Search results for "Ultrafast photonics"
showing 3 items of 3 documents
Unravelling the Intertwined Atomic and Bulk Nature of Localised Excitons by Attosecond Spectroscopy
2021
The electro-optical properties of most semiconductors and insulators of technological interest are dominated by the presence of electron-hole quasi-particles, called excitons. The manipulation of excitons in dielectrics has recently received great attention, with possible applications in different fields including optoelectronics and photonics. Here, we apply attosecond transient reflection spectroscopy in a sequential two-foci geometry and observe sub-femtosecond dynamics of a core-level exciton in bulk MgF2 single crystals. Furthermore, we access absolute phase delays, which allow for an unambiguous comparison with theoretical calculations. Our results show that excitons surprisingly exhi…
Coherent master equation for laser modelocking
2020
Modelocked lasers constitute the fundamental source of optically-coherent ultrashort-pulsed radiation, with huge impact in science and technology. Their modeling largely rests on the master equation (ME) approach introduced in 1975 by Hermann A. Haus. However, that description fails when the medium dynamics is fast and, ultimately, when light-matter quantum coherence is relevant. Here we set a rigorous and general ME framework, the coherent ME (CME), that overcomes both limitations. The CME predicts strong deviations from Haus ME, which we substantiate through an amplitude-modulated semiconductor laser experiment. Accounting for coherent effects, like the Risken-Nummedal-Graham-Haken multim…
Wideband THz time domain spectroscopy set-up based on ultrafast pulsed laser: model and experiments
2014
We present an analytical model describing the full electromagnetic propagation in a THz Time Domain Spectroscopy (THz-TDS) laser based system. We pay particular attention to the modelling of the time-frequency behavior of all the stages, which compose our experimental set-up. In particular, our model takes into account the following features: pump beam focusing into the generation crystal; phase-matching between pump and THz pulses inside both the generation and detection crystals; chromatic dispersion and absorption inside the materials; Fabry-Perot effect in both the crystals; diffraction along the propagation, focalization and overlapping between THz and probe beams; Electro-Optic Sampli…