Method of manufacturing silica glass member and silica glass member obtained by the method

A method of manufacturing a silica glass member, comprising:

• a step of heating a silica glass ingot to a predetermined temperature;
• a step of cooling the silica glass ingot with a temperature distribution in at least one plane perpendicular to a rotational axis of the silica glass ingot, the temperature distribution being symmetrical with respect to the rotational axis and having a maximal value between a center and a peripheral portion of the plane;
• and
• a step of obtaining a distribution of signed birefringence values on the basis of birefringence values and directions of phase advance axes measured at a plurality of points in the plane perpendicular to the rotational axis of the silica glass ingot and cutting, from the silica glass ingot, a silica glass member whose signed birefringence values monotonously increase from the center to the peripheral portion of the plane.

A silica glass member having a distribution of signed birefringence values which monotonously increase from a center to a peripheral portion of a plane of the glass member, said silica glass member being obtained by a manufacturing method comprising:

• a first step of making a silicon compound react in oxyhydrogen flame using a burner having a multi-tubular structure to obtain fine silica glass particles;
• a second step of depositing the fine silica glass particles on a support rotating and placed to oppose the burner to obtain a silica glass ingot with a temperature distribution in at least one plane perpendicular to a rotational axis of the silica glass ingot, the temperature distribution being symmetrical with respect to the rotational axis and having a maximal value between the center and the peripheral portion of the plane;
• and
• a third step of obtaining a distribution of signed birefringence values on the basis of birefringence values and directions of phase advance axes measured at a plurality of points in the plane perpendicular to the rotational axis of the silica glass ingot and cutting, from the silica glass ingot, a silica glass member whose signed birefringence values monotonously increase from the center to the peripheral portion of the plane of the glass member, and a maximum value of a gradient of a radial distribution curve of average signed birefringence values is 0.2 nm/cm or less for a radial width of 10 mm.

A silica glass member having a distribution of signed birefringence values, in which the signed birefringence values monotonously increase from a center to a peripheral portion of a plane of the glass member, said silica glass member being obtained by a manufacturing method comprising:

• a step of heating a silica glass ingot to a predetermined temperature;
• a step of cooling the silica glass ingot with a temperature distribution in at least one plane perpendicular to a rotational axis of the silica glass ingot, the temperature distribution being rotationally symmetrical with respect to the center of the plane and having a maximal value between the center and the peripheral portion of the plane;
• and
• a step of obtaining a distribution of signed birefringence values on the basis of birefringence values and directions of phase advance axes measured at a plurality of points in the plane perpendicular to the rotational axis of the silica glass ingot and cutting, from the silica glass ingot, a silica glass member whose signed birefringence values monotonously increase from the center to the peripheral portion of the plane of the glass member and a maximum value of a gradient of a radial distribution curve of average signed birefringence values is 0.2 nm/cm or less for a radial width of 10 mm.