Negative Dispersion Mirror: Design,Fabrication and Use in Ti∶Sapphire Lasers

Two kinds of the negative dispersion mirrors(NDM1 and NDM2) with good performance were designed in this paper.They provided constant group delay dispersion over broadband wavelength.NDM1 employed both chirped effect and Gires-Tournois(G-T) effect to obtain large group delay dispersion of(-60 fs~2.) NDM2 employed G-T effect to obtain group delay dispersion of(-40 fs~2.) These designed mirrors can compensate the most dispersion of the Ti∶sapphire crystal and some chirp.These mirrors were fabricated by using ion beam sputtering.The reflectance of the fabricated mirrors was nearly as good as that of the designed mirrors.When these negative dispersion mirrors were used in a Ti∶sapphire laser,as short as 15 fs ultra-short pulse has been obtained.