Matsushita Electric Industrial Co., Ltd.

Keiichro Yamanaka

Nobuaki Furuya

Takuhiro Ono

Takeo Miyata

Naoya Horiuchi

A laser apparatus comprises an optical resonator including first and second mirrors, and lasing medium. An wavelength selection element is provided in the resonator for narrowing band-width. A polarizing conversion element for changing ratio of S to P components and polarizing beam splitter are provided for amplifying laser beam to output after wavelength selection and for reducing light load of the wavelength selection element. The polarizing conversion element is provided in the resonator light path. In another embodiment, the polarizing conversion element is provided in a branch light path formed by a second polarizing conversion element and a third mirror, where the second polarizing conversion element reflects and transmits P component at a given ratio and reflects S component. The wavelength selection element comprises a Fabry-Perot etalon, grating, or prism. The polarizing conversion element comprises a quarter-wave plate or a phase retarder mirror. The polarizing beam splitting element comprises a polarizing beam splitter or polarizing beam splitting prism. The polarizing beam splitter and phase retarder prism may have a fine adjusting mechanism to adjust its optical axis to obtain desired characteristic. Such laser apparatus is suited for an exposure light source for photolithography.

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Kawasaki, Japan

Keiichro Yamanaka