This paper presents the methodology and reports the results concerning the Laser Induced Damage Threshold (LIDT), surface quality and group delay dispersion (GDD) measurements of large aperture femtosecond laser mirrors, achieved in a project funded by IFA under the contract number 02 ELI/18.10.20.17., having, as a main goal, the manufacturing of large aperture mirrors (150mm effective diameter) and tests performing for use in high energy ultra-short pulse laser systems, such as ELI-NP and CETAL infrastructures. The manufacturing process of the mirror substrates was described in a previous paper [1] and the coating technology will be presented in a future article. The novelty of this paper consists, mainly, in the method, experimental arrangement and test procedure to determine the Laser Induced Damage Threshold (LIDT) but also in the entire testing protocol, including Group Delay Dispersion (GDD) and other measurements presented here.

Fe and Fe-Cr-Al thin films, both as sputtered on Si substrates as well as after subsequent annealing treatments in hydrogen atmosphere, have been investigated by means of X-ray reflectometry, magneto-optic Kerr effect and Mossbauer spectroscopy with respect to structural and related magnetic characteristics. The as deposited films are showing chemically disordered bcc structures, assigned to Fe-Si and Fe-Cr-Al-Si phases, respectively, with soft magnetism and magnetic texture, both influenced by the presence of Si, Cr and Al atoms. The softness of the films as well as the magnetic texture are strongly modified via hydrogenation treatments. In addition, such treatments induce the expulsion of Si, Cr and Al atoms from the as deposited phases, providing almost pure Fe films of much well crystallized bcc structure.