the concentration in the solution and the E concentration (wt%) impregnated into the glass, calculated with respect to the porosity of the porous matrix. From this figure, it is easy to calculate the E concentration. It is possible to predict.

The porous base material is immersed in the solution for 15 hours in the manner shown in part (b1) of Figure 1, and the solution enters the capillary structure of the porous base material to perform impregnation. The base material was taken out of the solution and dried at room temperature for 24 hours to evaporate the solvent methanol.

The base material 1c, in which erbium chloride has been deposited over the entire porous base material, is then inserted into a heating furnace that has an atmosphere of dehydration gas, oxygen gas, and inert gas, and maintains the furnace temperature at 1000°C. [The flow rates of each gas in the fc1 subtree invention example shown in the figure are CJt100cC/min, Om 1)/min, He51! /minute. In addition to c, dehydration gases include st CL, s o
c is, Ce such as CCZ4, compound gas, and 31
A fluorine compound gas such as F4 can be used. As already explained, when a fluorine compound gas is used, it is not necessary to flow the 02 gas.

Through the above steps, the additive-containing base material of the present invention from which OH groups, impurities, etc. have been removed is then processed in the manner shown in the (d+ section) of the same figure, including the following gas (51/min), 0.0 gas ( A17 minutes)
A transparent glass base material 1d was prepared at 1600° C. in an atmosphere. In this example, the heat treatment was performed using a soaking furnace, but the effect will not be impaired even if the porous base material is partially heated and the entire porous base material is heat treated by traversing.

In the above two-stage heat treatment, since the furnace contains Ol, there is sufficient Ol in the voids of the porous base material, and therefore, as the base material is heated, the erbium chloride is oxidized by the oxygen. Erbium oxide E r, 0. is converted to

The erbium (E'')-containing silica glass thus obtained had a beautiful pink color and no bubbles were generated.Chemical analysis showed 400 ppm of Er, 0.
It was found to contain. Furthermore 3670es+-'i
When measured from the OH absorption that appears, the OH amount of the product of the present invention was 0.1)) I) m. When the amount of impurities was also analyzed, Fed, 5 ppm, Cuo,
It was sufficiently low, otppm or less, and NIo, 01ppm or less.

The functional quartz glass base material obtained above is used as a core, core diameter is 8.5μ, cladding diameter is 125μ, and relative refractive index difference is 0.3%.
A single mode fiber was fabricated.

When the gain of 2 m of this fiber was measured using the system shown in FIG. 3, a gain of 1 odB was obtained. In FIG. 3, the laser beam 32 from the laser 31 passes through the lens 33 to one end of the coupler 36, and the light from the DFB laser 34 passes through the V-groove A 35A to the coupler 36.
is connected to the other end and multiplexed.

The unnecessary end of the coupler was terminated with matching oil (37) so that the Fresnel reflected light would not return to the DBF laser and have an adverse effect. The combined light passes through the V groove B55B and
is guided into the doped fiber 38, amplification occurs, and this is converted into (,
The signal is received by the I fiber 39 and measured by the spectrum analyzer 40.

Example 2 In the same manner as in Example 1, a porous base material impregnated with E was heated in an atmosphere of )He51/min, 5IF4100cc/min,
Temperature 1) Dehydration treatment at 00℃, He51/min atmosphere 16
It was made into transparent glass at 00°C. The OH group and impurity concentrations of the obtained functional quartz glass base material were sufficiently low.

Using this base material as a core, the core diameter is 8.5 - and the cladding diameter is 1.
A single mode fiber with a diameter of 25μ and a relative refractive index difference of 0.3% was fabricated. When measuring the gain with a 2m fiber,
A gain of 9.1 dB was obtained.

Implementation f! 43 E'alkoxide [Er (OCI(S)
)3), methanol, 0 rich 0. Dimethylformamide.

Using a liquid in which Hα was mixed and stirred, a porous base material whose porosity was adjusted was impregnated with the solution for 1 hour.

The molar ratio of each solution is Hr (OCTo)s): methanol: HsO dimethylformamide: HaI=0
．． 5:10:20:4:0.2. The porous base material impregnated with the solution was heated at 120°C in a constant temperature bath at 80°C.
Leave to stand for a period of time to allow hydrolysis and polycondensation reactions to proceed.
It was left at ℃ for 24 hours. In the case of this example, since an alkoxide is used as the starting material, oxidation by heat treatment is not required. The gel body obtained above was heated with He 51/
min, C1*100,,/min, dehydration treatment at a temperature of 1000°C, followed by dehydration treatment in HaS atmosphere for 17 min at a temperature of 1600°C.
It was heated to ℃ to make it transparent. The obtained glass was a good pink glass body with no bubbles.

〔Effect of the invention〕

As explained above, according to the method for producing functional quartz glass according to the present invention, it is impregnated with a conventional solution, additives are added, and heat-treated in an atmosphere containing dehydration gas, oxygen gas, and inert gas. Low OH due to transparent vitrification
, glass with a small amount of impurities such as transition metals can be produced.

Using this method, various high-performance glasses such as optical amplification fibers, laser glasses, and glasses for electronic materials can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention in the order of steps. In the figure, 1a is a porous base material, lb and lc are porous base materials containing additives, ld is a transparent glass base material containing additives, and 2 is a porous base material containing additives. support rod,
3 is a furnace core tube, 4 is a heater, 5 is an additive-containing solution, and 6 is a graduated cylinder. Figure 2 is a chart (calculated values) showing the relationship between the porosity of the porous base material, the solution concentration, and the degree of Era impregnated into the glass.
FIG. 3 is a schematic diagram of the amplification experiment. FIG. 4 is a diagram showing addition by the conventional MCVD method, and FIG. 5 is a diagram showing vapor phase addition by the conventional VAD method.

Claims (6)

[Claims] (1) Impregnating a porous glass base material with a solution containing an oxide additive and/or a compound convertible into an oxide additive, and then heat-treating the porous glass base material to disperse it over at least a portion thereof. In the method for manufacturing functional quartz glass containing an oxide additive, the heat treatment includes heating in an atmosphere containing a dehydrating agent gas, oxygen, and an inert gas, or in an atmosphere consisting of a dehydrating agent gas and an inert gas. A method for producing functional quartz glass, comprising a heat treatment step of dehydrating a porous glass base material. (2) A heat treatment step in which the above heat treatment dehydrates the porous glass base material by heating in an atmosphere consisting of a dehydrating agent gas, oxygen, and an inert gas, or an atmosphere consisting of a dehydrating agent gas and an inert gas, and the subsequent inertization. The method for producing functional quartz glass according to claim 1, comprising a heat treatment step of heating in a gas-containing atmosphere or in vacuum to form transparent glass. (3) The above heat treatment is a heat treatment step in which the porous glass base material is dehydrated and made transparent by heating in an atmosphere consisting of a dehydrating agent gas, oxygen, and an inert gas, or in an atmosphere consisting of a dehydrating agent gas and an inert gas. The method for producing functional quartz glass according to claim (1). (4) The method for producing functional quartz glass according to any one of claims (1) to (3), wherein the dehydrating agent gas is a chlorine compound gas. (5) The method for producing functional quartz glass according to any one of claims (1) to (3), wherein the dehydrating agent gas is SiF_4 gas. (6) The porous glass base material impregnated with the solution has a porosity of 40 to 80% (
1) The method for producing functional quartz glass according to any one of (5).