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   Ultrafast all-optical switching enabled by epsilon-near-zero-tailored absorption in metal-insulator nanocavities; ; et al in Communications Physics (2020), 3 Ultrafast control of light−matter interactions is fundamental in view of new technological frontiers of information processing. However, conventional optical elements are either static or feature ... [more ▼] Ultrafast control of light−matter interactions is fundamental in view of new technological frontiers of information processing. However, conventional optical elements are either static or feature switching speeds that are extremely low with respect to the time scales at which it is possible to control light. Here, we exploit the artificial epsilon-near-zero (ENZ) modes of a metal-insulator-metal nanocavity to tailor the linear photon absorption of our system and realize a nondegenerate all-optical ultrafast modulation of the reflectance at a specific wavelength. Optical pumping of the system at its high energy ENZ mode leads to a strong redshift of the low energy mode because of the transient increase of the local dielectric function, which leads to a sub-3-ps control of the reflectance at a specific wavelength with a relative modulation depth approaching 120%. [less ▲] Detailed reference viewed: 81 (18 UL)Sub-femtosecond electron transport in a nanoscale gapLudwig, Markus  ; ; et alin Nature Physics (2019) The strong fields associated with few-cycle pulses can drive highly nonlinear phenomena, allowing the direct control of electrons in condensed matter systems. In this context, by employing near-infrared ... [more ▼] The strong fields associated with few-cycle pulses can drive highly nonlinear phenomena, allowing the direct control of electrons in condensed matter systems. In this context, by employing near-infrared single-cycle pulse pairs, we measure interferometric autocorrelations of the ultrafast currents induced by optical field emission at the nanogap of a single plasmonic nanocircuit. The dynamics of this ultrafast electron nanotransport depends on the precise temporal field profile of the optical driving pulse. Current autocorrelations are acquired with sub-femtosecond temporal resolution as a function of both pulse delay and absolute carrier-envelope phase. Quantitative modelling of the experiments enables us to monitor the spatiotemporal evolution of the electron density and currents induced in the system and to elucidate the physics underlying the electron transfer driven by strong optical fields in plasmonic gaps. Specifically, we clarify the interplay between the carrier-envelope phase of the driving pulse, plasmonic resonance and quiver motion. [less ▲] Detailed reference viewed: 178 (11 UL)Field-resolved response of plasmonic antennas; Maccaferri, Nicolò ; et alin Proceedings 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference (2019) We introduce a new experimental strategy to investigate the transient resonant behavior of plasmonic nanostructures. Our approach allows to access their full-time field-resolved response in amplitude and ... [more ▼] We introduce a new experimental strategy to investigate the transient resonant behavior of plasmonic nanostructures. Our approach allows to access their full-time field-resolved response in amplitude and phase. [less ▲] Detailed reference viewed: 34 (1 UL) Dynamics of electron-emission currents in plasmonic gaps induced by strong fields; ; et al in FARADAY DISCUSSIONS (2019), 214 The dynamics of ultrafast electron currents triggered by femtosecond laser pulse irradiation of narrow gaps in a plasmonic dimer is studied using quantum mechanical Time-Dependent Density Functional ... [more ▼] The dynamics of ultrafast electron currents triggered by femtosecond laser pulse irradiation of narrow gaps in a plasmonic dimer is studied using quantum mechanical Time-Dependent Density Functional Theory (TDDFT). The electrons are injected into the gap due to the optical field emission from the surfaces of the metal nanoparticles across the junction. Further evolution of the electron currents in the gap is governed by the locally enhanced electric fields. The combination of TDDFT and classical modelling of the electron trajectories allows us to study the quiver motion of the electrons in the gap region as a function of the Carrier Envelope Phase (CEP) of the incident pulse. In particular, we demonstrate the role of the quiver motion in establishing the CEP-sensitive net electric transport between nanoparticles. [less ▲] Detailed reference viewed: 41 (2 UL)Control of excitonic absorption by thickness variation in few-layer GaSe; ; et al in PHYSICAL REVIEW B (2019), 100(4), We control the thickness of GaSe on the level of individual layers and study the corresponding optical absorption via highly sensitive differential transmission measurements. Suppression of excitonic ... [more ▼] We control the thickness of GaSe on the level of individual layers and study the corresponding optical absorption via highly sensitive differential transmission measurements. Suppression of excitonic transitions is observed when the number of layers is smaller than a critical value of 8. Through ab initio modelling we are able to link this behavior to a fundamental change in the band structure that leads to the formation of a valence band shaped as an inverted Mexican hat in thin GaSe. The thickness-controlled modulation of the optical properties provides attractive resources for the development of functional optoelectronic devices based on a single material. [less ▲] Detailed reference viewed: 35 (1 UL)Ultrafast carrier recombination in highly n-doped Ge-on-Si films; ; et al in APPLIED PHYSICS LETTERS (2019), 114(24), We study the femtosecond carrier dynamics of n-type doped and biaxially strained Ge-on-Si films which occurs upon impulsive photoexcitation by means of broadband near-IR transient absorption spectroscopy ... [more ▼] We study the femtosecond carrier dynamics of n-type doped and biaxially strained Ge-on-Si films which occurs upon impulsive photoexcitation by means of broadband near-IR transient absorption spectroscopy. The modeling of the experimental data takes into account the static donor density in a modified rate equation for the description of the temporal recombination dynamics. The measurements confirm the negligible contribution at a high n-type doping concentration, in the 10(19)cm(-3) range, of Auger processes as compared to defect-related Shockley-Read-Hall recombination. Energy resolved dynamics reveal further insights into the doping-related band structure changes and suggest a reshaping of direct and indirect conduction band valleys to a single effective valley along with a significant spectral broadening of the optical transitions. [less ▲] Detailed reference viewed: 33 (1 UL)Pump-probe spectroscopy study of ultrafast temperature dynamics in nanoporous gold; ; et al in PHYSICAL REVIEW B (2019), 99(3), We explore the influence of the nanoporous structure on the thermal relaxation of electrons and holes excited by ultrashort laser pulses (similar to 7 fs) in thin gold films. Plasmon decay into hot ... [more ▼] We explore the influence of the nanoporous structure on the thermal relaxation of electrons and holes excited by ultrashort laser pulses (similar to 7 fs) in thin gold films. Plasmon decay into hot electron-hole pairs results in the generation of a Fermi-Dirac distribution thermalized at a temperature T-e higher than the lattice temperature T-1. 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 T-e 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 two-temperature model reproduces the data. The results open the way for electron temperature control in metals by engineering of the nanoporous geometry. [less ▲] Detailed reference viewed: 40 (2 UL)Plasmonic mid-infrared third harmonic generation in germanium nanoantennas; ; et al in Light: Science and Applications (2018) Detailed reference viewed: 122 (5 UL)Switchable dissociation of excitons bound at strained CdTe/CdS interfaces; ; et al in Nanoscale (2018) Detailed reference viewed: 130 (10 UL) |
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