Interband optical transitions in graphene are subject to pseudospin selection rules. Impulsive excitation with linearly polarized light generates an anisotropic photocarrier occupation in momentum space that evolves at timescales shorter than 100fs. Here, we investigate the evolution of non-equilibrium charges towards an isotropic distribution by means of fluence-dependent ultrafast spectroscopy and develop an analytical model able to quantify the isotropization process. In contrast to conventional semiconductors, the isotropization is governed by optical phonon emission, rather than electron-electron scattering, which nevertheless contributes in shaping the anisotropic photocarrier occupation within the first few fs.

Femtosecond systems based on ytterbium as active medium are ideal for driving ultrafast optical parametric ampliଏers in a broad frequency range. The excellent stability of the source and the repetition rate tunable to up to hundreds of kHz allow for the implementation of an advanced two-color pump probe setup with the capability to achieve excellent signal-to-noise performances with sub-10 fs temporal resolution.

Colloidal quantum dots are well-established probes for quantum optical experiments. However, they possess a limited stability toward their environment. Herein, the generation of hybrid particles composed of a high optical quality quantum dot centered in a polymer particle by means of a miniemulsion polymerization procedure is reported. This embedding strongly enhances emission intensity and photochemical stability of these single-photon emitters. At the same time, their colloidal mobile nature is not compromised.

We explore the influence of the nanoporous structure on the thermal relaxation of electrons and holes excited by ultrashort laser pulses (∼ 7 fs) in thin gold films. Plasmon decay into hot electronhole pairs results in the generation of a Fermi-Dirac distribution thermalized at a temperature Te higher than the lattice temperature T l . The relaxation times of the energy exchange between electrons and lattice, here measured by pump-probe spectroscopy, is slowed down by the nanoporous structure, resulting in much higher peak Te than for bulk gold films. The electron-phonon coupling constant and the Debye temperature are found to scale with the metal filling factor f and a twotemperature model reproduces the data. The results open the way for electron temperature control in metals by engineering of the nanoporous geometry.

Charge separation at a semiconductor nano-heterointerface is switched between an on and an off state based on a combination of lattice strain, coulomb interaction, and interface trap states.