T. Apostolova | Searcharxiv

arXiv2018

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/Å. 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.

physics.atom-ph↗

arXiv2004

Using a laser to cool a semiconductor

A nonlocal energy-balance equation is derived for the optical absorption, photoluminescence and inelastic electron-phonon scattering, which determines the electron and hole temperatures for any given lattice temperature. The evolution of the lattice temperature is found to be determined by the difference between the power-loss density due to photoluminescence and the power-gain density due to optical absorption, as well as by the initial lattice temperature. We find that in addition to the expected decrease in the lattice temperature, the electron temperature also decreases with time. A laser-cooling power as high as 380 eV/s is predicted for the wide bandgap semiconductor AlN initially at room temperature when the pump-laser field is only 10 V/cm. Laser cooling is found to be more efficient for a large bandgap material, a weaker laser field, and a high initial lattice temperature. The laser-cooling rate then decreases as the lattice cools. The theory presented here provides quantitative predictions that can guide future experiments.

cond-mat.other↗