Silica glass member

A silica glass member for use in an optical system using light of a wavelength equal to or less than about 400 nm as a light source, the silica glass member having striae in a direction different from a predetermined direction, the strength of the striae being equal to or less than about 2×10−6×(the value of the wavelength in nanometers)/632.8 (nm) in terms of refractive index differential, a spacing between striae is equal to or less than 1.2 mm and having a value greater than zero.

An optical system having an optical axis, comprising a silica glass member for processing light of a predetermined wavelength along the optical axis, the silica glass member having striae extending in a direction substantially perpendicular to the optical axis of the optical system, a strength of the striae in terms of refractive index differential being smaller than about 2×10−6×(a value of the predetermined wavelength in nanometers)632.8 (nm), a spacing between the striae in the silica glass member is equal to or less than 1.2 mm and having a value greater than zero.