We demonstrate a high-throughput and high-damage-threshold beam splitter for high-order harmonics in the soft-x-ray region that uses Si and (or) SiC plates set at Brewster's angle with respect to the pump wavelength. The beam splitters are guaranteed to have a damage threshold of at least 0.8TW/cm<sup>2</sup> (average power density, 0.25W/cm<sup>2</sup>) and an attenuation rate of 10<sup>-4</sup>–10<sup>-5</sup> for a 30-fs pump pulse. The measured reflection efficiency at the 27th harmonic (29.6 nm) was 0.56 for Si and 0.45 for SiC. These beam splitters are useful not only for high harmonics but also for longitudinally pumped x-ray lasers.
© 2004 Optical Society of America
(140.7240) Lasers and laser optics : UV, EUV, and X-ray lasers
(190.4160) Nonlinear optics : Multiharmonic generation
(230.1360) Optical devices : Beam splitters
(340.0340) X-ray optics : X-ray optics
Eiji J. Takahashi, Hirokazu Hasegawa, Yasuo Nabekawa, and Katsumi Midorikawa, "High-throughput, high-damage-threshold broadband beam splitter for high-order harmonics in the extreme-ultraviolet region," Opt. Lett. 29, 507-509 (2004)