Search results for "high harmonic generation"
showing 10 items of 66 documents
Laser driven quantum rings: one byte logic gate implementation
2018
We study the effect of the carrier-envelope-phase (CEP) on the high harmonic generation (HHG) from a quantum ring driven by two short orthogonal lasers polarized along the x and y axes. In particular, by varying only the phase of the laser polarized along y it is possible to control the intensity of the emitted harmonics. In fact, we show that the system can efficiently emit harmonics if the laser polarized along y is small and that the cut-off of the spectra can be controlled by changing the phase or the intensity ratio between the two lasers. The wavelet analysis of the emitted harmonics and the time dependence of the angular momentum and of the energy acquired by the electron show that t…
High-order-harmonic generation in dimensionally reduced systems
2013
The time-dependent wave function of a nanoring driven by a laser field is obtained by exploiting the symmetries inherent to the system and used for studying the properties of the electromagnetic radiation emitted by the nanoring as a function of the polarization state of the laser. The diffused radiation has the characteristics of high-order-harmonic generation. For a noncircularly polarized laser field an extension of the expected cutoff position is evident, indicating that nanorings are efficient sources of radiation. The polarization state of the emitted harmonics can be opportunely controlled by varying the parameters of the pump field. The profile of the absorbed angular moment shows t…
Strong field amplification of XUV: phase matching aspects
2011
The dependence of the yield of high-order harmonic generation (HHG) on several important experimental parameters has been successfully modeled in the last 20 years by taking into account the single atom response and propagation effects. We extended this description by adding a stimulated emission process and named it x-ray parametric amplification (XPA). Beyond the super-quadratic increase of the XUV signal, which can be explained only in a limited pressure range by HHG theory, other observed characteristics like exponential growth, gain narrowing, strong blue-shift, beam divergence, etc. and their dependence on laser intensity and gas pressure can be explained accurately only by the new XP…
Classical chaos and harmonic generation in laser driven nanorings
2016
A quantum ring driven by an intense laser field emits light in the form of high-harmonic radiation resulting from the strong acceleration experienced by the active electrons forced to move on a curved trajectory. The spectrum of the emitted light is rich and strongly dependent on the parameters of the problem. In order to investigate the physical origin of such variability, we focus on the seemingly simple problem of a laser-driven charge constrained to a ring from a classical standpoint. As it turns out, the dynamics of such a classical electron is governed by a nonlinear equation which results into a chaotic motion - by nature depending on the initial conditions in an unpredictable way. O…
Plasma emission at the laser tripled frequency
2003
The third harmonic generation in the skin-layer of a dense hot plasma due to inverse bremsstrahlung is investigated for regimes having increasing experimental relevance. New analytical dependencies of the radiation flux density at the frequency 3ω on the plasma and fundamental wave parameters are established.
Monte Carlo Simulation of Electron Dynamics in Doped Semiconductors Driven by Electric Fields: Harmonic Generation, Hot-Carrier Noise and Spin Relaxa…
2011
In solid state electronics the miniaturization of integrated circuits implies that, even at moderate applied voltages, the components can be exposed to very intense electric fields. Advances in electronics push the devices to operate also under cyclostationary conditions, i.e. under large-signal and time-periodic conditions. A main consequence of this fact is that circuits exhibit a strongly nonlinear behavior. Furthermore, semiconductor based devices are always imbedded into a noisy environment that could strongly affect their performance, setting the lower limit for signal detection in electronic circuits. For this reason, to fully understand the complex scenario of the nonlinear phenomen…
Plasma radiation spectra in the presence of static electric and high-frequency radiation fields
2004
Harmonics generation of high-frequency radiation in a plasma embedded in a constant electric field is investigated theoretically. It is shown that the electron directed motion due to the static electric field yields the appearance in the plasma emission spectrum of high-frequency radiation even harmonics. The conditions are established when the even harmonics generation is as effective as that of the odd ones. At variance with the odd harmonics, the even harmonics polarization plane is found to rotate with respect to that of the fundamental field. The basic dependencies concerning the rotation angle and the generation efficiency on the plasma and field parameters are established.
High order harmonic generation: The role of the acceleration matrix elements and of the bound and continuum transitions
2001
The electromagnetic spectrum emitted by a one-dimensional atom driven by a strong laser field is obtained by use of the acceleration form and interpreted by means of few general properties of the matrix elements of the acceleration operator. We show that the emission occurs essentially in a region near the atomic core where the acceleration is significant and we investigate the role of the various emission channels arising from interference effects between transitions involving the bare atomic levels.
The influence of the quantum nature of nuclei in high harmonic generation from H+2-like molecular ions
2013
We study the full quantum dynamics of a simple molecular ion driven by an intense laser field. In particular we show that the quantum nature of the nuclear dynamics affects the emitted high harmonic generation (HHG) spectra, strongly reshaping the plateau region. In fact, it is evident that the characteristic flat trend is transformed into a descending trend, with the lower harmonics being two orders of magnitude more intense than the higher harmonics. We show that this effect is more pronounced in the lighter isotopic species of H2+ molecular ions and we also demonstrate that in this case the contribution to HHG from the antibonding electronic energetic surface is of the same order of magn…
Fluctuating laser field that induces a blueshift in harmonic generation
1998
The spectrum of a two-level atom in the presence of a multimode laser pulse is calculated. The field is allowed to fluctuate in amplitude or in phase; the emitted spectrum has richer emission lines than in the case of the nonfluctuating field and shows peaks shifted toward the blue with respect to the traditional harmonic peaks. The position of the lines is predicted by the formula ω2n+1=(2n+1)(1+Δ)ωL with Δ being a parameter that can be found numerically. In this way the fluctuations seem to result in an effective increase of the laser frequency.