JP2004280091A - Optical waveguide material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide material having high mechanical strength. <P>SOLUTION: The optical waveguide material consists of a core part for guiding light and a cladding part, and has a fiber-like or a rod-like form. The core part and/or the cladding part have a plurality of air holes which are formed in parallel to the waveguide direction periodically or randomly. The material consists of glass containing monovalent or bivalent cations and the outer surface thereof is ion-exchanged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

For example, an optical waveguide material such as a photonic crystal fiber, holey fiber, or photonic band gap fiber has a core portion and a clad portion for guiding light, has a fiber shape or a rod shape, and has a core portion and / or a clad portion. A plurality of holes are formed in the portion in parallel with the waveguide direction and periodically or randomly. Such an optical waveguide material has attracted attention as an important material in future optical communication systems because of having excellent light propagation characteristics (for example, see Patent Document 1).
JP 2002-506533 A

  The silica glass fiber-shaped optical waveguide material described in Patent Literature 1 requires protection such as a coating in actual use, and is expected to be easily damaged if used without protection such as a coating. Therefore, it cannot be used without protection, and when used as an optical connection part, it is necessary to load it into a capillary or the like.

  An object of the present invention is to provide an optical waveguide material having high mechanical strength.

  The optical waveguide material of the present invention comprises a core portion and a clad portion for guiding light, has a fiber shape or a rod shape, and a plurality of holes are formed in the core portion and / or the clad portion in parallel to the waveguide direction. The optical waveguide material formed periodically or randomly is made of glass containing monovalent or divalent cations, and the outer surface is ion-exchanged.

  Since the optical waveguide material of the present invention is made of glass containing monovalent or divalent cations, the outer surface can be subjected to ion exchange treatment. When monovalent or divalent cations in glass are ion-exchanged with cations having a larger ionic radius, a compressive stress is applied to the ion exchange layer on the outer surface, and the mechanical strength of the optical waveguide material is reduced. improves. Therefore, the optical waveguide material of the present invention can be used as an optical waveguide component without protecting the coating or the like or loading the capillary.

As a glass containing a monovalent or divalent cation, various multi-component glasses can be used. In particular, when a glass containing an alkali ion as a monovalent cation is used, ion exchange can be efficiently and easily performed. It is preferable because it can be advanced. If the alkali ions contained in the glass are replaced with alkali ions having a larger ionic radius, an optical waveguide material having high mechanical strength can be obtained. For example, to produce an optical waveguide material using glass containing Na ⁺ ions as alkali ions, when replacing the Na ⁺ ions in the surface layer of the optical waveguide material as K ⁺ ions or Cs ⁺ ions, the ion exchange layer Compressive stress is generated in the steel, and it is chemically strengthened.

The optical waveguide material of the present invention is specifically a glass containing 55 to 95% of SiO ₂ and 0.1 to 20% of Na ₂ O by mass%, preferably 55 to 95% of SiO _{2 by} mass%. _{, B 2 O 3 0~30%,} Na 2 O 0.1~20%, it is preferably made of K ₃ O 0.1 to 15% and Al ₂ O ₃ 0~10% glass having a composition.

  The reason why the composition of the glass used is limited as described above will be described below.

SiO ₂ is a component constituting the skeleton of glass, and its content is preferably 55 to 95%, particularly preferably 60 to 90%, and more preferably 65 to 80%. If the content of SiO ₂ is more than 95%, the viscosity of the glass increases, and the molding temperature when the optical waveguide material is produced by stretch molding tends to be extremely high. If it is less than 55%, the weather resistance such as acid resistance and water resistance is significantly deteriorated, which is not preferable.

Na ₂ O is a component in which ion exchange proceeds easily, and its content is preferably 0.1 to 20%, particularly preferably 0.5 to 18%. If the content of Na ₂ O is more than 20%, the weather resistance is remarkably deteriorated, and the surface of the optical waveguide material is remarkably deteriorated in a high-temperature and high-humidity state, which is not preferable. If it is less than 0.1%, the effect of ion exchange will be significantly reduced.

K ₂ O is an Na ₂ O and ion exchange is likely proceeds as components, the content of 0.1 to 15%, preferably from 0.5 to 10%. If it is less than 0.1%, the effect of ion exchange is significantly reduced. If the content is more than 15%, devitrification occurs during the production of glass, and the productivity is reduced.

B ₂ O ₃ has an effect of lowering the viscosity of the glass, and its content is preferably 0 to 30%, particularly preferably 1 to 25%, and more preferably 2 to 20%. If B ₂ O ₃ is more than 30%, the weather resistance will be significantly deteriorated.

Al ₂ O ₃ is a component constituting a glass skeleton together with SiO ₂ , and has an effect of improving weather resistance. The content is preferably 0 to 10%, particularly preferably 0.5 to 8%. If the content of Al ₂ O ₃ is more than 10%, phase separation is likely to occur, and devitrification occurs during glass production. In aluminosilicate glass, Al ₂ O ₃ reduces non-crosslinking oxygen and facilitates the movement of alkali ions, and thus has an effect of promoting ion exchange.

  If the diameter of the optical waveguide material of the present invention is made larger than the conventional one (photonic crystal rod), it can be used as an optical waveguide component without using a holding member such as a ferrule. Its outer diameter is preferably 0.3 to 4 mm. That is, when the outer diameter is 0.3 mm or more, polishing can be performed without a fixing jig such as a ferrule when polishing the end face. In particular, it is preferable that the outer diameter is 1 mm or more, since it can be brought into contact with other devices or optical fibers without a fixing jig (positioning member) such as a ferrule. A preferred range of the outer diameter is 0.6 to 4 mm, more preferably 1 to 4 mm.

  Further, the optical waveguide material of the present invention, when the inner surface of the pores are ion-exchanged, by controlling the ion species to be ion-exchanged and the thickness of the ion-exchange layer, the refractive index of the ion-exchange layer is the same as the refractive index of the glass. Differently, even if the glass material and the number, size, and arrangement of the holes are the same, it is preferable because the optical waveguide material has an effective refractive index of various cladding layers.

In this case, if the alkali ions contained in the glass are further replaced with cations having a large mass number or cations having a small mass number, the refractive index of the ion exchange layer changes, and the effective refractive index of the cladding portion changes. be able to. For example, when Li ⁺ ions or Na ⁺ ions in glass are ion-exchanged with K ⁺ ions, Cs ⁺ ions, Ag ⁺ ions, Cu ⁺ ions, or the like, the refractive index of the ion exchange layer increases, and When the K ⁺ ion or Na ⁺ ion is ion-exchanged with Li ⁺ ion or H ⁺ ion, the refractive index of the ion exchange layer becomes low.

In particular, when alkali ions in glass are ion-exchanged with ions having a smaller mass number, for example, K ⁺ ions in glass with Na ⁺ ions or H ⁺ ions, the refractive index of the ion exchange layer becomes monovalent or bivalent. It becomes lower than the refractive index of glass containing a valent cation. As a result, the effective refractive index of the cladding decreases, and the refractive index difference from the core increases. Thereby, the effect of confining the guided light in the core part is improved, and the loss of the guided light due to the leakage of light to the clad part can be suppressed.

  Further, in the cross section of the optical waveguide material, when the inner surface of the hole existing in the region of the cladding portion symmetrical about the core portion is ion-exchanged, the effective refractive index difference between the region and the other region is reduced. The birefringence is produced by this, and it becomes a polarization-maintaining optical waveguide material. For example, when the effective refractive index of the region increases, the polarization is maintained in the other inter-region direction, and when the effective refractive index of the region decreases, the polarization is maintained in the inter-region direction. .

  Next, a method for producing the optical waveguide material of the present invention will be described.

  First, a glass capillary and a glass rod having a desired composition are prepared. These glass capillaries and glass rods are filled in an outer tube to produce a preform. The preform is drawn at a temperature at which the glass softens and deforms, and an optical waveguide material having a desired size is obtained. Thereafter, the obtained optical waveguide material is immersed in an alkali molten salt to perform an ion exchange treatment.

  In addition, when performing ion exchange treatment, if both ends of the optical waveguide material are sealed so that the alkali molten salt does not enter the pores, chemical conversion can be performed without changing the optical waveguide characteristics of the optical waveguide material. Can be strengthened. Further, if ion exchange is performed without sealing both ends of the optical waveguide material, an optical waveguide material in which both the outer surface and the inner surface of the hole are ion-exchanged can be obtained. If the ion exchange species is different between the outer surface and the inner surface of the hole, the ion exchange of the inner surface of the hole is performed first, and the ion exchange of the outer surface is performed later, so that the compressive stress layer on the outer surface is relaxed. This is preferable because it does not occur.

  Hereinafter, the present invention will be described based on examples.

  Table 1 shows Examples 1 to 3 and Comparative Examples 1 to 3.

<Example 1>
First, 70.5% of SiO ₂ , 6.0% of Al ₂ O ₃ , 12.6% of B ₂ O ₃ , 0.7% of CaO, 2.1% of BaO, 6.6% of Na ₂ O by mass%. , 1.3% of K ₂ O and 0.2% of Sb ₂ O ₃ , one glass outer tube, 238 glass capillaries, and one glass rod were prepared. The dimensions and shape of each component are as follows. The glass outer tube is cylindrical, has a bottom sealed, and has an outer diameter of 30 mmφ and an inner diameter of 24 mmφ. The end of the glass capillary is sealed, and has an outer diameter of 1 mmφ and an inner diameter of 125 μmφ. The glass rod has an outer diameter of 1 mmφ.

  Next, one glass rod was arranged at a substantially central portion inside the glass outer tube, and 238 glass capillaries were arranged around the glass rod so that a gap was almost eliminated.

  Next, the inside of the glass outer tube filled with the glass capillary and the glass rod was depressurized to -750 mmHg using a vacuum pump, and the glass outer tube was sequentially kept at 730 ° C. from the bottom toward the open end while maintaining the pressure. And shrunk. After the glass outer tube was heated and shrunk to the open end, it was gradually cooled to room temperature and then returned to normal pressure to produce a glass preform. Next, the above-mentioned glass preform was inserted into an electric furnace, pulled by a roller, and drawn to form an optical waveguide material having an outer diameter of 0.6 mmφ.

Both ends of the obtained optical waveguide material were sealed, immersed in a molten salt of potassium nitrate at 380 ° C. for 20 hours, and subjected to ion exchange treatment with K ⁺ ions.

<Example 2>
In Example 2, 79.5% of SiO ₂ , 2.5% of Al ₂ O ₃ , 13.4% of B ₂ O ₃ , 4.4% of Na ₂ O, 0.1% of K ₂ O, and Sb ₂ O ₃ An optical waveguide material subjected to an ion exchange treatment was produced in the same manner as in Example 1 except that glass having a composition of 0.1% was used.

<Example 3>
In Example 3, an optical waveguide material subjected to ion exchange treatment was produced in the same manner as in Example 1 except that the outer diameter of the produced optical waveguide material was 1.25 mmφ.

<Comparative Example 1>
In Comparative Example 1, an optical waveguide material was produced in the same manner as in Example 1 except that the ion exchange treatment was not performed.

<Comparative Example 2>
In Comparative Example 2, an optical waveguide material was produced in the same manner as in Example 2, except that the ion exchange treatment was not performed.

<Comparative Example 3>
In Comparative Example 3, an optical waveguide material was produced in the same manner as in Example 3, except that the ion exchange treatment was not performed.

  The optical waveguide materials of the examples and the comparative examples were subjected to a three-point bending strength test. The three-point bending strength test was performed using a small table test machine EZ Test-500N manufactured by Shimadzu Corporation.

  As shown in Table 1, Examples 1 to 3 exhibited high bending strength.

  On the other hand, Comparative Examples 1 to 3 had low flexural strength.

  As described above, the optical waveguide material of the present invention can improve the mechanical strength by chemical strengthening by performing ion exchange treatment using glass containing monovalent or divalent cations. It can be used as an optical waveguide component without protecting the coating or the like or loading the capillary.

Claims (9)

  It consists of a core part and a clad part that guides light and has a fiber shape or a rod shape, and a plurality of holes are formed in the core part and / or the clad part periodically or randomly in parallel with the waveguide direction. An optical waveguide material comprising: a glass material containing monovalent or divalent cations; and an outer surface of which is ion-exchanged.   The optical waveguide material according to claim 1, wherein a compressive stress is applied to an outer surface.   The optical waveguide material according to claim 1, wherein the glass containing a monovalent or divalent cation is an alkali ion-containing glass.   The optical waveguide material according to any one of claims 1 to 3, wherein the alkali ion is a Na ion or a K ion. By mass%, a SiO ₂ 55 to 95%, optical waveguide material according to any one of claims 1 to 4, characterized in that it consists of glass containing 0.1% to 20% of Na ₂ O. By mass%, a SiO ₂ 55 to 95%, more of claims 1 to 5, characterized in that it consists of glass containing 0.1% to 15% 0.1 to 20% and K ₂ O to Na ₂ O An optical waveguide material according to any one of the above. In mass%, and characterized in that it consists of glass having _{SiO 2 55~95%, Na 2 O} 0.1~20%, a composition of K ₂ O 0.1 to 15% and B ₂ O ₃ 0 to 30% The optical waveguide material according to claim 1. By _{mass%, SiO 2 55~95%, Na} 2 O 0.1~20%, K 2 O 0.1~15%, B 2 O 3 0~30% and Al ₂ O ₃ 0~10% of the composition The optical waveguide material according to any one of claims 1 to 7, wherein the optical waveguide material is made of glass having the following.   The optical waveguide material according to any one of claims 1 to 8, wherein the outer diameter is 0.3 to 4 mm.