Photon handling on femtosecond ultrafast beamlines

The main topics related to the optical design of table-top ultrafast beamlines with femtosecond or sub-femtosecond resolution for the generation and use of high-order laser harmonics are here discussed. After the generation through laser-gas interaction, the extreme-ultraviolet (XUV) photon beam has to be conditioned and handled. The paper is focused on two main issues: 1) beam monochromatization and 2) beam focusing. The available techniques to realize XUV ultrafast tunable monochromators using gratings are discussed. The main issue to be faced when designing a monochromator is the preservation of the ultrashort duration of the pulse after the monochromatization. The different available grating geometries and some practical realizations are presented. Furthermore, the problems related to the design of the focusing section of XUV ultrafast beamlines are discussed. The effects of the focusing properties on the ultrashort duration of the pulse are considered, namely the focal aberrations due to the optical design. Some optical solutions for XUV ultrafast micro-focusing and results measured on existing beamlines are discussed.