LOW STRIATION EXTREME ULTRAVIOLET OPTICAL ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide an extreme ultraviolet optical element having a low-level striation; and to provide a glass boule for manufacturing the extreme ultraviolet optical element.

SOLUTION: This low striation extreme ultraviolet optical element includes silica-titania glass having a polished and shaped surface and having a crest-to-trough striation level smaller than 0.2 MPa, and the glass contains titania in the range of 5-10 wt.%. The glass has a coefficient of thermal expansion (CTE) within a range of +30 ppb/°C to -30 ppb/°C at a temperature between 20-35°C.

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