Glass material and optical fiber

Abstract

A glass material according to the present invention includes a silica glass and a group 15 element. The concentration ratio of the single bonds and multiple bonds of the group 15 element satisfies [single bonds] / [multiple bonds]≥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. 2022-104468, filed on June 29, 2022, and incorporates by reference all of the contents of said Japanese application.

[0002] Non-Patent Document 1 discloses that the refractive index of oxynitride glass, i.e., nitrogen-containing glass, increases. Non-Patent Document 2 discloses that the ultraviolet absorption of phosphorus-containing glass shifts to shorter wavelengths. Glasses containing group 15 elements such as nitrogen and phosphorus can generally shift the ultraviolet absorption to shorter wavelengths than pure silica glass, and therefore can be used as optical glasses over a wide wavelength range.

[0003] Hampshire, Pomeroy, “Oxynitride Glasses”, Int. J. Appl. Ceram. Technol., 5 [2] 155-163 (2008) Kohei Kadono, “Optical Properties of Glass I”, NEW GLASS Vol.24 No.1 p.59-63 (2009)

[0004] A glass material according to one embodiment of the present disclosure is made of silica-based glass and contains a Group 15 element, in which the concentration ratio of single bonds to double bonds of the Group 15 element satisfies [single bond] / [double bond]≧1.

[0005] 1 is a cross-sectional view of an optical fiber according to an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the concentration ratio and the transmission loss.

[0006] [Problem to be Solved by the Present Disclosure] Glasses containing Group 15 elements, particularly nitrogen, have increased viscosity and glass transition temperatures, necessitating processing at high temperatures. This reduces processability and increases the likelihood of impurities being mixed in, potentially resulting in absorption due to the impurities. In this field, there is a need for glass materials and optical fibers that have high transmittance over a wide wavelength range.

[0007] 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.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a glass material and an optical fiber having high transmittance over a wide wavelength range. [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 containing silica-based glass and a Group 15 element, in which the concentration ratio of single bonds to double bonds of the Group 15 element satisfies [single bond] / [double bond]≧1. This glass material achieves high transmittance over a wide wavelength range.

[0009] (2) In the glass material of (1) above, the concentration ratio of single bonds to double bonds of the Group 15 element may satisfy [single bond] / [double bond] ≥ 9. In this case, higher transmittance is achieved over a wide wavelength range.

[0010] (3) In the glass material of (1) above, the concentration ratio of single bonds to double bonds of the Group 15 element may satisfy [single bond] / [double bond] ≥ 19. In this case, particularly high transmittance is achieved over a wide wavelength range.

[0011] (4) In any of the glass materials (1) to (3) above, 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 a core, excessive doping of a downdopant in the cladding can be suppressed.

[0012] (5) Any of the glass materials (1) to (4) above may contain silica glass in a mass ratio of 50% or more, which prevents adverse effects on optical properties.

[0013] (6) Any of the glass materials described in (1) to (5) above may further contain an alkali metal element, an alkaline earth metal element, a Group 13 element, or a halogen element. In this case, the valence state of the Group 15 element can be stabilized.

[0014] (7) A glass material according to another aspect of the present disclosure is a glass material containing silica-based glass and a Group 15 element, wherein the concentration ratio of single bonds to multiple bonds of the Group 15 element satisfies [single bond] / [multiple bond] ≥ 1. This glass material achieves high transmittance over a wide wavelength range.

[0015] (8) An optical fiber according to one aspect of the present disclosure includes a core containing silica-based glass and a Group 15 element, and a cladding containing silica-based glass and surrounding the core, wherein the concentration ratio of single bonds to double bonds of the Group 15 element in the core satisfies [single bonds] / [double bonds] ≥ 1. This optical fiber achieves high transmittance over a wide wavelength range, thereby reducing loss in the transmission wavelength band.

[0016] [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.

[0017] (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.

[0018] The glass material may 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), 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 Group 14 elements include germanium (Ge), tin (Sn), and lead (Pb).

[0019] The glass material may contain elements that are easy to stabilize the valence, such as alkali metal elements, alkaline earth metal elements, and elements from Group 13. As will be described later, these elements that are easy to stabilize the valence have the effect of stabilizing the valence of the elements from Group 15 added to the glass material.

[0020] The glass material may contain a halogen element, such as fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). Because the halogen element is an oxidizing agent, it has the effect of stabilizing the valence of the Group 15 element added to the glass material, as described below.

[0021] The glass material contains a Group 15 element. Examples of Group 15 elements include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). The glass material may contain multiple types of Group 15 elements. In the glass material, the concentration ratio of single bonds to double bonds of the Group 15 element satisfies [single bond] / [double bond]≧1. That is, the concentration (abundance) of the Group 15 element in a single bond state is equal to or greater than the concentration (abundance) of the Group 15 element in a double bond state. The concentration ratio of single bonds to double bonds of the Group 15 element may satisfy [single bond] / [double bond]≧9 or may satisfy [single bond] / [double bond]≧19.

[0022] In the glass material, the concentration ratio of single bonds to multiple bonds of the Group 15 element satisfies [single bond] / [multiple bond]≧1. That is, the concentration (abundance) of the Group 15 element in a single bond state is equal to or greater than the concentration (abundance) of the Group 15 element in a multiple bond state. The concentration ratio of single bonds to multiple bonds of the Group 15 element may satisfy [single bond] / [multiple bond]≧9 or may satisfy [single bond] / [multiple bond]≧19.

[0023] Nitrogen tends to be trivalent. In glass materials, nitrogen can take on various bonding states, from double bonds such as Si=N to single bonds such as Si-N. Generally, the stronger the bond strength, the more chemically durable the glass produced will be. On the other hand, the stronger the bond strength, the more likely the viscosity and glass transition temperature will increase, so the glass must be processed at higher temperatures. Processing at high temperatures makes it more likely that impurities such as water will be mixed in, making it unsuitable for producing optical glass.

[0024] By including a large amount of single bonded nitrogen such as Si-N in the glass material, it is possible to improve chemical durability compared to pure silica glass, while maintaining low viscosity and glass transition temperature. To increase the proportion of nitrogen in single bonded state, nitrogen may be added at high temperature and pressure as much as possible. High temperature and pressure allow nitrogen molecules (N ２ ) triple bond is broken, and nitrogen can be easily added as a single bond. Nitrogen can be ionized using plasma or ammonia (NH ３ ) or a substance containing many single bonds.

[0025] Although arsenic and antimony tend to be trivalent, they are known to be more likely to have various valences than nitrogen and phosphorus due to their elemental characteristics. Therefore, the valence states of arsenic and antimony may be stabilized by adding an element that easily stabilizes the valence, such as an alkali metal element, an alkaline earth metal element, or a halogen element. In particular, a halogen element may be co-doped. The total molar concentration of the added arsenic and antimony may be 0.1 to 10 times, 2 to 5 times, or 2.5 to 3.5 times the molar concentration of the total halogen elements added.

[0026] Particular care must be taken with phosphorus, as it is prone to pentavalent bonds. Silicon has four bonds, while phosphorus has five bonds. Therefore, when silicon is substituted with phosphorus, the remaining bond is likely to contribute to double bonds. This increases viscosity. Furthermore, distortion is imparted to the glass structure, promoting the generation of defects and increasing absorption components on the short wavelength side, i.e., in the ultraviolet region. Such glass materials are not suitable for optical glass, which requires high transmittance over a wide wavelength range. Therefore, with regard to phosphorus, a method of dispersing bonds by adding elements such as alkali metal elements or alkaline earth metal elements may be used.

[0027] When the total amount (molar concentration) of alkali metal elements added is x and the total amount (molar concentration) of alkaline earth metal elements added is y, x + 2y may be 0.1 to 10 times, 0.5 to 2 times, or 0.9 to 1.2 times the amount (molar concentration) of phosphorus added. Since alkali metal elements bond with phosphorus in a 1:1 ratio and the bonding state of phosphorus can be a single bond, the amount of alkali metal elements added may be greater than the amount of alkaline earth metal elements added.

[0028] Pure silica glass (SiO ２ ), that is, the relative refractive index difference Δ of the glass material with respect to the refractive index of silica glass as a reference may be −0.1% or more and 0.3% or less, 0.0% 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.

[0029] All Group 15 elements are upper dopants and are added according to the refractive index of the target glass material. The Group 15 elements may be added to the glass material in as large a quantity as possible. When a single element is added, i.e., when only one Group 15 element is added, the mass ratio of phosphorus may be 50 ppm or more, 1000 ppm or more, or 50,000 ppm or more. The mass ratio of nitrogen may be 50 ppm or more, 1000 ppm or more, or 20,000 ppm or more. The mass ratio of arsenic may be 50 ppm or more, 1000 ppm or more, or 10,000 ppm or more. The mass ratio of antimony may be 50 ppm or more, 1000 ppm or more, or 6,000 ppm or more. Here, the mass ratio refers to the mass fraction.

[0030] If phase separation occurs in the additive material due to the addition of multiple types of elements, it will have an adverse effect on the optical properties. Therefore, the proportion of silica glass, which is the main component, may be 50% or more, 80% or more, or 90% or more by mass ratio. Here, mass ratio means mass fraction.

[0031] The bonding state of phosphorus and oxygen is evaluated, for example, by X-ray photoelectron spectroscopy (XPS). A spectral peak due to the P=O bonding state is observed between 533 and 535 eV. A spectral peak due to the P-O bonding state is observed between 532 and 533 eV. These peaks are fitted using a Gaussian function to identify the peaks. The concentration ratio of the bonding states (the ratio of the abundance of the bonding states) is calculated from the area intensity ratio of the obtained fitting function.

[0032] The bonding state of nitrogen and silicon is also evaluated, for example, by XPS. When a double bond (Si=N) is contained, a spectral peak is observed at 397.9 eV. When only a single bond (Si-N) is contained, a spectral peak is observed at 399.4 eV. These peaks are fitted using a Gaussian function to identify the peaks. The concentration ratio of the bonding states (the ratio of the abundance of the bonding states) is determined from the area intensity ratio of the obtained fitting function. The concentration ratio of nitrogen single bonds to double bonds, [N single bond] / [N double bond], may be 1 or more, 9 or more, or 19 or more.

[0033] The bonding states of arsenic and oxygen and antimony and oxygen are also evaluated by, for example, XPS. In the case of arsenic, a spectral peak due to trivalent arsenic is observed between 44.5 and 45.5 eV, and a spectral peak due to pentavalent arsenic is observed between 45.5 and 46.5 eV. In the case of antimony, a spectral peak due to trivalent arsenic is observed between 529.5 and 530.5 eV, and a spectral peak due to pentavalent arsenic is observed between 530.5 and 531.5 eV. These peaks are fitted using a Gaussian function to identify the peaks. The concentration ratio of the bonding states (the ratio of the abundance of the bonding states) for each of arsenic and antimony is determined from the area intensity ratio of the obtained fitting function.

[0034] The glass material is synthesized using a method such as plasma melting or high-pressure synthesis. To minimize the inclusion of impurities, the materials of components such as furnaces used in the production may be made of quartz, which is the same element as the glass material.

[0035] (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.

[0036] Table 1 shows the relationship between the concentration ratio and the transmission loss.

[0037] Fig. 2 is a graph showing the relationship between the concentration ratio and the transmission loss. As shown in Table 1 and Fig. 2, it can be seen that the transmission loss tends to decrease as the concentration ratio increases. It can be confirmed that when [N single bond] / [N double bond]≧1, the transmission loss is suppressed to 0.165 dB / km or less.

[0038] 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.

[0039] REFERENCE SIGNS LIST 1...optical fiber 1a...central axis 10...core 20...cladding

Claims

1. A glass material containing a silica-based glass and a group 15 element, the concentration ratio of the single bond to the double bond of the Group 15 element satisfies [single bond] / [double bond]≧1; Glass material.

2. The concentration ratio of the single bond to the double bond of the Group 15 element satisfies [single bond] / [double bond]≧9. The glass material according to claim 1 .

3. the concentration ratio of the single bond to the double bond of the Group 15 element satisfies [single bond] / [double bond]≧19; The glass material according to claim 1 .

4. 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 3.

5. Contains 50% or more silica glass by mass ratio; The glass material according to any one of claims 1 to 3.

6. Further containing an alkali metal element, an alkaline earth metal element, a Group 13 element, or a halogen element; The glass material according to any one of claims 1 to 3.

7. A glass material containing a silica-based glass and a group 15 element, the concentration ratio of the single bond to the multiple bond of the Group 15 element satisfies [single bond] / [multiple bond]≧1; Glass material.

8. a core comprising a silica-based glass and a group 15 element; a cladding including a silica-based glass and surrounding the core; In the core, a concentration ratio of single bonds to double bonds of the Group 15 element satisfies [single bond] / [double bond]≧1. Optical fiber.