Broadband water window supercontinuum generation with a tailored mid-IR pulse in neutral media

We propose a new (to our knowledge) scheme to generate a broadband water window supercontinuum in a neutral rare-gas media. Using a phase-stabilized few-cycle mid-IR pulse tailored by a much weaker 800 nm pulse, a supercontinuum from 265 to 425 eV is observed, and the ionization probability is below 0.1%. The nonionized media enable us to adopt the right phase-matching technique to select the short path of the supercontinuum, and an isolated 80 as pulse with a central wavelength of 3.2 nm is straightforwardly obtained.