Laser system and method forming an edge section of a high purity fused silica glass sheet

A high purity fused silica glass sheet comprising:

• a first major surface;
• a second major surface opposite the first major surface;
• an edge section surrounding the first and second major surfaces and defining an outer perimeter of the silica glass sheet
• at least 99.9 mole % silica, wherein the silica is at least generally amorphous, having less than 1% crystalline content by weight;
• and
• an average thickness between the first major surface and the second major surface of less than 500 μm;
• wherein the edge section, in cross section, has an unrefined-bullnose shape such that the edge section has a surface that is outwardly rounded between the first and second major surfaces and curvature of the surface of the edge section smoothly transitions, free of sharp edges and/or discontinuities in curvature that extend around the perimeter, between the first and second major surfaces but in neither a geometric circular arc nor with radiused corners directly connected by a straight portion that is orthogonal to the first and second major surfaces;
• wherein a roughness (Ra) of the first major surface is between 0.025 nm and 1 nm over at least one 0.023 mm2 area of the first major surface,
• wherein the first major surface includes a plurality of raised and recessed features each having a length and a width, wherein within at least one 0.023 mm2 area of the first major surface, the maximum length and the maximum width of the raised features are less than 10 μm.

A high purity fused silica glass sheet comprising:

• a first major surface;
• a second major surface opposite the first major surface;
• an edge section surrounding the first and second major surfaces and defining an outer perimeter of the silica glass sheet
• at least 99.9 mole % silica, wherein the silica is at least generally amorphous, having less than 1% crystalline content by weight;
• and
• an average thickness between the first major surface and the second major surface of less than 500 μm;
• wherein the edge section, in cross section, has an unrefined-bullnose shape such that the edge section has a surface that is outwardly rounded between the first and second major surfaces and curvature of the surface of the edge section smoothly transitions, free of sharp edges and/or discontinuities in curvature that extend around the perimeter, between the first and second major surfaces but in neither a geometric circular arc nor with radiused corners directly connected by a straight portion that is orthogonal to the first and second major surfaces;
• wherein a roughness (Ra) of the first major surface is between 0.025 nm and 1 nm over at least one 0.023 mm2 area of the first major surface,
• wherein the second major surface has a roughness, and the roughness of the second major surface is greater than the roughness of the first major surface.

A high purity fused silica glass sheet comprising:

• a first major surface;
• a second major surface opposite the first major surface;
• an edge section comprising an outwardly protruding surface extending between the first and second major surfaces and defining an outer perimeter of the silica glass sheet, wherein the edge section and a centroid of the first major surface differ in fictive temperature from one another by at least 20° C.;
• at least 99.9 mole % silica, wherein a sodium (Na) content of silica glass sheet is less than 50 ppm;
• and
• an average thickness between the first major surface and the second major surface of less than 500 μm.