The average effective mass of charge carriers produced by an intense ultrashort laser pulse in a transparent solid increases significantly as the excitation mechanism changes from multiphoton transitions to interband tunneling. We theoretically investigate this phenomenon for several dielectrics and semiconductors. For diamond as a representative dielectric, we present a detailed analysis of the laser-induced change of optical properties. When the concentration of free carriers is high, we find that the average effective mass controls not only the intraband charge-carrier transport but also the interband contributions to the optical response. We observe that the excitation-induced birefringence is particularly large for parameters where the plasma response compensates for the linear response of an unperturbed solid.
We study the emission of femtosecond spin current pulses at Fe/Au interfaces. Using optical second harmonic generation we demonstrate the control of pulse shape and duration by varying the emitter thickness and show that it is determined by the parameters of hot electrons emission and the diffusive transport. Using a simple model of electron emission we develop a description of superdiffusive spin transport in Au allowing to extract electron velocity and scattering rates from the experimental data. The importance of carrier multiplication in Fe is demonstrated.
We investigate the non-linear response and energy absorption in bulk silicon irradiated by intense 12-fs near-infrared laser pulses. Depending on the laser intensity, we distinguish two regimes of non-linear absorption of the laser energy: for low intensities, energy deposition and photoionization involve perturbative three-photon transition through the direct bandgap of silicon. For laser intensities near and above 10$^{14}$ W/cm$^2$, corresponding to photocarrier density of order 10$^{22}$ cm$^{-3}$, we find that absorption at near-infrared wavelengths is greatly enhanced due to excitation o…
The theory on the magnetic field energy absorption by metal nanoparticles of a nonspherical shape irradiated with ultrashort laser pulses of different duration is developed. The effect of both the particle surface and the particle shape on the absorbed energy is studied. For the particles having an oblate or prolate spheroidal shape, the dependence of this energy on the orientation of the magnetic field upon a particle, the degree of its deviation from a spherical shape, a pulse duration, and the carrier frequency of the laser ray are found. A significant increase in the absorption is establis…
In the emerging field of magnonics, spin waves are foreseen as signal carriers for future spintronic information processing and communication devices, owing to both the very low power losses and a high device miniaturisation potential predicted for short-wavelength spin waves. Yet, the efficient excitation and controlled propagation of nanoscale spin waves remains a severe challenge. Here, we report the observation of high-amplitude, ultrashort dipole-exchange spin waves (down to 80 nm wavelength at 10 GHz frequency) in a ferromagnetic single layer system, coherently excited by the driven dyna…
A theoretical investigation on the coherent Dirac-like quasiparticle dynamics in monolayer $\text{MoS}_2$ under an ultrashort optical pulse irradiation is presented. Particularly, we remain specific features of ML-MDS associated with the mass asymmetry $α$ and topological aspect $β$ parameters resulting in Schr$\stackrel{..}{\text{o}}$dinger type wavevector of charge carriers. The direct band gap, spin-resolved valence band spilitting and valley degeneracy breaking due to strong spin-orbit coupling affect ultrafast dynamics of Dirac fermions. Because the duration of the optical pulse is less t…
We theoretically investigate tunneling through free-space or dielectric nanogaps between metallic nanocontacts driven by ultrashort ultrabroadband light pulses. For this purpose we develop a time-dependent quasiclassical theory being especially suitable to describe the tunneling process in the non-adiabatic regime, when this process can be significantly influenced by the photon absorption as the electron moves in the classically forbidden region. Firstly, the case of driving by an ideal half-cycle pulse is studied. For different distances between the contacts, we analyze the main solutions hav…
We develop the theory of pure dephasing in a solid exposed to an ultrashort laser pulse beyond the commonly used Markov approximation. This approach takes into account the finite cutoff energy of the bath and can be applied to both many-particle and phonon environments. With numerical simulations performed with the time-dependent Hartree-Fock equations, we investigate how the excitation probability and high-harmonic generation are described by different models of decoherence. It is shown that the time-dependent rates allow for temporally high dephasing to successfully reproduce the main featur…
Under continuous-wave laser excitation in an InGaAs multi-quantum-well (MQW) structure, the carrier temperature extracted from photoluminescence rises faster for 405 nm excitation compared with 980 nm excitation, as the injected carrier density increases. Ensemble Monte Carlo simulation of the carrier dynamics in the MQW system shows that this carrier temperature rise is dominated by nonequilibrium LO phonon effects, with the Pauli exclusion having a significant effect at high carrier densities. Further, we find a significant fraction of carriers reside in the satellite L-valleys for 405 nm ex…
A hallmark of spin-lasers, injected with spin-polarized carriers, is their threshold behavior with the onset of stimulated emission. Unlike the single threshold in conventional lasers with unpolarized carriers, two thresholds are expected in spin lasers. With the progress in scaled-down lasers and the use of novel two-dimensional materials it is unclear if the common description of spin lasers assuming a negligible spontaneous emission and linear optical gain remains relevant or even how to identify the lasing thresholds. Our rate-equation description addresses these questions by considering a…
Electronic coherence is of utmost importance for the access and control of quantum-mechanical solid-state properties. Using a purely electronic observable, the photocurrent, we measure an electronic coherence time of 22 +/- 4 fs in graphene. The photocurrent is ideally suited to measure electronic coherence as it is a direct result of quantum path interference, controlled by the delay between two ultrashort two-color laser pulses. The maximum delay for which interference between the population amplitude injected by the first pulse interferes with that generated by the second pulse determines t…
