Glass material and optical fiber

Abstract

This glass material is configured from silica glass and contains a halogen element, wherein the glass material contains at least one of bromine and iodine, and the concentration ratio of halogen molecules X2 and halogen ions X− satisfies [X−] / [X2]≥1.

Description

Glass materials and optical fibers

[0001] This disclosure relates to a glass material and an optical fiber. This application claims priority to Japanese Application No. 2022-094169, filed on June 10, 2022, and incorporates by reference all of the contents of said Japanese application.

[0002] Bromine and iodine can be used as upper dopants that increase the refractive index of glass. Patent Documents 1 and 2 disclose optical fibers whose cores are doped with bromine and iodine.

[0003] US Patent Application Publication No. 2020 / 0087195 US Patent Application Publication No. 2020 / 0049881

[0004] A glass material according to one aspect of the present disclosure is a glass material made of silica-based glass and containing a halogen element, and contains at least one of bromine and iodine, and a halogen molecule X ２ and halogen ion X － The concentration ratio of [X － ] / [X ２ ]≧1.

[0005] An optical fiber according to one aspect of the present disclosure includes a core made of silica-based glass and containing a halogen element, and a cladding made of silica-based glass and surrounding the core, the core containing at least one of bromine and iodine, and the core containing halogen molecules X ２ and halogen ion X － The concentration ratio of [X － ] / [X ２ ]≧1.

[0006] Fig. 1 is a cross-sectional view showing an optical fiber according to an embodiment. Fig. 2 is a graph showing the relationship between concentration ratio and transmission loss. Fig. 3 is a graph showing the relationship between concentration ratio and transmission loss. Fig. 4 is a graph showing the relationship between concentration ratio and transmission loss. Fig. 5 is a graph showing the relationship between concentration ratio and transmission loss.

[0007] [Problem to be Solved by the Present Disclosure] Compared with fluorine and chlorine, bromine and iodine have a higher rate of increase in refractive index per added amount (mass %). Therefore, glass materials with the same refractive index can be achieved with low added amounts, and the effects of other impurities generated during the doping process can be easily suppressed. On the other hand, halogen molecules formed by bonding halogen elements may cause absorption losses in short wavelengths, i.e., in the ultraviolet and visible wavelength ranges. This limits the applications of glass materials in the ultraviolet and visible wavelength ranges.

[0008] In optical fibers, the base of the absorption loss due to halogen molecules also affects the transmission wavelength band. Furthermore, when glass defects occur due to the debonding of halogen ions, the base of the glass defect absorption also affects the transmission wavelength band. As a result, there is a risk of increased transmission loss.

[0009] The present disclosure aims to provide a glass material and an optical fiber that exhibit low absorption in the ultraviolet and visible wavelength regions.

[0010] Effect of the Present Disclosure The present disclosure can provide a glass material and an optical fiber that exhibit low absorption in the ultraviolet and visible light wavelength ranges.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) A glass material according to one aspect of the present disclosure is a glass material made of silica-based glass and containing a halogen element, and contains at least one of bromine and iodine, and a halogen molecule X ２ and halogen ion X － The concentration ratio of － ] / [X ２ ] ≧ 1. This glass material has low absorption in the ultraviolet and visible light wavelength regions.

[0012] (2) In the above (1), halogen molecule X ２ and halogen ion X － The concentration ratio of － ] / [X ２ ]≧9. In this case, the absorption in the ultraviolet and visible light wavelength regions is further reduced.

[0013] (3) In the above (1) or (2), the relative refractive index difference based on the refractive index of silica glass may be −0.1% or more and 0.3% or less. When this glass material is used to form the core, excessive doping of the downdopant in the cladding can be suppressed.

[0014] (4) Any of the glass materials described in (1) to (3) above may contain two or more halogen elements. In this case, the inclusion of a large amount of a specific halogen element is suppressed. Therefore, the specific halogen element is prevented from reacting with other added elements to become an impurity.

[0015] (5) The glass material of (4) above may contain two or more halogen elements each in a mass fraction of 50 ppm or more, which further suppresses a specific halogen element from reacting with other added elements to become an impurity.

[0016] (6) The glass material of (4) above may contain two or more halogen elements each in a mass fraction of 500 ppm or more, which further suppresses a specific halogen element from reacting with other added elements to become an impurity.

[0017] (7) Any of the glass materials (1) to (6) above may contain silica glass in a mass fraction of 90% or more, which prevents adverse effects on optical properties.

[0018] (8) An optical fiber according to an aspect of the present disclosure includes a core made of silica-based glass and containing a halogen element, and a cladding made of silica-based glass and surrounding the core, the core containing at least one of bromine and iodine, and the core containing halogen molecules X ２ and halogen ion X － The concentration ratio of [X － ] / [X ２ ]≧1. This optical fiber has low absorption in the ultraviolet and visible light wavelength regions.

[0019] [Details of the embodiments of the present disclosure] Specific examples of the glass material and optical fiber of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the description of the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted.

[0020] (Glass Material) The glass material according to this embodiment is, for example, optical glass. More specifically, the glass material is, for example, a glass material for optical fibers, and is used to form the core of an optical fiber. The glass material is made of silica-based glass containing silica glass as a main component. The glass material further contains other elements in addition to silicon (Si) and oxygen (O), which constitute silica glass.

[0021] The glass material contains a halogen element X. The halogen element X is any one of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). The glass material may contain multiple types of halogen elements. The glass material contains at least one of bromine and iodine.

[0022] The concentration of the halogen element X contained in the glass material may be 50 ppm or more, 500 ppm or more, or 1000 ppm or more by mass. This reduces the amount of change in the viscosity of the glass caused by changes in the concentration of the added element, thereby reducing the variation in the optical properties of the glass. The concentration of the halogen element X contained in the glass material may be 50,000 ppm or less by mass. This reduces the influence of changes in optical properties caused by large additions, and allows for the production of a glass material with optical properties similar to those of silica glass. The above concentration range is the same regardless of whether the halogen element X is Cl, F, Br, or I. In other words, when two or more types of halogen element X are contained in the glass material, it is sufficient that the concentration of each halogen element X is within the above range. Here, the mass ratio means mass fraction.

[0023] The glass material may contain two or more types of halogen elements X, or may contain three or more types of halogen elements X. If a glass material is doped with a large amount of a specific type of halogen element X, the halogen element X may react with other doped elements, such as alkali metal elements, to transition to another substance phase and become an impurity. The generation of impurities may affect the optical properties, and may increase light absorption, particularly in the ultraviolet region. If the glass material contains multiple types of halogen elements X, the concentration of each halogen element X required to achieve a desired refractive index can be reduced. This makes it possible to suppress impurity formation.

[0024] In the case of glass materials for optical fibers, if other substance phases are generated during the fiberization process, the hardness within the glass becomes non-uniform, making it impossible to achieve the desired fiber diameter and refractive index profile. Therefore, in order to prevent a decrease in the yield of optical fibers, it is important to suppress the concentration of each halogen element X.

[0025] Pure silica glass (SiO ２ The relative refractive index difference Δ of the glass material with respect to the refractive index of the glass (i.e., silica glass) may be −0.1% or more and 0.3% or less, 0% or more and 0.3% or less, or 0.1% or more and 0.3% or less. When such a glass material is used to form the core, it is possible to prevent excessive doping of down dopants such as F in the cladding. Therefore, it is possible to prevent an increase in transmission loss due to an increase in the doping concentration.

[0026] While the relative refractive index difference of the glass material is within the above range, two or more halogen elements X selected from Cl, F, Br, and I may be added in a mass ratio of 500 ppm or more each. Three or more halogen elements X may be added in a mass ratio of 500 ppm or more each. Here, the mass ratio means mass fraction.

[0027] The glass material may further contain elements that easily become cations, such as alkali metal elements, alkaline earth metal elements, Group 13 elements, and Group 14 elements. Examples of alkali metal elements include lithium (Li), sodium (Na), and potassium (K). Examples of alkaline earth metal elements include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Examples of Group 13 elements include boron (B), aluminum (Al), gallium (Ga), and indium (In). Examples of Group 14 elements include germanium (Ge), tin (Sn), and lead (Pb).

[0028] The glass material contains cations, and as will be described later, the monovalent anions X of the halogen element X － This makes it easier for halogen molecules X to be generated. ２ On the other hand, if phase separation of the additive substances occurs due to the addition of multiple elements, it will have an adverse effect on the optical properties. Therefore, the proportion of silica glass, which is the main component, may be 90% or more, 95% or more, or 98% or more by mass.

[0029] Halogen molecule X ２ and halogen ion X － The concentration of I is calculated using, for example, X-ray photoelectron spectroscopy (XPS). XPS makes it possible to capture changes in the valence state of elements. － The peak due to I was observed between 618 and 620 eV. ２ The peaks due to Br are observed between 620 and 621 eV. － The peaks due to Br were observed between 70 and 72 eV. ２ A peak due to the above is observed between 68 and 69 eV.

[0030] These peaks are fitted with a Gaussian function, and the concentration ratio (molar ratio) is defined from the area intensity ratio of the obtained fitting function. ２ and halogen molecule X ２ The same halogen element X as halogen ion X －The concentration ratio of [X － ] / [X ２ ] ≧ 1. The concentration ratio is [X － ] / [X ２ ] ≧ 9, and [X － ] / [X ２ ] ≧ 90, and [X － ] / [X ２ ] ≧900. These concentration ratios also affect absorption in the ultraviolet region. － By increasing the concentration ratio of the elements, it is possible to produce a glass material with low absorption over a wide wavelength range. By forming an optical fiber using this glass material, it is possible to reduce the transmission loss of the optical fiber. Furthermore, when the glass material contains two or more halogen elements, it is sufficient that at least one of the elements satisfies the above concentration ratio.

[0031] Glass materials are synthesized using plasma melting methods. ２ In order to suppress the generation of halogen ions X － The halogen ion X may be generated by a method. － The addition may be carried out under high pressure to produce

[0032] (Optical fiber) Fig. 1 is a cross-sectional view showing an optical fiber according to an embodiment. The optical fiber 1 according to an embodiment includes a core 10 extending along a central axis 1a and a cladding 20 surrounding the core 10. The optical fiber 1 is formed using a glass material according to an embodiment. More specifically, the core 10 is formed using the glass material according to an embodiment. The cladding 20 is made of silica-based glass containing silica glass as a main component.

[0033] Table 1 shows the relationship between the concentration ratio and the transmission loss.

[0034] 2 to 5 are graphs showing the relationship between the concentration ratio and the transmission loss. FIG. 2 shows the case of chlorine. FIG. 3 shows the case of fluorine. FIG. 4 shows the case of bromine. FIG. 5 shows the case of iodine. As shown in Table 1 and FIGS. 2 to 5, it can be seen that the transmission loss tends to decrease as the concentration ratio increases. [X － ] / [X ２ ] ≧1, it can be confirmed that the transmission loss is suppressed for all halogen elements.

[0035] Although the embodiments have been described above, the present disclosure is not necessarily limited to the above-described embodiments and modifications, and various modifications are possible without departing from the spirit of the present disclosure.

[0036] REFERENCE SIGNS LIST 1...optical fiber 1a...central axis 10...core 20...cladding

Claims

1. A glass material made of silica-based glass and containing a halogen element, Contains at least one of bromine and iodine, Halogen molecule X ２ and halogen ion X － The concentration ratio of － ] / [X ２ ] ≧1; Glass material.

2. The halogen molecule X ２ and the halogen ion X － The concentration ratio of － ] / [X ２ ]≧9, The glass material according to claim 1 .

3. The relative refractive index difference based on the refractive index of silica glass is -0.1% or more and 0.3% or less. The glass material according to claim 1 .

4. Contains two or more of the halogen elements; The glass material according to claim 1 .

5. The two or more halogen elements each contain 50 ppm or more by mass fraction, The glass material according to claim 4.

6. The two or more halogen elements each contain 500 ppm or more by mass fraction. The glass material according to claim 4.

7. Contains silica glass at a mass fraction of 90% or more; The glass material according to any one of claims 1 to 6.

8. The two or more halogen elements each contain 50,000 ppm or less by mass fraction, The glass material according to any one of claims 4 to 6.

9. Further containing at least one of an alkali metal element, an alkaline earth metal element, a Group 13 element, and a Group 14 element, The glass material according to any one of claims 1 to 6.

10. The relative refractive index difference based on the refractive index of silica glass is 0% or more and 0.3% or less. The glass material according to any one of claims 1 to 6.

11. The relative refractive index difference based on the refractive index of silica glass is 0.1% or more and 0.3% or less. The glass material according to any one of claims 1 to 6.

12. The halogen molecule X ２ and the halogen ion X － The concentration ratio of － ] / [X ２ ] ≧90; The glass material according to any one of claims 1 to 6.

13. The halogen molecule X ２ and the halogen ion X － The concentration ratio of － ] / [X ２ ] ≧900; The glass material according to any one of claims 1 to 6.

14. The halogen element is any one of fluorine, chlorine, bromine, and iodine. The glass material according to any one of claims 1 to 6.

15. A core made of silica-based glass and containing halogen elements; a cladding made of silica-based glass and surrounding the core; the core comprises at least one of bromine and iodine; In the core, a halogen molecule X ２ and halogen ion X － The concentration ratio of － ] / [X ２ ] ≧1; Optical fiber.