公开(公告)号：US11500194B2

公开(公告)日：2022-11-15

申请号：US17036412

申请日：2020-09-29

Applicant: Gigaphoton Inc.

Inventor： Takashi Suganuma ,  Takahiro Tatsumi

IPC: H05G2/00 ,  G02B26/08 ,  G02B5/10 ,  G02B19/00

Abstract: A beam delivery system according to an aspect of the present disclosure is used for an extreme ultraviolet light generation apparatus and includes a propagation mirror disposed on an optical path between a laser apparatus and a condensation optical system and configured to change the propagation direction of a pulse laser beam, and a curvature mirror disposed on an optical path between the propagation mirror and the condensation optical system and having a concave reflective surface configured to convert the pulse laser beam to be incident on the condensation optical system into a convergent beam. The curvature mirror has a focal length selected so that the beam spread angle of the pulse laser beam from the curvature mirror is constant irrespective of thermal deformation of the propagation mirror or constant with change in a predetermined allowable range irrespective of thermal deformation of the propagation mirror.