Glass material and optical fiber

Abstract

This glass material is formed from silica glass and includes a Group 14 element. The glass material includes an element X that encompasses tin and / or lead, as tetravalent ions X4+ and divalent ions X2+.

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. 2022-094170, filed on June 10, 2022, and incorporates by reference all of the contents of said Japanese application.

[0002] Germanium can be used as an upper dopant to increase the refractive index of glass. Non-Patent Document 1 discloses an optical fiber whose core is doped with germanium.

[0003] Motohiro Nakahara and two others, "Loss Reduction in Optical Fibers," Applied Physics, Vol. 50, No. 10 (1981), pp. 1006-1020

[0004] A glass material according to one aspect of the present disclosure is a glass material made of silica-based glass and containing a Group 14 element, and the glass material contains tetravalent ions X of at least one element X selected from tin and lead. ４＋ and divalent ion X of element X ２＋ Includes.

[0005] An optical fiber according to one aspect of the present disclosure includes a core made of silica-based glass and containing a Group 14 element, and a cladding made of silica-based glass and surrounding the core, wherein the core contains tetravalent ions X of at least one element X selected from tin and lead. ４＋ and divalent ion X of element X ２＋ Includes.

[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 the concentration ratio and the transmission loss, and Fig. 3 is a graph showing the relationship between the concentration ratio and the transmission loss.

[0007] [Problems to be Solved by the Present Disclosure] Non-Patent Document 1 describes that Rayleigh scattering due to compositional fluctuations increases in proportion to the dopant concentration. Furthermore, an increase in the dopant concentration may cause the following problems: The probability of impurities contained in the dopant becoming mixed in increases, which may result in absorption in the ultraviolet and visible light regions due to the impurities. Furthermore, the probability that the added element (dopant) distorts the network structure of silica glass increases, which may result in glass defects and increase absorption in the ultraviolet wavelength region. In this field, glass materials and optical fibers with high transmittance over a wide wavelength region are desired.

[0008] An object of the present disclosure is to provide a glass material and an optical fiber that have high transmittance over a wide wavelength range.

[0009] Effect of the Present Disclosure The present disclosure can provide a glass material and an optical fiber that have high transmittance over a wide wavelength range.

[0010] [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 Group 14 element, and the glass material contains tetravalent ions X of at least one element X selected from tin and lead. ４＋ and divalent ion X of element X ２＋ This glass material provides high transmittance over a wide wavelength range.

[0011] (2) In the above (1), tetravalent ions X ４＋ and divalent ion X ２＋ The concentration ratio of [X ４＋ ] / [X ２＋ ] ≧ 1. In this case, higher transmittance is realized in a wide wavelength range.

[0012] (3) In the above (1), tetravalent ions X ４＋ and divalent ion X ２＋ The concentration ratio of [X ４＋ ] / [X ２＋ ] ≧ 10. In this case, particularly high transmittance is realized in a wide wavelength range.

[0013] (4) In any of the above (1) to (3), the relative refractive index difference based on the refractive index of silica glass may be 0% or more. When this glass material is used to form the core, excessive doping of the downdopant in the cladding can be suppressed.

[0014] (5) Any of the glass materials described in (1) to (4) above may contain two or more Group 14 elements. In this case, the inclusion of a large amount of a specific Group 14 element is suppressed. Therefore, phase separation into two components of the substance due to an increase in concentration can be suppressed.

[0015] (6) Any of the glass materials (1) to (5) above may contain silica glass in a mass ratio of 90% or more, which prevents adverse effects on optical properties.

[0016] (7) An optical fiber according to one aspect of the present disclosure includes a core made of silica-based glass and containing a Group 14 element, and a cladding made of silica-based glass and surrounding the core, wherein the core contains tetravalent ions X of at least one element X selected from tin and lead. ４＋ and divalent ion X of element X ２＋ This optical fiber has high transmittance over a wide wavelength range, thereby reducing loss in the transmission wavelength band.

[0017] [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.

[0018] (Glass Material) The glass material according to this embodiment is, for example, an optical glass material. 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.

[0019] The glass material contains a Group 14 element. Examples of the Group 14 element include germanium (Ge), tin (Sn), and Pb (lead). The glass material may contain a plurality of Group 14 elements. The glass material contains tetravalent ions X of at least one element X of tin and lead. ４＋ and divalent ion X ２＋ The glass material may further contain a Group 14 element other than tin and lead.

[0020] Tin and lead can change the refractive index difference of glass materials at lower concentrations than germanium. Therefore, tin and lead make it easier to produce high-refractive-index glasses, making them suitable for a wide range of optical glass applications. In particular, when used in optical fibers, they can suppress loss due to increased doping concentrations.

[0021] The valence of tin and lead tends to vary. When the valence differs, the absorption wavelength band due to the added element differs. Tetravalent ions X of at least one of elements X of tin and lead ４＋ and the absorption wavelength band of divalent ions X ２＋ The absorption wavelength bands of these ions are in the ultraviolet and visible light regions. ４＋ The absorption wavelength band of the divalent ion X ２＋ The peak is more likely to shift to the short wavelength side, that is, away from the near-infrared side, which is the transmission wavelength band, compared to the absorption wavelength band of tetravalent ions X ４＋ is a divalent ion X ２＋ In comparison, the tetravalent ion of silicon, Si ４＋ When substituted with SiO2, strain at the atomic level can be suppressed, and as a result, the occurrence of glass defects can be suppressed.

[0022] Tetravalent ions X of at least one element X selected from tin and lead ４＋ and divalent ion X ２＋ The concentration ratio of ４＋ ] / [X ２＋ ] ≧ 1, and [X ４＋ ] / [X ２＋ ] ≧ 10, and [X ４＋ ] / [X ２＋ ] ≧ 100. In other words, in the case of lead, [Pb ４＋] / [Pb ２＋ ] may be 1 or more, 10 or more, or 100 or more. In the case of tin, [Sn ４＋ ] / [Sn ２＋ ] may be 1 or more, 10 or more, or 100 or more.

[0023] The glass material may contain two or more Group 14 elements, or may contain three or more Group 14 elements. When the glass material contains multiple Group 14 elements, the concentration of each Group 14 element required to achieve a desired refractive index can be reduced. Therefore, it is possible to suppress phase separation of a compound of the Group 14 element and an element present in the glass into two components as the concentration increases. Furthermore, when the glass material contains two or more Group 14 elements, it is sufficient that at least one of the elements satisfies the above concentration ratio.

[0024] When such a phase separation state occurs, light absorption and scattering occur at the phase interface, resulting in changes in optical properties. These phase states change significantly depending on the cooling rate during the glass manufacturing process, or even on slight temperature variations of around 10°C, for example. This significantly reduces the controllability of optical properties. Therefore, it is extremely important to suppress phase separation in the first place. In optical fiber glass materials, 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, it is important to suppress the concentration of each Group 14 element in order to prevent a decrease in the yield of optical fibers.

[0025] The concentration of the group 14 element contained in the glass material is set according to the refractive index of the target glass material. ２ The change in the refractive index difference of the glass material based on the refractive index of the glass material (i.e., silica glass) is 0.06% per 1 mass % for germanium, 0.14% per 1 mass % for tin, and 0.12% per 1 mass % for lead.

[0026] Pure silica glass (SiO ２The relative refractive index difference Δ of the glass material with respect to the refractive index of a glass substrate (i.e., silica glass) may be 0% or more, 0.2% or more, or 0.3% or more. When such a glass material is used to form a core, it is possible to prevent excessive doping of a downdopant 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. The relative refractive index difference Δ may be greater than 0%.

[0027] In the case of single-element addition, i.e., when only one type of Group 14 element is added, in the case of germanium, the mass ratio may be 50 ppm or more, 30,000 ppm or more, or 50,000 ppm or more. In the case of tin and lead, the mass ratio may be 50 ppm or more, 14,000 ppm or more, or 20,000 ppm or more.

[0028] The glass material may further contain an alkali metal element, an alkaline earth metal element, a Group 13 element, a halogen element, etc. Examples of alkali metal elements include lithium (Li), sodium (Na), potassium (K), and rubidium (Rb). 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 halogen elements include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0029] In particular, halogen elements tend to oxidize other elements, and therefore tend to convert Group 14 elements into tetravalent ions. On the other hand, if phase separation occurs in the added substances due to the addition of multiple elements, it will have a negative 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.

[0030] The evaluation of the valence of lead and tin is carried out, for example, using X-ray photoelectron spectroscopy (XPS). ２＋ The peak due to Pb was observed between 137 and 138 eV. ４＋The peaks due to tin are observed between 138 and 139 eV. ２＋ The peak due to Sn was observed between 486 and 487 eV. ４＋ A peak due to the above is observed between 487 and 488 eV. These peaks are fitted using a Gaussian function to identify the peaks. The concentration ratio is defined from the area intensity ratio of the obtained fitting function.

[0031] The glass material is produced by using a plasma sintering method. In the plasma sintering method, nitrogen and oxygen (N ２ +O ２ The valence of the added tin and lead is easily controlled by the atmosphere during sintering. ４＋ In order to add the oxygen gas in this state, the gas partial pressure ratio of the oxygen gas to the non-oxygen gas may be [oxygen] / [non-oxygen]≧3, [oxygen] / [non-oxygen]≧5, or [oxygen] / [non-oxygen]≧10.

[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 and 3 are graphs showing the relationship between the concentration ratio and the transmission loss. FIG. 2 shows the case of lead, and FIG. 3 shows the case of tin. As shown in Table 1, FIG. 2 and FIG. 3, it can be seen that the transmission loss tends to decrease as the concentration ratio increases. [X ４＋ ] / [X ２＋ ] ≧1, it can be confirmed that the transmission loss is suppressed in both lead and tin.

[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 group 14 element, Tetravalent ions X of at least one of the elements X of tin and lead ４＋ and a divalent ion X of the element X ２＋ Including, Glass material.

2. The tetravalent ion X ４＋ and the divalent ion X ２＋ The concentration ratio of ４＋ ] / [X ２＋ ] ≧1; The glass material according to claim 1 .

3. The tetravalent ion X ４＋ and the divalent ion X ２＋ The concentration ratio of ４＋ ] / [X ２＋ ] ≧10; The glass material according to claim 1 or 2.

4. The relative refractive index difference based on the refractive index of silica glass is 0% or more. The glass material according to claim 1 or 2.

5. Contains two or more Group 14 elements, The glass material according to claim 1 or 2.

6. Contains 90% or more silica glass by mass ratio; The glass material according to claim 1 or 2.

7. The tetravalent ion X ４＋ and the divalent ion X ２＋ The concentration ratio of ４＋ ] / [X ２＋ ] ≧100; The glass material according to claim 1 or 2.

8. The relative refractive index difference based on the refractive index of silica glass is 0.2% or more. The glass material according to claim 1 or 2.

9. The relative refractive index difference based on the refractive index of silica glass is 0.3% or more. The glass material according to claim 1 or 2.

10. Contains 95% or more silica glass by mass ratio; The glass material according to claim 1 or 2.

11. Contains 98% or more silica glass by mass ratio; The glass material according to claim 1 or 2.

12. a core made of silica-based glass and containing one or more elements selected from the group of elements consisting of germanium, tin, and lead; a cladding made of silica-based glass and surrounding the core; The core is a tetravalent ion X of at least one of the elements X, tin and lead. ４＋ and a divalent ion X of the element X ２＋ Including, Optical fiber.