Process for making low-OH glass articles and low-OH optical resonator

• US 20050044893A1
• Filed: 08/25/2004
• Published: 03/03/2005
• Est. Priority Date: 08/28/2003
• Status: Abandoned Application

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Lasala, John E., Whalen, Joseph M., Tingley, James E., Sabia, Robert, Ukrainczyk, Ljerka, Coon, Jeffrey, Stewart, Ronald L., Quinn, Candace J.
• Application Number:
  US10/926,619
• Publication Number:
  US 20050044893A1
• Time in Patent Office: Days
• US Class Current: 65/32.100
• CPC Class Codes: C03B 19/12 by liquid-phase reaction processes
• CPC Class Codes: C03B 19/1453 Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
• CPC Class Codes: C03B 2201/075 Hydroxyl ion (OH)
• CPC Class Codes: C03B 2201/23 doped with hydroxyl groups
• CPC Class Codes: C03B 2201/31 doped with germanium
• CPC Class Codes: C03B 32/00 Thermal after-treatment of glass products not provided for in groups C03B19/00 , C03B25/00 - C03B31/00 or C03B37/00, e.g. crystallisation, eliminating gas inclusions or other impurities; Hot-pressing vitrified, non-porous, shaped glass products
• CPC Class Codes: C03B 32/005 Hot-pressing vitrified, non-porous, shaped glass products
• CPC Class Codes: C03C 2201/23 containing hydroxyl groups
• CPC Class Codes: C03C 2201/31 containing germanium
• CPC Class Codes: C03C 2203/50 After-treatment
• CPC Class Codes: C03C 23/008 comprising a lixiviation step
• CPC Class Codes: C03C 3/06 with more than 90% silica by weight, e.g. quartz C03C3/045 takes precedence
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29343 Cascade of loop resonators

Abstract

Disclosed are optical resonators having low OH content in at least the near-surface region and a process for making low OH glass article by chlorine treatment of consolidated glass of the article. Cl₂ gas was used to remove OH from depth as deep as 350 μm from the surface of the consolidated glass. The process can be used for treating flame-polished preformed optical resonator disks. A new process involving hot pressing or thermal reflowing for making planar optical resonator disks without the use of flame polishing is also disclosed.

Claims

1. A process for making a consolidated glass article having a low β

-OH level at least in the near-surface region, comprising at least one chlorine treatment step of subjecting the consolidated glass of the article to a chlorine-containing atmosphere at an elevated temperature for an effective amount of time.

2. A process in accordance with claim 1, wherein the glass article produced has a β

-OH level of lower than 100 ppm in the region within at least 10 μ

m from the surface of the article.

3. A process in accordance with claim 1, wherein the glass article is made of fused silica glass, optionally doped with alumina, boron oxide, fluorine, germania and/or titania, at an amount of up to 5% by weight each.

4. A process in accordance with claim 1, wherein in the chlorine treatment step, the chlorine-containing atmosphere is selected from chlorine and chlorine/inert gas mixtures, the temperature of the chlorine treatment step is at least 800°

C., and the chlorine treatment time is at least 2 hours.

5. A process in accordance with claim 1, wherein the glass article is an optical resonator.

6. A process in accordance with claim 5, wherein the optical resonator has a flame-polished portion.

7. A process in accordance with claim 6, wherein the resonator is a fused silica glass disk, optionally doped with glass modifiers, and the curved rim of the resonator disk is flame polished and has a β

-OH level of at least 100 ppm within at least 50 μ

m from the surface of the rim before the chlorine treatment.

8. A process in accordance with claim 7, wherein in the chlorine treatment step, the fused silica resonator disk is subjected to a chlorine/helium mixture at approximately 1000°

C. for at least 2 hours.

9. A process in accordance with claim 1, wherein the chlorine treatment of the consolidated glass is carried out before the glass article is finally formed.

10. A process in accordance with claim 1, wherein the glass article is a planar optical resonator, and the process comprises the following steps in sequence:

(i) providing a cylindrical shaped glass preform having a predetermined size;

(ii) optionally lapping, grinding and/or polishing the preform;

(iii) optionally subjecting the preform to chlorine treatment;

(iv) dicing the preform to form disks of a predetermined thickness;

(iv′

) optionally lapping and/or polishing the disks;

(v) optionally subjecting the disks to chlorine treatment;

(vi) hot pressing the disks or thermally reflowing the disks at an elevated temperature; and

(vii) cooling the disks to room temperature.

11. A process in accordance with claim 10, wherein after step (vi), an additional step (vi′

) is carried out;

(vi′

) subjecting the disks thus formed to chlorine treatment.

12. A process in accordance with claim 10, wherein step (vi) is carried out in an environment essentially free of water.

13. A process in accordance with claim 12, wherein step (vi) is carried out in vacuum.

14. A process in accordance with claim 12, wherein step (vi) is carried out in the presence of an inert gas.

15. A process in accordance with claim 10, wherein step (vi) involves hot pressing at a temperature where the glass has a viscosity less than 10¹⁰ poise.

16. A process in accordance with claim 10, wherein step (vi) involves hot pressing at a pressure ranging from 1,000 to 1,500 psi.

17. A process in accordance with claim 10, wherein step (vi) involves thermal reflowing at a temperature where the glass has a viscosity less than 10⁸ poise.

18. A process in accordance with claim 10, wherein step (vi) involves thermal reflowing at a temperature where the glass has a viscosity ranging from 10⁶ to 10⁷ poise.

19. A glass optical resonator for use in an opto-electronic oscillator having a low OH content at least in the near-surface region.

20. An optical resonator in accordance with claim 19 wherein the resonator is made of optionally doped fused silica glass, and has a β

-OH level of less than 80 ppm in the region within at least 10 μ

m from the surface of the resonator.

21. An optical resonator in accordance with claim 19, wherein the resonator is made of a fused silica material containing additional dopant material selected from the group consisting of boron oxide, fluorine, alumina, germania and titania.

22. An optical resonator in accordance with claim 19, wherein the resonator is made of a fused silica material containing germania, optionally loaded with molecular hydrogen, said silica material being photorefractive.

23. An optical resonator in accordance with claim 22, wherein the resonator contains a photo-induced grating having differing refractive index from that of the rest of the resonator.

24. An optical resonator in accordance with claim 19, wherein the resonator has a planar circular disk or ring shape having an outer diameter of about 1 to 10 mm, and a thickness of from about 20 to 200 μ

m, and a curved outer rim having a curvature radius of from about 25 to 50 μ

m.

25. An optical resonator in accordance with claim 24, wherein the resonator has a outer diameter of about 5 mm and a thickness of about 50 to 100 μ

m.