OPTICAL MEMBER MADE FROM SYNTHETIC QUARTZ GLASS

摘要

PROBLEM TO BE SOLVED: To provide an optical member made from a synthetic quartz glass, exhibiting a low birefringence, small in its variation and suitable for the optical member used for a light exposure apparatus of a refractive optical system or of a reflective optical system. SOLUTION: This optical member consists of the synthetic quartz having <=5 ppb Ma concentration and <=3 ppb difference between the maximum value and the minimum value of the Na concentration and has <=2 nm birefringence.