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Disclosed are synthetic silica glass body with a birefringence pattern having low fast axis direction randomness factor and glass reflow process. The glass reflow process comprises steps of: providing a glass tube having a notch; and thermally reflowing the glass tube to form a glass plate. The proc

Disclosed are synthetic silica glass body with a birefringence pattern having low fast axis direction randomness factor and glass reflow process. The glass reflow process comprises steps of: providing a glass tube having a notch; and thermally reflowing the glass tube to form a glass plate. The process can be advantageously used to produce fused silica glass plate without observable striae when viewed in the direction of optical axis. Also disclosed are optical members comprising the fused silica glass body and a process for reflowing glass cylinders.

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1. A process for making glass plate comprising the following steps: (I) providing a ready-to-flow notched glass tube having (a) a longitudinal tube center axis, (b) an identified section between two cross-sections perpendicular to the tube center axis having a longitudinal section length L1; and (c)

1. A process for making glass plate comprising the following steps: (I) providing a ready-to-flow notched glass tube having (a) a longitudinal tube center axis, (b) an identified section between two cross-sections perpendicular to the tube center axis having a longitudinal section length L1; and (c) a notch in the direction of the tube center axis of the ready-to-flow notched glass tube through the tube wall; and(II) thermally reflowing the ready-to-flow notched glass tube thus formed in step (I) at an elevated temperature to form a glass having a refractive index variation of less than or equal to 10 ppm, wherein the step of thermal reflowing comprises: (IIa) placing the ready-to-flow notched glass-tube on an essentially horizontal longitudinal mandrel, with the mandrel inserting into the inner cavity of the tube, and the notch placed facing sideways;(IIb) allowing the lower part of the notched glass tube to roll out to an essentially vertical position while restricting the upper part from rolling out, to result in a partially rolled out glass piece;(IIc) placing the partially rolled out glass piece on an inclined surface; and(IId) allowing imposing an external force on the mandrel to mechanically assist the partially rolled out glass piece to roll-out on the inclined surface to form an essentially flat glass plate. 2. A process in accordance with claim 1, wherein the glass tube has striae when viewed in the direction of the tube center axis. 3. A process in accordance with claim 2, wherein the glass tube has essentially circular striae when viewed in the direction of the tube center axis. 4. A process in accordance with claim 3, wherein after step (II), the striae are re-oriented to be essentially parallel to the two major surfaces of the resultant glass plate. 5. A process in accordance with claim 3, wherein after step (II), when viewed in the direction of the optical axis of the resultant glass plate, the glass plate is essentially free of striae. 6. A process in accordance with claim 5, wherein after step (II), when viewed in at least one direction perpendicular to the optical axis of the resultant glass plate, the glass plate is essentially free of striae. 7. A process in accordance with claim 5, wherein after step (II), when viewed in the direction of the center tube axis of the ready-to-flow glass tube, the resultant glass plate is essentially free of striae. 8. A process in accordance with claim 1, wherein the glass is consolidated fused silica. 9. A process in accordance with claim 8, wherein the silica glass is produced by outside vapor deposition. 10. A process in accordance with claim 8, wherein the silica glass is produced by inside vapor deposition. 11. A process in accordance with claim 8, wherein the glass is high purity consolidated fused silica and step (II) is conducted in the presence of a purifying atmosphere comprising a cleansing gas. 12. A process in accordance with claim 11, wherein the cleansing gas comprised in the purifying atmosphere is selected from F2, Cl2, Br2, a halogen-containing compound, and compatible mixtures thereof. 13. A process in accordance with claim 1, wherein in step (I), the notch is formed to have a center plane passing through the tube center axis of the ready-to-flow notched glass tube, and the two sides of the notch beside the center plane are essentially symmetric. 14. A process in accordance with claim 1, wherein in step (I), the notch is formed to have two essentially parallel sides. 15. A process in accordance with claim 1, wherein in step (I), the notch is formed to have an essentially truncated “V” shape cross-section when cut by a plane perpendicular to the tube center axis of the ready-to-flow notched glass tube. 16. A process in accordance with claim 1, wherein in step (I), the provided ready-to-flow notched glass tube has a cross-section that is part of a ring-shape defined by an essentially circular outer boundary having a diameter of OD1 and an essentially circular inner boundary having a diameter of ID1 when cut by a plane perpendicular to the center axis of the tube. 17. A process in accordance with claim 16, wherein in step (I), the outer boundary and the inner boundary of the ring-shape are essentially concentric. 18. A process in accordance with claim 16, wherein in step (I), the outer boundary and the inner boundary of the ring shape are essentially eccentric. 19. A process in accordance with claim 18, wherein in step (I), the notch is formed at the location such that the center plane of the notch is where the thickness of the wall of the ready-to-flow notched glass tube is essentially the minimal. 20. A process in accordance with claim 16, wherein in step (II), the identified section of the ready-to-flow notched glass tube is formed into a glass plate having two essentially flat major surfaces, a width of a first major flat surface of L3, a width of a second major surface of L4, L4≧L3, a length of both major surfaces of L2, and a thickness between the two essentially flat major surfaces of T. 21. A process in accordance with claim 20, wherein π·OD1−Larc≦L4≦2(π·OD1−Larc), where Larc is the outer arc length of the notch. 22. A process in accordance with claim 20, wherein L3≧1.0π·ID1. 23. A process in accordance with claim 20, wherein 0.10·(OD1−ID1)≦T≦0.45·(OD1−ID1). 24. A process in accordance with claim 1, wherein in step (II), the identified section of the ready-to-flow notched glass tube is formed into a glass plate having two essentially flat major surfaces, a width of a first major flat surface of L3, a width of a second major surface of L4, L4≧L3, a length of both major surfaces of L2, and a thickness between the two essentially flat major surfaces of T. 25. A process in accordance with claim 24, wherein L1≦L2≦2L1. 26. A process in accordance with claim 24, wherein L3≧0.5L4. 27. A process in accordance with claim 1, wherein: in step (II), the identified section of the ready-to-flow notched glass tube forms an identified glass plate having two essentially flat major surfaces, a width of the first major flat surface of L3, a width of a second major surface of L4, L4≧L3, a length of both major surfaces of L2, and a thickness between the two essentially flat major surfaces of T; andmeasured in a plane perpendicular to the optical axis of the identified glass plate, the identified glass plate upon edge removal and surface lapping with a surface area of about L3·L2 has a birefringence pattern in which fast axis directions have a randomness factor between −0.50 and 0.50. 28. A process in accordance with claim 1, wherein step (I) comprises the following steps: (Ia) providing a precursor glass tube having (a) a longitudinal tube axis, and (b) an identified section between two cross-sections perpendicular to the tube axis having a longitudinal section length L1; and(Ib) forming a notch in the direction of the tube axis of the precursor glass tube through the tube wall, whereby the ready-to-flow notched glass tube is formed. 29. A process in accordance with claim 28, wherein the glass is silica and step (Ia) comprises the following steps: (Ia1) forming a silica soot preform by the OVD process on a mandrel;(Ia2) consolidating the silica soot preform into fused silica glass without previously removing the mandrel; and(Ia3) removing the mandrel to form the precursor glass tube. 30. A process in accordance with claim 28, wherein the glass is silica and step (Ia) comprises the following steps: (Ia1) forming a silica soot preform by the OVD process on a mandrel;(Ia2) removing the mandrel from the soot preform; and(Ia3) consolidating the silica soot preform into fused silica glass, whereby the precursor glass tube is formed. 31. A process in accordance with claim 28, wherein the glass is silica; and step (Ia) comprises the following steps: (Ia1) forming a silica soot preform by the OVD process on a glass tube mandrel;(Ia2) consolidating the silica soot preform into fused silica glass without previously removing the mandrel, whereby the precursor glass tube is formed. 32. A process in accordance with claim 31 comprising the following step (III) after step (II): (III) removing the surface part of the glass plate resulting from the glass tube mandrel. 33. A process in accordance with claim 28, wherein the glass is silica and step (Ia) comprises the following steps: (Ia1) forming a silica soot preform by the IVD process on the inner surface of an outside tube;(Ia2) consolidating the silica soot preform into fused silica glass without previously removing the outside tube; and(Ia3) removing the outside tube to form the precursor glass tube. 34. A process in accordance with claim 28, wherein the glass is silica and step (Ia) comprises the following steps: (Ia1) forming a silica soot preform by the IVD process on the inner surface of an outside tube;(Ia2) removing the outside tube from the soot preform; and(Ia3) consolidating the silica soot preform into fused silica glass, whereby the precursor glass tube is formed. 35. A process in accordance with claim 28, wherein the glass is silica and step (Ia) comprises the following steps: (Ia1) forming a silica soot preform by the IVD process on the inner surface of an outside tube; and(Ia2) consolidating the silica soot preform into fused silica glass without previously removing the outside tube, whereby the precursor glass tube is formed. 36. A process in accordance with claim 35 comprising the following step (III) after step (II): (III) removing the surface part of the glass plate resulting from the outside tube. 37. A process in accordance with claim 28, wherein step (Ia) comprises the following steps: (I0) providing a precursor glass cylinder having a precursor cylinder axis, a length L0 in the direction of the precursor cylinder axis and a precursor cylinder outer diameter OD0;(I1) thermally reflowing, with optional pressing, the precursor glass cylinder; and(I2) optionally drilling in a direction essentially parallel to the precursor cylinder axis to form a cylindrical center cavity,whereby the precursor glass tube is formed to have a longitudinal tube axis, an outer diameter OD1 and a length L1 in the direction of the tube axis, where the tube axis is essentially parallel to the precursor cylinder axis of the precursor glass cylinder, L1OD0. 38. A process in accordance with claim 37, wherein 0.3L0≦L1≦0.8L0. 39. A process in accordance with claim 37, wherein: in step (I0), the precursor glass cylinder comprises an inner glass cane; said inner glass cane is located approximately at the center of the precursor glass cylinder and has a diameter of ID0; andin step (I2), the inner glass cane is essentially completely removed. 40. A process in accordance with claim 39, wherein after step (I2), the precursor glass tube has an inner cylindrical cavity with a diameter ID1, and OD0−ID0