JPH03218936A - Rare earth element-doped quartz glass and its production - Google Patents

Abstract

PURPOSE:To improve the intensity of emission spectrum and laser characteristics by incorporating rare earth elements and alkali metal chlorides oxides into quartz glass. CONSTITUTION:A porous glass base material having 0.3-1.0g/cm<3> average volume density is obtained by depositing fine particles of glass which are obtained from hydrolysis of Si compd. such as SiCl4 in flame. Then this base material is immersed in an org. solvent (e.g. methanol) solution containing a soluble salt of rare earth element (e.g. ErCl3), dried in air, immersed in an org. solvent solution containing alkali metal oxide (e.g. LiCl2), dried by heating at 30-80 deg.C, and sintered at 1100-1800 deg.C in a He gas atmosphere to form transparent glass.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to rare earth element-doped quartz glass, particularly to a functional rare earth element-doped quartz glass useful for optical fiber lasers and the like, and a method for producing the same.

[Conventional technology] It is known that glass doped with rare earth element ions such as Nd, Yb, }lo, and Gd exhibits laser action. It is said to be a multi-component chelate or phosphate glass, and phosphate-based glass is said to exhibit particularly excellent physical properties, but it also has thermal conductivity. It has the drawbacks of being inferior and having problems with chemical durability.

For this reason, products using quartz glass as the matrix glass have been proposed, and because they have functionality and are easy to connect with silica glass optical fibers, they can be used as optical fiber lasers and optical amplifiers. It is applied.

In addition, for the manufacture of this rare earth element-doped quartz glass, rare earth chloride raw materials are evaporated by high-temperature heating and supplied.
The MCVD method is known (Special Publication No. 63-501711).
Regarding this, a rare earth element compound is added to a porous glass matrix obtained by depositing silica glass particles produced by flame hydrolysis of a silicon compound, and then sintered at high temperature to form transparent glass. A method is also known (see Japanese Patent Publication No. 58-3980).

[Problems to be solved by the invention] However, since this MCVD method involves heating the rare earth chloride at high temperature to evaporate and supplying it to the reaction system, it is difficult to control the supply amount, and furthermore, it requires a large base material. However, rare earth element-doped silica glass made by this MCVD method and the above-mentioned method using a porous glass matrix has good laser properties because the rare earth ions are not uniformly dispersed. However, the drawback is that it is not possible to obtain a high-intensity emission spectrum.

Therefore, for the production of this type of quartz glass, a method has been proposed in which P205 and Aρ203 are added to the reaction system to uniformly disperse rare earth ions and increase luminous efficiency (see Japanese Patent Publication No. 41858/1983). However, since rare earth ions have a low probability of forming a network with P205 or AI203, the improvement in luminous efficiency is not necessarily sufficient, and in this regard, even higher efficiency is required.

[Several Steps to Solve the Problems] The present invention relates to a rare earth element-doped quartz glass and a method for producing the same which can solve these disadvantages. A porous glass base material obtained by depositing silica glass fine particles produced by flame hydrolysis of a rare earth element ion and a soluble salt containing a rare earth element ion. A rare earth element-doped quartz glass characterized in that the porous glass base material is sintered at a high temperature to become transparent glass. The present invention relates to a manufacturing method.

That is, the present inventors have conducted various studies on rare earth element-doped quartz glass in which rare earth element ions are uniformly dispersed in the quartz glass, and its manufacturing method. Regarding this alkali metal oxide, K. Although Rb is effective, it was discovered that Li and Na showed a remarkable effect, and in this production method, a porous glass base material was created by depositing silica glass fine particles produced by flame hydrolysis of a silicon compound. This is immersed in a solution of a soluble salt containing rare earth element ions to permeate the salt into the porous glass matrix, then immersed in a solution of an alkali metal compound, dried, and then heated to a high temperature. The present inventors have completed the present invention by discovering that when sintered to make transparent vitrification into quartz glass, rare earth element tob quartz glass in which rare earth elements and alkali metal oxides are uniformly dispersed can be obtained.

This will be explained in further detail below.

[Function] The rare earth element-doped quartz glass of the present invention has a rare earth element and an alkali metal oxide uniformly dispersed in quartz glass.

The quartz glass constituting the rare earth element-doped quartz glass of the present invention may be an artificial quartz glass made by a known method. Therefore, this involves exposing a silicon compound, such as silicon tetrachloride, to a heat-resistant carrier together with an oxyhydrogen flame.
The glass particles thus generated may be deposited, for example, on a quartz glass rod to create a porous glass base material, which is then sintered at high temperature to form transparent glass.

On the other hand, the rare earth elements dispersed in this quartz glass may be neosim, erbium, europium, cerium, etc.; Elements are often added as chlorides and nitrates, and the alkali metal oxides dispersed in this quartz glass are oxides of sodium, potassium, lithium, rubidium, etc., but these are also porous as described later. Since it is impregnated into a glass base material as a solution, it can be used as a soluble salt such as a chloride or nitrate of these alkali metals, and then heated to form an oxide.

The rare earth element-doped quartz glass of the present invention is produced by impregnating a porous glass base material made from glass particles produced by flame hydrolysis of a silicon compound with a rare earth compound and an alkali metal compound, as described later. However, this material has higher luminous efficiency than that doped only with a rare earth element, which contains an alkali metal oxide together with a rare earth element, and is therefore suitable for optical fiber lasers. It has the utility of being advantageously used as an optical amplifier.

Note that the amount of rare earth elements added to this quartz glass may be the same as that of conventionally known rare earth element-doped silica glass, and therefore, the amount of rare earth elements added to the quartz glass is 50 to 100,000.
The alkali metal oxide added here may be any of Na, K, Li, and Rh. K and Rh are also effective, but this is not true for Li, which has a small ionic radius. , Since Na shows a remarkable effect,
It is preferable to use Li or Na as the added amount.If the amount added is less than 0.5% by weight based on the quartz glass, the effect will be small, and if it is more than 20% by weight, no further effect can be expected. Therefore, it may be in the range of 0.5 to 20% by weight.

Next, a method for producing rare earth element-doped quartz glass of the present invention will be described.

The quartz glass constituting the rare earth element-doped quartz glass of the present invention is made by transparently vitrifying a porous glass base material made by flame hydrolysis of a silicon compound such as silicon tetrachloride, as described above. However, this porous glass matrix can be prepared using the known VAD method using quartz glass as a carrier. It may be one made using the OVA method. However, this material has enough mechanical strength that the cohesive force between the fine particles will not be lost and the material will not break when immersed in a solution of a soluble salt of a rare earth element or a solution of an alkali metal compound, which will be described later. Therefore, it is preferable to have an average bulk density of 0.3 g/cm3 or more. However, when this porous glass base material is immersed in a soluble salt solution of rare earth elements, the diffusion of the rare earth element solution , and to facilitate the diffusion of the alkali metal compound when impregnated with the alkali metal compound solution, the bulk density should be 0.
It is preferable that the amount is 1 g/cm3 or less. The porous glass base material may be made of silica alone, or may be made of germanium tetrachloride, which is well known as a dopant for optical fibers, added to the silicon compound when silica is produced by flame hydrolysis of the silicon compound. It may be added to contain germania (Ge02), or it may have a refractive index distribution necessary for forming an optical waveguide structure.

This porous glass base material is immersed in a solution of a soluble salt of a rare earth element to uniformly impregnate the rare earth element compound, and then immersed in an alkali metal compound solution to uniformly impregnate the alkali metal compound. Impregnate. The soluble salt of the rare earth element used here is not particularly limited as long as it has sufficient solubility in the solvent, and may be any salt, including neodymium, erbium, europium, and cerium. Examples include chlorides and nitrates of rare earth elements such as. These rare earth element soluble salts may be co-doped using two or more kinds,
Furthermore, a transition metal such as chromium may be added as a photosensitizer. Furthermore, the solvent used to make the solution of the soluble salt of the rare earth metal element is not particularly limited as long as it does not chemically react with the porous glass matrix; Alcohols such as methanol and ethanol have a strong effect of weakening the cohesive force between fine particles in the porous glass base material, so the stiffness is due to the solubility of rare earth element soluble salts, permeability to the porous glass base material, and drying speed. It is preferable that In order to impregnate the porous glass base material with this rare earth element soluble salt, it is sufficient to simply immerse the porous glass base material in a solution of the rare earth element soluble salt. It is best to air-dry the material in the air to volatilize the solvent before sending it to the next process.

The porous glass base material uniformly impregnated with rare earth elements in this way is then impregnated with a solution of an alkali metal compound, but the alkali metal compound used here is said to be soluble. For this reason, chlorides, nitrates, etc. may be used.For the same reason as above, this solution may also be an alcohol solution.According to this, a porous glass base material uniformly impregnated with rare earth elements and alkali metal compounds can be used. It can be easily obtained, and this product is then preferably air-dried in the air or heated to 30 to 80°C to evaporate the solvent.

The rare earth element-doped quartz glass of the present invention is produced by sintering the porous glass base material containing the rare earth element and the alkali metal compound obtained in this manner at high temperature to turn the porous glass base material into transparent glass. It is created by This sintering process is performed by sintering a porous glass base material in an electric furnace at a temperature of 1.10
It may be heated to 0 to 1,800°C, but the atmosphere in this case is preferably a helium gas atmosphere. In this way, the porous glass base material becomes transparent quartz glass,
Rare earth element compounds impregnated into a porous glass matrix,
Since all of the alkali metal compounds are oxides, it is possible to easily obtain the rare earth element-doped quartz glass of the present invention in which the rare earth element and the alkali metal oxide are uniformly dispersed in the quartz glass.

[Example] Next, examples of the present invention and comparative examples will be given.

Example 1 A quartz concentric multi-tube burner was charged with hydrogen gas for 5,511.7 minutes and oxygen gas for 8 minutes. OJ2/min is supplied to form an oxyhydrogen flame, and 0.11 of oxygen gas is in the center of this burner! 0.25 J2/min of silicon tetrachloride is supplied as a carrier gas, and this flame is applied to a 20 mm diameter quartz glass rod as a carrier, so that the silica glass fine particles generated by the flame hydrolysis of silicon tetrachloride are removed from the carrier gas. axially deposited and grown, 8
A porous glass preform having an outer diameter of 451 nll, a length of 300 mm, a weight of 170 g, and an average bulk density of 0.35 g/cm3 was produced by operating for hours.

Then, this porous glass base material was immersed in a methanol solution containing 0.1% by weight of erbium chloride to allow the erbium chloride to penetrate into the inside of the porous glass base material, and then impregnated with a 1.0% methanol aqueous solution of lithium chloride. When lithium chloride was permeated uniformly, a porous glass matrix containing erbium chloride and lithium chloride was obtained. After heating for 3 hours and sintering,
This porous glass base material was made into transparent vitrification to become quartz glass, and rare earth element-doped quartz glass in which erbium and lithium oxides were evenly dispersed was obtained, which was measured by ICP luminescence method. It contained 200 ppm of erbium oxide and 1.5% by weight of lithium oxide.

Next, an optical fiber preform is made using this quartz glass as a core and fluorine-doped silica glass as a cladding.
When a 1.46 μm pump light was input while transmitting a 3 μm signal light, a 1.53 μm signal was amplified.
The amplification gain at this time was 32 dB, and the guiding cross section at this time was 3.8 x 10-'' cm2.

In addition, an optical fiber was made in the same manner as above except that sodium chloride, potassium chloride, and rubidium chloride were used instead of lithium chloride, and the induced cross-sectional area of this fiber was measured, as shown below. The results were obtained.

NaCR 2.2X 10-20cm2KCj!
0.9X 10-”cm2RbCj! 0.7
x 10-20 cm2 Comparative Example A porous glass base material obtained in the same manner as in Example 1 was immersed in a 0.1% by weight methanol solution of erbium chloride, and this solution was spread inside the porous glass base material. After permeating, it was left in the air for 24 hours to air dry, and then heated at 1,600°C in an electric furnace in a hydrogen-helium gas atmosphere.
When we made rare earth element-doped quartz glass by heating it for 3 hours to make it transparent, we found that this quartz glass contained 280 ppm of erbium oxide, but when we made it into a fiber and evaluated its amplification characteristics, we found that this The amplification degree was as low as 9 dB.

[Effects of the Invention] The present invention relates to a rare earth element-doped quartz glass and a method for manufacturing the same, and as described above, this invention relates to a rare earth element-doped quartz glass in which a rare earth element and an alkali metal oxide are uniformly dispersed in quartz glass, A porous glass matrix obtained by depositing fine silica glass particles produced by flame hydrolysis of silicon compounds is immersed in a soluble salt solution of rare earth element ions, and then impregnated with a solution of an alkali metal compound. The present invention relates to a method for producing rare earth element-doped quartz glass in which this perforated glass base material is sintered at high temperature to produce quartz glass.Since this quartz glass can be obtained by the method described above, it contains rare earth elements and alkali metals. The oxide is uniformly dispersed, and therefore the emission spectrum intensity is large and it exhibits good laser characteristics.
It has the advantage of being particularly useful for optical fiber lasers and optical amplifiers.

Claims (1)

[Claims] 1. A rare earth element-doped quartz glass characterized by containing a rare earth element and an alkali metal oxide in the quartz glass. 2. The rare earth element-doped silica glass according to claim 1, wherein the alkali metal oxide is an oxide of Li or Na. 3. A porous glass base material obtained by depositing silica glass particles produced by flame hydrolysis of a silicon compound is immersed in a solution of a soluble salt containing rare earth element ions, and then immersed in a solution of an alkali metal oxide. Soak and then dry
A method for producing rare earth element-doped quartz glass, which is characterized in that the porous glass base material is then sintered at high temperature to form transparent glass. 4. The method for producing rare earth element-doped quartz glass according to claim 3, wherein the soluble salt containing rare earth element ions is a chloride or a nitrate. 5. Porous glass base material has an average bulk density of 0.3 to 1.0 g
5. The method for producing a rare earth element-doped quartz glass according to claim 3 or 4, wherein the quartz glass has a diameter of /cm^3.