JPH08183622A - Silica glass and its production - Google Patents

Abstract

PURPOSE: To obtain silica glass ensuring a high refractive index variation by irradiation with light in a short treatment time through a reduced number of processes by making a glass porous body made of SiO2 transparent by heating in an inert gaseous atmosphere contg. gaseous Cl2 . CONSTITUTION: A glass porous body made of SiO2 is held at >=1,000 deg.C in an inert gaseous atmosphere contg. >=20vol.% gaseous Cl2 or SiCl4 and then it is made transparent by heating in the atmosphere to obtain the objective silica glass as a transparent glass body having >=1cm<-1> light absorption coefft. at 165nm wavelength. Since this silica glass easily ensures a high refractive index variation without requiring doping with hydrogen, treatment time can be considerably shortened as compared with the conventional process for producing waveguide type optical parts. Since the silica glass can be efficiently mass-produced, it has very high industrial utility value.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel silica-based glass and a method for producing the same. The silica-based glass according to the present invention is advantageous as a silica-based glass for producing a waveguide type optical component used in optical communication equipment and the like.

[0002]

2. Description of the Related Art Conventionally, as a technique for producing an optical waveguide, a technique based on a microfabrication technique (reference: Hiroshi Nishihara, Masamitsu Haruna, Toshiaki Suhara, "Optical Integrated Circuits" (Ohm Co., Ltd., 1985)), and ion diffusion were used. (Reference: Ibid.) And that utilizing local change in refractive index due to light irradiation (Reference: V. Mizr
ahi et al. Appl. Phys. Lett. 63, 13 (1993) p.172
7) is known.

[0003]

Among the conventional optical waveguide fabrication techniques, one using a fine processing technique is to produce a transparent multilayer thin film whose refractive index is controlled with high precision, and to perform fine processing with higher precision. Since it requires technology, there are many processes,
Therefore, there is a problem that the stability of the product is not good. Further, the method utilizing the diffusion of ions utilizes the diffusion phenomenon from the solution to the inside of the solid, and therefore has a very slow process speed and is not suitable for mass production. The third method utilizes the fact that some silica-based glasses change their refractive index when irradiated with light. Although this phenomenon has not been completely clarified, it is a waveguide type optical component. Is expected as a method of mass-producing. But,
At present, in order to obtain a high refractive index change, it is necessary to introduce defects into the silica-based glass and to diffuse the hydrogen gas by exposing it to high-pressure hydrogen gas for a long time, and the treatment takes about 20 days. Therefore, it is an extremely inefficient industrial process. It is an object of the present invention to provide a novel silica-based glass that uses light irradiation, has fewer steps than conventional methods, a shorter processing time, and can obtain a high refractive index change, and a method for producing the same.

[0004]

[Means for Solving the Problems]

As a means for solving the above problems, the present invention provides
SiO₂Or SiO₂And GeO₂Made of glass porous
The body should contain at least 20% by volume of Cl₂Gas or Si
Cl _FourTemperature 100 in an inert gas atmosphere containing gas
Keep at 0 ℃ or higher, then heat transparent in an inert gas atmosphere
The absorption coefficient of light at a wavelength of 165 nm is reduced to 1
cm^-1Siri characterized by obtaining the above transparent glass body
A method for producing mosquito-based glass is provided. The present invention also provides the above
After clearing by heating in an inert gas atmosphere, heat up to 1000 ° C.
Characterized by rapidly cooling glass cooled to room temperature
A method for producing the above silica-based glass is provided. Book again
The invention is the above-mentioned SiO₂Or SiO₂And GeO₂Consists of
Do not introduce elements other than Si, Ge and O into the glass
A method for producing the above silica-based glass is provided.
It Furthermore, the present invention provides an absorption coefficient of light at a wavelength of 165 nm.
Is 1 cm^-1Silica-based glass characterized by the above
I will provide a. The absorption coefficient of light means that the length of light is tcm.
When passing through a substance (in this case glass) its strength is I
₀If I is changed to I, the absorption coefficient α is

[Equation 1] Is defined by

The present inventors have found a means for obtaining a silica-based glass capable of changing a high refractive index by light irradiation without requiring long-time exposure in a conventional hydrogen atmosphere. The silica-based glass of the present invention and the method for producing the same will be specifically described below.
The raw material silica-based glass porous body of the present invention includes S
Those containing no elements other than i, Ge and O are preferable.
This is not preferable because the elements necessary for changing the refractive index by light irradiation are only Si, O, and Ge, and the presence of other elements reduces the light transmittance. As such a glass of high purity quartz glass (containing SiO ₂ 99.9999% or higher), include such as a high-purity quartz glass GeO ₂ content (GeO ₂ -SiO ₂₎ is about to be particularly limited method is However, examples thereof include vapor phase methods such as sol-gel method and VAD method. The bulk density range of the porous body is not particularly limited as long as it can exist as the porous body and Cl ₂ can be taken into the glass by the first heat treatment described below.

At least 20% by volume of the glass porous body
In an inert gas atmosphere containing the above Cl ₂ gas or SiCl ₄ gas, particularly preferably 20% by volume or more of Cl ₂
Gas or He gas atmosphere containing SiCl ₄ gas,
The heat treatment is performed at 1000 ° C or higher, preferably 1000 to 1200 ° C, particularly preferably 1150 to 1200 ° C. 1
If it is less than 000 ℃, it is difficult to obtain the desired effect.
If it exceeds, it may become partially transparent. By this treatment, dehydration and Cl ₂ incorporation into glass are performed. The concentration of Cl ₂ gas or SiCl ₄ gas in the mixed gas atmosphere is 20% by volume to 100% by volume, and the treatment time is up to 3%.
0 minutes is common.

After the above first heat treatment is completed, it is further heated at a higher temperature to form a transparent glass. The atmosphere at the time of the second heat treatment is preferably only an inert gas, and particularly preferably, the heating is performed at a temperature of 1500 to 1650 ° C. in a 100% He atmosphere. After the transparent vitrification is completed, the glass body is slowly cooled to 1000 ° C. in a He atmosphere. 10
The transparent glass body cooled to 00 ° C. is then rapidly cooled to room temperature. Specifically, for example, it is put into a liquid at room temperature and rapidly cooled. Water is suitable as the liquid. The normal temperature referred to in the present invention is 10 to 30 ° C. The glass body obtained above is cut and polished for making parts, an optical circuit is drawn, and then the product is incorporated into a case to complete a product.

The operation of the present invention is as follows. (1) 20% by volume or more of Cl ₂ as an atmosphere gas for processing
Alternatively, since SiCl ₄ is used, the rate of incorporation of Cl ₂ into the glass is high, and a defect necessary for increasing the sensitivity to light irradiation, that is, a -Si-Si-defect having absorption at a wavelength of 165 nm, is highly concentrated. Can be introduced into the glass. Glass having such a high concentration of SiSi defects changes to a high refractive index by irradiation with light having a wavelength of 165 nm, and this change is permanent. (2) The effect of setting the fictive temperature in the glass can be obtained by relatively slowly cooling to 1000 ° C. after heating and transparentization. When the glass is rapidly cooled from a high temperature state, it solidifies while maintaining its structure, that is, the glass remembers the original state, and this temperature is called a fictive temperature. (3) By cooling from 1000 ° C during cooling, the fictive temperature in the glass can be fixed, the initial refractive index of the obtained transparent glass body can be suppressed low, and a large change in refractive index due to light irradiation is achieved. It becomes possible to do. (4) Since processing such as hydrogen doping is unnecessary, the processing time can be greatly shortened. (5) The glass according to the present invention, which has a high concentration of SiSi defects having a light absorption coefficient of 1 cm ⁻¹ or more at a wavelength of 165 nm, can have a large change in refractive index due to light irradiation. Such glass has never been obtained.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. [Example 1] In FIG. 1 in which a base material of silica-based glass was prepared by the VAD method having a structure as shown in FIG. A mixed gas of a glass raw material gas, a combustion gas, and an auxiliary combustion gas, which is introduced into, and 9 means exhaust gas. SiCl ₄ was used as the source gas. The obtained porous glass body was subjected to SiCl ₄ in a quartz furnace at a temperature of 1100 ° C .:
It was dehydrated for 60 minutes in a He (1: 1) atmosphere. Next, the furnace temperature was raised to 1600 ° C and He gas (100%)
It was kept in the atmosphere for 60 minutes to obtain transparent glass. Then slowly increase to 1000 ° C at a rate of 3 ° C / min.
The temperature was lowered to 0 ° C, the transparent glass body was taken out of the furnace, put into water kept at room temperature (27 ° C), and rapidly cooled. The absorption coefficient of light of the obtained glass at a wavelength of 165 nm is 30 cm ^-1.
Met. The initial refractive index of this glass is 1.459.
Although it was 8, SR light with a wavelength of 165 nm [Synchr
Otron Radiation: Synchrotron radiation], and the small SR ring NIJI-II undulator light was irradiated for 30 minutes, the refractive index was 1.4602.
It was confirmed to change to. Also, 165n after light irradiation
The absorption coefficient of light at m was 25 cm ^-1 .

The silica glass (not irradiated with light) obtained in Example 1 was cut and polished for making parts. As shown in FIG. 1A, the refractive index obtained in Example 1 was 1.45.
By covering the silica glass 2 of 98 with the pattern forming mask 3 and irradiating the SR light 1 having a wavelength of 165 nm, a portion 4 having a refractive index of 1.4602 or more is formed to form an optical circuit. After drawing, as shown in FIG. 1B, the coating portion 5 made of silica glass having a refractive index of 1.4598 was formed as a clad by the flame deposition method. The obtained optical component was incorporated into a case to make a product.

[Embodiment 2] In Embodiment 1, the temperature is 110.
The atmosphere of dehydration treatment at 0 ° C. was changed to SiCl ₄ : Cl ₂ : He.
A silica glass having an initial refractive index of 1.4578 after quenching and a light absorption coefficient of 20 cm ⁻¹ at a wavelength of 165 nm was obtained in the same manner except that the ratio was (1: 1: 1). Also, the wavelength 165
By irradiating SR light of nm for 30 minutes, the refractive index changed to 1.4582 and the light absorption coefficient changed to 18 cm ⁻¹ .

[0012]

As described above, the silica-based glass of the present invention and the method for producing the same do not require hydrogen doping and can easily obtain a high refractive index change. It is possible to significantly reduce the processing time as compared with, and it is possible to mass-produce efficiently, so it is very useful in industry.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating a process of manufacturing an optical component using the silica-based glass of the present invention.

FIG. 2 is a schematic view illustrating one specific example of the production of the glass porous body used in the production method of the present invention.

Claims (4)

[Claims] 1. A glass porous body comprising SiO ₂ or SiO ₂ and GeO ₂ is added with at least 20% by volume of Cl.
The absorption coefficient of light at a wavelength of 165 nm is 1 cm ^-1 or more by keeping the temperature at 1000 ° C or higher in an inert gas atmosphere containing ₂ gas or SiCl ₄ gas, and then heating and making transparent in an inert gas atmosphere. 1. A method for producing a silica-based glass, which comprises: 2. The method for producing a silica-based glass according to claim 1, wherein the glass cooled to 1000 ° C. is rapidly cooled to room temperature after heating and transparentizing in the inert gas atmosphere. 3. The method for producing a silica-based glass according to claim 1, wherein elements other than Si, Ge and O are not introduced into the glass composed of SiO ₂ or SiO ₂ and GeO _2. . 4. The absorption coefficient of light at a wavelength of 165 nm is 1c.
Silica-based glass characterized by having m ⁻¹ or more.