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Using intense, phase-locked multi-THz waveforms, we drive high-harmonic generation and quasiparticle collisions in solids, on sub-optical-cycle scales. By exploiting the crystal symmetry, we shape the high-harmonic field and control the polarization of the emission. Many-body effects and intraband acceleration are investigated by high-order sideband generation.
Time-resolved terahertz absorption by intra-excitonic 1s-2p transitions traces the matter part of cavity polaritons while they cool into a condensed phase. The population dynamics close to the zero-momentum state is correlated with simultaneous angle-resolved photoluminescence.
This paper summarizes the latest advances in THz optoelectronics and exploits this technology for two studies of THz nonlinearities that goes beyond the perturbative regime. In the first study, intense multi-terahertz fields are used to coherently promote optically dark and dense 1s para excitons in the Cu2O semiconductor into the 2p state. By utilizing the ultrabroadband electro-optic sampling, the...
A microscopic theory is applied to describe nonlinear terahertz excitations of optically-dark excitons in Cu2O. The theory is quantitatively compared to recent experiments. Signatures of Rabi flopping and ponderomotive contributions are discussed and disentangled.
Intense multi-terahertz fields of order MV/cm coherently promote 70% of the quasiparticles of an optically dark, dense, and cold 1s-para exciton gas in Cu2O into the 2p state via a partial internal Rabi oscillation. Electro-optic sampling monitors the Larmor precession of the Bloch vector in real time.
Excitons, Coulomb bound pairs of one electron with one hole, are among the most important elementary excitations in condensed matter physics. They are often seen as analogous to the hydrogen atom. However, a complex phase diagram due to intricate many-body interactions sets limits to this picture. Up to now, excitons have almost exclusively been investigated by optical techniques resonant to the band...
Stimulated THz emission from intra-excitonic 3p to 2s transitions in Cu2O is directly observed by ultrafast opto-electronics. The process occurs at a photon energy of 6.6 meV, with a cross section of ~10-14 cm2.
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