Generation of Broadband Supercontinuum and Isolated Attosecond Pulse in a Chirped Two-Colour Laser Field

We present a theoretical investigation of high-order harmonic generation in a chirped two-colour laser field, which is synthesized by an 800 nm fundamental chirped pulse and a 1200 nm subharmonic chirped pulse. With the introduction of a polarization angle, both the harmonic cutoff is significantly extended and the spectrum intensity is effectively enhanced compared with the orthogonally polarized chirped two-colour field. When the polarization angle between the two chirped pulses is less than or equal to 0.27π, the broadband supercontinuum with a single quantum path contribution is achieved, and then isolated attosecond pulses with the duration of about 40 as are directly obtained, which are all linearly polarized. In addition, the influences of other laser parameters on the supercontinuum are also investigated.