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24 May 1999 Short-pulse KrF laser with M2 reduction by a super-Gaussian mirror
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To improve the beam properties of a short-pulse KrF excimer laser (FWHM < 3.8 ns) with a low number of roundtrips (2...3) and limited magnification (< 5), unstable resonator designs have been developed. Resonators containing mirrors with super-Gaussian reflectivity distributions of different super-Gaussian orders have been investigated theoretically by beam propagation method as well as experimentally by measuring the near- and far-field beam profiles. Mirrors with radially varying multilayer systems have been fabricated by mask-shaded vacuum deposition of dielectric layers with planetary rotation of the substrate. It has been demonstrated that the (delta) -factor of the laser can be significantly improved with compact resonator configurations. For a resonator length of 400 mm, a beam spot size on the output coupler of 2 w equals 1.6 mm and a magnification of M equals 5, the optimum operation characteristics has been found for a super-Gaussian order of about k equals 10. Compared with a plane-parallel system, the (delta) -factor was enhanced by a factor of up to 7. The characteristic beam parameter M2 (times-diffraction- limited-factor) could be reduced in x- and y-directions by factors of 4 and 2, respectively. The experimental results are in good agreement with our theoretical predictions.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ruediger Grunwald, Hans Joachim Paetzold, and Uwe Griebner "Short-pulse KrF laser with M2 reduction by a super-Gaussian mirror", Proc. SPIE 3611, Laser Resonators II, (24 May 1999);

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