Isolated short attosecond pulse generation in an orthogonally polarized multicycle chirped laser field

Abstract

We theoretically demonstrate the generation of a high-order harmonic and isolated attosecond pulse in an orthogonally polarized laser field, which is synthesized by an 800-nm chirped laser pulse and an 800-nm chirp-free laser pulse. Owing to the instantaneous frequency increasingly reducing close to the center of the driving pulse, the extreme ultraviolet supercontinuum for the chirped synthesized field is even broader than that for an orthogonal chirp-free two-color laser field. It is found that the broadband supercontinuum spectrum can be achieved for the driving pulse with ten and above optical cycles. After phase compensation an isolated attosecond pulse with a duration of \ensuremath{\sim}16 as is produced. Furthermore, the optimization of the chirping rate parameters is investigated to achieve cutoff extension and an isolated short attosecond pulse.