Showing papers by "Stefano Dal Conte published in 2019"
24 Oct 2019
TL;DR: A femtosecond optical pump-probe study of the non-equilibrium behavior of coupled optical resonances in semiconducting WS2 nanotubes is presented in this paper.
Abstract: This paper presents a femtosecond optical pump-probe study of the non-equilibrium behavior of the coupled optical resonances in semiconducting WS2. The authors focus on the transient optical response of WS2 nanotubes and show that it arises primarily from the photoinduced shifts of the exciton and trion resonances due to band gap renormalization and screening of the Coulomb interaction providing the exciton and trion binding energy.
8 citations
Posted Content•
TL;DR: In this article, the authors demonstrate single-pass optical parametric amplification at the ultimate thickness limit using semiconducting transition-metal dichalcogenides, and show that amplification can be attained over a propagation through a single atomic layer.
Abstract: Optical parametric amplification is a second-order nonlinear process whereby an optical signal is amplified by a pump via the generation of an idler field. It is the key ingredient of tunable sources of radiation that play an important role in several photonic applications. This mechanism is inherently related to spontaneous parametric down-conversion that currently constitutes the building block for entangled photon pair generation, which has been exploited in modern quantum technologies ranging from computing to communications and cryptography. Here we demonstrate single-pass optical parametric amplification at the ultimate thickness limit; using semiconducting transition-metal dichalcogenides, we show that amplification can be attained over a propagation through a single atomic layer. Such a second-order nonlinear interaction at the 2D limit bypasses phase-matching requirements and achieves ultrabroad amplification bandwidths. The amplification process is independent on the in-plane polarization of the impinging signal and pump fields. First-principle calculations confirm the observed polarization invariance and linear relationship between idler and pump powers. Our results pave the way for the development of atom-sized tunable sources of radiation with applications in nanophotonics and quantum information technology.
3 citations
TL;DR: In this article, the authors measured exciton dynamics in single-layer MoS2 with unprecedented temporal resolution and directly extracted the characteristic time-scale for the Coulomb screening dynamics, which ranges between 15 and 35 fs.
Abstract: We measure exciton dynamics in single-layer MoS2 with unprecedented temporal resolution and we directly extract the characteristic time-scale for the Coulomb screening dynamics, which ranges between 15 and 35 fs.
05 May 2019
TL;DR: In this article, two-dimensional electron spectroscopy was exploited to coherently excite the A and B$ excitons in monolayer Mos 2, which can be used to distinguish ultrafast bright excITons decoherence and sub-ps scattering decays to dark exciton.
Abstract: We exploit two-dimensional electron spectroscopy to coherently excite the A and $\mathrm{B}$ excitons in monolayer Mos 2 . Combined with simulations, our data distinguish ultrafast bright excitons decoherence and sub-ps scattering decays to dark excitons. OCIS codes 300.6530. © 2019 The Author(s)
05 May 2019
TL;DR: In this paper, the authors use broadband optical pump-probe spectroscopy to study coherent optical phonons in lL-MoS2 and detect a strong coupling with the A': mode, which is enhanced around the C-exciton peak.
Abstract: We use broadband optical pump-probe spectroscopy to study coherent optical phonons in lL-MoS2. We detect a strong coupling with the A’: mode, which is enhanced around the C-exciton peak. Ab-initio calculations of the phonon-induced band structure variation fully confirm this result. © 2019 The Author(s)
TL;DR: In this article, the authors used helicity-resolved transient absorption spectroscopy to track intra-valley scattering dynamics in monolayer WS2 and found that spin-polarized carriers scatter from upper to lower conduction band by reversing their spin orientation on a sub-ps timescale.
Abstract: We use helicity-resolved transient absorption spectroscopy to track intravalley scattering dynamics in monolayer WS2 . We find that spin-polarized carriers scatter from upper to lower conduction band by reversing their spin orientation on a sub-ps timescale.