Broadband isolated attosecond pulse generation in a two-color laser field combined with an orthogonally polarized laser pulse

We present a method to generate broadband isolated attosecond pulses. Using a two-color laser field, which is synthesized by a mid-infrared (12.5 fs, 2000 nm) and a weaker (12 fs, 800 nm) pulse in the x direction, a modulated supercontinuum from 290 to 430 eV is obtainable. By properly adding a second-harmonic control field of the driving pulse in the y direction, the short quantum path is well selected and a smooth supercontinuum from 290 to 440 eV is generated. The bandwidth of the supercontinuum can be controlled by adjusting the electric field of the control pulse in the x direction. When the electric field increases to 0.051 a.u., a smooth supercontinuum from 295 to 520 eV is obtained. Using this method we expect that isolated 63-as attosecond pulses with tunable central wavelengths are straightforwardly obtained.