| 摘要 |
A catadioptric anamorphic beam expanding telescope expands an optical beam in a first axis substantially perpendicular to the beam propagation axis, and deflects it in a plane substantially perpendicular to the first axis. The beam expanding telescope can include reflective, refractive, and combined reflective/refractive elements. An embodiment includes an off axis convex spheric reflector and an off axis combined reflective/reflective optical element, commonly known as a Mangin mirror, incorporating a refractive first surface and a reflective rear surface, which compensate for aberrations introduced by the off axis deflection of the beam. The telescope is particularly useful for deep ultraviolet (DUV) applications at wavelengths shorter than about 250 nm. In some applications, the telescope illuminates a diffraction grating or other wavelength dispersive element, aligned to retroreflect a preferential wavelength, thereby providing wavelength narrowing. In some applications a combined telescope and diffraction grating are incorporated within a laser optical cavity, thereby narrowing the output wavelength spectrum of the laser. Embodiments are advantageous for intracavity line narrowing in an electric discharge laser, such as a KrF excimer laser, ArF excimer laser, or F2 molecular laser. Additionally, embodiments in accordance with the present invention provide an improved general purpose DUV beam expander.
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