In this work, an analytical and numerical study of the relativistic interaction of a linearly polarized laser field of ${\omega }_1$ and ${\omega }_2$ frequencies with highly overdense plasma at normal and oblique incidence is presented. Combining harmonics of ${\omega }_1$ and ${\omega }_2$ frequencies causes the amplitude oscillation of relativistic mirrors to be increased. Therefore, the intensity of generated harmonics will be increased considerably. Also, in agreement with the fully relativistic one-dimensional particle-in-cell (PIC) simulation, the relativistic mirror model explains the enhancement of the harmonic intensity of the upper spectra in the interaction of the two-color mixing laser pulse with overdense plasma. Our results show that increasing the intensity of high-order harmonics by using the two-color pulse will enhance sharply the intensity of ultrashort attosecond pulses.

• Received 25 January 2013

DOI:https://doi.org/10.1103/PhysRevA.87.063815