Sub-cycle dynamics of electron-hole pairs and high-harmonic generation in bulk diamond subjected to intense femtosecond laser pulse

We present calculation of photoexcitation and high-harmonic generation in bulk diamond induced by intense near-infrared laser pulse of photon energy 1.55 eV, time duration of 15 fs and peak field strength $F=$ 0.4 V/{\AA}. Depending on the laser polarization direction, the pulsed irradiation creates electron-hole pairs and transient density fluctuations in a localized region of the crystal momentum space. As a consequence energetic inter- and intra-band harmonics are generated with alternating phase during each half-cycle of the driving pulse. The corresponding inter- and intra-band currents are in definite phase relation with the laser pulse, reflecting the build-up of coherent superposition of population between valence and conduction bands, and the accelerated motion of charge carriers in their respective bands.