GAS DISCHARGE CHAMBER

摘要

Disclosed is a gas discharge chamber that uses calcium fluoride crystal, and that reduces damage from mechanical stress (window holder or laser gas pressure) and thermal stress from light absorption, increases the linear polarization of the output laser, and suppresses deterioration due to intense ultraviolet (ArF in particular) laser irradiation. The entrance plane and exit plane of a first window (2) and a second window (3) of the gas discharge chamber are parallel with the (111) crystal plane of the calcium fluoride crystal. For an arrangement in which laser light entering the interior of the calcium fluoride crystal passes through a plane including the <111> axis and <001> axis of both the first window (2) and the second window (3), viewed from the interior of the chamber (1), the first window (2) and the second window (3) are disposed at a position rotated at the same angle centered on the <111> axis.