Low scattering silica glass and method for heat-treating silica glass

Patent metadata

Field	Value
Publication number	US-10370281-B2
Application number	US-201615014359-A
Country	US
Kind code	B2
Filing date	Feb 3, 2016
Priority date	Aug 15, 2013
Publication date	Aug 6, 2019
Grant date	Aug 6, 2019

Abstract

Provides is low scattering silica glass suitable as a material of an optical communication fiber. Silica glass has a fictive temperature of at least 1,000° C. and a void radius of at most 0.240 nm, as measured by positron annihilation lifetime spectroscopy. A method for heat-treating silica glass is also provided, which comprises holding silica glass to be heat-treated in an atmosphere at a temperature of at least 1,200° C. and at most 2,000° C. under a pressure of at least 30 MPa, and cooling the silica glass at an average temperature-decreasing rate of at least 40° C./min during cooling within a temperature range of from 1,200° C. to 900° C. A method for heat-treating silica glass also comprises holding silica glass to be heat-treated in an atmosphere at a temperature of at least 1,200° C. and at most 2,000° C. under a pressure of at least 140 MPa, and cooling the silica glass in an atmosphere under a pressure of at least 140 MPa during cooling within a temperature range of from 1,200° C. to 900° C.

First claim

What is claimed is:

1. Silica glass, which has a fictive temperature of at least 1,000° C. and a void radius of at most 0.240 nm, as measured by positron annihilation lifetime spectroscopy,
wherein
a content of SiO 2 in the silica glass is at least 99.7 mass %,
an OH content in the silica glass is at most 50 ppm,
a content of an alkali metal component in the silica glass is at most 100 ppm, and
a Rayleigh scattering coefficient of the silica glass with respect to light at 1.55 μm is at most 0.065 dB/Km.

2. Silica glass, which has a refractive index of at least 1.460 and an annihilation lifetime τ 3 of at most 1.56 ns when a positron is captured by a void and annihilates,
wherein
a content of SiO 2 in the silica glass is at least 99.7 mass %,
an OH content in the silica glass is at most 50 ppm,
a content of an alkali metal component in the silica glass is at most 100 ppm, and
a Rayleigh scattering coefficient of the silica glass with respect to light at 1.55 μm is at most 0.065 dB/Km.

3. A method for heat-treating silica glass, which comprises holding silica glass to be heat-treated in an atmosphere at a temperature of at least 1,200° C. and at most 2,000° C. under a pressure of at least 30 MPa, and cooling the silica glass at an average temperature-decreasing rate of at least 55° C./min during cooling within a temperature range of from 1,200° C. to 900° C., wherein the silica glass of claim 2 is produced.

4. A method for heat-treating silica glass, which comprises holding silica glass to be heat-treated in an atmosphere at a temperature of at least 1,200° C. and at most 2,000° C. under a pressure of at least 140 MPa, and cooling the silica glass in an atmosphere under a pressure of at least 140 MPa during cooling within a temperature range of from 1,200° C. to 900° C., wherein the silica glass of claim 2 is produced.

5. The method for heat-treating silica glass according to claim 3 , which further comprises cooling the silica glass in an atmosphere under a pressure of at least 0.1 MPa within a temperature range of from 900° C. to 200° C.

6. The method for heat-treating silica glass according to claim 3 , wherein the scattering coefficient of the silica glass after the heat treatment decreases to 60% or less of the value before the heat treatment.

7. The method for heat-treating silica glass according to claim 3 , wherein the void radius of the silica glass as measured by positron annihilation lifetime spectroscopy after the heat treatment decreases to 98% or less of the value before the heat treatment.

8. An optical communication fiber, which uses the silica glass as defined in claim 1 .

9. An optical member for lithography, which uses the silica glass as defined in claim 1 .

10. An optical communication fiber, which uses the silica glass as defined in claim 2 .

11. An optical member for lithography, which uses the silica glass as defined in claim 2 .

Assignees

• Agc Inc

Inventors

• Ono Madoka
• Ito Setsuro
• Honma Osamu
• Amino Yousuke

Classifications

• C03C3/06

  with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)} · CPC title

• C03B2205/56

  Annealing or re-heating the drawn fibre prior to coating · CPC title

• C03B2201/42

  doped with titanium · CPC title

• C03B2201/31

  doped with germanium · CPC title

• C03B2201/075

  Hydroxyl ion (OH) · CPC title