Title: Intense keV isolated attosecond pulse generation by orthogonally polarized multicycle midinfrared two-color laser field,
Abstract: We theoretically investigate the generation of intense keV attosecond pulses
in an orthogonally polarized multicycle midinfrared two-color laser field. It
is demonstrated that multiple continuum-like humps, which have a spectral width
of about twenty orders of harmonics and an intensity of about one order higher
than adjacent normal harmonic peaks, are generated under proper two-color
delays, owing to the reduction of the number of electron-ion recollisions and
suppression of inter-half-cycle interference effect of multiple electron
trajectories when the long wavelength midinfrared driving field is used. Using
the semiclassical trajectory model, we have revealed the two-dimensional
manipulation of the electron-ion recollision process, which agrees well with
the time frequency analysis. By filtering these humps, intense isolated
attosecond pulses are directly generated without any phase compensation. Our
proposal provides a simple technique to generate intense isolated attosecond
pulses with various central photon energies covering the multi-keV spectral
regime by using multicycle driving pulses with high pump energy in experiment.